Daily Supplementation with 25 μg Cholecalciferol Does Not Increase Calcium Absorption or Skeletal Retention in Adolescent Girls with Low Serum 25-Hydroxyvitamin D

In healthy adolescents cross sectional studies show either no or negative relationships between serum 25-hydroxyvitamin D [25(OH)D] and calcium (Ca) absorption Using a 2-period metabolic balance study the effect of vitamin D supplementation on Ca absorption and retention in adolescent girls was investigated Eleven girls aged 12-14 y with a mean entry serum 25(OH)D of 35 1 nmol/L consumed a controlled intake (providing 5;kg vitamin D and 1117 mg Ca/d) for two 3-wk metabolic balance periods separated by a 1-wk washout period Sunlight exposure was minimized by sunscreen with a sun protection factor >= 15 After the first metabolic balance period participants received 25 mu g/d cholecalciferol supplementation for 4 wk Fractional Ca absorption was measured in each metabolic balance period using a stable Ca isotope method All urine and fecal samples were collected and analyzed to measure net Ca absorption and Ca retention Paired t tests and correlations were used to analyze the data Daily supplementation with 25 mu g vitamin D resulted in a mean increase in serum 25(OH)D of 13 3 nmol/L (P < 0 01) but a decrease in fractional Ca absorption of 8 3% (P < 0 05) and no significant change in fasting serum 1 25-dihydroxyvitamin D parathyroid hormone, net Ca absorption or Ca skeletal retention In pubertal girls with vitamin D status considered insufficient in adults vitamin D supplementation of 25 mu g/d for 4 wk did not improve fractional Ca absorption net Ca absorption or Ca retention J Nutr 140 2139-2144 2010