Vitamin D in pediatric health and disease

Vitamin D supplements reduce risk of viral upper respiratory infections in children with lower concentrations

AIM

Vitamin D is crucial for the immune system, as it enhances pathogen-fighting cells and reduces inflammation. We reviewed serum 25-hydroxyvitamin D (25(OH)D) concentrations in children with viral upper respiratory tract infections (URTIs) and the impact of vitamin D supplements on those infections.

METHODS

A mini literature review was conducted from 1 January 2000 to 30 April 2024. It used PubMed, Google Scholar, Cochrane and Scopus and focused on children aged 0-18 years.

RESULTS

The review comprised 12 studies: seven randomised controlled trials, two prospective studies, two case-control studies and one cross-sectional study. The findings included lower 25(OH)D concentrations in children more susceptible to URTIs and significantly lower levels in those with recurrent infections. One study found reduced 25(OH)D concentrations and immunoglobulin G levels in children with URTIs. Of the nine studies that examined vitamin D supplements, five reported benefits for children with URTIs, one only showed short-term effects and three found no significant reductions. Two reported that taking 2000 IU a day did not reduce URTIs any more than 400 IU and high-dose supplements may be unnecessary.

CONCLUSION

Children with viral URTIs often had lower vitamin D concentrations and supplements frequently helped to reduce the risk of these infections.

Association between childhood obesity and vitamin D: A Mendelian randomization study

BACKGROUND

This study evaluated the causal relationship between childhood obesity and vitamin D levels by performing a Mendelian randomization (MR) analysis using publicly available genome-wide association study (GWAS) summary statistics. To mitigate bias stemming from confounding and reverse causation, we conducted an MR analysis to assess the causal impact of childhood obesity on the major circulating form of vitamin D, 25-hydroxyvitamin D (25(OH)D).

METHODS

Vitamin D is present in the blood in the form of 25(OH)D; childhood obesity and 25(OH)D levels data were obtained from the IEU open GWAS project, which were subjected to MR analyses. The IVW method was used as the predominant analysis method and was complemented by MR-Egger, simple mode, weighted median, and weighted mode methods. The MR-PRESSO method was utilized to identify horizontal pleiotropy and potential outliers.

RESULTS

This study indicated that childhood obesity affects the serum of 25(OH)D, which was significant in the IVW (OR [95%CI], 0.977 [0.966-0.989], p = 0.0001), and weighted-median (OR [95%CI], 0.983 [0.969-0.997], p = 0.015) analyses, but nonsignificant in the MR-Egger (OR [95%CI], 0.985 [0.897-1.082], p = 0.784), simple mode (OR [95%CI], 0.985 [0.965-1.005], p = 0.233), and weighted mode (OR [95%CI], 0.985 [0.967-1.004], p = 0.214) analyses.

CONCLUSIONS

In summary, we found a potential inverse association between elevated childhood obesity and 25(OH)D levels, which suggested that obese children need to pay attention to their 25(OH)D levels, and vitamin D supplementation may be necessary when needed.

Effects of vitamin D supplementation on cardiac biomarkers: Results from the STURDY trial

Objectives

In observational studies, older adults with low serum vitamin D levels are at higher risk of cardiovascular disease (CVD), but randomized trials have failed to demonstrate reduction in CVD risk from vitamin D supplementation, possibly because the doses of vitamin D supplements tested were too low. Our objective was to determine if higher doses of vitamin D supplementation reduce high-sensitivity cardiac troponin (hs-cTnI) and N-terminal pro-b-type natriuretic peptide (NT-proBNP), markers of subclinical CVD.

