To study plasma 25-hydroxyvitamin D (25(OH)D) status of children in Kerala, southern India, and its relationship with sociodemographic variables.

Cross-sectional observational study.

Tertiary government hospital.

Children (n 296) with trivial acute illness were enrolled. Sun exposure and Ca and vitamin D intakes (7 d dietary recall) were documented. Serum Ca, P, alkaline phosphatase, plasma 25(OH)D and parathyroid hormone (PTH) were measured.

Prevalence of vitamin D deficiency (plasma 25(OH)D <30 nmol/l) was 11·1% (median, interquartile range (IQR): 52·6, 38·4–65·6 nmol/l). Children who ate fish daily had significantly higher plasma 25(OH)D than those who did not (median, IQR: 52·5, 40·8–68·9 v. 49·1, 36·2–60·7 nmol/l; P = 0·02). Those investigated in the months of March–May showed highest 25(OH)D v. those enrolled during other times (median, IQR: 58·7, 45·6–81·4 v. 45·5, 35·6–57·4 nmol/l; P <0·001). Plasma 25(OH)D correlated positively with serum P (r = 0·24, P <0·001) and Ca intake (r = 0·16, P 0·03), negatively with age (r = −0·13, P 0·03) and PTH (r = −0·22, P <0·001.). On linear regression, summer season (March–May), lower age, daily fish intake and higher Ca intake were independently associated with plasma 25(OH)D.

Prevalence of vitamin D deficiency is low in Kerala. The natural fish diet of coastal Kerala and the latitude may be protective. Public health policy in India should take account of this geographical diversity.