Why You Need Salt During Long Exercise

During World War II, Dr. James Gamble of Harvard Medical School showed that you have to take large amounts of salt when you exercise for several hours, particularly in hot weather. Nobody has improved on his research in the last 60 years.

After Gamble published his studies, people who work in the heat were given salt tablets, which is such a concentrated form of salt that they can cause nausea and stomach irritation. In the 1960s, doctors became concerned that too much salt can cause high blood pressure. They started recommending low-salt diets, which have caused many people to collapse and even die of heat stroke or dehydration during hot weather work and exercise.

A low-salt diet does not lower high blood pressure in most people with high blood pressure. A high-salt diet causes high blood pressure usually only in people with high blood insulin levels. Eating heavily salted foods and drinking salty drinks when you exercise for more than two hours in the heat should not raise blood pressure anyway. If you don't take salt and fluids during extended exercise in hot weather, you will tire earlier and increase your risk for cramps, dehydration and heat stroke.

Schmidt W et al. Plasma-electrolytes in natives to hypoxia after marathon races at different altitudes. Medicine and Science in Sport and Exercise. 1999 (October);31(10):1406-13.

Checked 7/31/09

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