Can my heart get healthier with water?
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. Because of the importance of cardiovascular disease, major efforts have been made to identify risk factors and to take steps to reduce these risks.
The findings of a six-year study of more than 20,000 healthy men and women aged 38-100 in the May 1, 2002 American Journal of Epidemiology found that women who drank more than five glasses of water a day were 41% less likely to die from a heart attack during the study period than those who drank less than two glasses. The protective effect of water was even greater in men.
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.
To minimize heart disease risk, the ideal water should contain sufficient calcium and magnesium to be moderately hard. No effort should be made to eliminate trace elements such as copper and iron where these elements are in short, dietary supply. Elements such as cadmium and lead, which can accumulate in the body, should be minimized. 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, primarily 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? A recent study tracked 7,172 men in the Honolulu Health Program. Baseline measurements were made between 1965 and 1968. Over a 30-year period follow-up 1,431 men developed coronary heart disease. There was a statistically significant increased risk of coronary heart disease in men in the lowest versus the highest quintiles of baseline magnesium intake after adjusting for other dietary and non-dietary cardiovascular disease risk factors both of which were also ascertained at baseline.
They did not present data on both calcium and magnesium intake for the various quintiles, making it impossible to determine the calcium to magnesium ratio. An interesting finding, however, was that systemic hypertension decreased with increasing magnesium intake. Unfortunately, in assessing the effects of both calcium and magnesium, some papers have adjusted for blood pressure, which appears to be an intermediate outcome of increased magnesium intake. By adjusting for such an intermediate outcome one can falsely conclude that calcium is protective but that magnesium has no effect on heart disease risks. In reality the effect of magnesium on heart disease could be through its effect on lowering blood pressure.
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