Vitamin D concentration in newborn cord blood is correlated with maternal intake of supplemental vitamin D, and lower levels are associated with increased risk of the infant developing eczema
- 1Depatment of Internal Medicine, Henry Ford Hospital, Detroit, Michigan, USA
- 2Depatment of Public Health Sciences, Henry Ford Hospital, Detroit, Michigan, USA
- Correspondence to: Edward M Zoratti
Depatment of Internal Medicine, Henry Ford Hospital, 4B One Ford Place, Detroit, MI 48202, USA;
Commentary on: 
Implications for practice and research
Conflicting evidence regarding the role of vitamin D in allergic disease highlights the need for well-designed clinical trials.
This study and others suggest that early life vitamin D insufficiency may increase eczema risk.
Supplementation during pregnancy may increase cord blood vitamin D and subsequent early life exposure.
The human fetus is dependent on maternal vitamin D status during gestation. Vitamin D deficiency rates in pregnant women have been reported as being more than 70% in some clinical practices.1 Our understanding of prenatal vitamin D's role in modulating immune function and the risk of developing allergic disorders is still in its infancy. Jones and colleagues recently examined whether vitamin D3 levels in cord blood were associated with the risk of eczema, allergic sensitisation or food allergy in the first year of life. This study also analysed the impact of maternal dietary and supplemental vitamin D intake on cord blood vitamin D.
Vitamin D (25(OH)D3) was measured in stored cord blood samples from a high-risk cohort of children with at least one allergic parent. Food frequency questionnaires were used to assign vitamin D intake during pregnancy. The authors investigated outcomes at 1 year of age, including whether the child had a doctor's diagnosis of eczema, IgE-mediated food allergy (based on symptom report and skin prick test results) or had positive skin tests to a panel of eight allergens. Statistical models were used to assess the associations between cord blood vitamin D levels and each outcome. The analyses were adjusted for season of birth, infant gender, pets at home, maternal age and maternal ethnicity. The 231 children were from non-smoking mothers with uncomplicated term pregnancies.
Higher cord blood vitamin D levels were associated with lower eczema occurrence by the age of one, but not associated with eczema severity, allergic sensitisation or IgE-mediated food allergy. For every 10 nmol/l increase in vitamin D, the odds of having eczema was decreased by 13.3% (OR 0.87, 95% CI 0.77% to 0.98%, p=0.02).
Maternal supplemental vitamin D intake during pregnancy was associated with higher cord blood vitamin D levels. Maternal dietary vitamin D intake was not correlated with vitamin D levels. Cord blood vitamin D levels were also higher during the summer months suggesting that sunlight exposure was an important determinant.
Understanding vitamin D's role in modulating immune function and the risk of developing allergic disorders is an area worthy of thorough scientific investigation. There are clear mechanisms by which vitamin D can affect allergic disease risk and a recent review summarises the ways that vitamin D affects immune development, both in utero and postnatally.2 Vitamin D can influence the immune system via vitamin D receptors found in most cells of the immune system. Insufficient vitamin D can affect both the function and balance of these adaptive immune cells, and result in an elevated risk for allergic disorders.
The present study provides important new evidence that vitamin D insufficiency may contribute to the risk of eczema, and that supplementation during pregnancy is potentially effective in increasing cord blood vitamin D levels. Several issues should be considered in placing the results in context and to highlight why further studies are needed. A single cord blood measurement of vitamin D was used in the analyses without the knowledge of the child's subsequent levels of circulating vitamin D during their first year of life. These levels could be influenced by sunlight, dietary intake including fortified formulas, solid foods and supplements which are frequently recommended for breastfed children. Additionally, the authors present OR (in contrast to relative risk) that sometimes overestimate true risk; thus, the association of cord blood vitamin D and eczema may have been overestimated. Studies specifically designed to address these limitations can provide more precise estimates of a potentially causative role and the degree of risk for allergic disease that may be attributable to vitamin D. These studies should have prenatal as well as multiple early life measurements of vitamin D to provide this information. Readily available methods to correct vitamin D insufficiency, including supplementation and light exposure, can be utilised to design intervention trials if a causative role in allergic disease is proven.
Competing interests Both EMZ and GW have received research funds from the US NIH to investigate the effects of Vitamin D on allergic disease.