Seasonal Variation in Serum 25-hydroxy Vitamin D and its Association with Clinical Morbidity in Healthy Infants from Northern India.

To evaluate the seasonal change in serum 25-hydroxyvitamin D (25-OHD) level in healthy infants and to relate it to common childhood morbidities. 72 healthy breastfed infants residing in Delhi were enrolled at the end of summer and followed till the end of winter [mean (SD) duration 200 (10) d]. Serum 25-OHD was estimated at baseline and follow-up. Infants were monitored for common childhood diseases. Mean (SD) serum 25-OHD level was lower at the end of winter (20.7 (8.02) ng/mL) than summer (22.9 (8.70) ng/mL) [mean difference (95% CI) −2.14 ng/mL (−3.36, −1.06), P<0.001). The seasonal distribution of children according to vitamin D status in summer and winter — Deficient (15.3%, 12.5%), Insufficient (19.4%, 30.6%) and Sufficient (65.3%, 56.9%), respectively was comparable P=0.17). The morbidity profile remained unaffected by change in vitamin D status from summer to winter. Seasonal changes in vitamin D levels do not have significant clinical effect or effect on overall vitamin D status in apparently healthy infants from North India. This may have implications for results of population surveys for vitamin D status, irrespective of the season when they are conducted.