I have noticed some posts going around social media highlighting a lack of scientific research to support the use of sodium intake for athletes to improve performance. It is interesting reviewing these comments and articles. Certainly, there is research that has investigated the intake of sodium and whether or not it exerts a performance effect and that research has failed to find a distinct performance-enhancing effect. However, as I will always say, a lack of evidence is not evidence of lack of effect.
From a clinical perspective, I have certainly seen athletes benefit from ingestion of higher amounts of sodium mixed into their fluids or through solids being ingested. I put forward the following thought recently to the head coach of Purple Patch Fitness, Matt Dixon and some of their athletes.
“My take on sodium is this. For those individuals who suffer historically from cramping, they begin to increase sodium intake, this drives some more fluid intake and when combined with better carb intake, low and behold, they have reduced cramping. Is it the sodium, the increased water intake or the increased carb intake? Who knows. I just know it works.”
One of the athletes, Elliot Block, an athlete I work with from Purple Patch who has historically had cramping issues and now has none, put forward the following;
“There’s no scientific proof, but that’s because it’s so hard to set up a valid experiment for endurance (can’t really get a lot of people on a treadmill for 3 plus hours or indoor cycle for 10 hours multiple times) so while it’s true there’s no scientific proof, that doesn’t mean it’s not true - just disappointing that these tweets aren’t put in context and it’s misleading if someone reads this and thinks they don’t sodium for their next marathon or IM. Ten years ago (or so) there was no scientific proof that one could, or should, consume 100+ grams of carbs an hour in endurance events”
Certainly, in his case (one of many), he suffered from cramping. Systematically, we went about understanding his sweat rate through repeated weighing self before and after sessions (bike, run and bricks) to gain an understanding of bodyweight percentage loss during exercise. This was completed in varying temperatures and in particular in temperatures over 85F (30C). It became apparent that Elliot had a very high sweat rate and required more fluids per hour than the average athlete. Coupled with this he had the sodium concentration testing completed, and it showed a higher than average sodium content. I will say that I do think the values being put forward for the consumption of sodium are a bit too high and do not take into account the habitual intake of sodium. Taking a starting point of 60% of the recommended sodium intake is a sensible starting point, in my opinion. So Elliot started drinking more fluids, consuming more sodium on his bike and running training sessions. He felt better and cramping became less and less. Was it the increased fluids? Was it the increased sodium intake? Hard to say. He also started to increase his carb consumption and went from what I would call low hourly ingestion of carbohydrates to 120-140g/hr on the bike and 80-100g/hr on the run (when required). I have no doubt that the increased carbohydrate consumption has a positive effect on his cramping given that sodium requires carbohydrates to be absorbed. Does improved glucose utilization of the mitochondria reduce cramping? Does the carbohydrate in the mouth result in some afferent response that reduces cramping?
Final thought. Alan McCubbin, who is widely regarded as an expert in hydration and someone who I respect immensely replied to my tweet with this.
“So I wouldn't dismiss the anecdotal reports, but instead ask how/why does it work, why haven't we designed a study capable of observing that, and most importantly, do we need sweat sodium testing & specifically quantified replacement strategies to achieve the desired outcome?”
Like most things in science, and especially in nutrition, more research is required. For now, I would urge athletes to monitor their sweat rate (bike, run, brick) in differing temperatures and in differing zones (lower vs higher intensity), drink to maintain hydration status (at least <3% bodyweight loss), improve carbohydrate capacity (g/hr on bike and run) and use some sodium in their products and adjust accordingly based onsigns & symptoms of cramping or other performance affected parameters.