Methods

The Study to Understand Fall Reduction and Vitamin D in You (STURDY) was a double-blind, randomized, response-adaptive trial that tested the effects of 4 doses of vitamin D3 supplementation (200, 1000, 2000, 4000 IU/day) on fall risk among older adults with low serum 25-hydroxyvitamin D concentrations (10-29 ng/mL). Hs-cTnI and NT-proBNP levels were measured at baseline, 3-, 12-, and 24-month follow-up visits. For this ancillary study, we used data from the original trial and compared participants by treatment group: low-dose (200 IU/day) or high-dose (1000+ IU/day). The effects of vitamin D dose on biomarkers were assessed via mixed effects tobit models.

Results

Among 688 participants (mean age of 76.5) hs-cTnI increased in both the low- and high-dose groups by 5.2 % and 7.0 %, respectively; likewise, NT-proBNP increased by 11.3 % and 9.3 %, respectively. Compared to the low-dose, high-dose vitamin D supplementation did not affect hs-cTnI (1.6 %-difference; 95 % CI: -5.3, 8.9) or NT-proBNP (-1.8 %-difference; 95 % CI: -9.3, 6.3).

Conclusions

Compared to low-dose vitamin D supplementation, doses ≥1,000 IU/ day did not affect markers of subclinical CVD in older adults with low serum vitamin D levels.

Role of nutraceuticals in viral infections as immunomodulators: A comprehensive review

Nutraceuticals are dietary supplements produced from food sources that are intended to improve health through immune system modulation or by helping to prevent and treat a variety of ailments. Their anti‐inflammatory, immunomodulatory, and antioxidant qualities are well recognized. In certain instances, they even show direct microbiological efficacy against viral infections. Because of their special capacity, they may be able to help slow the spread and effects of very infectious illnesses, such as pandemics like COVID‐19. Nutraceuticals work well against viral infections because of a number of intricate processes. Reducing the harm that infections do to the immune system is one of the main effects. Nutraceuticals have the power to stimulate and activate the immune system, improving the body's capacity to identify and eliminate infections. Additionally, they are essential in reducing oxidative damage, which can result in serious consequences and is frequently intensified during viral infections. Nutraceuticals also strengthen immunity by promoting regulatory T cell differentiation and proliferation, which is crucial for preserving immune system homeostasis and limiting hyperinflammatory reactions. They control the production of proinflammatory cytokines, which helps to avoid cytokine storms during viral infections that may seriously harm tissue. This regulation lowers the danger of hyperinflammation and enhances overall results by supporting a balanced immune response. Through a number of biochemical mechanisms, nutraceuticals can strengthen the body's defenses against viral infections. They promote a more effective and efficient immune response by regulating immune cell activities, oxidative stress reduction, and antioxidant pathway activation. Furthermore, by interacting with different cellular signaling pathways, nutraceuticals can affect the synthesis and function of important immune components. This study clarifies the molecular processes behind the immunomodulatory effects of nutraceuticals, highlighting their crucial role in both treating and preventing viral infections.

The importance of bone health for pediatric athletes: From juvenile osteochondritis dissecans to relative energy deficiency in sports

Vitamin D is pivotal for bone health, muscle strength, recovery, and overall athletic performance. This article discusses the effects of vitamin D deficiency among athletes, with a specific focus on its connection to sports-related conditions like Relative Energy Deficiency in Sport (RED-S) and Juvenile Osteochondritis Dissecans (JOCD). Additionally, we review the importance of vitamin D for muscle strength and muscle repair. Vitamin D deficiency exacerbates the risk of stress fractures in RED-S patients due to its impact on bone biology. Research points to an increased incidence of vitamin D deficiency in JOCD patients, indicating a potential connection between the condition and low vitamin D levels. Children and athletes should be screened for vitamin D deficiency as supplementation has been found to have positive outcomes. This article underscores the pivotal role of vitamin D in athletic performance. Further research is essential to elucidate how vitamin D deficiency contributes to sports-related pathologies and to establish the optimal vitamin D levels for injury prevention in athletes.

