Blood vitamin d levels in relation to genetic estimation of African ancestry.
BACKGROUND
African-Americans generally have lower circulating levels of 25 hydroxyvitamin D [25(OH)D] than Whites, attributed to skin pigmentation and dietary habits. Little is known about the genetic determinants of 25(OH)D levels nor whether the degree of African ancestry associates with circulating 25(OH)D.


METHODS
With the use of a panel of 276 ancestry informative genetic markers, we estimated African and European admixture for a sample of 758 African-American and non-Hispanic White Southern Community Cohort Study participants. For African-Americans, cut points of <85%, 85% to 95%, and >or=95% defined low, medium, and high African ancestry, respectively. We estimated the association between African ancestry and 25(OH)D and also explored whether vitamin D exposure (sunlight, diet) had varying effects on 25(OH)D levels dependent on ancestry level.


RESULTS
The mean serum 25(OH)D levels among Whites and among African-Americans of low, medium, and high African ancestry were 27.2, 19.5, 18.3, and 16.5 ng/mL, respectively. Serum 25(OH)D was estimated to decrease by 1.0 to 1.1 ng/mL per 10% increase in African ancestry. The effect of high vitamin D exposure from sunlight and diet was 46% lower among African-Americans with high African ancestry than among those with low/medium ancestry.


CONCLUSIONS
We found novel evidence that the level of African ancestry may play a role in clinical vitamin D status.


CONCLUSIONS
This is the first study to describe how 25(OH)D levels vary in relation to genetic estimation of African ancestry. Further study is warranted to replicate these findings and uncover the potential pathways involved.
Signorello
Lisa B
LB
1International Epidemiology Institute, Rockville, Maryland 20850, USA. Lisa@iei.us
Williams
Scott M
SM
Zheng
Wei
W
Smith
Jeffrey R
JR
Long
Jirong
J
Cai
Qiuyin
Q
Hargreaves
Margaret K
MK
Hollis
Bruce W
BW
Blot
William J
WJ
D001741:Black or African American / Q000235:genetics*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000235:genetics; D014808:Vitamin D Deficiency / Q000097:blood / Q000208:ethnology* / Q000235:genetics*
D014807:Vitamin D; C104450:25-hydroxyvitamin D