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Vitamin D blood levels vary with estimated amount of African Ancestry – Sept 2010

Blood Vitamin D Levels in Relation to Genetic Estimation of African Ancestry
Cancer Epidemiology, Biomarkers & Prevention September 2010, 19 (9)
1. Lisa B. Signorello1,2,; 2. Scott M. Williams3,; 3. Wei Zheng2,; 4. Jeffrey R. Smith4,; 5. Jirong Long2,; 6. Qiuyin Cai2,; 7. Margaret K. Hargreaves5,; 8. Bruce W. Hollis6 and; 9. William J. Blot1,2
Authors' Affiliations:1International Epidemiology Institute, Rockville, Maryland; 2Division of Epidemiology, Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University, and the Vanderbilt-Ingram Cancer Center; 3Division of Human Genomics, Department of Molecular Physiology and Biophysics, Vanderbilt University; 4Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center; 5Department of Internal Medicine, Meharry Medical College, Nashville, Tennessee; and 6Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina
1. Corresponding Author:
Lisa B. Signorello, International Epidemiology Institute, Suite 550, 1455 Research Boulevard, Rockville, MD 20850. Phone: 301-279-4272; Fax: 301-424-1053. E-mail: Lisa at iei.us

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 ?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.

Impact: 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. Cancer Epidemiol Biomarkers Prev; 19(9); 2325–31. ©2010 AACR.

< 85% 85%-95% > 95%
26 ng 18 ng 16 ng

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See also VitaminDWiki