Vitamin D deficiency in minority populations

Glen B Taksler, David M Cutler, Edward Giovannucci, Nancy L Keating
2014 Public Health Nutrition  
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
more » ... olar 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. Keywords Vitamins Vitamin D Disparities Race Survival The Institute of Medicine estimates that 54 % of non-Hispanic Blacks have very low levels of vitamin D (25-hydroxycholecalifierol (25(OH)D 3 ) < 16 ng/ml), v. 27 % of Mexican Americans and 11 % of non-Hispanic Whites (1,2) . A growing literature (1-3) suggests that vitamin D may be associated with reduced mortality (overall (4) and hospital-associated (5) ), incidence of cancer (6-13) , CVD (14, 15) , diabetes (16) , fractures (17, 18) and ageing-related functional limitations (19) , although some studies find an unclear relationship (20, 21) or a harmful association with disease (22) . Randomized controlled trials are underway to examine the potential role of vitamin D in the prevention of multiple diseases, including cancer, CVD and diabetes (20, 23) . There are known racial and seasonal variations in vitamin D. Black individuals synthesize less vitamin D per unit of sun exposure than white individuals, because darker complexion acts as a natural sunscreen (24, 25) . The majority of vitamin D is estimated to derive from sunshine for most people (26) , with the liver converting cholecalciferol into 25(OH)D 3 , the form of vitamin D typically measured in blood serum. 25(OH)D 3 has a reported half-life of 15 d (27) , and therefore decreases from summer (when solar radiation is highest) to winter (28) . Observational studies suggest higher cancer mortality rates for patients diagnosed in winter (29, 30) , at northern latitudes (31, 32) and in areas with less UV radiation from sunshine (33, 34) , although genetics may contribute (35) . Additionally, previous research suggests that racial differences in the synthesis of vitamin D from sunshine are largest in January (36) . However, studies have not adequately considered the association between the UV index and racial differences in vitamin D deficiency or insufficiency. We assessed the extent of vitamin D insufficiency by race/ethnicity and geography (as categorized by the
doi:10.1017/s1368980014000457 pmid:25112179 fatcat:gg4cta6ivjanhojfurbat4wfmy