High-dose (4000 IU) Vitamin D Supplementation Does Not Increase Circulating Concentrations of Free 25-hydroxyvitamin D
(The FASEB Journal. 2013;27:859.4) Meeting Abstract
Anthony M Belenchia1, Aneesh Tosh2, Laura Hillman2 and Catherine A Peterson2
1 Nutrition and Exercise Physiology, University of Missouri, Columbia, MO
2 University of Missouri, Columbia, MO
Free/bioavailable circulating 25-hydroxyvitamin D (25OHD) makes up a small fraction of total 25OHD concentration.
We demonstrated the efficacy of a daily 4000 IU vit D dosage in raising total 25OHD concentrations of obese adolescents.
However, it remained unclear whether the increase in total 25OHD was due to increases in the free form or that bound to vit D binding protein (DBP).
The ratio of total 25OHD:DBP has been used as a proxy measure of free 25OHD. 44 patients (age=13.9; BMI =39.2) were recruited from the University of Missouri-ADOBE clinic and were randomized to receive either placebo or vit D3 (4000 IU/day) treatment for 6 months. At baseline (BL), there was no difference between the vit D and placebo group in the ratio of 25OHD:DBP (0.19 vs 0.23; P=0.28). There no difference between groups in the change from BL (0.11 vs 0.05; P=0.10). There was a significant gender difference in the ratio at BL (M=0.17 vs F=0.12; P=0.015).
Change from BL of total 25OHD was positively correlated with the change in the ratio (r=0.57; P<0.001) but not DBP(r=0.28; P=0.14).
Supplementing obese adolescents with vit D3 does not increase free circulating 25OHD.