The use of vitamin D for patients with inflammatory bowel diseases

As vitamin D (VD) plays an essential role in inflammatory bowel diseases (IBD), this systematic review aimed to update the participation of this vitamin in the prevention or remission of these diseases. This review has included studies in MEDLINE-PubMed, EMBASE, and Cochrane databases. The authors have followed PRISMA (Preferred Reporting Items for a Systematic Review and Meta-analysis) guidelines. According to the inclusion and exclusion criteria, twenty-two randomized clinical trials were selected. In total, 1,209 patients were included in this systematic review: 1034 received only VD and 175 received VD in combination with calcium. The average doses of VD supplementation were from oral 400 IU daily to 10,000 IU per kilogram of body weight. Single injection of 300,000 IU of VD was also used. Several studies have shown the crucial role that VD plays in the therapeutic approach of IBD due to its effects on the immune system. It effectively decreased inflammatory cytokines such as TNF-α and IFN-γ (p<0.05) and provided a reduction in disease activity assessed through different scores such as Crohn's Disease Activity Index (CDAI) (p<0.05) and Ulcerative Colitis Disease Activity Index (UCDAI) (p<0.05). Unfortunately, the available clinical trials are not standardized for of doses and routes of administration. Existing meta-analyses are biased because they compare studies using different doses or treatments in combination with different drugs or supplements such as calcium. Even though VD has crucial effects on inflammatory processes, there is still a need for standardized studies to establish how the supplementation should be performed and the doses to be administered.

Nutrition in chronic inflammatory conditions: Bypassing the mucosal block for micronutrients

Nutritional Immunity is one of the most ancient innate immune responses, during which the body can restrict nutrients availability to pathogens and restricts their uptake by the gut mucosa (mucosal block). Though this can be a beneficial strategy during infection, it also is associated with non-communicable diseases-where the pathogen is missing; leading to increased morbidity and mortality as micronutritional uptake and distribution in the body is hindered. Here, we discuss the acute immune response in respect to nutrients, the opposing nutritional demands of regulatory and inflammatory cells and particularly focus on some nutrients linked with inflammation such as iron, vitamins A, Bs, C, and other antioxidants. We propose that while the absorption of certain micronutrients is hindered during inflammation, the dietary lymph path remains available. As such, several clinical trials investigated the role of the lymphatic system during protein absorption, following a ketogenic diet and an increased intake of antioxidants, vitamins, and minerals, in reducing inflammation and ameliorating disease.

Sex and obesity status modify the association between vitamin D and eczema among adolescents

BACKGROUND

Epidemiologic studies have reported inconsistent associations between vitamin D and eczema. This study sought to assess whether sex and obesity status could modify the association between vitamin D and eczema.

METHODS

A cross-sectional study enrolled 763 adolescents in Kuwait. 25-hydroxyvitamin D (25(OH)D) was measured in venous blood. Current eczema was defined according to clinical history and characteristic morphology and distribution.

RESULTS

In sex-stratified analysis, decreased 25(OH)D levels were associated with increased current eczema prevalence among males (adjusted odds ratio (aOR)tertile 1 vs. tertile 3: 2.14, 95% confidence intervals (CI): 1.07-4.56), but not among females (aORtertile 1 vs. tertile 3: 1.08, 95% CI: 0.71-1.66). Further stratification by obesity status showed that lower 25(OH)D levels were associated with increased current eczema prevalence among overweight/obese males (per 10-unit decrease in 25(OH)D levels: aOR: 1.70, 95% CI: 1.17-2.46). Such an association was weaker and statistically non-significant among overweight/obese females (per 10-unit decrease in 25(OH)D levels: aOR: 1.26, 95% CI: 0.93-1.70).

CONCLUSIONS

Sex and obesity status modified the association between vitamin D levels and eczema, with an inverse association observed among overweight/obese males, but not among overweight/obese females. These results suggest that preventive and clinical management strategies could vary by sex and obesity status.

