Cardiovascular disease (CVD) is a leading cause of sickness and death. Studies have shown higher risk of CVD in African Americans (AA). The reasons for this higher risk are not well understood. Vitamin D may play a role in blood vessel health and reduce risk of CVD. Darker skin absorbs light from the sun, and reduces the amount of vitamin D made by the body. We think that lower vitamin D in AA may lead to reduced blood vessel health and increased risk of CVD. We also think that risk of low vitamin D levels in those with increasingly darker skin pigmentation may predispose them to vascular dysfunction over time. This study will look at differences in nitric oxide that helps blood vessels relax across individuals with a wide range of skin pigmentation. We will also look at “oxidant stress,” which can reduce nitric oxide. In this study, we will examine the function of blood vessels in the skin. The blood vessels in the skin are a model for blood vessels in other organs in the body. We will also look at the function of other, larger blood vessels in the body. This research is being done to find out why blood vessel function is reduced in young AA adults who are healthy, and to determine if reduced vitamin D in those with darker skin may cause reduced blood vessel function. The research is also being done to find out if vitamin D will improve blood vessel function. Approximately 30 people will take part in this study at the Noll Lab.

For this study, you will be asked to take vitamin D tablets every day for four weeks. You will be asked to come into the lab for testing on two days; once before vitamin D treatment and once after. During each testing visit we will perform tests of blood vessel function.

430