Cardiovascular disease remains a major Public Health problem in the U.S. and is the result of diseases such as atherosclerosis and high blood pressure (BP). Several dietary factors have been implicated as risk factors including high sodium and low potassium diets. Indeed, it is well known that excess sodium can increase BP while potassium rich diets have BP lowering properties. While the role of these two nutrients on BP is widely accepted, their impact on the vasculature has received less attention. Endothelial dysfunction, characterized by impaired dilation is an important non-traditional risk factor for atherosclerosis. Data in animal models suggest that salt loading, independent of changes in BP, results in endothelial dysfunction while evidence is mounting that potassium may be beneficial to vascular health. Further, potassium may be more effective in the presence of high sodium however the role of potassium in protecting the vasculature from a high sodium diet in salt-resistant adults has not been explored. A potential mechanism responsible for sodium induced vascular dysfunction is overproduction of reactive oxygen species resulting in reduced nitric oxide (NO) production/ bioavailability. It has been suggested that potassium can counteract sodium's effect by reducing ROS. The central hypothesis is that potassium can protect against the deleterious effects of high sodium on the vasculature by reducing oxidative stress and preserving NO. In this grant, the investigators propose to use a 21-day controlled feeding study to compare the effects of a high sodium diet (300 mmol) combined with either a high (120 mmol) or moderate (65 mmol) amount of potassium and low sodium (50 mmol) combined with moderate potassium (crossover design, diet order sequence randomized) on 2 levels of the vasculature, conduit artery and microvasculature. These experiments will be performed in salt-resistant participants to study the vascular effects alone, independent of changes in BP.