Seasonal Changes in Vitamin D Levels in Women in Reproductive Age

Global and Indian studies have shown that there are substantial seasonal variations in vitamin (vit) D levels. A study to assess seasonal changes in vit D levels in women in reproductive age was undertaken in urban low middle income families in Delhi. Paired blood samples were collected in spring and autumn in Group 1; and in summer and winter in Group 2. Vit D3 estimation was done using electro-chemo-luminescence immunoassay. Mean vit D levels were highest in autumn and lowest in summer. The differences in mean vit D levels between spring and autumn, summer and winter, spring and summer, summer and autumn, autumn and winter were statistically significant. Prevalence of vit D deficiency (vit D levels below 20 ng/ml) were higher in spring and summer as compared to autumn and winter; these differences were statistically significant. Nearly half of the women had vit D level ≥ 20 ng/ml in both the paired samples (spring and autumn as well as summer and winter). About 14% had vit D levels <20 ng/ml in both paired samples (spring and autumn as well as summer and winter). About one third of women with paired samples were deficient in one season but not in the other season. Pregnant women received calcium and vit D supplementation from early second trimester till delivery. It is essential to take into account the seasonal variation in vit D levels, while undertaking impact assessment of calcium and vit D supplementation in pregnancy on vit D levels prior to and after the supplementation.