How much salt do runners really need?

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Salty sweaters, put down those crisps: you may not need extra salt after all. 

For years sports publications, including Runner’s World, sports dietitians and researchers have advised runners with “salty sweat” (usually trademarked by white, crusty stains left on clothing during hot runs) to ingest more salt. The idea was that because you lost more sodium than the average athlete, you needed to be fastidious in replacing it. But a new paper published in the International Journal of Sport Nutrition and Exercise Metabolism is challenging that logic. 

One of the authors of the paper, Martin Turner, Ph.D, became interested in reviewing the literature on dietary sodium after switching to a low-sodium diet. A recreational cyclist, he noticed a change almost immediately after nixing added salt - but not in performance. “The only noticeable effects of a diet free of added salt appeared to be sweat that was almost salt-free, didn't sting my eyes and was much less sticky,” he told Runner’s World by email. But he wasn’t wracked with muscle cramps or on the verge of suffering from exercise-associated hyponatremia - two reasons runners often cite for why they should ingest salt. 

Turner wondered if perhaps the levels of sodium in our sweat could be tied to the over-saltiness of our diets, as many Western diets include unholy sodium levels. He posited that perhaps salty sweaters were simply shedding some of the excess they’d ingested, and that it might be unnecessary to take in more. In fact, he wondered if perhaps some of the benefits of exercise - things like lowered blood pressure and reducing stroke risk - were simply attributable to the fact that athletes shed more of their excess sodium than sedentary folks.  

When he started reviewing research, he found that there wasn’t overwhelming evidence that sodium intake correlates to enhanced performance. Some studies did show salt could improve performance, but some didn’t. It doesn’t stop muscle cramps, either. (In fact, this theory has been debunked numerous times but is pervasive among recreational athletes nonetheless). 

Turner also didn’t find proof that sodium intake could prevent hyponatremia. “The evidence we reviewed suggests that healthy runners do not need to consume additional salt, even if they are on a low-salt diet. As Tim Noakes and others have shown, the primary cause of EAH [exercise-associated hyponatremia] is drinking too much water, although other factors such as inappropriate secretion of certain water-regulating hormones may contribute,” Turner said. 

READ: How much sodium do runners really need?

Because this was a review of literature and not a well-designed, replicated scientific study, it’s probably best not to change your electrolyte strategy quite yet. Plus, Turner did find evidence that drastically decreasing your salt intake over a short period of time could have negative health consequences. “Therefore it is probably not a good idea to blindly advise all people with salty sweat to drastically cut their salt intake, until further research on this phenomenon has been done,” he said. “People with salty sweat who would like to reduce their salt intake should do so gradually and preferably under medical supervision.” 

“The hypothesis that yet another benefit of physical exercise is salt loss, potentially reducing the risk of hypertension and other chronic health issues related to high salt intake, is novel,”said Heather Caplan, R.D, and running coach. “For someone who has a risk or history of hypertension, this may be worth exploring under the guidance of both a physician and a sports or cardiovascular dietitian. However, quickly doing a ‘study of one’ and reducing salt intake while engaging in more physical activity is likely not going to go well,” she said.

If nothing else, this paper may open up a conversation about what role exercise plays in regulating sodium intake, and whether adding more sodium to our diets is really necessary - or even good for us. Turner doesn’t have any follow-up studies planned at this time due to a lack of funding, but he hopes other researchers will pick up where he’s left off and test this hypothesis in a laboratory environment. 

For now, though, keep doing what you’re doing, said Caplan. Current dietary guidelines recommend healthy adults get 2,000 to 2,300 milligrams of sodium, with runners and endurance athletes taking more as necessary, so long as their blood pressure remains in a healthy range (according to the American Heart Association, that’s less than 120/80 mm Hg).  

Marie Spano, R.D., points out that sweat losses, both in fluid and sodium, range dramatically between people, and both over-hydrating and under-hydrating can lead to poor performance and potential negative health consequences. 

“I think many people are so afraid of sodium because of the press around salt. I have to remind them that the average person is overweight or obese and inactive,” she said. 

In Spano’s practice, she tries to tailor salt recommendations based on her athletes’ actual sweat losses. 

“When they follow an individualised hydration plan the effects are dramatic,” she said. “They feel so much better when training and competing.”

READ: What dehydration does to your body and how you can prevent it