Vitamin D supplementation during pregnancy and infancy reduces aeroallergen sensitization: a randomized controlled trial

Prenatal Vitamin D Deficiency and Maternal and Fetal Health Outcomes

Vitamin D deficiency (VDD) is a significant health issue that could have serious implications for the well-being of women and their offspring. Prenatal vitamins are widely used, but deficiency still occurs frequently in the preconception period, during pregnancy, and in breastfed infants. We analyzed the association between prenatal VDD and maternal and fetal health outcomes by reviewing studies conducted in Europe. The literature was searched for articles published in the last 10 years focusing on preeclampsia, gestational diabetes mellitus, preterm birth, low birth weight, asthma, and autism spectrum disorder. We identified a total of 43 review articles, 31 original articles, and two guidelines. During pregnancy, VDD is associated with a higher likelihood of developing gestational diabetes mellitus and preeclampsia. It may also lead to an increase in the risk of preterm birth, low birth weight, as well as asthma, and autism spectrum disorder in the offspring. While the official guidelines for vitamin D dosage differ in various countries, health authorities usually recommend a total daily supplement intake of 400-2,000 IU. In conclusion, this review emphasizes the importance of establishing guidelines for vitamin D supplementation as well as the requirement of official standards for the consumption of vitamin D in the prenatal period. Future research should concentrate on developing more unified approaches to vitamin D assessment and establishing preventative measures that can be incorporated into prenatal care programs.

Vitamin D supplementation for women during pregnancy

BACKGROUND

Vitamin D supplementation during pregnancy may help improve maternal and neonatal health outcomes (such as fewer preterm birth and low birthweight babies) and reduce the risk of adverse pregnancy outcomes (such as severe postpartum haemorrhage).

OBJECTIVES

To examine whether vitamin D supplementation alone or in combination with calcium or other vitamins and minerals given to women during pregnancy can safely improve certain maternal and neonatal outcomes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Trials Register (which includes results of comprehensive searches of CENTRAL, MEDLINE, Embase, CINAHL, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform, and relevant conference proceedings) (3 December 2022). We also searched the reference lists of retrieved studies.

SELECTION CRITERIA

Randomised and quasi-randomised trials evaluating the effect of supplementation with vitamin D alone or in combination with other micronutrients for women during pregnancy in comparison to placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently i) assessed the eligibility of studies against the inclusion criteria, ii) assessed trustworthiness based on pre-defined criteria of scientific integrity, iii) extracted data from included studies, and iv) assessed the risk of bias of the included studies. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

The previous version of this review included 30 studies; in this update, we have removed 20 of these studies to 'awaiting classification' following assessments of trustworthiness, one study has been excluded, and one new study included. This current review has a total of 10 included studies, 117 excluded studies, 34 studies in awaiting assessment, and seven ongoing studies. We used the GRADE approach to assess the certainty of the evidence. This removal of the studies resulted in evidence that was downgraded to low-certainty or very low-certainty due to study design limitations, inconsistency between studies, and imprecision. Supplementation with vitamin D compared to no intervention or a placebo A total of eight studies involving 2313 pregnant women were included in this comparison. We assessed four studies as having a low risk of bias for most domains and four studies as having high risk or unclear risk of bias for most domains. The evidence is very uncertain about the effect of supplementation with vitamin D during pregnancy compared to placebo or no intervention on pre-eclampsia (risk ratio (RR) 0.53, 95% confidence interval (CI) 0.21 to 1.33; 1 study, 165 women), gestational diabetes (RR 0.53, 95% CI 0.03 to 8.28; 1 study, 165 women), preterm birth (< 37 weeks) (RR 0.76, 95% CI 0.25 to 2.33; 3 studies, 1368 women), nephritic syndrome (RR 0.17, 95% CI 0.01 to 4.06; 1 study, 135 women), or hypercalcaemia (1 study; no cases reported). Supplementation with vitamin D during pregnancy may reduce the risk of severe postpartum haemorrhage; however, only one study reported this outcome (RR 0.68, 95% CI 0.51 to 0.91; 1 study, 1134 women; low-certainty evidence) and may reduce the risk of low birthweight; however, the upper CI suggests that an increase in risk cannot be ruled out (RR 0.69, 95% CI 0.44 to 1.08; 3 studies, 371 infants; low-certainty evidence). Supplementation with vitamin D + calcium compared to no intervention or a placebo One study involving 84 pregnant women was included in this comparison. Overall, this study was at moderate to high risk of bias. Pre-eclampsia, gestational diabetes, and maternal adverse events were not reported. The evidence is very uncertain about the effect of supplementation with vitamin D and calcium on preterm birth (RR not estimable; very low-certainty evidence) or for low birthweight (RR 1.45, 95% CI 0.14 to 14.94; very low-certainty evidence) compared to women who received placebo or no intervention. Supplementation with vitamin D + calcium + other vitamins and minerals versus calcium + other vitamins and minerals (but no vitamin D) One study involving 1298 pregnant women was included in this comparison. We assessed this study as having a low risk of bias in all domains. Pre-eclampsia was not reported. The evidence is very uncertain about the effect of supplementation with vitamin D, calcium, and other vitamins and minerals during pregnancy compared to no vitamin D on gestational diabetes (RR 0.42, 95% CI 0.10 to 1.73; very low-certainty evidence), maternal adverse events (hypercalcaemia no events and hypercalciuria RR 0.25, 95% CI 0.02 to 3.97; very low-certainty evidence), preterm birth (RR 1.04, 95% CI 0.68 to 1.59; low-certainty evidence), or low birthweight (RR 1.12, 95% CI 0.82 to 1.51; low-certainty evidence).

AUTHORS' CONCLUSIONS

This updated review using the trustworthy assessment tool removed 21 studies from the previous update and added one new study for a total of 10 included studies. In this setting, supplementation with vitamin D alone compared to no intervention or a placebo resulted in very uncertain evidence on pre-eclampsia, gestational diabetes, preterm birth, or nephritic syndrome. It may reduce the risk of severe postpartum haemorrhage; however, only one study reported this outcome. It may also reduce the risk of low birthweight; however, the upper CI suggests that an increase in risk cannot be ruled out. Supplementation with vitamin D and calcium versus placebo or no intervention resulted in very uncertain evidence on preterm birth and low birthweight. Pre-eclampsia, gestational diabetes, and maternal adverse events were not reported in the only study included in this comparison. Supplementation with vitamin D + calcium + other vitamins and minerals versus calcium + other vitamins and minerals (but no vitamin D) resulted in very uncertain evidence on gestational diabetes and maternal adverse events (hypercalciuria) and uncertain evidence on preterm birth and low birthweight. Pre-eclampsia was not reported in the only study included in this comparison. All findings warrant further research. Additional rigorous, high-quality, and larger randomised trials are required to evaluate the effects of vitamin D supplementation in pregnancy, particularly in relation to the risk of maternal adverse events.

Vitamin D Primary Prevention of Respiratory Infections and Asthma in Early Childhood: Evidence and Mechanisms

Respiratory infections are a leading cause of child morbidity worldwide, and asthma is the most common chronic disorder in childhood. Both conditions associate with high socioeconomic costs and are major reasons for medication prescriptions and hospitalizations in children. Vitamin D deficiency has concomitantly increased with asthma prevalence and is hypothesized to play a key role in the development. Current evidence suggests that high prenatal and early childhood vitamin D could be protective against respiratory infections and asthma in some studies where several mechanisms are proposed. However, other studies have reported no effects on these outcomes. Therefore, future large intervention studies on this topic are warranted. Mechanistic studies have shown that vitamin D holds antimicrobial properties by inducing production of several peptides through altered gene expression. Others have shown a complex interplay between asthma risk genotypes, the sphingolipid pathway, and prenatal vitamin D in early childhood asthma. Vitamin D has also been suggested to change both airway immune and microbiota profiles, which are directly related to asthma risk. Finally, systemic low-grade inflammation seems to be regulated by vitamin D exposure. This review presents the current literature of the primary preventive effect of vitamin D on early childhood asthma and respiratory infections. Mechanisms of actions are discussed, and gaps in knowledge are highlighted to facilitate planning of future intervention trials.

High-dose oral vitamin D supplementation for prevention of infections in children aged 0 to 59 months: a systematic review and meta-analysis

CONTEXT

Vitamin D plays an important role in immune function, and the deficiency thereof has been associated with several infections, most notably respiratory tract infections. However, data from intervention studies investigating the effect of high-dose vitamin D supplementation on infections have been inconclusive.

OBJECTIVE

The aim of this study was to evaluate the level of evidence regarding the efficacy of vitamin D supplementation above the standard dose (400 IU) in preventing infections in apparently healthy children < 5 years of age.

DATA SOURCES

PubMed, Scopus, Science Direct, Web of Science, Google Scholar, CINAHL, and MEDLINE electronic databases were searched between August 2022 and November 2022. Seven studies met the inclusion criteria.

DATA EXTRACTION

Meta-analyses of outcomes in more than one study were performed using Review Manager software. Heterogeneity was evaluated using the I2 statistic. Randomized controlled trials in which vitamin D was supplemented at > 400 IU compared with placebo, no treatment, or standard dose were included.

DATA ANALYSIS

Seven trials that enrolled a total of 5748 children were included. Odds ratios (ORs) with 95%CIs were calculated using random- and fixed-effects models. There was no significant effect of high-dose vitamin D supplementation on the incidence of upper respiratory tract infection (OR, 0.83; 95%CI, 0.62-1.10). There was a 57% (95%CI, 0.30-0.61), 56% (95%CI, 0.27-0.07), and 59% (95%CI, 0.26-0.65) reduction in the odds of influenza/cold, cough, and fever incidence, respectively, with daily supplementation of vitamin D > 1000 IU. No effect was found on bronchitis, otitis media, diarrhea/gastroenteritis, primary care visits for infections, hospitalizations, or mortality.

CONCLUSION

High-dose vitamin D supplementation provided no benefit in preventing upper respiratory tract infections (moderate certainty of evidence) but reduced the incidence influenza/cold (moderate certainty of evidence), cough, and fever (low certainty of evidence). These findings are based on a limited number of trials and should be interpreted with caution. Further research is needed.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42022355206.

