Observational data on vitamin D and eczema, also called atopic eczema, is mixed. Some studies show low 25(OH)D levels are associated with less eczema and some studies show the opposite.
Recently Professor Christian Apfelbacher’s research lab at the University of Regensburg in Germany found that in children and adolescents, higher vitamin D levels were associated with a higher prevalence of eczema in their study population in Germany.
Certainly, studies are mixed, some showing what Professor Apfelbacher’s group found and some showing the opposite. A recent metanalysis found vitamin D improved eczema.
Furthermore, there has been a randomized controlled trial showing some potential benefit in supplementing with vitamin D in eczema.
Hata TR, Audish D, Kotol P, et al. A randomized controlled double-blind investigation of the effects of vitamin D dietary supplementation in subjects with atopic dermatitis. J Eur Acad Dermatol Venereol. 2013; [Epub ahead of print]
However, this present German study used the largest sample size yet for an observational study, collecting data from 9838 children and adolescents. They did a cross sectional analysis, finding eczema was more prevalent in those with higher vitamin D levels. Weighted eczema prevalence increased with 25(OH)D category, yielding a prevalence of 10.5% in the children with the lowest levels, 14.2% in the second quartile, 14.6% in the third quartile, and 14.8%, in the quartile of children with the highest levels (P < 0.0001). As you can see, there was not much difference in eczema prevalence between the 2nd, 3rd, and 4th quartile. However, perplexingly, children with the very lowest levels, (< 8 ng/ml) had significantly less eczema.
What explains these mixed results?
- Lower levels may protect against eczema.
- There is some kind of confounding factor where children that don’t get outside much don’t have eczema, for whatever reason.
- Natural levels may protect against eczema.
- As the authors point out, some have hypothesized a U shaped curve for eczema, with those with high levels and low levels being protected against asthma. The authors did not break down their fourth quartile to see if children with levels above 40 ng/ml had less eczema.
- As eczema improves dramatically in the summer, it may be something else in sunshine, besides vitamin D, that helps eczema.
I used to have eczema every winter. I don’t remember if my eczema got better or worse when I first started supplementing on low dose of vitamin D (which I did for a year or so until I learned more about it). However, now my 25(OH)D is around 60 ng/ml and has been for many years and my eczema has disappeared.
I wonder if readers have noted that their eczema got better or worse with higher vitamin D supplementation. Please share your experiences.