Are sodium supplements necessary?

It’s that time of the year when you may start noticing a layer of salt residue caked on your clothes and skin. Between that, worries about cramping and/or hyponatremia, and the hype of electrolyte supplements (chews, tablets, liquids, etc.) available on the market, the confusion around sodium is real!

Sweat losses increase to dissipate heat when the environmental temperature increases. During the seasonal transition (or the process of heat acclimation), sweat electrolyte losses, particularly sodium, can increase prior to the sweat glands acclimating. Eventually upon heat acclimation, sweat glands better conserve sodium even with higher sweat losses. Sweat rates and sweat sodium vary between individuals and depend on genetics, fitness, sodium content of the diet, sweat rate and acclimatization to the environment. Sodium losses have been reported to vary between 230 to 1600 mg/L of sweat loss. What is still unclear, is how much of this needs to be replaced to maintain hydration, fluid balance and performance?

Overconsumption and underconsumption of sodium can both lead to issues. Paying attention to your “taste” for sodium can help you narrow down your hydration strategy. During periods of training in hot, humid environments, you can and should consume foods that are salty/salted to increase sodium intake, assuming your fluid intake has also increased. Sodium is also helpful for stimulating thirst during exercise, to better maintain hydration when sweat losses are high. Recent research suggests that excess sodium supplementation is not necessary even in up to 30 hours of endurance activity, even in hot conditions, provided an athlete is also not “overdrinking” water. In addition, the crusty salt on your skin and gear should not be used as a sign to supplement more sodium as it may simply be reflective of recent sodium intake. Having access to salty foods during endurance training and racing, as well as options for hydration (plain water and a carbohydrate electrolyte beverage ) can help you best use thirst and sodium appetite to sort out your individual hydration strategy. That being said, there are some recommendations that can offer you a starting point for sodium supplementation. Although there is no well-established agreement on sodium intake during exercise, the Institute of Medicine recommends carbohydrate-electrolyte sports drinks containing ~500-700 mg of sodium/L of fluid. The American College of Sports Medicine recommends pre-hydrating before exercise with fluids that contain 460-1150 mg sodium/L of fluid or eating salty foods with your pre-exercise fluids. For reference, nuun sport hydration tablets mixed according to instructions provide a sodium concentration of 631 mg/L.

PMID: 33553508, 17277604, 30056755

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