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April 18, 1990

Exercise, Fitness, and Mortality

Author Affiliations

Massachusetts General Hospital Harvard Medical School Boston

Massachusetts General Hospital Harvard Medical School Boston

JAMA. 1990;263(15):2047. doi:10.1001/jama.1990.03440150051014

To the Editor.—  The study by Blair et al1 clearly demonstrates the beneficial effect of fitness, if not exercise itself, in decreasing the mortality rate from both heart disease and cancer. A number of distinct mechanisms, none of which are totally satisfactory, have been proposed to account for this effect on these two very different diseases. In the case of coronary artery disease, the beneficial effect of exercise is thought to arise from improvements in lipid profile, ventricular function, or other cardiocirculatory parameters. For colon cancer, on the other hand, exercise is thought to increase bowel motility and thus reduce exposure to potential carcinogens.I propose the hypothesis that the preventive effects of exercise are due in part to lower body iron levels that result from exercise-induced blood loss or other alterations in iron metabolism.The evidence for the role of iron in both coronary artery disease and