Association of Degree of European Genetic Ancestry With Serum Vitamin D Levels in African Americans.

Circulating levels of vitamin D are generally lower in African Americans than in US whites, and 1 prior analysis carried out in a small number of African Americans suggested that, within this population, vitamin D levels may be related to the degree of genetic admixture. We assessed the association between percentage of European ancestry and serum vitamin D level (assessed in 2013-2015) among 2,183 African-American women from the Black Women's Health Study whose DNA had been genotyped for ancestry-informative markers. ADMIXMAP software was used to estimate the percentage of European ancestry versus African ancestry in each individual. In linear regression analyses with adjustment for genotype batch, age, body mass index, supplemental vitamin D use, ultraviolet B radiation flux in the participant's state of residence, and season of blood draw, each 10% increase in European ancestry was associated with a 0.67-ng/mL increase in serum vitamin D concentration (95% confidence interval: 0.17, 1.17). The association was statistically significant only among women who were not taking vitamin D supplements (for each 10% increase in European ancestry, β = 0.86, 95% confidence interval: 0.14, 1.57). Among African Americans, use of vitamin D supplements may help to reduce vitamin D deficiency associated with genetic ancestry.