In infants with sufficient vitamin D status at birth, vitamin D supplementation does not impact immune development.

Abstract

Low vitamin D levels have been associated with allergic diseases. Vitamin D has potent immunomodulatory properties, but the mechanisms remain unclear. We have investigated the effect of oral vitamin D supplementation on circulating immune cell phenotypes in infants. A double-blinded randomised controlled trial was conducted to investigate the effect of oral vitamin D supplementation (400IU/d) on eczema and immune development. A subset of 78 infants was included in this analysis. Phenotypic analysis of immune cell subsets was performed using flow cytometry. Vitamin D supplementation resulted in median 25(OH)D levels of 80.5 vs 59.5nmol/L in the placebo group at 3months of age (P=.002) and 87.5 vs 77nmol/L at 6months of age (P=.08). We observed significant changes in immune cell composition from birth (cord blood) to 6months of age. Vitamin D supplementation did not impact these changes, nor did immune cell composition correlate with plasma 25(OH)D levels. Through exploratory analysis, we identified possible associations with eczema development and increased abundance of naïve CD4- T cells at birth, as well as associations with basophils, iNKT and central memory CD4+ T cells, and altered expression patterns of IgE receptor (FcεR1) on monocytes and dendritic cells with eczema at 6months. Vitamin D supplementation in infants who were vitamin D sufficient at birth did not affect developmental changes in immune cells during the first 6months of life. However, immune cell profiles at birth and at 6months of age were associated with early life eczema.