Randomised controlled trial of perinatal vitamin D supplementation to prevent early-onset acute respiratory infections among Australian First Nations children: the 'D-Kids' study protocol

INTRODUCTION

Globally, acute respiratory infections (ARIs) are a leading cause of childhood morbidity and mortality. While ARI-related mortality is low in Australia, First Nations infants are hospitalised with ARIs up to nine times more often than their non-First Nations counterparts. The gap is widest in the Northern Territory (NT) where rates of both acute and chronic respiratory infection are among the highest reported in the world. Vitamin D deficiency is common among NT First Nations neonates and associated with an increased risk of ARI hospitalisation. We hypothesise that perinatal vitamin D supplementation will reduce the risk of ARI in the first year of life.

METHODS AND ANALYSIS

'D-Kids' is a parallel (1:1), double-blind (allocation concealed), randomised placebo-controlled trial conducted among NT First Nations mother-infant pairs. Pregnant women and their babies (n=314) receive either vitamin D or placebo. Women receive 14 000 IU/week or placebo from 28 to 34 weeks gestation until birth and babies receive 4200 IU/week or placebo from birth until age 4 months. The primary outcome is the incidence of ARI episodes receiving medical attention in the first year of life. Secondary outcomes include circulating vitamin D level and nasal pathogen prevalence. Tertiary outcomes include infant immune cell phenotypes and challenge responses. Blood, nasal swabs, breast milk and saliva are collected longitudinally across four study visits: enrolment, birth, infant age 4 and 12 months. The sample size provides 90% power to detect a 27.5% relative reduction in new ARI episodes between groups.

ETHICS AND DISSEMINATION

This trial is approved by the NT Human Research Ethics Committee (2018-3160). Study outcomes will be disseminated to participant families, communities, local policy-makers, the broader research and clinical community via written and oral reports, education workshops, peer-reviewed journals, national and international conferences.

TRIAL REGISTRATION NUMBER

ACTRN12618001174279.

The Impact of Baseline 25-Hydroxyvitamin D Level and Gestational Age on Prenatal Vitamin D Supplementation to Prevent Offspring Asthma or Recurrent Wheezing

BACKGROUND

Prenatal vitamin D deficiency is associated with asthma or recurrent wheezing in offspring. However, evidence from randomized trials on the efficacy of vitamin D supplementation is inconclusive.

OBJECTIVES

We aimed to examine the differential efficacy of prenatal vitamin D supplementation based on the maternal baseline vitamin D status and the starting time of supplementation to prevent early life asthma or recurrent wheezing.

METHODS

We conducted a secondary analysis of the Vitamin D Antenatal Asthma Reduction Trial (VDAART), a randomized double-blind trial of prenatal vitamin D supplementation initiated at 10-18 weeks (wks) of gestation (4400 IU of intervention/day compared with 400 IU of placebo/day) to prevent offspring asthma or recurrent wheezing by the age of 6 years. We assessed the effect of modification of supplementation by maternal baseline vitamin D status at enrollment and the timing of initiation of supplementation.

RESULTS

An inverse relationship was observed between maternal 25-hydroxyvitamin D (25(OH)D) levels at trial entry and 25(OH)D levels during late pregnancy (32-38 wks of gestation) in both supplementation arms (P < 0.001). Overall, supplementation efficacy was not dependent on the maternal baseline 25(OH)D status. However, a trend toward the reduction of asthma or recurrent wheezing was observed across the baseline groups in the intervention arm (P = 0.01), with the greatest reduction observed in the most severely vitamin D-deficient women (25(OH)D < 12 ng/mL; adjusted odds ratio [aOR] = 0.48; confidence interval [CI]: 0.17, 1.34). Gestational age at trial enrollment modified supplementation efficacy, showing a greater reduction of offspring asthma or recurrent wheezing with earlier intervention during pregnancy (aOR = 0.85; CI = 0.76, 0.95), particularly in women who were 9-12 wk pregnant (aOR = 0.45; CI = 0.24, 0.82).

CONCLUSIONS

Pregnant women with severe vitamin D deficiency show the greatest 25(OH)D improvement because of supplementation. In these women, a vitamin D dose of 4400 IU might have a preventive role in the development of early life offspring asthma or recurrent wheezing. Gestational age is suggested to modify the efficacy of prenatal vitamin D supplementation, showing the highest beneficial effect if supplementation is started during the first trimester of pregnancy. This study is an ancillary analysis from the VDAART, which is registered in ClinicalTrials.gov as NCT00902621.

Association of Maternal Gestational Vitamin D Supplementation with Respiratory Health of Young Children

This study aimed to evaluate the association between maternal gestational Vitamin D3 supplementation and early respiratory health in offspring. This was a population-based record-linkage study which used data from the French National Health Database System. Maternal Vitamin D3 supplementation consisted of a single high oral dose of cholecalciferol, (100,000 IU) from the seventh month of pregnancy, according to national guidelines. In total, 125,756 term-born singleton children were included, of which 37% had respiratory illness defined as hospital admission due to respiratory causes or inhalation treatment up to 24 months of age. Infants prenatally exposed to maternal Vitamin D3 supplementation (n = 54,596) were more likely to have a longer gestational age (GA) at birth (GA 36-38 weeks, 22% vs. 20%, p < 0.001 in exposed vs. non-exposed infants, respectively). After adjusting for the main risk factors (maternal age, socioeconomic level, mode of delivery, obstetrical and neonatal pathology, birth weight appropriateness, sex, and birth season), the risk of RD was found to be 3% lower than their counterparts (aOR [IC 95%], 0.97 [0.95-0.99], p = 0.01). In conclusion, this study provides evidence for the association between maternal gestational Vitamin D3 supplementation and improved early respiratory outcomes in young children.

Fish Oil and Vitamin D Supplementations in Pregnancy Protect Against Childhood Croup

BACKGROUND

Croup is a prevalent respiratory disorder in early childhood most often caused by parainfluenza virus infections. There are no preventive strategies; therefore, we investigated the potential effects of prenatal micronutrient supplementations.

OBJECTIVE

To investigate the supplementation effects of (1) 2.4-g n-3 long-chained polyunsaturated fatty acid (n-3 LCPUFA) (fish oil) versus olive oil and (2) high-dose (2800 IU/d) versus standard-dose (400 IU/d) of vitamin D from pregnancy week 24 until 1 week after birth on the risk for offspring croup during the double-blinded first 3 years of life in a secondary analysis of a 2 × 2 factorial designed randomized controlled trial.

METHODS

The study was completed in the Danish population-based single-center Copenhagen Prospective Studies on Asthma in Childhood 2010 mother-child cohort, which included 736 pregnant women. Croup was diagnosed by physicians' clinical examinations and medical record checks. Potential mediating mechanisms were investigated using blood metabolomics, airway cytokines, and airway microbiome.

RESULTS

Of 695 children, 97 had croup before age 3 years (14%). The risk of croup was reduced in the n-3 LCPUFA (n_cases / n_total = 38/346; 11%) versus olive oil group (59 of 349 children; 17%) (hazard ratio = 0.62; 95% CI, 0.41-0.93; P = .02) and in the high-dose vitamin D group (32 of 295 children; 11%) versus the standard-dose group (51 of 286 children; 18%) (hazard ratio = 0.60; 95% CI, 0.38-0.93; P = .02). There was no evidence of interaction or additive effects between the supplements (P_interaction = .56). Furthermore, the results did not change when they were adjusted for each other, persistent wheeze, and lower respiratory tract infection.

CONCLUSIONS

This analysis of the double-blinded period of the Copenhagen Prospective Studies on Asthma in Childhood 2010 randomized controlled trial of n-3 LCPUFA and high-dose vitamin D supplementation during pregnancy demonstrated a reduced risk of croup in early childhood.

Vitamin D intakes and health outcomes in infants and preschool children: Summary of an evidence report

BACKGROUND

A systematic review was commissioned to support an international expert group charged to update the Food and Agriculture Organisation of the United Nations (FAO)/World Health Organisation (WHO)'s vitamin D intake recommendations for children aged 0-4 years.

MATERIALS AND METHODS

Multiple electronic databases were searched to capture studies published from database inception to the 2^nd week of June 2020 according to key questions formulated by the FAO/WHO. Relevant studies were summarised and synthesised by key questions and by health outcomes using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

The 146 included studies examined the effects of different vitamin D intake levels on a variety of health outcomes (e.g. infectious disease, growth, neurodevelopment, rickets, and bone mineral density), and on outcomes for setting vitamin D upper limits (e.g. hypercalcemia, hypercalciuria, and nephrocalcinosis). For most outcomes, the strength of evidence was low or very low. Evidence was rated moderate for the effect of daily vitamin D supplementation on raising serum 25(OH)D concentrations, and a random-effects meta-regression analysis of 28 randomised controlled trials (mostly in infants 0-12 months) showed that each 100 IU/d increase in vitamin D supplementation was associated with an average of 1.92 (95% CI 0.28, 3.56) nmol/L increase in achieved 25-hydroxy-vitaminn D (25[OH]D) concentration (n = 53 intervention arms; p = .022) with large residual heterogeneity (I² = 99.39%). Evidence was very low on two of the upper limit outcomes - hypercalcemia and hypercalciuria.

CONCLUSIONS

The evidence report provided the expert group with a foundation and core set of data to begin their work to set vitamin D nutrient reference values. To move the field forward, future studies should use standardised 25(OH)D assay measurements and should examine the relationship between long-term vitamin D status and health outcomes.Key MessagesResults of a large complex systematic review suggest the current totality of evidence from trials and prospective observational studies do not reach sufficient certainty level to support a causal relationship between vitamin D intake and asthma, wheeze, eczema, infectious diseases, or rickets (most trials reported no rickets) in generally healthy infants and young children.In this systematic review, the only body of evidence that reached a moderate level of certainty was regarding the effect of daily vitamin D supplementation (vitamin D₃ or D₂ supplements to infants/children) on increasing serum 25(OH)D concentrations. However, currently there is no consensus on the definitions of vitamin D status, e.g. deficiency, insufficiency, sufficiency and toxicity, based on serum 25(OH)D concentrations.This systematic review provided an international expert group a foundation and core set of data through intake-response modelling to help set vitamin D nutrient reference values for infants and children up to 4 years of age.

