1. Vitamin D Status of Black and White Americans and Changes in Vitamin D Metabolites after Varied Doses of Vitamin D Supplementation
Naweed Alzaman1, Bess Dawson-Hughes1,2, Jason Nelson3, David D’Alessio4, Anastassios G. Pittas1
1 Division of Endocrinology, Diabetes and Metabolism, 2Bone Metabolism Laboratory, Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging,
3 Predictive Analytics and Comparative Effectiveness (PACE) Center Tufts Medical Center Boston, MA
4 Division of Endocrinology, Duke University Medical Center, Durham, North Carolina
Background
Vitamin D metabolites at baseline according to race
Relationship between total and directly measured free 25-hydroxyvitamin D (25OHD) in ng/mL according to race
Controversy exists over the disparate circulating 25-hydroxyvitaminD (25OHD) concentration between black and white Americans. Our objective was
to determine whether there are differences in total and directly measured free 25OHD between black and white American adults
determine the effect of daily supplementation with cholecalciferol on directly measured free 25OHD between black and white Americans.
Blacks and whites: Pearson r=0.82; p<0.001
Blacks: Pearson r=0.87; p<0.001
Whites: Pearson r=0.77; p<0.001
Overall (N=208)
Unadjusted median (inter-quartile range)
Adjusted median (95% confidence interval)2
Black
(N=57)
White
(N=151)
P value1
P value3
Total 25OHD, ng/mL
26.0 ( )
22.0 ( )
26.8 ( )
0.011
20.3 ( )
26.7 ( )
0.026
Total 25OHD < 20 ng/mL, % (No.)
26.0 (54)
45.6 (26)
18.5 (28)
<0.001 -
Directly measured free 25OHD, pg/mL
5.45 ( )
4.88 ( )
5.73 ( )
0.006
4.54 ( )
5.66 ( )
0.044
Measured free 25OHD as percent of total 25OHD
0.022 ( )
0.023 ( )
0.021 ( )
0.115
0.024 ( )
0.022 ( )
0.211
Calculated free 25OHD (based on monoclonal assay for vitamin D binding protein), pg/mL4
9.17 ( )
11.89 ( )
8.84 ( )
11.83 ( )
8.88 ( )
0.080
Calculated free 25OHD (based on polyclonal assay for vitamin D binding protein), pg/mL4
9.14 ( )
7.75 ( )
9.52 ( )
0.008
8.32 ( )
9.41 ( )
0.320
Vitamin D binding protein - monoclonal assay, mg/L5
194 ( )
105 (82-154)
212 ( )
109 (90-129)
220 ( )
Vitamin D binding protein - polyclonal assay, mg/L5
199 ( )
195 ( )
199 ( )
0.796
192 ( )
201 ( )
0.540
Parathyroid hormone, pg/mL
54.9 ( )
60.9 ( )
52.5 ( )
0.065
58.8 ( )
51.2 ( )
0.308
Design
Results
Change in total (upper panels) and directly measured free (lower panels) 25OHD after
supplementation by dose (2000 IU/day, left panels; 4000 IU/day, right panels) and race (Black or White)
Cross-sectional and longitudinal analyses
Two double-blind, placebo-controlled randomized trials at two academic medical centers in the United States.
208 people with pre-diabetes or well-controlled diabetes
Mean age of 59.1 years and BMI of 31.6 kg/m2 9 were randomized to receive daily cholecalciferol supplementation at two doses (2000 or 4000 international units) or matching placebo for 16 weeks.
We measured serum total 25OHD, vitamin D binding protein by two different immunoassays (using monoclonal or polyclonal antibodies), parathyroid hormone (PTH) and albumin.
Free 25OHD level was directly measured and calculated.
Blacks had lower total 25OHD concentration than whites (adjusted median [95%CI], 20.3 ng/mL [16.2,24.5] vs ng/mL [25.2, 28.1] respectively; p=0.026).
Directly measured free 25OHD concentration was lower in blacks than whites (adjusted median 4.5 pg/mL [3.7, 5.4] vs. 5.7 pg/mL [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 when measured by the polyclonal antibody immunoassay.
Supplementation with cholecalciferol increased total and measured free 25OHD concentrations proportionally to the dose and without difference between races.