African-Americans have higher rates of cardiovascular disease morbidity and mortality, as well as vitamin D deficiency. Multiple observational studies have demonstrated an increased risk of vitamin D deficiency in African Americans with type 2 diabetes and correlation between cardiovascular disease and vitamin D levels; however, there is a lack of interventional trials exploring this connection. The objective of this proposal is to address the hypothesis that treatment of vitamin D deficiency in African Americans with type 2 diabetes will improve subclinical markers of cardiovascular disease.

This study will be a double blinded, randomized controlled trial of vitamin D3 supplementation, 4,000 international units per day versus 600 international units per day, for one year to determine the effects on markers of subclinical cardiovascular disease in African Americans with type 2 diabetes and vitamin D deficiency. Outcome assessment will focus on changes in carotid intima-medial thickness (CIMT - ultrasound of the thickness of blood vessels in the neck), as well as markers of systemic inflammation.

Inclusion Criteria:

• African Americans of both genders
• Age 50-70 years
• Type 2 diabetes (A1C < 9.0%), on stable therapy with oral medications, insulin, or a combination
• 25(OH)D level < 20 ng/ml
• BP < 140/90 mmHg; LDL < 140 mg/dl

Exclusion Criteria:

• Pregnancy
• Cardiovascular disease
• Stage 3 or worse chronic kidney disease
• High urine or serum calcium or history of recurrent kidney stones
• Unstable medical conditions or major systemic diseases such as malignancy