Vitamin D deficiency in minority populations

Abstract

Objective: Black and Hispanic individuals synthesize less vitamin D per unit of sun exposure than white individuals. The relationship between UV radiation and vitamin D insufficiency in minorities has not been well explored. Design: Prospective cohort study. Setting: Using the National Health and Nutrition Examination Survey, we obtained serum vitamin D levels for non-Hispanic Whites, Hispanics and non-Hispanic Blacks aged ≥18 years from 2000-2006. We linked these data with the average monthly solar UV index by census tract and data on sun exposure, vitamin D supplementation, health and demographics. We used multivariable regression analyses to assess vitamin D deficiency (<15 ng/ml) and insufficiency (<20 ng/ml) in January (when the UV index was lowest) by race/ethnicity and geography. Subjects: Adults (n 14 319) aged ≥18 years. Results: A 1-point increase in the UV index was associated with a 0·51 ng/ml increase in vitamin D (95 % CI 0·35, 0·67 ng/ml; P<0·001). Non-Hispanic Black race and Hispanic ethnicity were associated with a 7·47 and 3·41 ng/ml decrease in vitamin D, respectively (both P<0·001). In January, an estimated 65·4 % of non-Hispanic Blacks were deficient in vitamin D, compared with 28·9 % of Hispanics and 14·0 % of non-Hispanic Whites. An estimated 84·2 % of non-Hispanic Blacks were insufficient in vitamin D v. 56·3 % of Hispanics and 34·8 % of non-Hispanic Whites. More non-Hispanic Blacks were estimated to be deficient in vitamin D in January in the highest UV index quartile than were non-Hispanic Whites in the lowest UV index quartile (60·2 % v. 25·7 %). Conclusions: Wintertime vitamin D insufficiency is pervasive among minority populations, and not uncommon among non-Hispanic Whites.