Insulin sensitivity associated with Vit D in A-A April 2010

Vitamin D intake is associated with insulin sensitivity in African American, but not European American, women

Nutr Metab (Lond). 2010; 7: 28.
Published online 2010 April 14. doi: 10.1186/1743-7075-7-28.
PMCID: PMC2868016
Copyright ©2010 Alvarez et al; licensee BioMed Central Ltd.
Jessica A Alvarez,corresponding author1 Nikki C Bush,1 Suzanne S Choquette,2 Gary R Hunter,3 Betty E Darnell,2 Robert A Oster,4 and Barbara A Gower1
1Department of Nutrition Sciences, University of Alabama at Birmingham, 1625 University Blvd, Birmingham, Alabama, 35294, USA
2Center for Clinical and Translational Science, University of Alabama at Birmingham, JT 1502, 619 19th Street S, Birmingham, Alabama, 35249, USA
3Department of Human Studies, University of Alabama at Birmingham, 901 13th Street S, Birmingham, Alabama, 35294, USA
4Division of Preventative Medicine, University of Alabama at Birmingham, 1717 11th Avenue S, Birmingham, Alabama, 35205, USA
corresponding authorCorresponding author.
Jessica A Alvarez: jalvar2@uab.edu; Nikki C Bush: ncbush@uabmc.edu; Suzanne S Choquette: schoquette@uabmc.edu; Gary R Hunter: ghunter@uab.edu; Betty E Darnell: bdarnell@uab.edu; Robert A Oster: ROster@mail.dopm.uab.edu; Barbara A Gower: bgower@uab.edu
Received February 11, 2010; Accepted April 14, 2010.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background The prevalence of type 2 diabetes is higher among African Americans (AA) vs European Americans (EA), independent of obesity and other known confounders. Although the reason for this disparity is not known, it is possible that relatively low levels of vitamin D among AA may contribute, as vitamin D has been positively associated with insulin sensitivity in some studies. The objective of this study was to test the hypothesis that dietary vitamin D would be associated with a robust measure of insulin sensitivity in AA and EA women.
Methods Subjects were 115 African American (AA) and 137 European American (EA) healthy, premenopausal women. Dietary intake was determined with 4-day food records; the insulin sensitivity index (SI) with a frequently-sampled intravenous glucose tolerance test and minimal modeling; the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) with fasting insulin and glucose; and body composition with dual-energy X-ray absorptiometry.
Results Vitamin D intake was positively associated with SI (standardized ? = 0.18, P = 0.05) and inversely associated with HOMA-IR (standardized ? = -0.26, P = 0.007) in AA, and the relationships were independent of age, total body fat, energy intake, and % kcal from fat. Vitamin D intake was not significantly associated with indices of insulin sensitivity/resistance in EA (standardized ? = 0.03, P = 0.74 and standardized ? = 0.02, P = 0.85 for SI and HOMA-IR, respectively). Similar to vitamin D, dietary calcium was associated with SI and HOMA-IR among AA but not EA.
Conclusions This study provides novel findings that dietary vitamin D and calcium were independently associated with insulin sensitivity in AA, but not EA. Promotion of these nutrients in the diet may reduce health disparities in type 2 diabetes risk among AA, although longitudinal and intervention studies are required.

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