IMPACT

The current study showed that sex and obesity modify the association between vitamin D and eczema among adolescents. An inverse association between vitamin D and eczema was observed among overweight/obese males, but this association was not as pronounced among overweight/obese females. Vitamin D was not associated with eczema among underweight/normal weight males and females. The identification of effect modification by sex and obesity status add to the current scientific knowledge and further highlight the complexity of the association between vitamin D and eczema. These results may promote a more individualized approach to the future prevention and clinical management of eczema.

An inflammation-responsive double-layer microneedle patch for recurrent atopic dermatitis therapy

Seeking a potent therapeutic strategy for alleviating atopic dermatitis (AD) attack and preventing its recurrence is highly desired but remains challenging in clinical practice. Here, we propose an inflammation-responsive double-layer microneedle (IDMN) patch in situ delivering VD3 for recurrent AD therapy. IDMN comprises the backing layer part and the double-layer microneedle part, in which the inner layer is gelatin methacryloyl (GelMA) loaded with VD3 while the outer layer is composed of hyaluronic acid (HA). Introduction of the HA backing layer and outer layer around the GelMA tips can not only provide sufficient mechanical strength to penetrate into hardened AD skin with minimal invasiveness, but also exert a strong moisturizing effect after being rapidly dissolved. The inner layer of GelMA is degraded by the matrix metalloproteinase (MMP) in a dose dependent manner, which is secreted according to the disease progression of AD. The responsive degradation of GelMA tips result in corresponding release of VD3 to treat AD, triggering negative feedback against GelMA degradation. The IDMN administration on AD-bearing mice reveals efficient "curing" performances (including suppress erythema, scaling and lichenification, reduce epidermal thickness, inhibit mast cells infiltration, and down-regulate inflammatory factor secretion), which are basically realized through synergistic effect of the released VD3 and the dissolved HA molecules. Importantly, the residual tips of IDMN with VD3 are retained in the skin after the first AD relief, showing promising "warning" ability to inhibit the recurrence of AD. Hence, the developed IDMN patch is expected to be one of the excellent candidates for AD therapy and other relapsing diseases in clinical fields.

Analysis of hot trends in research on the association between vitamin D and cardiovascular disease

Objective

Vitamin D deficiency is the most common nutrient deficiency. Numerous studies suggest that vitamin D is an independent risk factor for cardiovascular disease. The objective is to visualize the research hotspots and evolution trends of the correlation between vitamin D and cardiovascular disease by using multivariate statistics and social network analysis techniques and to compare adult research with that of children in this field.

Methods

(Vitamin D [MeSH Major Topic]) AND (cardiovascular disease [MeSH Major Topic]) were retrieved from the PubMed database by time period. The bibliographic items co-occurrence matrix builder (BICOMB) was adopted to extract high-frequency subject terms and establish the core subject term co-occurrence matrix. With the Netdraw function of Ucinet 6.0 software, the social network of core subject terms was completed.

Results

Before 2010, there was a slow increase in the number of research papers covering all age groups in this field (157, 54, 84, and 211 papers were published in stages 1-4, respectively). From 2010 to 2020, there were 1,423 papers retrieved, showing a significantly increased research heat. The overall development trend of the research on the association between vitamin D and cardiovascular disease in children is similar to that in all age groups. From 2010 to 2020, 122 related papers were published (while before 2009, there were only 43 papers in all), presenting a good overall development trend. The social network analysis of core subject terms showed gradually increased correlations between research hotspots, from the early studies limited on the physiological function of vitamin D in cardiovascular diseases, to the role of vitamin D in the comorbidities of various cardiovascular diseases and its value as an intervention measure. Researches on the association between vitamin D and cardiovascular disease has a good overall development trend. Study of the mechanisms and the role of vitamin D in the common co-morbidities of cardiovascular disease and its therapeutic value will be the focus of future research.

