Sodium intake for athletes before, during and after exercise: review and recommendations

Abstract Athletes training and competing in sports with a large body water turnover (e.g., team, endurance, and racquet sports) commonly focus on sodium containing foods, beverages, and supplements before, during and after exercise. Despite this, current guidelines for these scenarios are non-specific, primarily due to a lack of available evidence at the time of their writing. Recent evidence, plus a more detailed interpretation of the existing literature, may allow for more specific recommendations. This review examines the common rationales given by athletes, coaches, and practitioners for the planned intake of sodium on a daily basis, before, during, and after exercise. Currently there is no evidence that athletes require a greater dietary sodium intake day-to-day, due to regulation of sodium losses via the kidneys and sweat glands. Whether before, during or after exercise, evidence suggests that it is the relationship between sodium and water that influences health and performance outcomes, not sodium balance or total body sodium content in isolation. This relationship between water and sodium, given its influence on extracellular osmolality, influences thirst drive and fluid retention (i.e., overall body water balance), as well as the distribution of fluid between intracellular and extracellular compartments. Recommendations for sodium must therefore be made relative to changes in both sodium losses and fluid balance (i.e., fluid losses and intake), rather than planning based on sodium losses alone as many athletes, coaches, and practitioners have traditionally done. Common problems relating to sodium intake or balance (e.g., gastrointestinal issues and exercise-associated hyponatraemia) generally arise because of a mismatch between sodium and fluid balance. Questions remain about the form of sodium (i.e., sodium chloride or sodium citrate), and the delivery method (i.e., in solution, foods, or capsules), and the role, if any, of oral sensing of salty taste generally, or sodium specifically. Finally, some recommendations provided are based on limited evidence, extrapolations of research to specific scenarios, and/or theoretical modelling. Further research should address these gaps, as well as reproducing findings across a broader range of athletes (based on age, sex and athletic ability) and exercise types (e.g., weight-bearing exercise, intermittent exercise).