Maternal intake of vitamin D during pregnancy and risk of advanced beta cell autoimmunity and type 1 diabetes in offspring

The Impact of Dietary Factors during Pregnancy on the Development of Islet Autoimmunity and Type 1 Diabetes: A Systematic Literature Review

AIMS AND HYPOTHESIS

The incidence of type 1 diabetes mellitus in children is considerably increasing in western countries. Thus, identification of the environmental determinants involved could ultimately lead to disease prevention. Here, we aimed to systematically review (PROSPERO ID: CRD42022362522) the current evidence of the association between maternal dietary factors during gestation and the risk of developing type 1 diabetes and/or islet autoimmunity (IA) in murine and human offspring.

METHODS

In accordance with PRISMA guidelines, the present systematic review searched PubMed and Scopus (n = 343) for different combinations of MeSH terms, such as type 1 diabetes, diet, islet autoimmunity, prenatal, nutrient, gluten, gliadin, vitamin, milk, and fibers.

RESULTS

We found that the most investigated dietary factors in the present literature were gluten, dietary advanced glycosylated end products (dAGEs), vitamin D, fatty acids, and iron. The results concerning prenatal exposure to a gluten-free environment showed a consistently protective effect on the development of IA. Prenatal exposures to vitamin D and certain fatty acids appeared to protect against the development of IA, whereas in utero iron and fat exposures correlated with increased risks of IA.

CONCLUSION

We conclude that a definite association is not established for most factors investigated as the literature represents a heterogeneous pool of data, although fetal exposures to some maternal dietary components, such as gluten, show consistent associations with increased risks of IA. We suggest that human prospective dietary intervention studies in both cohort and clinical settings are crucial to better evaluate critical and protective prenatal exposures from the maternal diet during pregnancy.

Vitamin D in pediatric age: Current evidence, recommendations, and misunderstandings

In recent years vitamin D has been in the spotlight of many researchers for its possible role in various disorders, including autoimmune and infectious diseases. Even if vitamin D deficiency remains a major public health problem, its symptomatic manifestations are less and less common in clinical practice, and pediatric age represents a “gray area” where vitamin D supplementation is often administered in the absence of an effective evaluation of its status. Moreover, a poor knowledge about different definitions of “deficiency,” “insufficiency,” and similar terms is spread among clinicians, while guidelines are not univocal, especially after the first year of life. The aim of this brief opinion paper is to sum up recent evidence about vitamin D status and its supplementation in pediatrics, in order to better clarify a common definition of its deficiency. The aim of this opinion article is to raise awareness on this topic among clinicians and encourage a discussion on the real need for routine 25-hydroxycholecalciferol serum evaluation and its supplementation.

Vitamin D and Beta Cells in Type 1 Diabetes: A Systematic Review

The prevalence of type 1 diabetes (T1D) is rising steadily. A potential contributor to the rise is vitamin D. In this systematic review, we examined the literature around vitamin D and T1D. We identified 22 papers examining the role of vitamin D in cultured β-cell lines, islets, or perfused pancreas, and 28 papers examining vitamin D in humans or human islets. The literature reports strong associations between T1D and low circulating vitamin D. There is also high-level (systematic reviews, meta-analyses) evidence that adequate vitamin D status in early life reduces T1D risk. Several animal studies, particularly in NOD mice, show harm from D-deficiency and benefit in most studies from vitamin D treatment/supplementation. Short-term streptozotocin studies show a β-cell survival effect with supplementation. Human studies report associations between VDR polymorphisms and T1D risk and β-cell function, as assessed by C-peptide. In view of those outcomes, the variable results in human trials are generally disappointing. Most studies using 1,25D, the active form of vitamin D were ineffective. Similarly, studies using other forms of vitamin D were predominantly ineffective. However, it is interesting to note that all but one of the studies testing 25D reported benefit. Together, this suggests that maintenance of optimal circulating 25D levels may reduce the risk of T1D and that it may have potential for benefits in delaying the development of absolute or near-absolute C-peptide deficiency. Given the near-complete loss of β-cells by the time of clinical diagnosis, vitamin D is much less likely to be useful after disease-onset. However, given the very low toxicity of 25D, and the known benefits of preservation of C-peptide positivity for long-term complications risk, we recommend considering daily cholecalciferol supplementation in people with T1D and people at high risk of T1D, especially if they have vitamin D insufficiency.

Vitamin D as a Nutri-Epigenetic Factor in Autoimmunity-A Review of Current Research and Reports on Vitamin D Deficiency in Autoimmune Diseases

Epigenetics is a series of alterations regulating gene expression without disrupting the DNA sequence of bases. These regulatory mechanisms can result in embryogenesis, cellular differentiation, X-chromosome inactivation, and DNA-protein interactions. The main epigenetic mechanisms considered to play a major role in both health and disease are DNA methylation, histone modifications, and profiling of non-coding RNA. When the fragile balance between these simultaneously occurring phenomena is disrupted, the risk of pathology increases. Thus, the factors that determine proper epigenetic modeling are defined and those with disruptive influence are sought. Several such factors with proven negative effects have already been described. Diet and nutritional substances have recently been one of the most interesting targets of exploration for epigenetic modeling in disease states, including autoimmunity. The preventive role of proper nutrition and maintaining sufficient vitamin D concentration in maternal blood during pregnancy, as well as in the early years of life, is emphasized. Opportunities are also being investigated for affecting the course of the disease by exploring nutriepigenetics. The authors aim to review the literature presenting vitamin D as one of the important nutrients potentially modeling the course of disease in selected autoimmune disorders.

The Gestational Effects of Maternal Bone Marker Molecules on Fetal Growth, Metabolism and Long-Term Metabolic Health: A Systematic Review

Fetal exposure in adverse environmental factors during intrauterine life can lead to various biological adjustments, affecting not only in utero development of the conceptus, but also its later metabolic and endocrine wellbeing. During human gestation, maternal bone turnover increases, as reflected by molecules involved in bone metabolism, such as vitamin D, osteocalcin, sclerostin, sRANKL, and osteoprotegerin; however, recent studies support their emerging role in endocrine functions and glucose homeostasis regulation. Herein, we sought to systematically review current knowledge on the effects of aforementioned maternal bone biomarkers during pregnancy on fetal intrauterine growth and metabolism, neonatal anthropometric measures at birth, as well as on future endocrine and metabolic wellbeing of the offspring. A growing body of literature converges on the view that maternal bone turnover is likely implicated in fetal growth, and at least to some extent, in neonatal and childhood body composition and metabolic wellbeing. Maternal sclerostin and sRANKL are positively linked with fetal abdominal circumference and subcutaneous fat deposition, contributing to greater birthweights. Vitamin D deficiency correlates with lower birthweights, while research is still needed on intrauterine fetal metabolism, as well as on vitamin D dosing supplementation during pregnancy, to diminish the risks of low birthweight or SGA neonates in high-risk populations.

Different Vitamin D Supplementation Strategies in the First Years of Life: A Systematic Review

Vitamin D (VD) is an essential micronutrient with multiple functions for human growth, and adequate intake should be guaranteed throughout life. However, VD insufficiency is observed in infants all over the world. Low VD concentration in the breast milk of non-supplemented mothers and low compliance to VD daily supplementation are the main causes of VD insufficiency, especially in the long term. Furthermore, VD supplementation dosages are still debated and differ by country. We conducted a systematic review to compare the most recent evidence on different postnatal VD supplementation strategies, determining whether supplementation given to the mother is as effective as that administered directly to the child, and whether different dosages and administration schedules differ significantly in terms of efficacy and safety. We identified 18 randomized controlled trials (RCTs) addressing the role of infant (n = 961), maternal (n = 652) or combined infant and maternal VD supplementation (n = 260 pairs). In all studies, similar outcomes emerged in terms of efficacy and safety. According to our findings, alternative approaches of VD supplementation may be adopted, especially in cases where the adherence to daily supplementation strategies is poor. This review shows that different dosages and supplementation strategies result in similar VD sufficiency rates. Therefore, international guidelines may be revised in the future to offer multiple and different options of supplementation for specific settings and ages.