Impact of dietary vitamin D on immunoregulation and disease pathology in lupus-prone NZB/W F1 mice

Vitamin D (VD) deficiency is a highly prevalent worldwide phenomenon and is extensively discussed as a risk factor for the development of systemic lupus erythematosus (SLE) and other immune-mediated diseases. In addition, it is now appreciated that VD possesses multiple immunomodulatory effects. This study aims to explore the impact of dietary VD intake on lupus manifestation and pathology in lupus-prone NZB/W F1 mice and identify the underlying immunological mechanisms modulated by VD. Here, we show that low VD intake accelerates lupus progression, reflected in reduced overall survival and an earlier onset of proteinuria, as well higher concentrations of anti-double-stranded DNA autoantibodies. This unfavorable effect gained statistical significance with additional low maternal VD intake during the prenatal period. Among examined immunological effects, we found that low VD intake consistently hampered the adoption of a regulatory phenotype in lymphocytes, significantly reducing both IL-10-expressing and regulatory CD4+ T cells. This goes along with a mildly decreased frequency of IL-10-expressing B cells. We did not observe consistent effects on the phenotype and function of innate immune cells, including cytokine production, costimulatory molecule expression, and phagocytic capacity. Hence, our study reveals that low VD intake promotes lupus pathology, likely via the deviation of adaptive immunity, and suggests that the correction of VD deficiency might not only exert beneficial functions by preventing osteoporosis but also serve as an important module in prophylaxis and as an add-on in the treatment of lupus and possibly other immune-mediated diseases. Further research is required to determine the most appropriate dosage, as too-high VD serum levels may also induce adverse effects, possibly also on lupus pathology.

Particulate matter may have a limited influence on maternal vitamin D levels

Evidence for an association between the amount of particulate matter (PM) in the atmosphere and vitamin D status of pregnant women is limited. We aimed to examine the independent association between PM and maternal levels of serum 25-hydroxyvitamin D (25OHD) during the second trimester and to explore possible modifications to the association by meteorological factors. 27,768 pregnant women presenting for prenatal examination who were tested for serum 25OHD concentration during the second trimester between January 1, 2016, and December 31, 2020, were included in this retrospective analysis. Exposure to PM was evaluated based on daily average PM with an aerodynamic diameter of ≤ 2.5 μm (PM_2.5) and PM with an aerodynamic diameter of ≤ 10 μm (PM₁₀). Corresponding meteorological data for daily average atmospheric temperature, atmospheric pressure, relative humidity, sunshine duration, and wind speed were collected. The maximum cumulative effects of PM_2.5 occurred at lag 45 days, and the maximum cumulative effects of PM₁₀ occurred at lag 60 days. In crude models, 45-day moving daily average PM_2.5 concentrations were negatively associated with 25OHD levels (β, − 0.20; 95% CI − 0.21 to − 0.19), as were 60-day moving daily average PM₁₀ concentrations (β, − 0.14; 95% CI − 0.15 to − 0.14). After adjusting for temporal and meteorological factors, the effect values were drastically reduced (adjusted β of PM_2.5, − 0.032; 95% CI − 0.046 to − 0.018; adjusted β of PM₁₀, − 0.039; 95% CI − 0.049 to − 0.028). Our study showed there was a small, independent, negative association between PM in the atmosphere and maternal serum 25OHD levels during the second trimester of pregnancy after adjusting for temporal and/or meteorological factors, which indicates that PM may have a limited influence on maternal serum 25OHD levels. Besides taking vitamin D supplements, pregnant women should keep participating in outdoor activities while taking PM protection measures to improve their vitamin D levels when PM levels are high in winter and spring.

Vitamin D: Before, during and after Pregnancy: Effect on Neonates and Children

A worldwide high prevalence of vitamin D (VD) deficiency has become of growing concern because of potential adverse effects on human health, including pregnant women and their offsprings. Beyond its classical function as a regulator of calcium and phosphate metabolism, together with its fundamental role in bone health in every stage of life, its deficiency has been associated to multiple adverse health effects. The classic effects of VD deficiency in pregnancy and neonates have been late hypocalcemia and nutritional rickets. Nevertheless, recent studies have linked VD to fertility and 25(OH)D with several clinical conditions in pregnancy: preeclampsia, gestational diabetes, higher incidence of cesarean section and preterm birth, while in infants, the clinical conditions are low birth weight, lower bone mass and possible relationship with the development of such diseases as bronchiolitis, asthma, type 1 diabetes, multiple sclerosis and autism included as VD non-classical actions. The supplementation with Vitamin D and achievement of optimal levels reduce maternal-fetal and newborn complications. Supplementation in children with VD deficiency reduces the risk of respiratory infections and possibly autoimmune diseases and autism. This review emphasizes the roles of Vitamin D deficiency and the consequences of intervention from preconception to infancy.

Maternal Vitamin D Supplementation for the Prevention of Respiratory Tract Infections in Offspring: A Meta-Analysis

BACKGROUND

Vitamin D may enhance immune system function and provide a protective effect against infections. Feto-maternal circulation plays an important role in supplying the developing fetus with nutrients and antibodies for its development and health during pregnancy and for its early years of life after birth. This meta-analysis aimed to determine the effectiveness of maternal vitamin D supplementation in preventing respiratory tract infections (RTIs) in children.

METHODS

We searched the Central and MEDLINE databases and went through all the reference lists in the related articles. We also searched for ongoing trials at http://www.who.int/ictrp/en/ and www.clinicaltrials.gov. Randomized controlled trials comparing vitamin D supplementation with a placebo or no treatment in pregnant women published in the English language up to March 2019 were included. Two reviewers extracted data independently using a predefined protocol and assessed the risk of bias using the Cochrane risk of bias tool, with differences agreed upon by consensus. The predefined primary outcome was the number of offspring who had RTIs. The secondary outcome was the presence of measurable serum immunoglobulin E levels.

RESULTS

Three trials involving 3,224 participants (mother-child pairs) met the inclusion criteria and were included in this review. The present analysis reported that maternal supplementation with vitamin D had no effect on RTIs among children (n=1,486 offspring; risk ratio, 0.95; 95% confidence interval, 0.82-1.11; random effects; I2 statistics, 0%).

CONCLUSION

Maternal vitamin D supplementation had no effect on RTIs in children. Therefore, consideration of other prevention methods in this regard is recommended.

Pre- and Postnatal Vitamin D Status and Allergy Outcomes in Early Childhood

The dramatic increase in the prevalence of allergic disease in recent decades reflects environmental and behavioural changes that have altered patterns of early immune development. The very early onset of allergic diseases points to the specific vulnerability of the developing immune system to environmental changes and the development of primary intervention strategies is crucial to address this unparalleled burden. Vitamin D is known to have immunomodulatory functions. While allergic disease is multifactorial, associations with reduced sunlight exposure have led to the hypothesis that suboptimal vitamin D levels during critical early periods may be one possible explanation. Interventions to improve vitamin D status, especially in early life, may be the key to allergic disease prevention.

Primary Prevention of Pediatric Asthma through Nutritional Interventions

Asthma is the most common chronic non-communicable disease in children, the pathogenesis of which involves several factors. The increasing burden of asthma worldwide has emphasized the need to identify the modifiable factors associated with the development of the disease. Recent research has focused on the relationship between dietary factors during the first 1000 days of life (including pregnancy)—when the immune system is particularly vulnerable to exogenous interferences—and allergic outcomes in children. Specific nutrients have been analyzed as potential targets for the prevention of childhood wheeze and asthma. Recent randomized controlled trials show that vitamin D supplementation during pregnancy, using higher doses than currently recommended, may be protective against early childhood wheezing but not school-age asthma. Omega-3 fatty acid supplementation during pregnancy and infancy may be associated with a reduced risk of childhood wheeze, although the evidence is conflicting. Data from observational studies suggest that some dietary patterns during pregnancy and infancy might also influence the risk of childhood asthma. However, the quality of the available evidence is insufficient to allow recommendations regarding dietary changes for the prevention of pediatric asthma. This review outlines the available high-quality evidence on the role of prenatal and perinatal nutritional interventions for the primary prevention of asthma in children and attempts to address unmet areas for future research in pediatric asthma prevention.

Vitamin D supplementation in pregnant women or infants for preventing allergic diseases

Background:

It is still unclear if and to what extent antenatal or infant or childhood vitamin D supplementation would affect the development of allergy diseases later in life. This study aimed to review the efficacy of vitamin D supplementation in pregnant women, infants, or children for the prevention of allergies.

Methods:

MEDLINE (PubMed), EMBASE (OVID), and the Cochrane Central Register of Controlled Trials were searched up to March 1, 2020. We included only randomized controlled trials (RCTs). We performed a systematic review and meta-analysis for vitamin D supplementation in primary allergy prevention. These trials were assessed for risk of bias using the Cochrane Collaboration domains and the consensus was reached via discussion with the full study group. We descriptively summarized and quantitatively synthesized original data to evaluate vitamin D supplementation in primary allergy prevention by using Review Manager software for meta-analysis.

Results:

The search yielded 1251 studies. Seven RCTs were included in this analysis. A meta-analysis revealed that vitamin D supplementation for pregnant women or infants may not decrease the risk of developing allergic diseases, such as asthma or wheezing (supplementation for pregnant women, risk ratio [RR]: 1.01, 95% confidence interval [CI]: 0.81–1.26, P = 0.90, I² = 47%; supplementation for infants, RR: 1.00, 95% CI: 0.70–1.43, P = 0.99, I² = 0%; supplementation for pregnant women and infants, RR: 0.35, 95% CI: 0.10–1.25, P = 0.11), eczema (supplementation for pregnant women, RR: 0.95, 95% CI: 0.80–1.13, P = 0.77, I² = 0%; supplementation for infants, RR: 0.84, 95% CI: 0.64–1.11, P = 0.19, I² = 42%), allergic rhinitis (supplementation for pregnant women, RR: 0.93, 95% CI: 0.78–1.11, P = 0.15, I² = 47%), lower respiratory tract infection (LRTI) (supplementation for pregnant women, RR: 0.97, 95% CI: 0.85–1.11, P = 0.59, I² = 0%), or food allergy.

Conclusions:

Supplementation of vitamin D in pregnant women or infants does not have an effect on the primary prevention of allergic diseases.

