Endurance athletes, like marathon runners and triathletes for example, are commonly advised to replenish sodium while performing for long periods of time to help make up for high rates of sweat loss.
Because this is frequently advised and has long been a generally accepted way to help improve performance, researchers at the Saint Louis University Medical Center sought to determine whether or not replenishing sodium can actually help to improve performance during endurance exercise.
They felt that athletes likely consume large quantities—beyond what is necessary—of salt or electrolyte supplements fortified with sodium during training and competition.
The main thought behind this advice, besides the fact that sodium levels need to be replaced, is that consuming salt will cause the body to sweat more—a biological mechanism for cooling off—and in turn increase performance.
To determine how high-dose sodium supplementation effects athletic performance and the body’s ability to maintain its core temperature (thermoregulation), the researchers examined 11 endurance athletes as part of a double-blind study.
On two separate occasions, the subjects performed for two hours at 60 percent of their maximum heart rate and then afterwards during an exercise performance test.
The researchers reported that the athletes lost more than two liters of water in the form of sweat during the first two-hour bout of exercise. During one session the subjects were given 1,800 milligrams of sodium supplementation and during the other they were given a placebo.
The results found that the sodium supplementation did not have an effect on thermoregulation, and therefore did not help to improve performance.
Among other factors, the researchers also measured the subjects’ perceived levels of exertion, heart rates, skin temperatures and dehydration levels and found no statistically significant differences as a result of the sodium supplement.
The researchers concluded that while it’s certainly important for endurance exercisers to replenish liquid and electrolytes (including sodium), they should take a more conservative approach when it comes to supplementing with salt.
“While moderate sodium consumption is perfectly reasonable and should be encouraged, high sodium intake is associated with health concerns, like hypertension," said Edward Weiss, Ph.D., assistant professor of nutrition and dietetics at Saint Louis University and one of the study’s authors.
As Runner’s World points out, if you eat a typical diet you likely meet the daily recommended sodium allowance of 2,300 milligrams.
According to Kris Osterberg, R.D., of the Gatorade Sports Science Institute in Barrington, Illinois who spoke with Runner's World reporter Julie Cederborg, determining how much salt you need after exercising is dependent on several highly individual factors including the weather (you’ll probably sweat more if it’s hotter outside).
Osterberg suggested consuming about 200 milligrams of sodium after a workout, especially if your skin literally has salt residue on it.
Another expert, Bob Seebohar, R.D., director of sports nutrition at the University of Florida, recommend that athletes only need to replenish sodium during exercise if they’re performing for five hours or longer.