Metagenomic analysis of the gut microbiome composition associated with vitamin D supplementation in Taiwanese infants

Early childhood is a critical stage for the foundation and development of the gut microbiome, large amounts of essential nutrients are required such as vitamin D. Vitamin D plays an important role in regulating calcium homeostasis, and deficiency can impair bone mineralization. In addition, most people know that breastfeeding is advocated to be the best thing for a newborn; however, exclusively breastfeeding infants are not easily able to absorb an adequate amount of vitamin D from breast milk. Understanding the effects of vitamin D supplementation on gut microbiome can improve the knowledge of infant health and development. A total of 62 fecal sample from healthy infants were collected in Taiwan. Of the 62 infants, 31 were exclusively breastfed infants and 31 were mixed- or formula-fed infants. For each feeding type, one subgroup of infants received 400 IU of vitamin D per day, and the remaining infants received a placebo. In total, there are 15 breastfed and 20 formula-fed infants with additional vitamin D supplementation, and 16 breastfed and 11 formula-fed infants belong to control group, respectively. We performed a comparative metagenomic analysis to investigate the distribution and diversity of infant gut microbiota among different types of feeding regimes with and without vitamin D supplementation. Our results reveal that the characteristics of infant gut microbiota not only depend on the feeding types but also on nutrients intake, and demonstrated that the vitamin D plays an important role in modulating the infant gut microbiota, especially increase the proportion of probiotics in breast-fed infants.

Maternal Level of 25-Hydroxyvitamin D during Pregnancy Associated with Risk of Type 1 Diabetes in the Offspring, a Meta-Analysis

This aim of this meta-analysis was to evaluate the association between risk of childhood type 1 diabetes and maternal 25-hydroxyvitamin D [25(OH)D] levels during pregnancy. A literature search on databases including PubMed and Embase was conducted up to December 2018. The pooled odds radio weighted mean difference (WMD) and the corresponding 95% confidence intervals (CIs) were calculated using the RevMan 5.3 software. A total of 4 studies were included in this meta-analysis. The overall analysis indicated that the maternal 25(OH)D levels during pregnancy was significantly associated with the risk of type 1 diabetes in offspring (WMD=-2.54, 95% CI=-4.65 to -0.44, p=0.02). The subgroup analyses showed that sample for detection vitamin D (serum/plasma) may not a factor influencing the results of this meta-analysis. However, gestational trimester may be a factor affecting the results. The results showed that no significant association was observed between risk of type 1 diabetes in offspring and 25(OH)D level during first or second gestational trimester (p>0.05). Lower maternal 25(OH)D levels during pregnancy is associated with higher risk of type 1 diabetes in offspring. Gestational trimester may be a factor influencing the results of this meta-analysis.

Selected Micronutrients: An Option to Boost Immunity against COVID-19 and Prevent Adverse Pregnancy Outcomes in Pregnant Women: A Narrative Review

The coronavirus disease-19 (COVID-19) negatively affects immune system. It is linked with adverse pregnancy outcomes. These complications may be linked with the infections mediated deficiency of micronutrients in pregnant women. COVID-19 cause's malabsorption of micronutrients thereby increases the risk of their deficiency. Both micronutrients deficiencies and poor micronutrients intake can compromise immune function and may increase the risk of pregnancy complications associated with COVID-19 infection. Vita-min A, C, D, E, and selected minerals iron (Fe), selenium (Se), and zinc (Zn) are the micronutrients essential for immuno-competency and play a significant role in the prevention of adverse pregnancy outcomes. Immune function and pregnancy outcomes can be improved by adequate intake of micronutrients in diet or in supplements form. Based on regulatory links between viral infection, micronutrients, immunity, and pregnancy outcomes, this review highlights the role of micronutrients in boosting immunity to reduce or prevent pregnancy complications in COVID-19 infected women.

Association of Maternal Dietary Components During Pregnancy and/or Lactation with Insulin-Dependent Diabetes Mellitus

CONTEXT

Considering the increasing trend in the incidence of type 1 diabetes mellitus (T1DM), the identification of its environmental determinants, especially those related to the prenatal and lactation period, might ultimately result in primary prevention of the disease. We aimed to review the evidence of the association between mothers' dietary components during pregnancy and/or lactation with T1DM.

EVIDENCE ACQUISITION

An electronic and comprehensive literature search was performed until August 2019 in the international databases, including Web of Science (ISI), PubMed, and Scopus, using the following keywords: type 1 diabetes mellitus, autoimmunity, mother, maternal, diet and lactation in different combinations. Papers related to the objectives of the study were selected.

RESULTS

Based on our review, the maternal consumption of meat, especially processed meat, was associated with increased risk of T1DM, whereas the maternal use of vegetables, potato, low-fat margarine, and berries showed protective effects against the development of T1DM in offspring. There was no significant association between the use of multivitamins and mineral supplements with T1DM, according to the available data. The results of the reviewed studies regarding the association between the maternal use of vitamin D, fatty acids, and coffee during pregnancy with T1DM were not consistent and conclusive.

CONCLUSIONS

Findings of this review indicate that the maternal consumption of some foods is associated with increased or decreased risk of T1DM. However, for some foods or dietary components, including coffee, vitamin D, and fatty acids, the results are not conclusive. We conclude that although maternal diet could influence the development of insulin autoantibodies (IA) and T1DM in offspring, there is no sufficient evidence for most nutrients, and available data are controversial, which should be dealt with in future cohort or interventional studies.

Vitamin D effects and endocrine diseases

A lack of vitamin D has been linked to autoimmune diseases including type 1 diabetes, autoimmune thyroiditis and to obesity. The prevalence of vitamin D deficiency is higher in diabetic or obese children and patients with thyroiditis compared to healthy controls. Moreover, low vitamin D values seem to be associated with major complications and poor glycemic control, in particular in obese children. Supplementation with vitamin D, which has immune-regulatory properties, may support our therapies and improve the outcomes in different diseases. Although some studies suggest a possible role of vitamin D in the etiology of autoimmune diseases and obesity, data on supplementation benefits are inconclusive and further studies are needed. In this paper, we focus on the current evidence regarding vitamin D function in endocrine diseases and possible benefits of its supplementation in pediatric age.

Vitamin D's Effect on Immune Function

Ever since its discovery by Windhaus, the importance of the active metabolite of vitamin D (1,25-dihydroxyvitamin D₃; 1,25-(OH)2D₃) has been ever expanding. In this review, the attention is shifted towards the importance of the extra-skeletal effects of vitamin D, with special emphasis on the immune system. The first hint of the significant role of vitamin D on the immune system was made by the discovery of the presence of the vitamin D receptor on almost all cells of the immune system. In vitro, the overwhelming effect of supra-physiological doses of vitamin D on the individual components of the immune system is very clear. Despite these promising pre-clinical results, the translation of the in vitro observations to solid clinical effects has mostly failed. Nevertheless, the evidence of a link between vitamin D deficiency and adverse outcomes is overwhelming and clearly points towards avoidance of vitamin D deficiency especially in early life.

