A study by Elizabeth Earhart suggests that taking in extra salt during endurance exercise does not influence your performances. As too much salt can be bad for your health, you might consider abandoning the supplements.
Dehydrating too much during exercise is not good for you, as it makes it more difficult to sweat enough to keep your core temperature down. It also means that you have less plasma volume to pump around your body. You have therefore to make sure that you drink enough.
On the other hand, it is important that you keep the amount of electrolytes per litre plasma within normal limits. In practice this means that the concentration of sodium in your blood needs to remain normal. Drinking too much can lead to too little sodium in your blood (hyponatremia), which is usually fatal.
You would therefore conclude that the best you can do is to take sodium supplements with your drinks, but is that true? Unfortunately, scientific studies show contradictory results.
No effect at all
In the latest study, Elizabeth Earhart and her colleagues made 11 trained endurance athletes run or cycle for 2 hours on 2 different days. During one of the workouts the athletes received 1800mg sodium with their water and during the other one none. The researchers could not notice any difference in perceived effort, performance or thermoregulation between the 2 workouts. Two of the athletes however, reported nausea after taking the sodium supplements, and a third one suffered from cramps in the evening after the workout with the supplements.
Of course, this is only a small study and it should be repeated to make sure the results are correct indeed. It is true that other studies have shown different results. The problem is that all those studies use slightly different protocols, which makes it very difficult to compare them.
In a similar study, Cosgrove could not find any effect of sodium supplements, but he noted that the athletes were thirstier when using supplements. Although on average there was no difference between the workouts performed with supplements and those without, he observed that some athletes performed better using the supplements. He thought that this might be due to their training status, to the amount of sodium they had from their regular diet or to small differences in metabolism.
The safest solution
Drinking to your thirst is still the safest way to avoid dehydration and hyponatremia. Do not forget that you will get plenty of electrolytes from food.
As your unconscious brain is determined to keep you safe, it will send you the right signal –as long as you are normally healthy- by making you thirsty. It is therefore a good idea to listen to it!
Earhart EL, Weiss EP, Rahman R and Kelly PV. Effects of oral sodium supplementation on indices of thermoregulation in trained, endurance athletes. J Sports Sci Med 2015; 14(1): 172. eCollection 2015.
Cosgrove SD and Black KE. Sodium supplementation has no effect on endurance performance during a cycling time-trial in cool conditions: a randomised cross-over trial. J Int Soc Sports Nutr 2013; 10:30. doi: 10.1186/1550-2783-10-30. eCollection 2013.
Cosgrove SD, Love TD and Black KE. Sodium supplementation during prolonged exercise: effects on plasma sodium and performance. OA Sports Medicine 2013; 1(2):12.
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