Gabe Mirkin, M.D.
During World War II, Dr. James Gamble of Harvard Medical School showed that you have to take huge
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 it can cause nausea, so some doctors stopped prescribing salt tablets. In
the 1960s, doctors became concerned that too much salt can cause high blood pressure, so many doctors
stopped recommending heavy salting of food, causing many people to die of heat stroke and 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. Heavily salting
food and drinking salty drinks when you exercise for more than 2 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 heat stroke, dehydration and cramps.
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.