Vitamin D Augmentation of Tekturna (Aliskiren) in Hypertension

The overarching hypothesis is that African Americans with hypertension have an overactive RAS (Renin Angiotensin System) in the body that is responsible for internally regulating blood pressure. Many blood pressure medications change regulation of the RAS system in order to keep blood pressure down. The purpose of this research study is to determine whether or not African American adults with hypertension have an overactive RAS system due to Vitamin D deficiency, resulting in the inability of the medication Tekturna to lower blood pressure. In this study, all participants will receive 300mg of Tekturna per day. Additionally half of the participants will randomly be selected to receive either 50,000 IU of Vitamin D (in its cholecalciferol form) orally once every other week or a vitamin D placebo once every other week. There will be 4 study visits over 18 weeks and follow up phone calls every two weeks for the duration of the study. Specific Aims: To demonstrate in African American Hypertensives consuming a calcium replete diet that Tekturna + Vitamin D will lower blood pressure more than Tekturna + placebo. To demonstrate in African American hypertensives consuming a calcium replete diet that albuminuria will be lowered more with Tekturna + Vitamin D versus Tekturna + placebo. To demonstrate in African American hypertensives consuming a calcium replete diet that Tekturna + Vitamin D will improve measures on non-invasively measured vascular function (peripheral vascular resistance, augmentation index, carotid-femoral pulse wave velocity and central aortic pressure) more than Tekturna + placebo.