Studies of mineral and cardiac health in selected populations
Introduction
Cardiovascular diseases are, as a group, the leading cause of death in western countries. Sudden death from cardiovascular disease accounts for over 300,000 deaths per year in the U.S. (Eisenberg et al. 1992). Because of the importance of cardiovascular disease, major efforts have been made to identify risk factors and to take steps to reduce these risks.
There is an increasing body of evidence that drinking water hardness and elevated concentrations of certain minerals in hard water may reduce the risk of cardiac death and, in particular, the risk of sudden cardiac death. Recent interest has focused on deficits in dietary magnesium. In developed countries, these deficits are potentially compounded by use of medications, such as diuretics, that further reduce body stores of magnesium (McLean 1994). There is also concern that increased use of calcium supplements to prevent osteoporosis may alter the ratio of calcium to magnesium intake, further exacerbating the deficiency in magnesium intake. Since calcium and magnesium compete for absorption, there is concern that increasing calcium intake without also increasing magnesium intake can result in a deficit of magnesium. The optimal ratio of calcium to magnesium is unknown. In this chapter, the plausibility of a relationship between waterborne and dietary magnesium ingestion and cardiac disease is discussed, primary in terms of persons who are on magnesium therapy or participate in rigorous exercise. In particular, can studies of these two high-risk populations provide evidence for or against the hypothesis of a causal relationship between water hardness and the risk of cardiovascular disease?