The Effect of Vitamin D Supplementation on Glucose Metabolism in Non-Diabetic African American Adults (AVIS)

The Effect of Vitamin D Supplementation on Glucose Metabolism in Non-Diabetic African American Adults

The Effect of Vitamin D Supplementation on Glucose Metabolism in Non-Diabetic African American Adults

Type 2 diabetes is more common among African Americans than Caucasians. African Americans are also at a higher risk for lower levels of vitamin D compared to other ethnic groups. The investigators don't yet know if there is a connection between not having enough vitamin D and type 2 diabetes in African Americans. Researchers have found that the less vitamin D Caucasians had the higher the chance they would have type 2 diabetes but it is less clear if this is the case for African Americans. The investigators want to better understand how vitamin D status and diabetes risk are linked in African Americans. Also, the investigators want to see if supplementation with vitamin D will improve your blood pressure, blood sugar, & insulin. All of these are in some way related to diabetes. The investigators want to measure changes in blood sugar & blood pressure in people who do not have diabetes with the hope of learning new information to help treat those that do have diabetes. The investigators hypothesize that vitamin D status is related to diabetes risk measured by hemoglobin A1c (a test of glucose level over time), fasting glucose and insulin in non-diabetic African American adults and that body weight status may affect vitamin D status in response to vitamin D supplements compared to placebo.

Participants will be randomly assigned to receive either a 60,000 IU vitamin D3 supplement every four weeks or an inactive placebo. All investigators and the participants will be blinded to the assignment group of each participant until all testing is completed.

vitamin D status, 25-OH D, ionized calcium, fasting glucose, hemoglobin A1c, fasting insulin, glucose metabolism, HOMA index, blood lipids, type 2 diabetes, PTH, adiposity, body fat percentage, dual energy x-ray absorptiometry, pulse wave velocity, arterial stiffness, flow-mediated dilation, African American, inflammatory markers

60,000 IU vitamin D3 oral supplement provided every four weeks at weeks 0, 4, 8, and 12 in the form of one 50,000 and two 5,000 IU vitamin D3 supplements in gelcap form.

Inactive placebo tablets identical in appearance to the active comparator provided every four weeks at weeks 0,4,8,and 12.

1 gelcap of 50,000 IU vitamin D3 plus 2 gelcaps of 5,000 IU vitamin D3 each; a total of 60,000 IU vitamin D3 dosed four weeks apart at weeks 0, 4, 8, and 12 of the 16 week study.

The inactive comparator dose provided was identical in appearance to the active comparator but contained no vitamin D3

Inclusion Criteria: African American by self-report In good health Exclusion Criteria: Diagnosis of diabetes Health problems/medication affecting calcium and/or vitamin D metabolism Current use of vitamin/mineral/herbal/nutritional supplements Inability to swallow pills Pregnancy

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