Role of Calcium Deficiency in Development of Nutritional Rickets in Indian Children: A Case Control Study

Context: Nutritional rickets is usually attributed to vitamin D deficiency. Studies from some tropical countries have postulated low dietary intake of calcium as the cause of nutritional rickets. Both vitamin D and dietary calcium deficiency are highly prevalent in India. Information on their relative contribution in the development of rickets in Indian children is limited. Objective: The aim was to study the role of calcium and vitamin D deficiency in causation of nutritional rickets in young Indian children. Design and Methods: In a case-control study, 67 children with nutritional rickets and 68 age- and sex-matched healthy controls were compared for demographic factors, nutritional status, sun exposure (UV score), dietary calcium and phytate intake (for subjects not breast-fed at presentation), and biochemical parameters [serum calcium, inorganic phosphate, alkaline phosphatase, 25-hydroxyvitamin D (25OHD), and PTH]. Results: Mean intake of calcium (204 +/- 129 vs. 453 +/- 234 mg/d; P < 0.001) and proportion of calcium from dairy sources (41.7 vs. 88.6%; P < 0.001) were significantly lower in cases vs. controls. The dietary intake of phytate was also significantly higher in cases (P = 0.01). Median serum 25OHD level (interquartile range) in both cases and controls was in the range of deficiency [13.7 (10; 17.9) and 19.4 (12.3; 24.6) ng/ml, respectively]. There was no significant difference in the serum 25OHD level (P = 0.08) or sun exposure as measured by UV score ( P = 0.39) among the cases and controls. In cases with rickets, significant negative correlations were seen between dietary calcium intake and radiological score (r = -0.28; P = 0.03) and PTH (r = -0.26; P = 0.02). No correlation was found between serum 25OHD level and radiological score or biochemical parameters of rickets. Conclusions: Rickets develops when low dietary calcium intake coexists with a low or borderline vitamin D nutrition status. (J Clin Endocrinol Metab 97: 3461-3466, 2012)