Systematic Review Registration:

PROSPERO (CRD42020167747)

Early Oral Nutritional Supplements in the Prevention of Wheezing, Asthma, and Respiratory Infections

Wheezing, asthma, and respiratory infections (RTI) are among the most common causes of morbidity in children and their economic and social burden could be significantly reduced by specific prevention strategies. Epidemiological studies suggest that lower levels of some nutrients are associated with higher prevalence of these conditions, but the possible protective effect of early supplementation with these nutrients has not yet been established. Aim of our review is to synthetize the available scientific evidence on the role of supplementation with pre- and probiotics, vitamin D, fish and poly-unsaturated fatty acids (PUFA), vitamin A, C, and E, given during the first year of life, in the prevention of wheezing, asthma and RTI. We searched studies published on this topic in the PubMed database between January 2000 and September 2021. As for pre- and probiotics, most of the studies showed that an early supplementation had no protective effect toward the development of asthma and wheezing, while conflicting results were reported on their role in the reduction of RTI. As for vitamin D, the available data suggest that early and regular (on a daily or weekly base) supplementation of vitamin D during infancy could have a role in the prevention of RTI, while most studies showed no effect in the prevention of wheezing or asthma. Finally, early introduction of fish in the diet in most studies has proved protective toward wheezing and asthma development.

Effect of vitamin D supplementation on total and allergen-specific IgE in children with asthma and low vitamin D levels

BACKGROUND

Observational studies have yielded inconsistent findings for the relation between vitamin D level and total IgE or allergic sensitization.

OBJECTIVE

To determine whether vitamin D supplementation reduces levels of total IgE and IgE to each of 2 common indoor allergens in children with asthma and low vitamin D levels.

METHODS

Total IgE, IgE to Dermatophagoides pteronyssinus, and IgE to Blattella germanica were measured at the randomization and exit visits for 174 participants in the Vitamin D Kids Asthma Study, a multicenter, double-blind, randomized placebo-controlled trial of vitamin D₃ supplementation (4000 IU/d) to prevent severe exacerbations in children with persistent asthma and vitamin D levels less than 30 ng/mL. Multivariable linear regression was used for the analysis of the effect of vitamin D supplementation on change in each IgE measure.

RESULTS

Participants were followed for an average of 316 days. At the exit visit, more subjects in the vitamin D arm achieved a vitamin D level equal to or more than 30 ng/mL compared with those in the placebo arm (87% vs 30%; P < .001). In a multivariable analysis, vitamin D₃ supplementation had no significant effect on change in total IgE, IgE to Dermatophagoides pteronyssinus, or IgE to Blattella germanica between the exit and randomization visits (eg, for log₁₀ total IgE, β = 0.007; 95% CI, -0.061 to 0.074; P = .85).

CONCLUSIONS

Vitamin D supplementation, compared with placebo, has no significant effect on serum levels of total IgE, IgE to dust mite, or IgE to cockroach in children with asthma and low vitamin D levels.

EFFECTS OF VITAMIN D SUPPLEMENTATION DURING PREGNANCY ON NEWBORNS AND INFANTS: AN INTEGRATIVE REVIEW

OBJECTIVE

To identify the effects of vitamin D supplementation during pregnancy on newborns and infants.

DATA SOURCES

The present study is an integrative review of literature based on clinical trials published in journals indexed in the PubMed and Web of Science databases. Two searches were carried out, starting with the association (and) of the health term "vitamin D" with "pregnancy". In the search for information, selection criteria were established, and there was no language limitation and year of publication.

DATA SYNTHESIS

The final selection resulted in 44 clinical trials, most of which were randomized and double blind, which were carried out in outpatient clinics, referral hospitals and universities, mainly in Europe. The samples studied were predominantly of newborns. In these 44 trials, 23 types of different doses of vitamin D during pregnancy, with different doses, regimens and times of use, and 14 different outcomes were studied in newborns (NB) and infants. Of the 44 studies performed, 35 showed statistically significant beneficial effects of vitamin D supplementation during pregnancy on newborns and infants compared to control groups.

CONCLUSIONS

Vitamin D supplementation during pregnancy for at least three months before delivery has the potential of positively influencing calcium metabolism, physical growth and immune system development in newborns and infants. However, there is insufficient knowledge to define the optimal dose and to guarantee the absence of possible long-term adverse effects.

Perinatal and Early-Life Nutrition, Epigenetics, and Allergy

Epidemiological studies have shown a dramatic increase in the incidence and the prevalence of allergic diseases over the last several decades. Environmental triggers including risk factors (e.g., pollution), the loss of rural living conditions (e.g., farming conditions), and nutritional status (e.g., maternal, breastfeeding) are considered major contributors to this increase. The influences of these environmental factors are thought to be mediated by epigenetic mechanisms which are heritable, reversible, and biologically relevant biochemical modifications of the chromatin carrying the genetic information without changing the nucleotide sequence of the genome. An important feature characterizing epigenetically-mediated processes is the existence of a time frame where the induced effects are the strongest and therefore most crucial. This period between conception, pregnancy, and the first years of life (e.g., first 1000 days) is considered the optimal time for environmental factors, such as nutrition, to exert their beneficial epigenetic effects. In the current review, we discussed the impact of the exposure to bacteria, viruses, parasites, fungal components, microbiome metabolites, and specific nutritional components (e.g., polyunsaturated fatty acids (PUFA), vitamins, plant- and animal-derived microRNAs, breast milk) on the epigenetic patterns related to allergic manifestations. We gave insight into the epigenetic signature of bioactive milk components and the effects of specific nutrition on neonatal T cell development. Several lines of evidence suggest that atypical metabolic reprogramming induced by extrinsic factors such as allergens, viruses, pollutants, diet, or microbiome might drive cellular metabolic dysfunctions and defective immune responses in allergic disease. Therefore, we described the current knowledge on the relationship between immunometabolism and allergy mediated by epigenetic mechanisms. The knowledge as presented will give insight into epigenetic changes and the potential of maternal and post-natal nutrition on the development of allergic disease.

Association Between Vitamin D and Novel SARS-CoV-2 Respiratory Dysfunction - A Scoping Review of Current Evidence and Its Implication for COVID-19 Pandemic

OBJECTIVES

To assess the association between vitamin D deficiency and increased morbidity/mortality with COVID-19 respiratory dysfunction.

DESIGN

Scoping review.

DATA SOURCES

Ovid MEDLINE (1946 to 24 of April 2020) and PubMed (2020 to 17 of September 2020).

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

A search using the search terms: [(cholecalciferol or ergocalciferol or vitamin D2 or vitamin D3 or vitamin D or 25OHD) and (SARS-CoV-2 or coronavirus or COVID or betacoronavirus or MERS-CoV or SARS-CoV or respiratory infection or acute respiratory distress syndrome or ARDS)]m.p. was conducted on the 24/04/2020 (Search A) and 17/09/2020 (Search B).

RESULTS

91 studies were identified as being concerned with Acute Respiratory Infection (ARI)/Acute Respiratory Distress Syndrome (ARDS) and vitamin D, and 25 publications specifically explored the role of vitamin D deficiency in the development and progression of SARS-CoV-2/COVID-19 related ARDS. Search "A" identified three main themes of indirect evidence supporting such an association. Consistent epidemiological evidence exists linking low vitamin D levels to increased risk and severity of respiratory tract infections. We also report on plausible biological processes supporting such an association; and present weaker evidence supporting the benefit of vitamin D supplementation in reducing the risk and severity of ARIs. Uncertainty remains about what constitutes an appropriate dosing regimen in relation to reducing risk/severity of ARI/ARDS. More recent evidence (Search B) provided new insights into some direct links between vitamin D and COVID-19; with a number of cohort and ecological studies supporting an association with PCR-positivity for SARS-CoV-2 and vitamin D deficiency. The exact efficacy of the vitamin D supplementation for prevention of, or as an adjunct treatment for COVID-19 remains to be determined; but a number of randomized control trials (RCTs) currently underway are actively investigating these potential benefits.

CONCLUSION

Our rapid review of literature supports the need for observational studies with COVID-19 infected populations to measure and assess vitamin D levels in relation to risk/severity and outcomes; alongside RCTs designed to evaluate the efficacy of supplementation both in preventive and therapeutic contexts. The overlap in the vitamin D associated biological pathways with the dysregulation reported to drive COVID-19 outcomes warrants further investigation.

Prenatal vitamin D supplementation and child respiratory health: A systematic review and meta-analysis of randomized controlled trials

Background

Systematic review and meta-analyses of observational studies on maternal vitamin D status and risk of respiratory allergic conditions indicated that mothers who had supplementation during pregnancy could decrease the risk of recurrent wheeze or asthma in their offspring.

Objectives

We conducted this meta-analysis of Randomized Controlled Trials with the primary intention of detecting the effect of prenatal vitamin D supplementation on the offspring's asthma. Secondary outcomes under respiratory health include eczema, lower respiratory tract infections, Immunoglobulin E positive test, upper respiratory tract infections, and allergic rhinitis.

Methods

A comprehensive search of PubMed, ScienceDirect, Google Scholar, and Cochrane Library databases was performed to retrieve randomized controlled trials. Risk Ratio with 95% confidence intervals was computed from dichotomous data using a random-effects model, with I² >50% representing notable heterogeneity.

Results

Six clinical trials met the inclusion criteria, involving a total of 2898 subjects (1461 experimental group and 1437 control group). There was non-significant inverse relationship between vitamin D intake during pregnancy and the occurrence of asthma in offspring (pooled RR = 0.89, 95% CI = 0.69-1.15, I ²  = 46% and Z-static = 0.90, P-value = 0.37). There is no significant difference in the risk of assessed childhood respiratory problems due to maternal supplementation of vitamin D during pregnancy.

Conclusion and implications

Currently, there is no fertile evidence to promote vitamin D supplementation in pregnancy for childhood respiratory health. Future clinical trials should emphasize early initiation of vitamin D supplementation, consider 6 weeks to 6 months postnatal critical window for vitamin D deficiency for offspring, lower risk dose of vitamin D, and identify different phenotypes of asthma and response to vitamin D supplementation.

Null association between serum 25-hydroxyvitamin D levels with allergic rhinitis, allergic sensitization and non-allergic rhinitis: A Mendelian randomization study

BACKGROUND

Previous observational studies have not found a conclusive association between serum 25-hydroxyvitamin D (25(OH)D) levels and allergic rhinitis (AR) or allergic sensitization (AS).

OBJECTIVE

To investigate a causal association between 25(OH)D levels with risk of AR and AS, using a two-sample Mendelian randomization (MR) approach.

