REN and Hypertension: The effects of vitamin D on the renin-angiotensin-aldosterone system were assessed ina study comparing essential hypertensive patients with hypovitaminosis D, essentialhypertensive patients with normal vitamin D levels, and normotensive individuals.When the individuals with hypertension and hypovitaminosis D were givensupplementation with cholecalciferol for 8 weeks, they exhibited reductions in plasmarenin levels and increases in blood flow-mediated vasodilation.18