By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

Magnesium is a mineral which may be involved in the development of heart disease. It is a vital component of many enzymes, which are proteins involved in the manufacture of other proteins and chemicals in the body. The major source of magnesium is leafy vegetables, beans, nuts, and grains, and about 25 percent comes from the drinking water. The average daily intake for Americans is about 400 milligrams a day, which is the recommended daily intake. Most of the magnesium in our bodies is inside the cells, and blood levels do not provide a good measure of whether we are deficient in it.

The main reason for the interest in the possible health benefits of taking extra magnesium is that several surveys, conducted in countries such as Germany, Sweden, and South Africa, have found that coronary heart disease is much more prevelant in areas where the level of magnesium in the drinking water is low (this usually means that the water is soft rather than hard). Animals fed a diet lacking magnesium develop high blood pressure and heart disease. However, human studies have failed to show any consistent effect of taking extra magnesium on blood pressure.

Factors which lead to magnesium deficiency, apart from inadequate intake, include excessive alcohol intake, diuretic therapy, and kidney disease. A recent study conducted in Japan has raised the possibility that people with high blood pressure are likely to be deficient in magnesium. The researchers found that people with high blood pressure retained more magnesium when it was infused intravenously than the those with normal blood pressure, which they interpreted as indicating that the body stores were depleted in the hypertensives. The blood levels of magnesium were not any different between the two groups, however.

Doctor’s comments

Many of us probably do not get enough magnesium in our diets, and it is possible that this increases the risk of having a heart attack. We don’t yet know whether taking extra magnesium will reduce our risk, but this is a possibility.

Where it was published

Rylander R. Environmental magnesium deficiency as a cardiovascular risk factor. Journal of Cardiovascular Risk 1966;3:4-10.