Explain about the Calcium and Hypertension?

Chronic inadequate intake of calcium may play some role in etiologies of hypertension. Calcium deficiency has been linked to hypertension. Numbers of epidemiological studies, animal experiments and human clinical studies have reported an inverse relationship between Ca intake and blood pressure. Meta- analysis of studies reveal that Ca supplementation (median intake lg of Ca) resulted in reduction in systolic blood pressure in selected hypertensive patients. People who appear to benefit from calcium therapy are those who have low calcium intakes, low ionized calcium concentration or elevated PTH and those who have low renin activity and are salt-sensitive. The precise nature of the anti-hypertensive action of dietary calcium is not clear.

Calcium has a membrane stabilizing vasorelaxing effect on smooth muscle cells. Calcium can exert its effect through other mechanisms also. Salt sensitive, low renin individuals exhibit low plasma ionized calcium concentration, increased urinary calcium excretion and elevated PTH and calcitriol. Further work is still warranted in this aspect. It is, therefore, clear from our discussion above, that a positive calcium balance (i.e. net calcium retention) is required throughout life. A positive calcium balance is required throughout growth, particularly during the first 2 years of life and during puberty and adolescence. These age groups therefore constitute populations at-risk for calcium deficiency, as do pregnant women (especially in the last trimester), lactating women, post menopausal women and possibly, elderly men.