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Too Little Magnesium Makes One Work Harder

By Judy McBride
April 7, 1997

Older people whose heart rate soars and energy dives during aerobic exercise may want to take a closer look at their magnesium intake, according to new Agricultural Research Service findings.

In a study, a group of post-menopausal women experienced a significant drop in their work efficiency when their magnesium intake was reduced to a little more than half of the Recommended Dietary Allowance for three months. That occurred even though blood magnesium levels showed no sign of deficiency, the study leader reports today at the Experimental Biology 97 meeting in New Orleans.

The study is the first to look at the effect of low magnesium intakes on the physiological function of people over age 55. According to the latest USDA nationwide food consumption survey, fewer than one-third of people over age 50 consume the recommended amount of magnesium through their diet.

During the study, the low-magnesium diet affected the women’s physiological function in three ways as they cycled on an ergometer. First, they spent 10 to 15 percent more energy, as indicated by a rise in oxygen consumption, compared to when they were getting ample magnesium. Second, their heart rate increased about 10 beats a minute. And third, the amount of magnesium stored in their muscle tissue dropped measurably.

Watching your diet takes on new meaning with these findings. But it’s easy to get ample magnesium in a low-fat diet, the scientist said. Eat more vegetables, especially dark leafy greens; more whole wheat and other whole grain breads, cereals and pastas; and more dried beans.