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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #329775
Title: Vitamin D status of black and white Americans and changes in vitamin D metabolites after varied doses of vitamin D supplementation

Author
item ALZAMAN, NAWEED - Taibah University
item DAWSON-HUGHES, BESS - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item NELSON, JASON - Tufts - New England Medical Center
item D'ALESSIO, DAVID - Duke University Medical Center
item PITTAS, ANASTASSIOS - Tufts - New England Medical Center

Submitted to: Annals of Internal Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2016
Publication Date: 5/18/2016
Citation: Alzaman, N., Dawson-Hughes, B., Nelson, J., D'Alessio, D., Pittas, A.G. 2016. Vitamin D status of black and white Americans and changes in vitamin D metabolites after varied doses of vitamin D supplementation. Annals Of Internal Medicine. 104:205-214. https://doi.org/10.3945/ajcn.115.129478.

Interpretive Summary: Controversy exists over the cause of disparate circulating 25-hydroxyvitaminD (25OHD) between black and white Americans. The objective of this study was to determine whether there are differences in total and directly measured free 25OHD between black and white American adults and to assess the degree to which daily supplementation with cholecalciferol changes these levels. We analyzed data using cross-sectional and longitudinal methods from two double-blind, placebo-controlled randomized trials held at 2 academic medical centers in the United States. 208 people with pre-diabetes or well controlled diabetes with mean age of 59.1 years and BMI of 31.6 participated. They were asked to take daily cholecalciferol supplementation at two doses (2000 or 4000 international units) or a matching placebo for 16 weeks. Total vitamin D in the blood, vitamin D binding protein concentration, parathyroid hormone and albumin were measured, and free 25OHD level was calculated. Free circulating 25OHD in the blood was also measured directly. Blacks had lower total vitamin D concentration than whites, and a higher proportion of blacks had total 25OHD below 20 ng/mL. Directly measured free 25OHD concentration was lower in blacks than whites and was strongly correlated with total 25OHD without an effect of race. Supplementation with cholecalciferol increased total and measured free 25OHD concentrations proportionally to the dose and without difference between races. The study results are limited by the short duration of supplementation and the fact that all participants were overweight. The relationship between free and total 25OHD does not vary systematically by race. Therefore, the clinical assessment of vitamin D status in blacks and whites should follow a single standard.

Technical Abstract: Background. Controversy exists over the cause of disparate circulating 25-hydroxyvitaminD (25OHD) between black and white Americans. Objective: To determine whether there are differences in total and directly measured free 25OHD between black and white American adults and to assess the degree to which daily supplementation with cholecalciferol changes these levels. Design: Cross-sectional and longitudinal analyses using data from two double-blind, placebo-controlled randomized trials. Setting: 2 academic medical centers in the United States. Participants: 208 people with pre-diabetes or well-controlled diabetes with mean age of 59.1 years and BMI of 31.6 kg/m2. Interventions: Daily cholecalciferol supplementation at two doses (2000 or 4000 international units) or matching placebo for 16 weeks. Measurements: Serum total 25OHD, vitamin D binding protein by two different immunoassays (using monoclonal or polyclonal antibodies), parathyroid hormone (PTH) and albumin were measured, and free 25OHD level was calculated. Serum free 25OHD was also measured directly. Results: Blacks had lower total 25OHD concentration than whites (adjusted median [95%CI], 20.3 [16.2-24.5] vs. 26.7 [25.2-28.1] respectively; p=0.026) and a higher proportion of blacks had total 25OHD < 20 ng/mL (46 vs. 19 percent respectively, p<0.001). Directly measured free 25OHD concentration was lower in blacks than whites (4.5 [3.7-5.4] vs. 5.7 [5.4-5.9] respectively; p=0.044) and was strongly correlated with total 25OHD without an effect of race. Vitamin D binding protein was lower in blacks when measured by the monoclonal but not by the polyclonal antibody immunoassay. Supplementation with cholecalciferol increased total and measured free 25OHD concentrations proportionally to the dose and without difference between races. Limitations: Duration of supplementation was limited and all participants were overweight. Conclusions: The relationship between free and total 25OHD does not vary systematically by race. Therefore, the clinical assessment of vitamin D status in blacks and whites should follow a single standard.