Type 1 diabetes-early life origins and changing epidemiology

Type 1 diabetes is a chronic, immune-mediated disease characterised by the destruction of insulin-producing cells. Standardised registry data show that type 1 diabetes incidence has increased 3-4% over the past three decades, supporting the role of environmental factors. Although several factors have been associated with type 1 diabetes, none of the associations are of a magnitude that could explain the rapid increase in incidence alone. Moreover, evidence of changing prevalence of these exposures over time is insufficient. Multiple factors could simultaneously explain the changing type 1 diabetes incidence, or the magnitude of observed associations could have been underestimated because of exposure measurement error, or the mismodelling of complex exposure-time-response relationships. The identification of environmental factors influencing the risk of type 1 diabetes and increased understanding of the cause at the individual level, regardless of the ability to explain the changing incidence at the population level, is important because of the implications for prevention.

The prevalence of hypovitaminosis D and its risk factors in pregnant women and their newborns in the Middle East: A systematic review

BACKGROUND

Pregnant women and newborns are at risk for vitamin D deficiency (VDD). Also, poor health outcomes for pregnant women with VDD are reported in the published literature.

OBJECTIVE

The aim of this systematic review was to estimate the prevalence of hypovitaminosis D and the associated risk factors for hypovitaminosis D in Middle Eastern pregnant women and their newborns.

RESULTS

The prevalence of circulating 25-hydroxyvitamin D (25(OH)D) < 50 nmol/L as a marker of vitamin D status in pregnant women and their newborns was between 24.5-98% and 22-100%, respectively. The prevalence of 25(OH) D < 25 nmol/L in pregnant women and their newborns was over a wide range between 16.7-80% and 22-82%, respectively. Predictors for low maternal and neonatal 25(OH)D concentrations included decreased vitamin D synthesis due to reduced exposure to sunlight and decreased nutritional intake of vitamin D. A predictor of low neonatal 25(OH)D concentrations included maternal vitamin D status and the correlation between vitamin D concentrations in maternal and cord blood.

CONCLUSION

The high prevalence of VDD in the pregnant women of the Middle East underscores the necessity of implementing national prevention and intervention strategies. A clear policy for clinicians and healthcare workers is needed for screening and maintaining sufficient vitamin D status during pregnancy.

Influence of Vitamin D on Islet Autoimmunity and Beta-Cell Function in Type 1 Diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease leading to immune-mediated destruction of pancreatic beta cells, resulting in the need for insulin therapy. The incidence of T1D is increasing worldwide, thus prompting researchers to investigate novel immunomodulatory strategies to halt autoimmunity and modify disease progression. T1D is considered as a multifactorial disease, in which genetic predisposition and environmental factors interact to promote the triggering of autoimmune responses against beta cells. Over the last decades, it has become clear that vitamin D exerts anti-inflammatory and immunomodulatory effects, apart from its well-established role in the regulation of calcium homeostasis and bone metabolism. Importantly, the global incidence of vitamin D deficiency is also dramatically increasing and epidemiologic evidence suggests an involvement of vitamin D deficiency in T1D pathogenesis. Polymorphisms in genes critical for vitamin D metabolism have also been shown to modulate the risk of T1D. Moreover, several studies have investigated the role of vitamin D (in different doses and formulations) as a potential adjuvant immunomodulatory therapy in patients with new-onset and established T1D. This review aims to present the current knowledge on the immunomodulatory effects of vitamin D and summarize the clinical interventional studies investigating its use for prevention or treatment of T1D.

Serum 25-Hydroxyvitamin D Concentrations at Birth in Children Screened for HLA-DQB1 Conferred Risk for Type 1 Diabetes

CONTEXT

Vitamin D has several effects on the immune system that might be of relevance for the pathogenesis of type 1 diabetes (T1D).

OBJECTIVE

To evaluate whether umbilical cord serum concentrations of 25-hydroxy-vitamin D (25[OH]D) differ in children developing either islet autoimmunity (IA) or overt T1D during childhood and adolescence.

DESIGN

Umbilical cord serum samples from 764 children born from 1994 to 2004 with HLA-DQB1 conferred risk for T1D participating in the Type 1 Diabetes Prediction and Prevention Study were analyzed for 25(OH)D using an enzyme immunoassay.

SETTING

DIPP clinics in Turku, Oulu, and Tampere University Hospitals, Finland.

PARTICIPANTS

Two hundred fifty children who developed T1D diabetes at a median age of 6.7 years (interquartile range [IQR] 4.0 to 10.1 years) and 132 additional case children who developed IA, i.e., positivity for multiple islet autoantibodies. Cases were matched for date of birth, gender, and area of birth with 382 control children who remained autoantibody negative. The median duration of follow up was 9.8 years (IQR 5.7 to 13.1 years).

MAIN OUTCOME MEASURE

The median 25(OH)D concentrations.

RESULTS

The median 25(OH)D concentration in cord serum was low [31.1 nmol/L (IQR 24.0 to 41.8); 88% <50 nmol/L], but not statistically different between children who developed T1D or IA and their control groups (P = 0.70). The levels were associated mainly with geographical location, year and month of birth, age of the mother, and maternal intake of vitamin D during pregnancy.

CONCLUSIONS

The 25(OH)D concentrations at birth are not associated with the development of T1D during childhood.

Maternal dietary supplement use and development of islet autoimmunity in the offspring: TEDDY study

OBJECTIVE

We investigated the association between maternal use of vitamin D and omega-3 fatty acids (n-3 FAs) supplements during pregnancy and risk of islet autoimmunity (IA) in the offspring.

METHODS

The Environmental Determinants of Diabetes in the Young (TEDDY) Study is prospectively following 8676 children with increased genetic risk for type 1 diabetes in Finland, Germany, Sweden, and the United States. Blood samples were collected every 3 months between 3 and 48 months of age then every 6 months thereafter to determine persistent IA. Duration, frequency, and supplement dose during pregnancy were recalled by mothers at 3 to 4 months postpartum. Cumulative intakes of supplemental vitamin D and n-3 FAs were analyzed as continuous or binary variables. We applied time-to-event analysis to study the association between maternal supplement use and IA, adjusting for country, human leukocyte antigen-DR-DQ genotype, family history of type 1 diabetes and sex. Secondary outcomes included insulin autoantibodies (IAA) or glutamic acid decarboxylase (GADA) as the first appearing autoantibody.

RESULTS

As of February 2018, there were 747 (9.0%) children with IA. Vitamin D supplement intake during pregnancy (any vs none) was not associated with risk for IA (hazard ratio [HR] 1.11; 95% confidence interval [CI] 0.94, 1.31); neither was cumulative vitamin D supplement intake. Supplemental n-3 FA intake was similarly not associated with IA risk (HR: 1.19, 95% CI 0.98, 1.45). Similar lack of association was observed for either IAA or GADA as the first appearing autoantibody.

CONCLUSIONS

The TEDDY cohort showed no evidence of benefit regarding IA risk for vitamin D or n-3 FA supplementation during pregnancy.

