Nutrition Bytes

Hypertension affects millions of Americans. Twenty-five years ago, researchers observed that calcium might be inversely related to the development and severity of hypertension. Consequently, several epidemiological, animal, and clinical studies have addressed this potential correlation. Dietary deficiencies or altered calcium metabolism can result in low serum calcium levels. Disturbances in calcium metabolism include increased urinary calcium excretion and abundance of calcium-regulating hormones such as parathyroid hormone and calcitriol. These hormones cause decreases in bone mineral content and increase intracellular calcium in vascular smooth muscle. Increased [Ca2+]i produces contraction and therefore vasoconstriction. Low calcium levels and elevated PTH and calcitriol may also affect blood pressure control by the central and peripheral nervous systems by stimulating the release of norepinephrine (a potent vasoconstrictor) and increasing its post-synaptic effect. Calcium supplementation and/or increased dietary calcium have been used to increase calcium intake. Not all studies have shown a definite inverse correlation between calcium intake and hypertension, however certain patient groups (pregnant women, salt-sensitive hypertensives) clearly benefit from increased calcium intake. Calcium interacts with other nutrients (sodium, potassium, magnesium) in affecting blood pressure. Due to its probable beneficial effects on hypertension, osteoporosis, and other diseases, RDA intake for calcium should be strongly encouraged.