METHODS

Seven single nucleotide polymorphisms (SNPs), previously shown to be associated with serum 25(OH)D levels, were identified as instrumental variables. The primary outcome was AR, and the secondary outcomes were AS and non-allergic rhinitis (NAR). The genome-wide association (GWA) summary statistics of the outcomes were obtained from two cohort studies (EAGLE Consortium and UK Biobank). An MR analysis with random-effects inverse-variance weighted method was performed as the primary analysis to estimate overall effect size (odds ratio [OR] and 95% confidence interval [CI]). Sensitivity analysis using weighted median method and MR-Egger regression method was conducted. A subgroup analysis based on 25(OH)D synthesis-related SNPs was further applied.

RESULTS

Serum 25(OH)D levels were not causally associated with risk of AR (OR: 0.960; 95% CI: 0.779-1.184), AS (OR: 1.059; 95% CI: 0.686 to 1.634) or NAR (OR: 0.937; 95% CI: 0.588-1.491). Subgroup analysis also showed null association between 25(OH)D synthesis-related SNPs and the outcomes. Sensitivity analyses yielded similar results.

CONCLUSIONS AND CLINICAL RELEVANCE

This MR study found no evidence supporting a causal association between serum 25(OH)D levels and risk of AR, AS and NAR in European-ancestry population. This argues against the previous postulation that vitamin D supplementation is effective in prevention of allergic diseases.

In "High-Risk" Infants with Sufficient Vitamin D Status at Birth, Infant Vitamin D Supplementation Had No Effect on Allergy Outcomes: A Randomized Controlled Trial

Lower vitamin D status at birth and during infancy has been associated with increased incidence of eczema and food allergies. The aim of this study was to investigate the effect of early infancy vitamin D supplementation on allergic disease outcomes in infants at “hereditary risk” of allergic disease, but who had sufficient vitamin D levels at birth. Here, we report the early childhood follow-up to 2.5 years of age of “high-risk” infants who participated in a double-blinded, randomized controlled trial. For inclusion in this trial, late gestation (36–40 weeks) maternal 25-hydroxyvitamin D levels needed to be ≥50 nmol/L. Infants were randomized to either oral vitamin D supplementation of 400 IU/day (n = 97) or a placebo (n = 98) for the first six months of life. Vitamin D levels and allergic disease outcomes were followed up. There were no statistically significant differences in incidence of any medically diagnosed allergic disease outcomes or allergen sensitization rates between the vitamin D-supplemented and placebo groups at either 1 year or at 2.5 years of age. In conclusion, for “allergy high-risk” infants who had sufficient vitamin D status at birth, early infancy oral vitamin D supplementation does not appear to reduce the development of early childhood allergic disease.

Vitamin D and Immunity in Infants and Children

The last couple of decades have seen an explosion in our interest and understanding of the role of vitamin D in the regulation of immunity. At the molecular level, the hormonal form of vitamin D signals through the nuclear vitamin D receptor (VDR), a ligand-regulated transcription factor. The VDR and vitamin D metabolic enzymes are expressed throughout the innate and adaptive arms of the immune system. The advent of genome-wide approaches to gene expression profiling have led to the identification of numerous VDR-regulated genes implicated in the regulation of innate and adaptive immunity. The molecular data infer that vitamin D signaling should boost innate immunity against pathogens of bacterial or viral origin. Vitamin D signaling also suppresses inflammatory immune responses that underlie autoimmunity and regulate allergic responses. These findings have been bolstered by clinical studies linking vitamin D deficiency to increased rates of infections, autoimmunity, and allergies. Our goals here are to provide an overview of the molecular basis for immune system regulation and to survey the clinical data from pediatric populations, using randomized placebo-controlled trials and meta-analyses where possible, linking vitamin D deficiency to increased rates of infections, autoimmune conditions, and allergies, and addressing the impact of supplementation on these conditions.

Translating vitamin D transcriptomics to clinical evidence: Analysis of data in asthma and chronic obstructive pulmonary disease, followed by clinical data meta-analysis

Vitamin D (VitD) continues to trigger intense scientific controversy, regarding both its bi ological targets and its supplementation doses and regimens. In an effort to resolve this dispute, we mapped VitD transcriptome-wide events in humans, in order to unveil shared patterns or mechanisms with diverse pathologies/tissue profiles and reveal causal effects between VitD actions and specific human diseases, using a recently developed bioinformatics methodology. Using the similarities in analyzed transcriptome data (c-SKL method), we validated our methodology with osteoporosis as an example and further analyzed two other strong hits, specifically chronic obstructive pulmonary disease (COPD) and asthma. The latter revealed no impact of VitD on known molecular pathways. In accordance to this finding, review and meta-analysis of published data, based on an objective measure (Forced Expiratory Volume at one second, FEV₁%) did not further reveal any significant effect of VitD on the objective amelioration of either condition. This study may, therefore, be regarded as the first one to explore, in an objective, unbiased and unsupervised manner, the impact of VitD levels and/or interventions in a number of human pathologies.

Vitamin D in pediatric health and disease

Several scientific societies established that vitamin D (VD), in its metabolized form 25(OH)D, levels higher than 20 ng/mL are sufficient to ensure optimal bone health, while 25(OH)D levels higher than 30 ng/mL are needed to favor VD extraskeletal actions. However, it has been estimated that approximately 30% of children and 60% of adults worldwide are VD deficient and insufficient, respectively. This is the reason why it is important to provide a practical approach to VD supplementation for infants, children, and adolescents. It is the pediatrician's role to evaluate the modifiable lifestyle risk factors for deficiency, particularly a reduced sun exposure, following an evidence-based approach, and to suggest VD supplementation only when there is a rational reason to support its use.

Nutritional Factors in the Prevention of Atopic Dermatitis in Children

Atopic dermatitis is one of the most frequent chronic skin diseases worldwide and often develops within the first few years of life. Recent advancements in our knowledge of its pathophysiology have brought to light the role of genetic predisposition and environmental triggers. With the increasing prevalence of allergic diseases, there is a strong need for a better understanding of the various modifiable eliciting factors of such conditions. The concomitant rise in food allergy and insights into the skin barrier function has highlighted the role of nutrition and diet in the prevention and modification of allergic disorders. Furthermore, the identification of the skin as an important route of sensitization, and the risk of progression to asthma later in life, stress the significance of optimizing our management of skin inflammation in the prevention of allergies. Many nutritional factors, including the type of maternal diet during pregnancy, the duration of breastfeeding, the epicutaneous exposure of allergenic food proteins in the first few years of life, the timing of the introduction of complementary foods, the supplementation of vitamins and probiotics/prebiotics during prenatal and early life, have been assessed as potential targets for the prevention of atopy and eczema. Here, we review the latest data addressing prenatal and perinatal nutritional and dietary interventions in the primary prevention of atopic dermatitis. Also, we define knowledge gaps and targets for future research in the prevention of atopic dermatitis.

Dietary Interventions and Nutritional Factors in the Prevention of Pediatric Asthma

Asthma is the most frequent chronic disease in children, and its pathogenesis involves genetic, epigenetic, and environmental factors. The rapid rise in the prevalence of asthma registered over the last few decades has stressed the need to identify the environmental and modifiable factors associated with the development of the disease. In particular, there is increasing interest in the role of modifiable nutritional factors specific to both the prenatal and post-natal early life as, during this time, the immune system is particularly vulnerable to exogenous interferences. Several dietary factors, including maternal diet during pregnancy, the duration of breastfeeding, the use of special milk formulas, the timing of the introduction of complementary foods, and prenatal and early life supplementation with vitamins and probiotics/prebiotics, have been addressed as potential targets for the prevention of asthma. In this review, we outline recent findings on the potential role of prenatal and perinatal dietary and nutritional interventions for the primary prevention of pediatric asthma. Moreover, we addressed unmet needs and areas for future research in the prevention of childhood-onset asthma.

Regimens of vitamin D supplementation for women during pregnancy

BACKGROUND

Vitamin D deficiency during pregnancy increases the risk of pre-eclampsia, gestational diabetes, preterm birth, and low birthweight. In a previous Cochrane Review we found that supplementing pregnant women with vitamin D alone compared to no vitamin D supplementation may reduce the risk of pre-eclampsia, gestational diabetes, and low birthweight and may increase the risk of preterm births if it is combined with calcium. However the effects of different vitamin D regimens are not yet clear.

OBJECTIVES

To assess the effects and safety of different regimens of vitamin D supplementation alone or in combination with calcium or other vitamins, minerals or nutrients during pregnancy, specifically doses of 601 international units per day (IU/d) or more versus 600 IU/d or less; and 4000 IU/d or more versus 3999 IU/d or less.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (12 July 2018), and the reference lists of retrieved studies.

SELECTION CRITERIA

Randomised trials evaluating the effect of different vitamin D regimens (dose, frequency, duration, and time of commencement of supplementation during pregnancy), alone or in combination with other nutrients on pregnancy and neonatal health outcomes. We only included trials that compared 601 IU/d or more versus 600 IU/d or less and 4000 IU/d or more versus 3999 IU/d or less. We did not include in the analysis groups that received no vitamin D, as that comparison is assessed in another Cochrane Review.

DATA COLLECTION AND ANALYSIS

Two review authors independently: i) assessed the eligibility of studies against the inclusion criteria; ii) extracted data from included studies, and iii) assessed the risk of bias of the included studies. Our primary maternal outcomes were: pre-eclampsia, gestational diabetes, and any adverse effects; our primary infant outcomes were preterm birth and low birthweight. Data were checked for accuracy. The certainty of the evidence was assessed using the GRADE approach.

MAIN RESULTS

In this review, we included data from 30 trials involving 7289 women. We excluded 11 trials, identified 16 ongoing/unpublished trials and two trials are awaiting classification. Overall risk of bias for the trials was mixed.Comparison 1. 601 IU/d or more versus 600 IU/d or less of vitamin D alone or with any other nutrient (19 trials; 5214 participants)Supplementation with 601 IU/d or more of vitamin D during pregnancy may make little or no difference to the risk of pre-eclampsia (risk ratio (RR) 0.96, 95% confidence interval (CI) 0.65 to 1.42); 5 trials; 1553 participants,low-certainty evidence), may reduce the risk of gestational diabetes (RR 0.54, 95% CI 0.34 to 0.86; 5 trials; 1846 participants; moderate-certainty evidence), may make little or no difference to the risk of preterm birth (RR 1.25, 95% CI 0.92 to 1.69; 4 trials; 2294 participants; low-certainty evidence); and may make little or no difference to the risk of low birthweight (RR 0.90, 95% CI 0.66 to 1.24; 4 trials; 1550 participants; very low-certainty evidence) compared to women receiving 600 IU/d or less.Comparison 2. 4000 IU or more versus 3999 IU or less of vitamin D alone (15 trials; 4763 participants)Supplementation with 4000 IU/d or more of vitamin D during pregnancy may make little or no difference to the risk of: pre-eclampsia (RR 0.87, 95% CI 0.62 to 1.22; 4 trials, 1903 participants, low-certainty evidence); gestational diabetes (RR 0.89, 95% CI 0.56 to 1.42; 5 trials, 2276 participants; low-certainty evidence); preterm birth (RR 0.85, 95% CI 0.64 to 1.12; 6 trials, 2948 participants, low-certainty evidence); and low birthweight (RR 0.92, 95% CI 0.49 to 1.70; 2 trials; 1099 participants; low-certainty evidence) compared to women receiving 3999 IU/d or less.Adverse events (such as hypercalcaemia, hypocalcaemia, hypercalciuria, and hypovitaminosis D) were reported differently in most trials; however, in general, there was little to no side effects reported or similar cases between groups.