Vitamin D: effects on pregnancy, maternal, fetal and postnatal outcomes

A high prevalence of vitamin D deficiency and its negative consequences for health is identified as area of primary concern for scientists and clinicians worldwide. Vitamin D deficiency affects not only bone health but many socially significant acute and chronic diseases. Observational studies support that pregnant and lactating women, children and teenagers represent the high risk groups for developing vitamin D deficiency. Current evidence highlights a crucial role of vitamin D in providing the fetal life-support system and fetus development, including implantation, placental formation, intra - and postpartum periods. Hypovitaminosis D during pregnancy is associated with a higher incidence of placental insufficiency, spontaneous abortions and preterm birth, preeclampsia, gestational diabetes, impaired fetal and childhood growth, increased risk of autoimmune diseases for offsprings. Potential mechanisms for the observed associations contain metabolic, immunomodulatory and antiinflammatory effects of vitamin D. Epigenetic modifications in vitamin D-associated genes and fetal programming are of particular interest. The concept of preventing vitamin D deficiency is actively discussed, including supplementation in different ethnic groups, required doses, time of initiation and therapy duration, influence on gestation and childbirth. An adequate supply of vitamin D during pregnancy improves the maternal and fetal outcomes, short and long term health of the offspring. Still current data on relationship between maternal vitamin D status and pregnancy outcomes remains controversial. The large observational and interventional randomized control trials are required to create evidence-based guidelines for the supplementation of vitamin D in pregnant and lactating women.

Impact of vitamin D on pregnancy-related disorders and on offspring outcome

Observational studies from all over the world continue to find high prevalence rates of vitamin D insufficiency and deficiency in many populations, including pregnant women. Beyond its classical function as a regulator of calcium and phosphate metabolism, vitamin D elicits numerous effects in the human body. Current evidence highlights a vital role of vitamin D in mammalian gestation. During pregnancy, adaptations in maternal vitamin D metabolism lead to a physiologic increase of vitamin D levels, mainly because of an increased renal production, although other potential sources like the placenta are being discussed. A sufficient supply of mother and child with calcium and vitamin D during pregnancy ensures a healthy bone development of the fetus, whereas lack of either of these nutrients can lead to the development of rickets in the child. Moreover, vitamin D insufficiency during pregnancy has consistently been associated with adverse maternal and neonatal pregnancy outcomes. In multitudinous studies, low maternal vitamin D status was associated with a higher risk for preeclampsia, gestational diabetes mellitus and other gestational diseases. Likewise, several negative consequences for the fetus have been reported, including fetal growth restriction, increased risk of preterm birth and a changed susceptibility for later-life diseases. However, study results are diverging and causality has not been proven so far. Meta-analyses on the relationship between maternal vitamin D status and pregnancy outcomes revealed a wide heterogeneity of studied populations and the applied methodology in vitamin D assessment. Until today, clinical guidelines for supplementation cannot be based on high-quality evidence and it is not clear if the required intake for pregnant women differs from non-pregnant women. Long-term safety data of vitamin D supplementation in pregnant women has not been established and overdosing of vitamin D might have unfavorable effects, especially in mothers and newborns with mutations of genes involved in vitamin D metabolism. Reliable data from large observational and interventional randomized control trials are urgently needed as a basis for any detailed and safe recommendations for supplementation in the general population and, most importantly, in pregnant women. This is of utmost importance, as ensuring a sufficient vitamin D-supply of mother and child implies a great potential for the prevention of birth complications and development of diseases.

Lack of Association Between Maternal or Neonatal Vitamin D Status and Risk of Childhood Type 1 Diabetes: A Scandinavian Case-Cohort Study

Studies on vitamin D status during pregnancy and risk of type 1 diabetes mellitus (T1D) lack consistency and are limited by small sample sizes or single measures of 25-hydroxyvitamin D (25(OH)D). We investigated whether average maternal 25(OH)D plasma concentrations during pregnancy are associated with risk of childhood T1D. In a case-cohort design, we identified 459 children with T1D and a random sample (n = 1,561) from the Danish National Birth Cohort (n = 97,127) and Norwegian Mother and Child Cohort Study (n = 113,053). Participants were born between 1996 and 2009. The primary exposure was the estimated average 25(OH)D concentration, based on serial samples from the first trimester until delivery and on umbilical cord plasma. We estimated hazard ratios using weighted Cox regression adjusting for multiple confounders. The adjusted hazard ratio for T1D per 10-nmol/L increase in the estimated average 25(OH)D concentration was 1.00 (95% confidence interval: 0.90, 1.10). Results were consistent in both cohorts, in multiple sensitivity analyses, and when we analyzed mid-pregnancy or cord blood separately. In conclusion, our large study demonstrated that normal variation in maternal or neonatal 25(OH)D is unlikely to have a clinically important effect on risk of childhood T1D.

Maternal early pregnancy vitamin D status in relation to low birth weight and small-for-gestational-age offspring

Maternal vitamin D deficiency is an independent risk factor for fetal growth. We examined the associations between maternal vitamin D status (defined by 25-hydroxyvitamin D [25(OH)D]) at the first prenatal visit and measures of newborn and placental weight, in a large China cohort of singleton, term, live births. From July 2015 to June 2016, women delivering singleton, term, live births with 25(OH)D measured at a first prenatal visit (N=747). Birth weight, placental weight, the placental to fetal weight ratio, and small for gestational age (SGA) were measured. The relationship between levels of 25(OH)D and SGA were evaluated using univariate and multivariate regression analysis. Vitamin D deficiency was defined as 25(OH)D less than 20ng/ml. In those women, 76.9% (95%CI: 74%-78%) were defined as vitamin D deficiency. Incidence of SGA was also high (13.3%; 95%CI: 10.8%-15.7%). We found a nonlinear relation between 25(OH)D and birth weight as well as head circumference (P<0.01). Birth weight and head circumference increased by 69 [95%CI: 38-122] g and 0.31 (0.22-0.40) cm, respectively, per 1ng/ml increase in maternal 25(OH)D up to 20ng/ml and then leveled off thereafter. The SGA distribution across the 25(OH)D quartiles ranged between 3.7% (fourth quartile) to 24.1% (first quartile). For each 1 unit decrease of plasma concentration of 25(OH)D, the unadjusted and adjusted risk of SGA increased by 19% (odds ratio 1.19 [95% CI 1.13-1.25], P<0.001) and 9% (1.08 [1.03-1.16], P=0.009), respectively. In a multivariate model using the vitamin D deficiency vs. other together with the clinical variables, the adjusted risk of SGA increased by 205% (odds ratio 3.05 [95% CI 2.24-4.40], P=0.001). Maternal vitamin D insufficiency is common during pregnancy and is independently associated with low birth weight and high risk of SGA in term infants.

Early life origin of type 1 diabetes

Type 1 diabetes (T1D) is perceived as a chronic immune-mediated disease with a subclinical prodromal period characterized by selective loss of insulin-producing beta cells in the pancreatic islets in genetically susceptible subjects. The incidence of T1D has increased manifold in most developed countries after World War II in parallel with a series of other immune-mediated diseases. T1D results from gene-environmental interactions. The appearance of disease-associated autoantibodies into the peripheral circulation is the first detectable sign of the initiation of the disease process leading to clinical T1D. The first autoantibodies may appear already before the age of 6 months and the seroconversion rate peaks during the second year of life. This implies that exogenous factors involved in the pathogenesis of T1D must be operative in early life, some of them most likely already during pregnancy. Here, we discuss putative endogenous factors that may contribute to the development of T1D during fetal and early postnatal life. Many environmental factors operative in early life have been implicated in the pathogenesis of T1D, but relatively few have been firmly confirmed.

Genetic determinants of serum 25-hydroxyvitamin D concentration during pregnancy and type 1 diabetes in the child

Objective

The in utero environment plays an important role in shaping development and later life health of the fetus. It has been shown that maternal genetic factors in the metabolic pathway of vitamin D associate with type 1 diabetes in the child. In this study we analyzed the genetic determinants of serum 25-hydroxyvitamin D (25OHD) concentration during pregnancy in mothers whose children later developed type 1 diabetes and in control mothers.

