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The Straight Dope On Salt By Matt F itzgerald
The average health-conscious American believes that salt is “bad for you” because it promotes high-blood pressure. This is a myth. The research-supported truth is that salt avoidance is beneficial only for the roughly 30 percent of already-hypertensive individuals who are “salt sensitive.” For the rest of us, salt intake does not have a significant effect on blood pressure. A recent review of 114 studies performed by researchers from the University of Copenhagen and published in the Journal of the American Medical Association found that even an extreme reduction in salt intake would barely lower blood pressure to a measurable degree in those with normal blood pressure. Triathletes have a more favorable view of salt than the average person does. That’s because we know that we lose a lot of salt every day through exercise-induced sweating, and we’re used to consuming salt in sports drinks to compensate for those losses. Failure to do so, we’ve been taught, will cause internal fluid imbalances and muscle cramps. It turns out these notions are somewhat mythical, too. There is surprisingly little scientific evidence that salt consumption during exercise provides any benefit. However, the practice does no harm and is advisable whenever large volumes of sweat are lost and large volumes of fluid are 3 8 T R I AT H L E T E
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consumed during very prolonged exercise. The notion that sodium depletion during exercise causes muscle cramps is clearly false. A 2005 study found no difference in blood sodium levels between athletes who suffered muscle cramps and athletes who did not during an Ironman. The fact that some athletes are especially prone to muscle cramps while others are not also suggests that sodium depletion is not the cause. The latest theory is that exercise-induced muscle cramps represent a type of tendon fatigue that occurs during unaccustomed levels of exertion. However, there is evidence that consuming fluid and salt during prolonged exercise may at least delay cramping in those who are susceptible. In a study from the University of North Carolina, crampsusceptible athletes were able to exercise twice as long before experiencing cramps when they consumed a sports drink during activity than they when they did not drink. What about the idea that adding sodium to a sports drink improves hydration by increasing the rate at which fluid is absorbed into the bloodstream and by slowing the decline in blood volume? Most research supports neither of these claims. A study from the University of Iowa found that sports drinks with different levels of osmolality, both with and without salt, were absorbed at the same rate during exercise and none reduced blood volume decline more than another. Studies from the University of Cape Town, South Africa and the University of Auckland, New Zealand, found that sodium
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supplementation during an Ironman had no effect on blood sodium concentration or blood plasma volume. Interestingly, the studies showing the greatest beneficial impact of salt on exercise have involved sodium loading before exercise instead of sodium intake during exercise. Another group of New Zealand researchers found that when runners consumed a highly concentrated sodium beverage prior to running to exhaustion at 70 percent of VO2max in a hot environment, they maintained a higher blood volume, lower core body temperature and lower level of perceived exertion than when they consumed a low-sodium beverage before running. It’s tough to know what to make of this result, though, since no fluid was consumed during the runs. While there is little evidence that salt boosts endurance performance, there is no evidence that it has a detrimental effect on performance. What’s more, there are countless real athletes who swear that salt intake is beneficial to them in extreme endurance events. Based on these facts, I suggest that you consume salt in the normal amounts contained in sports drinks and energy gels during prolonged endurance exercise, but don’t knock yourself out to get more salt in the form of salt tablets or salty foods, except for reassurance. You don’t need to add salt to your diet either. But you might do it unconsciously anyway. A 1999 Israeli study found that exercise increased the preference for salty foods. So that’s why you crave potato chips after a long weekend endurance session.