Lack of iron, zinc, and vitamins as a contributor to the etiology of atopic diseases

Micronutritional deficiencies are common in atopic children suffering from atopic dermatitis, food allergy, rhinitis, and asthma. A lack of iron, in particular, may impact immune activation with prolonged deficiencies of iron, zinc, vitamin A, and vitamin D associated with a Th2 signature, maturation of macrophages and dendritic cells (DCs), and the generation of IgE antibodies. In contrast, the sufficiency of these micronutrients establishes immune resilience, promotion of regulatory cells, and tolerance induction. As micronutritional deficiencies mimic an infection, the body's innate response is to limit access to these nutrients and also impede their dietary uptake. Here, we summarize our current understanding of the physiological function of iron, zinc, and vitamins A and D in relation to immune cells and the clinical consequences of deficiencies in these important nutrients, especially in the perinatal period. Improved dietary uptake of iron is achieved by vitamin C, vitamin A, and whey compounds, whereas zinc bioavailability improves through citrates and proteins. The addition of oil is essential for the dietary uptake of beta-carotene and vitamin D. As for vitamin D, the major source comes via sun exposure and only a small amount is consumed via diet, which should be factored into clinical nutritional studies. We summarize the prevalence of micronutritional deficiencies of iron, zinc, and vitamins in the pediatric population as well as nutritional intervention studies on atopic diseases with whole food, food components, and micronutrients. Dietary uptake via the lymphatic route seems promising and is associated with a lower atopy risk and symptom amelioration. This review provides useful information for clinical studies and concludes/emphasizes that a healthy, varied diet containing dairy products, fish, nuts, fruits, and vegetables as well as supplementing foods or supplementation with micronutrients as needed is essential to combat the atopic march.

Endotypes of Prematurity and Phenotypes of Bronchopulmonary Dysplasia: Toward Personalized Neonatology

Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is increasingly recognized as the consequence of a pathological reparative response of the developing lung to both antenatal and postnatal injury. According to this view, the pathogenesis of BPD is multifactorial and heterogeneous with different patterns of antenatal stress (endotypes) that combine with varying postnatal insults and might distinctively damage the development of airways, lung parenchyma, interstitium, lymphatic system, and pulmonary vasculature. This results in different clinical phenotypes of BPD. There is no clear consensus on which are the endotypes of prematurity but the combination of clinical information with placental and bacteriological data enables the identification of two main pathways leading to birth before 32 weeks of gestation: (1) infection/inflammation and (2) dysfunctional placentation. Regarding BPD phenotypes, the following have been proposed: parenchymal, peripheral airway, central airway, interstitial, congestive, vascular, and mixed phenotype. In line with the approach of personalized medicine, endotyping prematurity and phenotyping BPD will facilitate the design of more targeted therapeutic and prognostic approaches.

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.

Analysis of Development Trends of the Research Hotspots of Vitamin D in Children

OBJECTIVE

Using multivariate statistics and social network analysis techniques, we present a realistic and intuitive visualization of the research hotspots and development trends of vitamin D in children.

METHODS

The Medical Subject Headings (MeSH) term "vitamin D" was used to search all the publications (the study subjects were 0-18 years old) included in PubMed by time period. The subject terms for each development stage were extracted, the high-frequency subject terms were extracted using the Bibliographic Items Co-occurrence Matrix Builder (BICOMB), and a core subject term co-occurrence matrix was established. The Netdraw function of Ucinet 6.0 software was used to complete the social network drawing of the core subject term co-occurrence matrix to form a co-word network diagram composed of core subject terms.

RESULTS

Prior to 1979, there were 890 papers with 1,899 core subject terms; from 2010 to 2020, there were 3,773 papers with 12,682 core subject terms. Before 1979, the research direction of vitamin D in children focused on vitamin D in the classical regulation of calcium and phosphorus metabolism. From 1980 to 1989, studies focused on vitamin D metabolites and therapeutic drugs such as "calcitriol" and "calcifediol." From 1990 to 1999, studies focused on "calcitriol" and its association with "psoriasis," "chronic renal failure," and "dermatological drugs." From 2000 to 2009, studies focused on "vitamin D" and "vitamin D deficiency." From 2010 to 2020, studies focused on "vitamin D₃" and its association with "vitamins," "bone mineral density protectants," "asthma," "obesity," "pregnancy complications" and "fetal blood."