Study design

474 mothers of type 1 diabetic children and 348 mothers of non-diabetic children were included in the study. We previously selected 7 single nucleotide polymorphisms (SNPs) in four genes in the metabolic pathway of vitamin D vitamin based on our previously published data demonstrating an association between genotype and serum 25OHD concentration. In this re-analysis, possible differences in strength in the association between the SNPs and serum 25OHD concentration in mothers of type 1 diabetic and non-diabetic children were investigated. Serum 25OHD concentrations were previously shown to be similar between the mothers of type 1 diabetic and non-diabetic children and vitamin D deficiency prevalent in both groups.

Results

Associations between serum 25OHD concentration and 2 SNPs, one in the vitamin D receptor (VDR) gene (rs4516035) and one in the group-specific component (GC) gene (rs12512631), were stronger during pregnancy in mothers whose children later developed type 1 diabetes than in mothers whose children did not (p_interaction = 0.03, 0.02, respectively).

Conclusions

We show for the first time that there are differences in the strength of genetic determinants of serum 25OHD concentration during pregnancy between the mothers of type 1 diabetic and non-diabetic children. Our results emphasize that the in utero environment including maternal vitamin D metabolism should be important lines of investigation when searching for factors that lead to early programming of type 1 diabetes.

Does vitamin D play a role in autoimmune endocrine disorders? A proof of concept

In the last few years, more attention has been given to the "non-calcemic" effect of vitamin D. Several observational studies and meta-analyses demonstrated an association between circulating levels of vitamin D and outcome of many common diseases, including endocrine diseases, chronic diseases, cancer progression, and autoimmune diseases. In particular, cells of the immune system (B cells, T cells, and antigen presenting cells), due to the expression of 1α-hydroxylase (CYP27B1), are able to synthesize the active metabolite of vitamin D, which shows immunomodulatory properties. Moreover, the expression of the vitamin D receptor (VDR) in these cells suggests a local action of vitamin D in the immune response. These findings are supported by the correlation between the polymorphisms of the VDR or the CYP27B1 gene and the pathogenesis of several autoimmune diseases. Currently, the optimal plasma 25-hydroxyvitamin D concentration that is necessary to prevent or treat autoimmune diseases is still under debate. However, experimental studies in humans have suggested beneficial effects of vitamin D supplementation in reducing the severity of disease activity. In this review, we summarize the evidence regarding the role of vitamin D in the pathogenesis of autoimmune endocrine diseases, including type 1 diabetes mellitus, Addison's disease, Hashimoto's thyroiditis, Graves' disease and autoimmune polyendocrine syndromes. Furthermore, we discuss the supplementation with vitamin D to prevent or treat autoimmune diseases.

An examination of whether associations exist between maternal and neonatal 25OHD and infant size and adiposity at birth, 6-9 months and 2-2.5 years of age - a longitudinal observational study from the ROLO study

BACKGROUND

Vitamin D status in pregnancy and offspring bone health effects are well established, yet limited knowledge exists on the effect of maternal vitamin D status on offspring size/adiposity. This study examines the association of early (13 weeks), late (28 weeks) pregnancy and neonatal (umbilical) 25-hydroxyvitamin D (25OHD) on offspring size/adiposity.

METHODS

This analysis included mother-infant pairs from the ROLO study at birth (n = 292), 6-9 months (n = 160) and 2-2.5 years (n = 287) postpartum.

RESULTS

Using Institute of Medicine 2011 Report criteria, 30% of women in early pregnancy and 38% in late pregnancy were at risk of vitamin D deficiency (25OHD < 30 nmol/L). Birthweight was negatively associated with early-pregnancy 25OHD (p = 0.004) and neonatal 25OHD (p < 0.001). Birth length was not associated with 25OHD. Neonatal measures of overall adiposity were negatively associated with neonatal 25OHD (p = 0.001, and p = <0.001 respectively). At 2-2.5 years there was a negative association between weight-for-age z-score and early-pregnancy 25OHD (p < 0.041).

CONCLUSIONS

Maternal and neonatal 25OHD were negatively associated with offspring size/adiposity at birth and offspring weight-for-age at 2-2.5 years. Results may not reflect a general population replete in vitamin D, due to high prevalence of macrosomia and high risk of deficiency in this cohort. Improvement of pregnancy vitamin D status remains a public health concern.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN54392969. 22/04/2009 retrospectively registered.

Vitamin D and diabetes mellitus: Causal or casual association?

The incidence of both type 2 and type 1 diabetes mellitus has been increasing worldwide. Vitamin D deficiency, or the awareness of its prevalence, has also been increasing. Vitamin D may have a role in the pathogenic mechanisms predisposing to type 2 diabetes by modulating insulin resistance and/or pancreatic β-cell function. Vitamin D status or elements involved in its activation or transport may also be involved in the development of type 1 diabetes mellitus through immunomodulatory role . Based on these observations a potential association between vitamin D and diabetes has been hypothesized. In this review we discuss up to date evidence linking vitamin D with the development of diabetes. Moreover, the role of vitamin D supplementation in the prevention of both types of diabetes is analysed together with its role in improving glycemic control in diabetic patients. We also address the potential role of vitamin D deficiency in the development of macro- and microvascular complications in diabetes. Finally, we provide recommendation for Vitamin D therapy in diabetes in view of current evidence and highlight areas for potential future research in this area.

Efficacy and safety of early supplementation with 800 IU of vitamin D in very preterm infants followed by underlying levels of vitamin D at birth

Background

To determine the efficacy and safety of early supplementation with 800 IU of vitamin D in very low birth weight (VLBW) infants.

Methods

Sixty-six infants with a birth weight less than 1500 g admitted to the Neonatal Intensive Care Unit. Of these, 52 infants were eligible and received 800 IU/day vitamin D from 2 weeks of age. We examined 25-hydroxyvitamin-D (25[OH]D) levels from cord blood at birth and serum at 32 and 36 weeks of postmenstrual age.

Results

The study infants were divided by cord-blood levels of 25(OH)D at birth into 25(OH)D concentrations < 10 ng/mL (n = 20) or ≥ 10 ng/mL (n = 29). Vitamin D intake of 800 IU/day safely achieved an 88% probability of vitamin D sufficiency at 36 weeks postmenstrual age in VLBW infants with cord-blood levels of 25(OH)D ≥ 10 ng/mL, and 65% probability of vitamin D sufficiency was observed in infants with 25 OHD concentrations < 10 ng/mL at birth.

Conclusion

Considering the efficacy and safety of vitamin D supplementation in this study, vitamin D intake of 800 IU/day may enhance vitamin D status during early hospitalization in VLBW infants with 25 OHD concentrations < 10 ng/mL at birth. The clinical significance of optimal vitamin D intake in VLBW infants needs to be studied in larger controlled studies.

The Role of Vitamin D in the Immune System as a Pro-survival Molecule

PURPOSE

Vitamin D is a fascinating and attractive molecule that has gained particular attention in medicine in recent years. Its immunomodulatory and anti-inflammatory potential might resemble the activity of many nature-derived molecules (eg, flavonoids), but its role in biology was selected during a long evolutionary pathway to dampen the damaging effect of cell stress response and of the immune reaction. In this sense, this molecule can be considered an ancient hormone that serves, in its primary role, as a pro-survival agent. The goal of this review was to elucidate this topic.

METHODS

The article reviews current literature on the field, focusing on issues regarding the role of vitamin D in immunity.

FINDINGS

Vitamin D participates in the survival machinery used by the cell, and in particular it plays a major role in synchronizing calcium oscillatory signaling to allow cell autophagy or apoptosis during a stress response.