AUTHORS' CONCLUSIONS

Supplementing pregnant women with more than the current vitamin D recommendation may reduce the risk of gestational diabetes; however, it may make little or no difference to the risk of pre-eclampsia, preterm birth and low birthweight. Supplementing pregnant women with more than the current upper limit for vitamin D seems not to increase the risk of the outcomes evaluated. In general, the GRADE was considered low certainty for most of the primary outcomes due to serious risk of bias and imprecision of results. With respect to safety, it appears that vitamin D supplementation is a safe intervention during pregnancy, although the parameters used to determine this were either not reported or not consistent between trials. Future trials should be consistent in their reports of adverse events. There are 16 ongoing trials that when published, will increase the body of knowledge.

Calcium Metabolic Disorders in Pregnancy: Primary Hyperparathyroidism, Pregnancy-Induced Osteoporosis, and Vitamin D Deficiency in Pregnancy

Physiologic changes during pregnancy include calcium, phosphate, and calciotropic hormone status. Calcium metabolic disorders are rare in pregnancy and management with close calcium and vitamin D control and supplementation. Primary hyperparathyroidism is mostly asymptomatic and does not affect conception or pregnancy. It requires control of plasma calcium levels. Surgical intervention may be indicated. Data on severe cases are missing. Osteoporosis in or before pregnancy is rare but usually diagnosed from fractures. Medical treatment other than supplementation is contraindicated. Vitamin D deficiency is common and may affect conception and increase complications. Current evidence does not prove vitamin D supplements effective in improving outcomes.

Vitamin D supplementation for women during pregnancy

BACKGROUND

Vitamin D supplementation during pregnancy may be needed to protect against adverse pregnancy outcomes. This is an update of a review that was first published in 2012 and then in 2016.

OBJECTIVES

To examine whether vitamin D supplementation alone or in combination with calcium or other vitamins and minerals given to women during pregnancy can safely improve maternal and neonatal outcomes.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register (12 July 2018), contacted relevant organisations (15 May 2018), reference lists of retrieved trials and registries at clinicaltrials.gov and WHO International Clinical Trials Registry Platform (12 July 2018). Abstracts were included if they had enough information to extract the data.

SELECTION CRITERIA

Randomised and quasi-randomised trials evaluating the effect of supplementation with vitamin D alone or in combination with other micronutrients for women during pregnancy in comparison to placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently i) assessed the eligibility of trials against the inclusion criteria, ii) extracted data from included trials, and iii) assessed the risk of bias of the included trials. The certainty of the evidence was assessed using the GRADE approach.

MAIN RESULTS

We included 30 trials (7033 women), excluded 60 trials, identified six as ongoing/unpublished trials and two trials are awaiting assessments.Supplementation with vitamin D alone versus placebo/no interventionA total of 22 trials involving 3725 pregnant women were included in this comparison; 19 trials were assessed as having low-to-moderate risk of bias for most domains and three trials were assessed as having high risk of bias for most domains. Supplementation with vitamin D alone during pregnancy probably reduces the risk of pre-eclampsia (risk ratio (RR) 0.48, 95% confidence interval (CI) 0.30 to 0.79; 4 trials, 499 women, moderate-certainty evidence) and gestational diabetes (RR 0.51, 95% CI 0.27 to 0.97; 4 trials, 446 women, moderate-certainty evidence); and probably reduces the risk of having a baby with low birthweight (less than 2500 g) (RR 0.55, 95% CI 0.35 to 0.87; 5 trials, 697 women, moderate-certainty evidence) compared to women who received placebo or no intervention. Vitamin D supplementation may make little or no difference in the risk of having a preterm birth < 37 weeks compared to no intervention or placebo (RR 0.66, 95% CI 0.34 to 1.30; 7 trials, 1640 women, low-certainty evidence). In terms of maternal adverse events, vitamin D supplementation may reduce the risk of severe postpartum haemorrhage (RR 0.68, 95% CI 0.51 to 0.91; 1 trial, 1134 women, low-certainty evidence). There were no cases of hypercalcaemia (1 trial, 1134 women, low-certainty evidence), and we are very uncertain as to whether vitamin D increases or decreases the risk of nephritic syndrome (RR 0.17, 95% CI 0.01 to 4.06; 1 trial, 135 women, very low-certainty evidence). However, given the scarcity of data in general for maternal adverse events, no firm conclusions can be drawn.Supplementation with vitamin D and calcium versus placebo/no interventionNine trials involving 1916 pregnant women were included in this comparison; three trials were assessed as having low risk of bias for allocation and blinding, four trials were assessed as having high risk of bias and two had some components having a low risk, high risk, or unclear risk. Supplementation with vitamin D and calcium during pregnancy probably reduces the risk of pre-eclampsia (RR 0.50, 95% CI 0.32 to 0.78; 4 trials, 1174 women, moderate-certainty evidence). The effect of the intervention is uncertain on gestational diabetes (RR 0.33,% CI 0.01 to 7.84; 1 trial, 54 women, very low-certainty evidence); and low birthweight (less than 2500 g) (RR 0.68, 95% CI 0.10 to 4.55; 2 trials, 110 women, very low-certainty evidence) compared to women who received placebo or no intervention. Supplementation with vitamin D and calcium during pregnancy may increase the risk of preterm birth < 37 weeks in comparison to women who received placebo or no intervention (RR 1.52, 95% CI 1.01 to 2.28; 5 trials, 942 women, low-certainty evidence). No trial in this comparison reported on maternal adverse events.Supplementation with vitamin D + calcium + other vitamins and minerals versus calcium + other vitamins and minerals (but no vitamin D)One trial in 1300 participants was included in this comparison; it was assessed as having low risk of bias. Pre-eclampsia was not assessed. Supplementation with vitamin D + other nutrients may make little or no difference in the risk of preterm birth < 37 weeks (RR 1.04, 95% CI 0.68 to 1.59; 1 trial, 1298 women, low-certainty evidence); or low birthweight (less than 2500 g) (RR 1.12, 95% CI 0.82 to 1.51; 1 trial, 1298 women, low-certainty evidence). It is unclear whether it makes any difference to the risk of gestational diabetes (RR 0.42, 95% CI 0.10 to 1.73) or maternal adverse events (hypercalcaemia no events; hypercalciuria RR 0.25, 95% CI 0.02 to 3.97; 1 trial, 1298 women,) because the certainty of the evidence for both outcomes was found to be very low.

AUTHORS' CONCLUSIONS

We included 30 trials (7033 women) across three separate comparisons. Our GRADE assessments ranged from moderate to very low, with downgrading decisions based on limitations in study design, imprecision and indirectness.Supplementing pregnant women with vitamin D alone probably reduces the risk of pre-eclampsia, gestational diabetes, low birthweight and may reduce the risk of severe postpartum haemorrhage. It may make little or no difference in the risk of having a preterm birth < 37 weeks' gestation. Supplementing pregnant women with vitamin D and calcium probably reduces the risk of pre-eclampsia but may increase the risk of preterm births < 37 weeks (these findings warrant further research). Supplementing pregnant women with vitamin D and other nutrients may make little or no difference in the risk of preterm birth < 37 weeks' gestation or low birthweight (less than 2500 g). Additional rigorous high quality and larger randomised trials are required to evaluate the effects of vitamin D supplementation in pregnancy, particularly in relation to the risk of maternal adverse events.

Nutrigenomics of Vitamin D

Nutrigenomics studies how environmental factors, such as food intake and lifestyle, influence the expression of the genome. Vitamin D₃ represents a master example of nutrigenomics, since via its metabolite 1α,25-dihydroxyvitamin D₃, which binds with high-affinity to the vitamin D receptor, the secosteroid directly affects the epigenome and transcriptome at thousands of loci within the human genome. Vitamin D is important for both cellular metabolism and immunity, as it controls calcium homeostasis and modulates the response of the innate and adaptive immune system. At sufficient UV-B exposure, humans can synthesize vitamin D₃ endogenously in their skin, but today's lifestyle often makes the molecule a true vitamin and micronutrient that needs to be taken up by diet or supplementation with pills. The individual's molecular response to vitamin D requires personalized supplementation with vitamin D₃, in order to obtain optimized clinical benefits in the prevention of osteoporosis, sarcopenia, autoimmune diseases, and possibly different types of cancer. The importance of endogenous synthesis of vitamin D₃ created an evolutionary pressure for reduced skin pigmentation, when, during the past 50,000 years, modern humans migrated from Africa towards Asia and Europe. This review will discuss different aspects of how vitamin D interacts with the human genome, focusing on nutritional epigenomics in context of immune responses. This should lead to a better understanding of the clinical benefits of vitamin D.

High prevalence of IgE sensitization against house dust mites in pregnant women

There is an increase in prevalence and financial burden of childhood atopic disorders in recent years. Understanding allergic conditions of pregnant women is important for developing strategies for prevention and management of allergy-related diseases. However, little is currently known about the atopic conditions in pregnant women.The sera from 46 pregnant women were analyzed for allergen-specific IgE antibodies using the Optigen assay and SDS-PAGE immunoblot analysis.Results from the Optigen assay showed that 20 (43%) of the 46 serum samples analyzed demonstrated IgE reactivity against mite p (Dermatophagoides pteronyssinus) (95%), mite f (D farinae) (95%), house dust (60%), cat (25%), shrimp (20%), crab (15%), cockroach (10%), dog (5%), latex (5%), willow black (5%), and timothy grass (5%). Nineteen of the 20 Optigen-positive sera demonstrated IgE reactivity against both the house dust mites D pteronyssinus and D farina, with 10 of them having a high IgE CLA class value of 4. IgE reactivity to the house dust mite D pteronyssinus was confirmed in SDS-PAGE-immunoblots, which correlated well with the intensity of IgE-binding to the 15-kDa D pteronyssinus component and to the purified recombinant Der p 2 major house dust mite allergen.A high prevalence of IgE sensitization against house dust mites during pregnancy is noted, which is worthy of clinical attention. Children of IgE-sensitized mothers should be closely monitored for development of allergenic disorders.