CONCLUSION

Since 2010, the research direction of vitamin D in children has been growing rapidly, and the overall development trend is good. Studies extend from the study of the skeletal effect of vitamin D to the study of its extraskeletal effect and the investigation of mechanisms of its association with related diseases.

Chronic respiratory diseases other than asthma in children: the COVID-19 tsunami

Coronavirus disease 2019 (COVID-19) affects all components of the respiratory system, including the neuromuscular breathing apparatus, conducting and respiratory airways, pulmonary vascular endothelium, and pulmonary blood flow. In contrast to other respiratory viruses, children have less severe symptoms when infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A minority of children experience a post-infectious inflammatory syndrome, the pathology and long-term outcomes of which are poorly understood. The reason for the lower burden of symptomatic disease in children is not yet clear, but several pathophysiological characteristics are postulated. The SARS-CoV-2 pandemic has brought distinct challenges to the care of children globally. Proper recommendations have been proposed for a range of non-asthmatic respiratory disorders in children, including primary ciliary dyskinesia and cystic fibrosis. These recommendations involve the continuation of the treatment during this period and ways to maintain stability. School closures, loss of follow-up visit attendance, and loss of other protective systems for children are the indirect outcomes of measures to mitigate the COVID-19 pandemic. Moreover, COVID-19 has reshaped the delivery of respiratory care in children, with non-urgent and elective procedures being postponed, and distancing imperatives have led to rapid scaling of telemedicine. The pandemic has seen an unprecedented reorientation in clinical trial research towards COVID-19 and a disruption in other trials worldwide, which will have long-lasting effects on medical science. In this narrative review, we sought to outline the most recent findings on the direct and indirect effects of SARS-CoV-2 pandemic on pediatric respiratory chronic diseases other than asthma, by critically revising the most recent literature on the subject.

The Relationship between Bronchiolitis Severity and Vitamin D Status

BACKGROUND/AIM

Acute bronchiolitis is mostly caused by viral agents in children under 2 years of age. The disease mostly has a mild clinical course however severe cases are not uncommon. Vitamin D is known to exert immune-regulatory functions. We aimed to examine the association between the clinical severity of acute bronchiolitis and serum vitamin D levels in infants.

MATERIALS AND METHODS

A total of 182 children with acute bronchiolitis were prospectively enrolled. The disease severity was assessed using the Modified Tal Scoring System and their vitamin D levels were evaluated.

RESULTS

Vitamin D deficiency or insufficiency was as high as 47.8% in infants with bronchiolitis. Infants with low vitamin D levels comprised a significantly larger proportion of patients with severe bronchiolitis (p = 0.002). Infants admitted to intensive care unit had significantly higher degrees of vitamin D deficiency or insufficiency (p < 0.001).

CONCLUSION

Vitamin D deficiency is closely linked with severe bronchiolitis and the need for intensive care unit admission in infants. We believe that assessment of vitamin D levels in infants prior to bronchiolitis season and appropriate supplementation may have a protective effect against severe bronchiolitis.

Vitamin D status and healthy Egyptian adolescents: Where do we stand?