IMPLICATIONS

Vitamin D should be better highlighted in its molecular action and vitamin D receptor genomics to conceive a more suited therapeutic supplementation protocol in clinics.

Are low sun exposure and/or vitamin D risk factors for type 1 diabetes?

Ultraviolet radiation and vitamin D, with their known immunosuppressive effects, have the potential to delay or inhibit type 1 diabetes.

No association between use of multivitamin supplement containing vitamin D during pregnancy and risk of Type 1 Diabetes in the child

BACKGROUND

Sweden has the second highest incidence of type 1 diabetes in the world. Nutritional aspects in utero and in infancy affect the development. We conducted a survey to determine whether reported maternal use of vitamin D-containing micronutrient supplements during pregnancy was associated with the risk of developing type 1 diabetes in the child.

METHODS

This report was based on data from the ABIS (All Babies In Southeast Sweden) study, with questionnaire data on 16 339 mother and infant pairs at birth and at 1-yr of age (n = 10 879), of whom 108 children were registered with type 1 diabetes before 14-16 yr of age. The questions 'during pregnancy, did you take any vitamin/mineral supplements?' and 'if yes, which? (open answer)' in addition to other lifestyle questions were answered. Logistic regression was performed with onset of type 1 diabetes as the dependent variable and vitamin D supplementation use as the independent variable, adjusted for relevant factors.

RESULTS

Vitamin D supplementation during pregnancy was consumed by 9.3% of mothers whose children later got type1 diabetes and among 11.3% of those mothers whose children did not get type 1 diabetes (p = 0.532). No significant association was found between reported supplement intake of vitamin D during pregnancy and risk of type 1 diabetes, even when adjusting for factors which could influence the association.

CONCLUSION

Maternal use of vitamin D-containing multivitamin supplements during pregnancy was not related to the risk of developing type 1 diabetes in children before 14-16 yr of age in Southeast of Sweden.

Association of serum 25-hydroxyvitamin D concentration with HLA-B, -DRB1 and -DQB1 genetic polymorphisms

BACKGROUND/OBJECTIVES

The human leukocyte antigen (HLA) gene region associates with the risk for several autoimmune diseases, including type 1 diabetes. An association between vitamin D deficiency and several autoimmune diseases has been suggested. We tested the association between serum 25-hydroxyvitamin D (25OHD) concentrations and HLA alleles in pregnant Finnish women.

SUBJECTS/METHODS

HLA-B (n=395), HLA-DRB1 (n=501) and HLA-DQB1 (n=475) alleles were genotyped in pregnant women (mothers of children who later developed type 1 diabetes and mothers of non-diabetic children). HLA-B alleles were divided into supertypes that share similar peptide-binding specificity. Serum 25OHD concentration had been previously measured in these women from sera collected during the first trimester of pregnancy. Multiple testing was controlled for using the false discovery rate method.

RESULTS

An association was found between 25OHD concentration and HLA-B44 supertype (P=0.009); women with HLA-B44 supertype (B*18, B*37, B*40 and B*44 alleles) had lower 25OHD concentrations. No association was found between HLA-DRB1 or -DQB1 alleles and 25OHD concentration.

CONCLUSIONS

In this study we found for the first time an association between HLA genetic polymorphisms and 25OHD concentration. In future studies, the mechanistic background of this association and the role of vitamin D in the regulation of HLA gene expression should be investigated.

Environmental Risk Factors and Type 1 Diabetes: Past, Present, and Future

Type 1 diabetes is an autoimmune condition that results from the destruction of the insulin-producing beta cells of the pancreas. The excess morbidity and mortality resulting from its complications, coupled with its increasing incidence, emphasize the importance of better understanding the causes of this condition. Over the past several decades, a substantive amount of work has been done and, although many advances have occurred in identifying disease-susceptibility genes, there has been a lag in understanding the environmental triggers. Several putative environmental risk factors have been proposed, including infections, dietary factors, air pollution, vaccines, location of residence, family environment and stress. However, most of these factors have been inconclusive, thus supporting the need for further study into the causes of type 1 diabetes.

Dietary factors in the development of type 1 diabetes

There are several indicators concerning the putative importance of dietary factors during the fetal period lactation, infancy and childhood in the etiology of type 1 diabetes. Among foods, cow's milk consumption has been associated with an increased risk of preclinical and/or clinical type 1 diabetes and sugars with a progression from preclinical to clinical disease. Breast milk, on the other hand, may be protective. Processed foods may be related to a greater risk of type 1 diabetes because they contain higher amounts of advanced glycation end-products. Nitrites or N-nitroso compounds in processed meat products could increase the risk of this disease. Among nutrients, n-3 fatty acids, vitamins D and E, and zinc may protect from preclinical and/or clinical type 1 diabetes. The microbial composition of foods or food's other effects on gut microbiota are receiving increasing attention, also due to their putative role in the development of type 1 diabetes. Still the number of prospective studies in this research field is limited and most of the findings remain to be replicated.

Maternal VDR variants rather than 25-hydroxyvitamin D concentration during early pregnancy are associated with type 1 diabetes in the offspring

AIMS/HYPOTHESIS

We investigated whether single nucleotide polymorphisms (SNPs) associated with 25-hydroxyvitamin D concentration in the metabolic pathway of vitamin D show different genotype distributions between Finnish families with an offspring with type 1 diabetes (cases) and families with a healthy offspring (controls).

METHODS

A total of 31 SNPs in eight genes were studied in case and control mothers and family members (offspring with type 1 diabetes and healthy siblings, healthy control children and fathers) (n = 2,854). The 25-hydroxyvitamin D concentration was studied in 474 case and 348 matched control mothers during pregnancy.

RESULTS

The genotype distributions of 13 SNPs (in the following genes: 7-dehydrocholesterol reductase NADSYN1/DHCR7, vitamin D receptor VDR, group-specific component GC and CYP27A1) that showed a nominal association with 25-hydroxyvitamin D concentration (p < 0.05) were compared between case and control families. SNPs in VDR had different genotype distributions between the case and control mothers (rs1544410, p = 0.007; rs731236, p = 0.003; rs4516035, p = 0.015), two SNPs (rs1544410 and rs731236) remaining significant after correction for multiple testing using a false discovery rate. The mean 25-hydroxyvitamin D concentrations during pregnancy did not differ between the case and control mothers.

CONCLUSIONS/INTERPRETATION

Our preliminary results suggest that the maternal genotypes of SNPs in VDR may influence the in utero environment and thus contribute to the early programming of type 1 diabetes in the fetus. It is possible that the effects are only relevant in the presence of vitamin D insufficiency.

Plant-Based and Plant-Rich Diet Patterns during Gestation: Beneficial Effects and Possible Shortcomings

Environmental and lifestyle factors are known to play an important role during gestation, determining newborns' health status and influencing their risk of being subject to certain noncommunicable diseases later in life. In particular, maternal nutritional patterns characterized by a low intake of plant-derived foods could increase the risk of gestation-related issues, such as preeclampsia and pregravid obesity, increase genotoxicant susceptibility, and contribute to the onset of pediatric diseases. In particular, the risk of pediatric wheeze, diabetes, neural tube defects, orofacial clefts, and some pediatric tumors seems to be reduced by maternal intake of adequate amounts of vegetables, fruits, and selected antioxidants. Nevertheless, plant-based diets, like any other diet, if improperly balanced, could be deficient in some specific nutrients that are particularly relevant during gestation, such as n-3 (ω-3) fatty acids, vitamin B-12, iron, zinc, and iodine, possibly affecting the offspring's health state. Here we review the scientific literature in this field, focusing specifically on observational studies in humans, and highlight protective effects elicited by maternal diets enriched in plant-derived foods and possible issues related to maternal plant-based diets.