Direct infant UV light exposure is associated with eczema and immune development

BACKGROUND

Suboptimal vitamin D levels during critical periods of immune development have emerged as an explanation for higher rates of allergic diseases associated with industrialization and residing at higher latitudes.

OBJECTIVE

We sought to determine the effects of early postnatal vitamin D supplementation on infant eczema and immune development.

METHODS

By using a double-blind randomized controlled trial, newborn infants were randomized to receive vitamin D supplementation (400 IU/d) or a placebo until 6 months of age. Some infants also wore personal UV dosimeters to measure direct UV light (290-380 nm) exposure. Infant vitamin D levels were measured at 3 and 6 months of age. Eczema, wheeze, and immune function outcomes were assessed at 6 months of age.

RESULTS

At 3 (P < .01) and 6 (P = .02) months of age, vitamin D levels were greater for the vitamin D-supplemented group than the placebo group, but there was no difference in eczema incidence between groups. Infants with eczema were found to have had less UV light exposure (median, 555 Joules per square meter [J/m²; interquartile range, 322-1210 J/m²]) compared with those without eczema (median, 998 J/m² [interquartile range, 676-1577 J/m²]; P = .02). UV light exposure was also inversely correlated with IL-2, GM-CSF, and eotaxin production to Toll-like receptor ligands.

CONCLUSION

This study is the first to demonstrate an association between greater direct UV light exposures in early infancy with lower incidence of eczema and proinflammatory immune markers by 6 months of age. Our findings indicate that UV light exposure appears more beneficial than vitamin D supplementation as an allergy prevention strategy in early life.

Compared with Cow Milk, a Growing-Up Milk Increases Vitamin D and Iron Status in Healthy Children at 2 Years of Age: The Growing-Up Milk-Lite (GUMLi) Randomized Controlled Trial

Background

Iron deficiency (ID) and vitamin D deficiency (VDD) are significant pediatric health issues in New Zealand and Australia and remain prevalent micronutrient deficiencies in young children globally.

Objective

We aimed to investigate the effect of a micronutrient-fortified, reduced-energy growing-up milk (GUMLi) compared with cow milk (CM) consumed for 1 y on dietary iron and vitamin D intakes and the status of New Zealand and Australian children at 2 y of age.

Methods

The GUMLi Trial was a multicenter, double-blind, randomized controlled trial in 160 healthy 1-y-old New Zealand and Australian children conducted in 2015-2017. Participants were randomly assigned 1:1 to receive GUMLi (1.7 mg Fe/100 mL; 1.3 µg cholecalciferol/100 mL) or CM (0.02 mg Fe/100 mL; 0.06 µg cholecalciferol/100 mL) for 12 mo. Secondary outcomes, reported here, included change in dietary iron and vitamin D intakes, iron status, and 25-hydroxyvitamin D [25(OH)D] concentrations from blood samples at age 2 y. All regression models were adjusted for baseline outcome and study center.

Results

GUMLi was a large contributor to dietary intakes of iron and vitamin D after 12 mo when compared with intakes from food and CM. The adjusted mean difference between groups for serum ferritin concentrations was 17.8 µg/L (95% CI: 13.6, 22.0 µg/L; P < 0.0001), and for 25(OH)D it was 16.6 nmol/L (95% CI: 9.9, 23.3 nmol/L; P < 0.0001). After 12 mo, ID was present in 16 (24%) participants in the CM group and 5 (7%) participants in the GUMLi group (P = 0.009), and the prevalence of VDD in the CM group increased to 14% (n = 10) and decreased to 3% (n = 2) (P = 0.03) in the GUMLi group.

Conclusion

In comparison with CM, GUMLi significantly improved dietary iron and vitamin D intakes and the iron and vitamin D status of healthy children at 2 y of age. This trial was registered with the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as ACTRN12614000918628.

Prenatal Diet and the Development of Childhood Allergic Diseases: Food for Thought

PURPOSE OF REVIEW

The development of allergic disease is shaped by genetics and the environment, including diet. Many studies suggest a role for maternal diet during pregnancy. In this article, we discuss potential mechanisms by which specific nutrients, particular foods, and dietary patterns may influence allergic disease development and review studies examining the relationship between prenatal diet and the risk of childhood allergy.

RECENT FINDINGS

The combination of in utero exposures and genetic predisposition may contribute to the development of allergic disease by altering immune and organ development. Inflammation predominates in the first and third trimesters whereas the second trimester is characterized by anti-inflammatory and Th2 immune responses. Maternal dietary exposures during pregnancy may interact with inherited genetic risk factors influence immune system development. There are varied results regarding the impact of maternal prenatal diet on the development of childhood allergies. Well-designed randomized controlled studies are needed to clarify this area.

The Implications of Vitamin D Status During Pregnancy on Mother and her Developing Child

Pregnancy is a time of tremendous growth and physiological changes for mother and her developing fetus with lifelong implications for the child. The concert of actions that must occur so mother does not reject the foreign tissue of the fetus is substantial. There must be exquisite balance between maternal tolerance to these foreign proteins of paternal origin but also immune surveillance and function such that the mother is not immunocompromised. When this process goes awry, the mother may experience such pregnancy complications as preeclampsia and infections. Vitamin D deficiency affects these processes. Controversy continues with regard to the optimal daily intake of vitamin D, when sunlight exposure should be taken into account, and how to define sufficiency during such vulnerable and critical periods of development. The importance of vitamin D supplementation during pregnancy in preventing some of the health risks to the mother and fetus appears linked to achieving 25(OH)D concentrations >40 ng/mL, the beginning point of the plateau where conversion of the vitamin D metabolite 25(OH)D, the pre-hormone, to 1,25(OH)2D, the active hormone, is optimized. Throughout pregnancy, the delivery of adequate vitamin D substrate-through sunlight or supplement-is required to protect both mother and fetus, and when in sufficient supply, favorably impacts the epigenome of the fetus, and in turn, long term health. There is a growing need for future research endeavors to focus not only on critical period(s) from pre-conception through pregnancy, but throughout life to prevent certain epigenetic changes that adversely affect health. There is urgency based on emerging research to correct deficiency and maintain optimal vitamin D status. The impact of vitamin D and its metabolites on genetic signaling during pregnancy in both mother and fetus is an area of great activity and still in its early stages. While vitamin D repletion during pregnancy minimizes the risk of certain adverse outcomes (e.g., preterm birth, asthma, preeclampsia, and gestational diabetes), the mechanisms of how these processes occur are not fully understood. As we intensify our research efforts in these areas. it is only a matter of time that such mechanisms will be defined.

Eating fish and farm life reduce allergic rhinitis at the age of twelve

BACKGROUND

The prevalence of allergic rhinitis has increased, but the cause of this rise is partly unknown. Our aim was to analyse the prevalence, risk factors, and protective factors for allergic rhinitis in 12-year-old Swedish children.

METHODS

Data were collected from a prospective, longitudinal cohort study of children born in western Sweden in 2003. The parents answered questionnaires when the children were 6 months to 12 years. The response rate at 12 years was 76% (3637/4777) of the questionnaires distributed.

RESULTS

At the age of 12, 22% of children had allergic rhinitis and 57% were boys. Mean age at onset was 7.8 years, and 55% reported their first symptoms after 8 years. The most common trigger factors were pollen (85%), furry animals (34%), and house dust mites (17%). A multivariate analysis showed that the adjusted odds ratios and 95% confidence intervals for the independent risk factors for allergic rhinitis at 12 were as follows: parental allergic rhinitis (2.32, 1.94-2.77), doctor-diagnosed food allergy in the first year (1.75, 1.21-2.52), eczema in the first year (1.61, 1.31-1.97), and male gender (1.25, 1.06-1.47). Eating fish once a month or more at age of 12 months reduced the risk of allergic rhinitis at 12 years of age (0.70, 0.50-0.98) as did living on a farm with farm animals at 4 years (0.51, 0.32-0.84). Continuous farm living from age 4 to 12 seemed to drive the association.

CONCLUSIONS

Allergic rhinitis affected > 20% of 12-year-olds, but was lower in children who ate fish at 12 months or grew up on a farm with farm animals.

Serum 25-hydroxyvitamin D levels in patients with skin diseases including psoriasis, infections, and atopic dermatitis

The pathogenetic role of vitamin D as well as its clinical correlation in inflammatory skin diseases is still uncertain. This study aimed to compare serum levels of 25(OH) vitamin D (calcidiol) in outpatients suffering from different skin diseases using the same laboratory method in one study. In routine serum samples of 1,532 patients from the previous 12 months we identified retrospectively 180 (mean age 49.4 years, 80 female, 100 male) and 205 (mean age 36.3 years, 116 female, 89 male) patients with psoriasis (PSO) and atopic dermatitis (AD), respectively. Clinical disease activity and quality of life was evaluated using Physicians Global Assessment Scores (PGA), Dermatology Life Quality Index (DLQI), and a Visual Analog Scale for pruritus in AD, respectively. The median 25(OH)D serum level of all patients (22.97 ng/mL, range 2.61–96.0, n = 1,461) was significantly lower in comparison to healthy controls (41.6 ng/mL, range 16.9–77.57, p < 0.0001, n = 71). In PSO and AD we measured 21.05 ng/mL (44% < 20 ng/mL) and 22.7 ng/mL (39% < 20 ng/mL), respectively (p = 0.152). Among all subgroups, patients with severe acute or chronic infectious skin diseases had the lowest median 25(OH)D serum levels (17.11 ng/mL, n = 94, 66% <20 ng/mL, p < 0,001 vs. AD, p = 0,007 vs. PSO). For PSO and AD there was no significant correlation between 25(OH)D levels and PGA scores and DLQI values, respectively, or the extent of pruritus in AD. 25(OH)D serum levels in inflammatory skin diseases might correlate more with the type of disease and the degree of inflammation than with clinical activity itself.

