Variable response of serum magnesium and total cholesterol to different magnesium intakes and exercise levels in rats.

Thirty-two Sprague-Dawley rats were divided into four groups: control, exercise, low-magnesium diet, and a combination of low-magnesium diet and exercise. The low-magnesium diet contained 80 ppm of magnesium and the exercise consisted of 1-hour swim sessions, 5 days per week for 4 weeks. Serum magnesium was depressed and total cholesterol was elevated (p less than 0.05) in the low-magnesium diet, sedentary animals as compared to both sedentary and exercised rats fed a normal magnesium diet. The group on the combination of hypomagnesemic diet and exercise was not statistically different from the normal-diet group. It is concluded that exercise favorably affects the serum magnesium and cholesterol responses induced by a hypomagnesemic diet. There may be a threshold serum magnesium level to elicit the elevated cholesterol response, or other metabolic factors affected by exercise may modify the expected cholesterol response associated with deprivation or severe deficiency of dietary magnesium and related serum magnesium levels.