Maternal intake of fatty acids and their food sources during lactation and the risk of preclinical and clinical type 1 diabetes in the offspring

AIMS

We examined maternal dietary intake of fatty acids and foods which are sources of fatty acids during lactation and whether they are associated with the risk of preclinical and clinical type 1 diabetes in the offspring.

METHODS

The subjects comprised a cohort of 2,939 mother-child pairs from the prospective Type 1 Diabetes Prediction and Prevention Study. Composition of maternal diet during the third month of lactation was assessed by a validated food frequency questionnaire. Among the children with HLA-conferred susceptibility to type 1 diabetes, 172 developed preclinical and 81 clinical diabetes. Average follow-up for preclinical type 1 diabetes was 7.5 years (range 0.2-14.0 years) and for clinical type 1 diabetes 7.7 years (0.2-14.0 years).

RESULTS

Maternal intake of fatty acids during lactation was not associated with the risk of type 1 diabetes in the offspring. After adjusting for putative confounders, maternal total consumption of red meat and meat products during lactation was associated both with increased risk for preclinical [hazard ratio (HR) 1.19, 95 % CI 1.02-1.40, p = 0.038] and clinical type 1 diabetes (HR 1.27, 95 % CI 1.06-1.52, p = 0.025). In particular, consumption of processed meat products showed an association with increased risk for type 1 diabetes (HR 1.23, 95 % CI 1.02-1.48, p = 0.045). Maternal use of vegetable oils was associated with increased risk for preclinical type 1 diabetes (HR 1.21, 95 % CI 1.03-1.41, p = 0.023).

CONCLUSIONS

Maternal consumption of red meat, especially processed meat, during lactation may increase the risk of type 1 diabetes.

Role of nutritional factors at the early life stages in the pathogenesis and clinical course of type 1 diabetes

Nutrition has been suggested as an important environmental factor other than viruses and chemicals in the pathogenesis of type 1 diabetes (T1D). Whereas various maternal dietary nutritional elements have been suggested and examined in T1D of both humans and experimental animals, the results largely remain controversial. In a series of studies using T1D model nonobese diabetic (NOD) mice, maternal dietary n-6/n-3 essential fatty acid ratio during pregnancy and lactation period, that is, early life stages of the offspring, has been shown to affect pathogenesis of insulitis and strongly prevent overt T1D of the offspring, which is consistent with its preventive effects on other allergic diseases.

No association between vitamin D and β-cell autoimmunity in Finnish and Estonian children

BACKGROUND

Vitamin D has immunomodulatory properties, such as regulation of FOXP3 expression and regulatory T-cell activity. Our aim was to investigate whether plasma 25-hydroxyvitamin D [25(OH)D] concentrations associate with the development of β-cell autoimmunity and the transcriptional activity of FOXP3 or vitamin D3 convertase gene (CYP27B1) in CD4+ memory T cells.

METHODS

We studied 83 Finnish and 32 Estonian children participating in the DIABIMMUNE and DIPP studies. Twenty-nine Finnish and six Estonian children tested positive for at least one diabetes-associated autoantibody. The plasma concentrations of 25(OH)D and 1,25(OH)₂D were analysed with an enzyme immunoassay. Gene expression of FOXP3 and CYP27B1 in the isolated CD4+ memory T cells was studied with reverse transcription quantitative polymerase chain reaction.

RESULTS

Vitamin D status did not differ between subjects positive and negative for β-cell autoantibodies. Finnish children had higher vitamin D status than Estonian children (p < 0.001). FOXP3 expression was higher in Estonian CD4+ memory T-cell samples than in Finnish samples (p < 0.01) even when including in both groups only children with serum 25(OH)D concentrations in the range of 50-80 nmol/L (p < 0.001).

CONCLUSIONS

These findings do not support a crucial role of circulating 25(OH)D as a regulator of β-cell autoimmunity or FOXP3 expression.

Dietary supplementation with high doses of regular vitamin D3 safely reduces diabetes incidence in NOD mice when given early and long term

High doses of the active form of vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], prevent diabetes in the NOD mouse but also elicit unwanted calcemic side effects. Because immune cells themselves can convert vitamin D3 into 1,25(OH)2D3 locally, we hypothesized that dietary vitamin D3 can also prevent disease. Thus, we evaluated whether dietary administration of high doses of regular vitamin D3 (800 IU/day) during different periods of life (pregnancy and lactation, early life [3-14 weeks of age], or lifelong [3-35 weeks of age]) safely prevents diabetes in NOD mice. We found that only lifelong treatment raised serum 25-hydroxyvitamin D3 from 173 nmol/L in controls to 290 nmol/L, without inducing signs of calcemic or bone toxicity, and significantly reduced diabetes development in both male and female NOD mice. This diabetes protection by vitamin D3 correlated with preserved pancreatic insulin content and improved insulitis scores. Moreover, vitamin D3 treatment decreased interferon-γ-positive CD8(+) T cells and increased CD4(+)(CD25(+))FoxP3(+) T cells in pancreatic draining lymph nodes. In conclusion, this study shows for the first time that high doses of regular dietary vitamin D3 can safely prevent diabetes in NOD mice when administered lifelong, although caution is warranted with regards to administering equivalently high doses in humans.

Vitamin D requirement in pregnancy to prevent deficiency in neonates: a randomised trial

INTRODUCTION

The exact amount of vitamin D required for pregnant women to adequately supply the foetus during pregnancy is still unclear. This randomised trial attempted to determine the optimal dose of vitamin D necessary during pregnancy in order to attain a vitamin D level > 20 ng/mL in neonates.

METHODS

A total of 51 healthy, pregnant women in Yazd, Iran, were recruited in 2009. Of these, 34 were randomised to receive either 50,000 IU (Group A) or 100,000 IU (Group B) of vitamin D3 per month from the second trimester of pregnancy. The remaining 17 pregnant women, who formed the third group (Group C) and were found to have vitamin D deficiency, were initially treated with 200,000 IU of vitamin D3, following which the dose was adjusted to 50,000 IU per month. 25-hydroxyvitamin D (25[OH]D) in cord blood was measured by chemiluminescence immunoassay, and a serum 25(OH)D level < 20 ng/mL was defined as deficiency.

RESULTS

All the pregnant women had a vitamin D level < 30 ng/mL at the beginning of the second trimester. The neonates of 76% of women from Group A had sufficient levels of 25(OH)D. All the neonates born to women in Groups B and C had 25(OH)D > 20 ng/mL. No side effects were observed in our participants during the period of vitamin D supplementation.

CONCLUSION

A vitamin D3dose > 50,000 IU/month is required during the second and third trimesters of pregnancy for vitamin D-deficient pregnant women in order for their neonates to achieve serum 25(OH)D levels > 20 ng/mL. Supplementation with < 50,000 IU/month is insufficient to ensure a vitamin D level > 20 ng/mL in all neonates born to vitamin D-deficient pregnant women.

Vitamin D intake and risk of type 1 diabetes: a meta-analysis of observational studies

Vitamin D is suggested to have protective effects against type 1 diabetes. However, the results from observational studies have been inconsistent. We aimed to examine their association by conducting a meta-analysis of observational studies. Multiple databases were searched in June 2013 to identify relevant studies including both case-control and cohort studies. Either a fixed- or random-effects model was used to calculate the pooled risk estimate. We identified eight studies (two cohort studies and six case-control studies) on vitamin D intake during early life and three studies (two cohort studies and one case-control study) on maternal vitamin D intake during pregnancy. The pooled odds ratio for type 1 diabetes comparing vitamin D supplementation with non-supplementation during early life was 0.71 (95% confidence interval [CI], 0.51–0.98). Similar results were observed in the case-control subgroup analysis but not in the cohort subgroup analysis. The pooled odds ratio with maternal intake of vitamin D during pregnancy was 0.95 (95% CI, 0.66–1.36). In conclusion, vitamin D intake during early life may be associated with a reduced risk of type 1 diabetes. However, there was not enough evidence for an association between maternal intake of vitamin D and risk of type 1 diabetes in the offspring.

