Does calcium aggravate and cause hypertension?

Albert Szent-Gyorgyi around 30 years ago proposed that "ions were the powerful tools of life as it developed in oceans". The purpose of this fundamental concept was to divert the attention of investigators towards the basic role of cations such as Na, K, Ca and Mg in muscle contraction. There is now sufficient evidence to support this prediction. Until recently the strongest evidence pointed to a positive relationship between raised Ca and blood pressure. More recent evidence claimed that increased dietary Ca can lower blood pressure and populations taking lowered dietary Ca, have a higher incidence of hypertension. It has been suggested that in susceptible persons, in the presence of high Na intake, Ca accumulation in the arterial cell becomes rapid due to impaired Na-Ca exchange causing an early rise in blood pressure. This is possibly due to abnormal handling of Ca by the smooth muscle cells in most forms of hypertension. Clinical experimental and epidemiologic studies showed that Ca not only mediates arterial smooth muscle contraction but excess of Ca can also cause an increase in peripheral vascular resistance leading to essential hypertension. Ca entry blockers such as verapamil and nifedipine which reduce the influx of Ca into the arterial smooth muscle cell have been successfully used in the management of these patients. The effect of Ca on blood pressure could be independent of other factors. Recent studies strongly favour a significant relationship between raised serum Ca and high blood pressure. Such a relationship has also been described between dietary Ca, 24 urinary Ca and high blood pressure. A large number of studies, particularly from the USA, contradicting the above view, suggest that the rate of Ca flux rather than the absolute quantity that enters the cell, is the deciding factor in arterial smooth muscle contraction. These investigators in the last 6 years have studied a large area of north America and suggested that Ca deficiency rather than an excess is the cause of hypertension. Persons consuming less than 300 mg Ca per day have 11-14% risk of developing hypertension compared to person taking 1200 mg per day of dietary Ca and exposed to only 3-6% risk.(ABSTRACT TRUNCATED AT 400 WORDS)