Adaptation of Inuit children to a low-calcium diet.

For Inuit children, a traditional diet contains 20 mg of elemental calcium per day, well below the recommended daily intake. To identify alterations in intestinal or renal calcium absorption, 10 healthy Inuit children (5 to 17 years of age) were given a standardized calcium load (Pak test). Five had hypercalciuria (hyperabsorptive in 3 and renal leak in 2), a frequency markedly different from that for white children (p < 0.004) and not explained by calcitropic hormone and serum calcium levels, which were normal. There was a preponderance of the bb vitamin D receptor genotype (8 of 10 subjects; p < 0.01 for comparison with white populations). Dietary calcium absorption appeared to be more efficient in these Inuit children, with an increased frequency of hypercalciuria associated with the bb genotype. This may represent a genetic adaptation to dietary constraints and may predispose to nephrolithiasis or nephrocalcinosis if standard nutritional guidelines are followed.