The prenatal environment and type 1 diabetes

There is ample evidence that environmental factors are involved in the aetiology of type 1 diabetes, but the nature and timing of the interactions are poorly understood. The intrauterine environment is known to play a role in the later development of type 2 diabetes, and this review considers a possible role in type 1 diabetes. Autoimmune type 1 diabetes is rare in those diagnosed before 6 months of age, but endogenous autoantibodies predictive of future type 1 diabetes may be detectable by 6-12 months of age, suggesting that environmental factors may operate before this age in some cases. Indirect evidence of a protective effect for the intrauterine environment comes from the observation that mothers with type 1 diabetes are less likely than affected fathers to transmit diabetes to their offspring, although the precise role (if any) is unclear. The risk of childhood-onset type 1 diabetes increases with maternal age at delivery, and with high birthweight, but these associations are weak and heterogeneous, and these factors are unlikely to be directly causally related to type 1 diabetes. No firm conclusion can be drawn from studies of maternal enteroviral infection or from various nutritional exposures. The birth process itself may play a role, as suggested by the slightly increased risk in children born by Caesarean section; lack of contact with maternal bacteria is one suggested mechanism. In sum, there is circumstantial evidence, but no proof of principle, that maternal or intrauterine conditions may modulate genetic risk of type 1 diabetes. The disease process culminating in type 1 diabetes typically begins in early life, but it is not clear whether the trail begins before or after birth.

Use of dietary supplements in pregnant women in relation to sociodemographic factors - a report from The Environmental Determinants of Diabetes in the Young (TEDDY) study

OBJECTIVES

The aim of the present study was to examine the prevalence and associated factors of dietary supplement use, particularly supplements containing vitamin D and fatty acids, in pregnant women enrolled in a multi-national study.

DESIGN

The Environmental Determinants of Diabetes in the Young (TEDDY) study is a prospective longitudinal cohort study. Maternal dietary supplement use was self-reported through questionnaires at month 3 to 4 postpartum.

SETTING

Six clinical research centres; three in the USA (Colorado, Georgia/Florida and Washington) and three in Europe (Sweden, Finland and Germany).

SUBJECTS

Mothers (n 7326) to infants screened for high-risk HLA-DQ genotypes of type 1 diabetes.

RESULTS

Ninety-two per cent of the 7326 women used one or more types of supplement during pregnancy. Vitamin D supplements were taken by 65% of the women, with the highest proportion of users in the USA (80.5 %). Overall, 16% of the women reported taking fatty acid supplements and a growing trend was seen in all countries between 2004 and 2010 (P,0.0001). The use was more common in Germany (32 %) and the USA (24 %) compared with Finland (8.5%) and Sweden (7.0 %). Being pregnant with the first child was a strong predictor for any supplement use in all countries. Low maternal age (<25 years), higher education, BMI<=25.0 kg/m2 and smoking during pregnancy were factors associated with supplement use in some but not all countries.

CONCLUSIONS

The majority of the women used dietary supplements during pregnancy. The use was associated with sociodemographic and behavioural factors, such as parity, maternal age, education, BMI and maternal smoking.

Vitamin D: effects on childhood health and disease

Vitamin D is a key nutrient for both healthy children and those with chronic illnesses. Understanding its roles in health and disease has become one of the most important issues in the nutritional management of children. Formal guidelines related to nutrient requirements for vitamin D in healthy children, recommending dietary intakes of 400 IU per day for infants and 600 IU per day for children over 1 year of age, were released by the Institute of Medicine in November 2010. However, application of these guidelines to children with acute and chronic illnesses is less clear. In this Review, we consider major illness categories and specific examples of conditions in children that might be affected by vitamin D. This information can be used in developing both model systems of investigation and clinical trials of vitamin D in children with acute and chronic illnesses.

Effects of vitamin D on antigen-specific and non-antigen-specific immune modulation: relevance for type 1 diabetes

Vitamin D is a fat-soluble precursor of the circulating 25-hydroxyvitamin D₃ (25(OH)D₃)which can be converted by the 1α-hydroxylase (1α(OH)ase) enzyme into the bioactive hormonal metabolite 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), generally known to promote bone mineralization through its ability to enhance calcium absorption from the gut. Importantly, in humans, vitamin D is mainly derived from endogenous production of vitamin D₃ from ultraviolet (UV) radiation exposure to the skin while a small part (<10%) is obtained via dietary intake of dairy products and fatty fish (1). Taking these factors into account, geographic distribution and seasonality, skin pigmentation, age, and lifestyle may predispose certain populations to be at a higher risk of developing vitamin D insufficiency or deficiency (2). The first valid reports correlating the importance of an adequate vitamin D status to optimal human health originate from the early part of the 20th century, when vitamin D was described to prevent and treat the bone disease rickets. Since then, the findings that vitamin D receptors (VDR) are present in many body tissues and that vitamin D metabolizing enzymes can be found in various cells outside the kidney, including the intestine, prostate, immune cells, and within the skin itself (reviewed in reference 3), have revolutionized the vitamin D business. In this review, we will mainly focus on vitamin D as a component of immune regulation and on the role of vitamin D in antigen-specific and non-specific therapies with potential relevance for type 1 diabetes (T1D).

Why is type 1 diabetes increasing?

A series of studies have reported a constant global rise in the incidence of type 1 diabetes. Epidemiological and immunological studies have demonstrated that environmental factors may influence the pathogenesis, leading to a cell-mediated pancreatic β-cell destruction associated with humoral immunity. The search for the triggering factor(s) has been going on for the past century, and yet they are still unknown. This review provides an overview of some of the most well-known theories found in the literature: hygiene, viral, vitamin D deficiency, breast milk and cow's milk hypotheses. Although the hygiene hypothesis appears to be the most promising, positive evidence from animal, human and epidemiological studies precludes us from completely discarding any of the other hypotheses. Moreover, due to contrasting evidence in the literature, a single factor is unlikely to cause an increase in the incidence of diabetes all over the world, which suggests that a multifactorial process might be involved. Although the immunological mechanisms are still unclear, there seems to be some overlap between the various hypotheses. It is thought that the emphasis should be shifted from a single to a multifactorial process and that perhaps the 'balance shift' model should be considered as a possible explanation for the rise in the incidence of type 1 diabetes.

The role of vitamin d deficiency in the incidence, progression, and complications of type 1 diabetes mellitus

The "nonclassic" role of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has been recently widely recognized. In type 1 diabetes mellitus (T1D), it plays an immunomodulatory role through the vitamin D receptor (VDR) present on pancreatic and immune cells. Specific VDR allelic variants have been associated with T1D in many countries. Furthermore, vitamin D deficiency has been prevalent in T1D, and the seasonal and latitude variability in the incidence of T1D can be partly explained by the related variability in vitamin D level. In fact, retrospective studies of vitamin D supplementation during pregnancy or infancy showed a lower incidence of T1D. We will review the different mechanisms of the vitamin D protective effect against insulitis and present the available data on the role of vitamin D deficiency in the control, progression, and complications of T1D.