Vitamin D deficiency is a worldwide public health problem. Low vitamin D and its consequences among children and adolescents could be considered as one of the most important health-related problems. This study aimed to estimate the prevalence of vitamin D deficiency in healthy Egyptian adolescents and investigate factors associated with vitamin D status.A cross-sectional study was conducted on 572 school children (270 males and 302 females) aged 14 to 18 years, who were randomly selected from high schools in one governorate in Egypt. Data were collected through a self-administered questionnaire. Vitamin D level, serum calcium, phosphorus, alkaline phosphates were measured.Vitamin D deficiency was almost present in all the studied Egyptian healthy adolescents (99%), 94.8% had vitamin D deficiency and 4.2% had vitamin D insufficiency. Girls had a higher prevalence of vitamin D deficiency than boys. There was a significant association between lack of physical activity, sun exposure, and vitamin D deficiency.Vitamin D deficiency and insufficiency are highly prevalent. In sunny countries, the special pattern of conservative clothing and the lack of outdoor physical activity might be the underlying factors for the high prevalence in females. Vitamin D supplementation seems to be mandatory to halt the problem.

Nutraceuticals in Viral Infections: An Overview of the Immunomodulating Properties

Nutraceuticals, including vitamin D, vitamin A, zinc, lactoferrin, polyphenols coenzyme Q, magnesium, and selenium, are implicated in the modulation of the complex molecular pathways involved in the immune response against viral pathogens. A common element of the activity of nutraceuticals is their ability to enhance the innate immune response against pathogens by acting on the major cellular subsets and inducing the release of pro-inflammatory cytokines and antimicrobial peptides. In some cases, this action is accompanied by a direct antimicrobial effect, as evidenced in the specific case of lactoferrin. Furthermore, nutraceuticals act through complex molecular mechanisms to minimize the damage caused by the activation of the immune system against pathogens, reducing the oxidative damage, influencing the antigen presentation, enhancing the differentiation and proliferation of regulatory T cells, driving the differentiation of lymphocyte subsets, and modulating the production of pro-inflammatory cytokines. In this paper, we review the main molecular mechanisms responsible for the immunomodulatory function of nutraceuticals, focusing on the most relevant aspects for the prevention and treatment of viral infections.

Association of serum 25-Hydroxyvitamin D with Vitamin D intervention and outdoor activity among children in North China: an observational study

Background

Living at high latitudes is one of the risk factors for vitamin D deficiency in children. However, evidence on vitamin D improvement for this pediatric population to date is limited. This study aims at evaluating the association of different vitamin D intervention methods and outdoor activity on the vitamin D status of children in North China.

Methods

In this observational study, a total of 55,925 children aged 1 month to 18 years old were recruited from pediatric outpatient departments from July 2016 to June 2017. Data on demographics, anthropometric measurements, vitamin D intervention (either prescribed by physicians or given by parents) and outdoor activity were recorded. The serum levels of 25-hydroxycholecalciferol (25(OH)D) were determined by high performance liquid chromatography tandem–mass spectrometry. Logistic regression analysis was performed to assess the association of vitamin D intervention or outdoor activity with blood vitamin D status, adjusted for age, gender, BMI for age, and seasons.

Results

The overall rate of hypovitaminosis D was 65.60%. Of the children’s outdoor activity, 35.63, 31.95, and 32.42% were below 30 min/d, 30–60 min/d and over 60 min/d, respectively. Furthermore, the proportion of therapeutic intervention, supplementation intervention and no vitamin D intervention among the children was 16.48, 32.87, and 50.65%, respectively. After adjusted for confounding factors, vitamin D intervention was associated with a lower risk of hypovitaminosis D, with OR (95% CI) of 0.191 (0.180, 0.202) in children with therapeutic doses and 0.423 (0.404, 0.443) in those with supplementation doses, compared with children without vitamin D intervention. In addition, longer outdoor time was associated with a lower risk of hypovitaminosis D [0.479 (0.456, 0.504) for 60 min/d, 0.737 (0.701, 0.776) for 30–60 min/d], independent of vitamin D intervention.

Conclusions

High prevalence of vitamin D deficiency was found in children living at high latitudes. Vitamin D intervention and outdoor activity are all negatively associated with children’s vitamin D deficiency. Routine vitamin D intervention combined with increased outdoor time might be an effective approach to prevent hypovitaminosis D among children, especially those at school, living at high latitudes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-020-02435-9.