Abstract
BackgroundA critical need exists to better understand the physiological sequel of vitamin D supplementation in obese individuals and African Americans. The aim was to comprehensively evaluate dose- and time-responses of a panel of vitamin D biomarkers to vitamin D supplements in this population.MethodsWe conducted a 16-week randomized, double-blinded, and placebo-controlled clinical trial. Seventy overweight/obese African Americans (age 13–45 years, 84 % females) with 25-hydroxyvitamin D [25(OH)D] concentrations ≤20 ng/mL were randomly assigned to receive a supervised monthly oral vitamin D3 of 18,000 IU (~600 IU/day, n = 17), 60,000 IU (~2000 IU/day, n = 18), 120,000 IU (~4000 IU/day, n = 18), or placebo (n = 17).ResultsThere were significant dose- and time-responses of circulating 25(OH)D, 1,25-dihydroxyvitamin D [1,25(OH)2D], and intact parathyroid hormone (iPTH), but not fibroblast growth factor-23 (FGF-23), phosphorus and urine calcium to the vitamin D supplements. The mean 25(OH)D concentrations in the 2000 IU and 4000 IU groups reached ≥30 ng/mL as early as 8-weeks and remained at similar level at 16-weeks. The increase of 25(OH)D was significantly higher in the 4000 IU group than all the other groups at 8-weeks. The increase of 1,25(OH)2D was significantly higher in the 2000 IU and 4000 IU groups than the placebo at 8-weeks. Only the 4000 IU compared to the placebo significantly reduced iPTH at 8- and 16-weeks.ConclusionsOur RCT, for the first time, comprehensively evaluated time- and dose- responses of vitamin D supplementation in overweight/obese African Americans with suboptimal vitamin D status. Circulating 25(OH)D, 1,25(OH)2D, and iPTH, but not FGF-23, phosphorus and urine calcium, respond to vitamin D supplementation in a time- and dose–response manner. By monthly dosing, 2000 IU appears to be sufficient in achieving a 25(OH)D level of 30 ng/mL in this population. However, importantly, 4000 IU, rather than 2000 IU, seems to suppress iPTH. If replicated, these data might be informative in optimizing vitamin D status and providing individualized dosing recommendation in overweight/obese African Americans.Trial registrationClinicalTrials.gov number: NCT01583621, Registered on April 3, 2012.
Highlights
A critical need exists to better understand the physiological sequel of vitamin D supplementation in obese individuals and African Americans
In another study of younger (25–45 years) African American (n = 39) and Caucasian (n = 90) females living in Nebraska, 400–2400 IU/day vitamin D plus calcium supplements resulted in a dose and time-responsive increase in serum 25(OH)D concentrations
Gender distribution, body mass index (BMI), serum 25(OH)D, plasma intact parathyroid hormone (iPTH), 1,25(OH)2D, Fibroblast growth factor-23 (FGF23) and phosphorus did not differ among the groups at baseline
Summary
A critical need exists to better understand the physiological sequel of vitamin D supplementation in obese individuals and African Americans. In an earlier placebo-controlled RCT, 208 healthy postmenopausal African American females residing in New York (~40.8°N latitude) were given a daily dose of 800 IU vitamin D plus calcium for two years [11]. Gallagher and colleagues [12] supplemented 110 postmenopausal African American females with suboptimal vitamin D status living in Nebraska (~41°N latitude) and Indiana (~40°N latitude) with daily doses between 400–4800 IU vitamin D plus calcium for 12 months. In another study of younger (25–45 years) African American (n = 39) and Caucasian (n = 90) females living in Nebraska, 400–2400 IU/day vitamin D plus calcium supplements resulted in a dose and time-responsive increase in serum 25(OH)D concentrations. The authors estimated a daily dose between 800–1600 IU in young African American females, to achieve a level of serum 25(OH)D at 20 ng/mL [12]. Dose-responsive RCTs with exclusive vitamin D supplementation are lacking in young African Americans, in overweight/ obese individuals
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
