CHAPTER 30: The Effects of Dietary Calcium on Hypertension

The role of Ca in the prevention of hypertension is controversial, with some research showing a lowering of blood pressure due to Ca supplementation and other studies that were not able to detect any ipotensive effect of this mineral. According to recent and less recent studies, Ca can lower blood pressure in two ways: (1) by increasing the endothelial synthesis of nitric oxide, a strong vasodilator; (2) by removing the misregulation of plasma renin activity in salt-sensitive subjects. As a consequence, an increase in Ca intake will be detected in the juxta-glomerular apparatus with a consequent reduction in renin and angiotensin synthesis. Renin is an enzyme, produced by the kidney, that converts angiotensinogen, secreted from the liver, in angiotensin I. At the pulmonary level angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II determines a blood-vessel contraction and an increase in blood pressure.