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Recently, researchers found that low levels of 25-hydroxyvitamin D (25[OH]D) in black Americans, compared with white Americans, reflected lower levels of vitamin D binding protein; bioavailable (free) 25(OH)D levels actually were similar in the two groups (NEJM JW Gen Med Dec 15 2013 and N Engl J Med 2013; 369:1991). However, in that study, free 25(OH)D was calculated indirectly rather than measured directly.
In this new study, researchers sought to corroborate the previous findings using a direct immunoassay; they evaluated 82 healthy postmenopausal black women and 82 white women matched for age and body-mass index. Mean serum total 25(OH)D was significantly lower in the black cohort than in the white cohort (19.5 vs. 26.9 ng/mL). However, …