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 µg 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 µg/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 µg 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 µg/d for 4 wk did not improve fractional Ca absorption, net Ca absorption, or Ca retention.
Author disclosures: C. M. Weaver is on the Advisory Boards of Wyeth Global Nutrition and Pharmavite. C. Y. Park, K. M. Hill, A. E. Elble, B. R. Martin, L. A. DiMeglio, M. Peacock, and G. P. McCabe, no conflicts of interest.
Abstract presented at Experimental Biology 2009, New Orleans, LA [Park, CY, Hill, KM, Elble AE, Martin BR, Peacock M, McCabe GP, Weaver CM. FASEB J. 2009;23:112.]