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.