Prenatal vitamin D supplementation reduces risk of asthma/recurrent wheeze in early childhood: A combined analysis of two randomized controlled trials

BACKGROUND

We recently published two independent randomized controlled trials of vitamin D supplementation during pregnancy, both indicating a >20% reduced risk of asthma/recurrent wheeze in the offspring by 3 years of age. However, neither reached statistical significance.

OBJECTIVE

To perform a combined analysis of the two trials and investigate whether maternal 25-hydroxy-vitamin D (25(OH)D) level at trial entry modified the intervention effect.

METHODS

VDAART (N = 806) and COPSAC2010. (N = 581) randomized pregnant women to daily high-dose vitamin D3 (4,000 IU/d and 2,400 IU/d, respectively) or placebo. All women also received a prenatal vitamin containing 400 IU/d vitamin D3. The primary outcome was asthma/recurrent wheeze from 0-3yrs. Secondary end-points were specific IgE, total IgE, eczema and lower respiratory tract infections (LRTI). We conducted random effects combined analyses of the treatment effect, individual patient data (IPD) meta-analyses, and analyses stratified by 25(OH)D level at study entry.

RESULTS

The analysis showed a 25% reduced risk of asthma/recurrent wheeze at 0-3yrs: adjusted odds ratio (aOR) = 0.74 (95% CI, 0.57-0.96), p = 0.02. The effect was strongest among women with 25(OH)D level ≥30ng/ml at study entry: aOR = 0.54 (0.33-0.88), p = 0.01, whereas no significant effect was observed among women with 25(OH)D level <30ng/ml at study entry: aOR = 0.84 (0.62-1.15), p = 0.25. The IPD meta-analyses showed similar results. There was no effect on the secondary end-points.

CONCLUSIONS

This combined analysis shows that vitamin D supplementation during pregnancy results in a significant reduced risk of asthma/recurrent wheeze in the offspring, especially among women with 25(OH)D level ≥ 30 ng/ml at randomization, where the risk was almost halved. Future studies should examine the possibility of raising 25(OH)D levels to at least 30 ng/ml early in pregnancy or using higher doses than used in our studies.

TRIAL REGISTRATION

COPSAC2010: ClinicalTrials.gov NCT00856947; VDAART: ClinicalTrials.gov NCT00920621.

Vitamin D supplementation during pregnancy: Improvements in birth outcomes and complications through direct genomic alteration

Pregnancy represents a time of rapid change, including dramatic shifts in vitamin D metabolism. Circulating concentrations of the active form of vitamin D-1,25(OH)2D skyrocket early in pregnancy to levels that would be toxic to a nonpregnant adult, signaling a decoupling of vitamin D from the classic endocrine calcium metabolic pathway, likely serving an immunomodulatory function in the mother and her developing fetus. In this review, we summarize the unique aspects of vitamin D metabolism and the data surrounding vitamin D requirements during this important period. Both observational and clinical trials are reviewed in the context of vitamin D's health effects during pregnancy that include preeclampsia, preterm birth, and later disease states such as asthma and multiple sclerosis. With enhanced knowledge about vitamin D's role as a preprohormone, it is clear that recommendations about supplementation must mirror what is clinically relevant and evidence-based. Future research that focuses on the critical period(s) leading up to conception and during pregnancy to correct deficiency or maintain optimal vitamin D status remains to be studied. In addition, what effects vitamin D has on genetic signatures that minimize the risk to the mother and her developing fetus have not been elucidated. Clearly, while there is much more research that needs to be performed, our understanding of vitamin D requirements during pregnancy has advanced significantly during the last few decades.

New insights into the vitamin D requirements during pregnancy

Pregnancy represents a dynamic period with physical and physiological changes in both the mother and her developing fetus. The dramatic 2–3 fold increase in the active hormone 1,25(OH)₂D concentrations during the early weeks of pregnancy despite minimal increased calcium demands during that time of gestation and which are sustained throughout pregnancy in both the mother and fetus suggests an immunomodulatory role in preventing fetal rejection by the mother. While there have been numerous observational studies that support the premise of vitamin D's role in maintaining maternal and fetal well-being, until recently, there have been few randomized clinical trials with vitamin D supplementation. One has to exhibit caution, however, even with RCTs, whose results can be problematic when analyzed on an intent-to-treat basis and when there is high non-adherence to protocol (as if often the case), thereby diluting the potential good or harm of a given treatment at higher doses. As such, a biomarker of a drug or in this case “vitamin” or pre-prohormone is better served. For these reasons, the effect of vitamin D therapies using the biomarker circulating 25(OH)D is a far better indicator of true “effect.” When pregnancy outcomes are analyzed using the biomarker 25(OH)D instead of treatment dose, there are notable differences in maternal and fetal outcomes across diverse racial/ethnic groups, with improved health in those women who attain a circulating 25(OH)D concentration of at least 100 nmol·L⁻¹ (40 ng·mL⁻¹). Because an important issue is the timing or initiation of vitamin D treatment/supplementation, and given the potential effect of vitamin D on placental gene expression and its effects on inflammation within the placenta, it appears crucial to start vitamin D treatment before placentation (and trophoblast invasion); however, this question remains unanswered. Additional work is needed to decipher the vitamin D requirements of pregnant women and the optimal timing of supplementation, taking into account a variety of lifestyles, body types, baseline vitamin D status, and maternal and fetal vitamin D receptor (VDR) and vitamin D binding protein (VDBP) genotypes. Determining the role of vitamin D in nonclassical, immune pathways continues to be a challenge that once answered will substantiate recommendations and public health policies.

Vitamin D and Bronchial Asthma: An Overview of Data From the Past 5 Years

PURPOSE

Vitamin D is a potent immunomodulator capable of dampening inflammatory signals in several cell types involved in the asthmatic response. Its deficiency has been associated with increased inflammation, exacerbations, and overall poor outcomes in patients with asthma. Given the increase in the prevalence of asthma over the past few decades, there has been enormous interest in the use of vitamin D supplementation as a potential therapeutic option. Here, we critically reviewed the most recent findings from in vitro studies, animal models, and clinical trials regarding the role of vitamin D in treating bronchial asthma.

METHODS

Using the key terms [Vitamin D, asthma, clinical trials, in vivo and in vitro studies], the [PubMed, Google Scholar] databases were searched for [clinical trials, original research articles, meta-analyses, and reviews], English-language articles published from [2012] to the present. Articles that were [Articles that did not meet these criteria were excluded] excluded from the analysis.

FINDINGS

Several studies have found that low serum levels of vitamin D (< 20 ng/mL) are associated with increased exacerbations, increased airway inflammation, decreased lung function, and poor prognosis in asthmatic patients. Results from in vitro and in vivo studies in animals and humans have suggested that supplementation with vitamin D may ameliorate several hallmark features of asthma. However, the findings obtained from clinical trials are controversial and do not unequivocally support a beneficial role of vitamin D in asthma. Largely, interventional studies in children, pregnant women, and adults have primarily found little to no effect of vitamin D supplementation on improved asthma symptoms, onset, or progression of the disease. This could be related to the severity of the disease process and other confounding factors.

IMPLICATIONS

Despite the conflicting data obtained from clinical trials, vitamin D deficiency may influence the inflammatory response in the airways. Further studies are needed to determine the exact mechanisms by which vitamin D supplementation may induce antiinflammatory effects.

The role of vitamin D in allergic rhinitis

Recent studies suggest that vitamin D is related to allergic rhinitis (AR). In this review, we first discuss the physiology and metabolism of vitamin D, then we review the function of vitamin D in the immune system, and above all, we highlight the current research regarding the role of vitamin D in AR. Finally, we find that there are both experimental and clinical studies showing that vitamin D is associated with AR, although the results are not consistent and even conflicting. Evidences from those clinical studies show a slightly tendency that serum vitamin D level might be inversely associated with the risk of AR. Meanwhile, it seems that gender and age may influence the relationship between vitamin D and AR. However, because of the heterogeneity in defining AR, differences in study design and so on, all these findings need to be confirmed by further studies. Additional clinical studies as well as experimental research are needed to better understand how vitamin D influences AR.

Strategies to alter the natural history of childhood asthma

PURPOSE OF REVIEW

Asthma exhibits significant heterogeneity in occurrence and severity over the lifespan. Our goal is to discuss recent evidence regarding determinants of the natural history of asthma during childhood, and review the rationale behind and status of major efforts to alter its course.

RECENT FINDINGS

Variations in microbial exposures are associated with risk of allergic disease, and the use of bacterial lysates may be a promising preventive strategy. Exposure to air pollution appears to be particularly damaging in prenatal and early life, and interventions to reduce pollution are feasible and result in clinical benefit. E-cigarette use may have a role in harm reduction for conventional cigarette smokers with asthma, but has undefined short-term and long-term effects that must be clarified. Vitamin D insufficiency over the first several years of life is associated with risk of asthma, and vitamin D supplementation reduces the risk of severe exacerbations.

SUMMARY

The identification of risk factors for asthma occurrence, persistence and severity will continue to guide efforts to alter the natural history of the disease. We have reviewed several promising strategies that are currently under investigation. Vitamin D supplementation and air pollution reduction have been shown to be effective strategies and warrant increased investigation and implementation.

Maternal dietary intake in pregnancy and lactation and allergic disease outcomes in offspring

As the prevalence of allergic disease dramatically rises worldwide, prevention strategies are increasingly being considered. Given the potential modulatory effect of nutritional factors on disease, altering maternal diet during pregnancy and/or lactation has been considered in preventing allergic disease in offspring. Although there are a number of observational studies that have examined possible associations between maternal diet and allergic outcomes in offspring, interventional trials are limited. Furthermore, there is a paucity of studies that have prospectively studied maternal dietary intake as well as measuring maternal and infant biologic samples (blood, urine, breast milk) and their relation to allergic outcomes in infants. There is also a particular need to define terminology such as 'fruit and vegetables intake', 'healthy diet', and 'diet diversity' in order to make studies comparable. In this review, we discuss current evidence of maternal dietary factors during pregnancy and/or lactation that may play a role in the offspring developing allergic disease, including factors such as overall dietary intake patterns, specific whole food consumption (fish, fruit and vegetables, and common allergic foods), and individual immunomodulatory nutrient intakes. Additionally, we discuss the limitations of previous studies and propose improvements to study design for future investigation.