Electrolyte Supplements and Sports Drinks

An average 3.6 percent of body mass is more dehydration than most recreational exercisers ever reach, and the performance tests averaged 22 minutes. The dehydration was deliberately induced, usually by heat or fluid restriction, which brings its own fatigue on top of the water deficit. The confidence interval on the headline runs from 0.8 to 4.0 percent. Nothing here compares an electrolyte drink with water.

The people tested were mostly older adults with night-time leg cramps, not athletes cramping mid-race, so this settles the mineral rather than the sport. The pregnancy trials in the same review could not be pooled at all because their outcomes were reported inconsistently, and a separate Cochrane review graded those same trials as far less biased than this one did. Nothing here tests magnesium during exercise.

Children with gastroenteritis, which is nobody in a gym. The trials were graded poor to moderate quality and mostly unblinded, since a drink cannot be disguised as a drip. Each route carries its own complication: vein inflammation with the drip, a stalled gut with drinking, roughly one in 50 and one in 33. The death counts, six against two across four trials, are far too small to read anything into.

Hospitalised children with acute diarrhoea, compared against another rehydration solution rather than against water, so nothing here reaches a well person drinking one. This is the 2002 version of a review since updated, cited for the finding that changed the formulation. The trials were mostly unblinded and largely in low- and middle-income hospital settings. Low blood sodium was looked for in only six trials with events in three, so that reassurance rests on thin data.

A position stand is expert consensus with no stated search and no risk-of-bias grading, and panels in this field have included researchers with sports-drink funding. It was written before the 2015 consensus on exercise-related low blood sodium and before the field studies that found sodium supplements did not prevent it. Advising people to individualise because sweat varies is not evidence that individualising improves any outcome, which is the step the personalised-hydration industry takes.

One real exception sits inside the largest of these studies: among American footballers alone, sweat measurements did carry a weak signal, and in the other ten sports none did. Beyond that, cramping was self-reported throughout, and serum electrolytes were sampled before and after a race rather than inside the muscle at the moment a cramp struck, which is where the theory actually locates the problem. Forty-three crampers is enough to rule out a dominant effect, not a small one.

Twenty crampers is a small group, and the finish-line enzyme gap is borderline at p = 0.034 with spreads wide enough to swallow it. The blood was drawn after the cramp, so muscle damage could as easily follow a cramp as cause one. Crampers and non-crampers only diverged in pace from 25 kilometres onward, which points back at effort. The paper's own abstract calls 20 of 88 a rate of 24 percent; it is 22.7 percent.

This concerns water, not electrolyte products, which were not tested here, so it undercuts the theory the hangover sachets rest on rather than testing the sachets themselves. It is a narrative review with no protocol or stated search, by a group that has argued this position for years. Much of the underlying evidence is people recalling their own drinking and their own hangovers. The authors do report that dehydration after alcohol is real, just mild and short-lived.

Fully hydrated, fasted men, all 72 of them male, drinking a litre in half an hour. Retention was measured as urine volume over four hours, not as anything a person would notice. And milk brings protein, fat and lactose along with its sodium and potassium, so what did the holding is not separated out here.

This is transport physiology rather than a trial, and the two-to-one ratio is standard textbook mechanism restated by the review, not a new finding of it. The review was written to argue for developing drugs that improve on rehydration therapy, which frames how generously that therapy is described. Its own authors note the treatment reverses dehydration without shortening the illness or reducing stool output.

A survey of what runners believe; nothing in it tests whether the capsules work. Participants opted into a longitudinal tracking study, so they are more engaged with the sport than average, which makes the belief's persistence more striking rather than less. One country dominates the sample, one sport, 2018 data. The authors' verdict that the evidence is settled rests partly on their own earlier studies.

The men were fully hydrated and fasted when they drank, which is nobody's state when they reach for one of these, and retention behaves differently in someone already short of fluid. All 72 were male. The outcome is urine volume over four hours, a stand-in for retention rather than for feeling or performing better. The drinks were not matched for sodium, so this ranks these particular products, not electrolytes as an idea.

Weak discrimination is not a screening test, and the authors do not offer it as one. Cramp history was self-reported, and sweat was collected during ordinary training, never during a cramp. Forearm patches estimate whole-body sweat sodium indirectly and carry real measurement error. One other significant result among roughly fourteen comparisons, potassium content in women, is what chance produces at that many tests.

A label proves what a company was permitted to print, not that anything printed on it is true, and being listed on the US drug label database is not approval. This is one product, so it shows such a thing exists and is listed rather than that the category behaves this way. Its marketing text, including the three-bottles promise, sits inside the section reserved for safe-handling warnings, while the sections for indications, purpose, active ingredient and precautions are all empty.

Nobody was randomised: runners chose their own salt and their own drinking, so everything else they did differently comes along with the comparison. Intake was reconstructed from a questionnaire filled in after the race. Almost everyone supplemented, 94 in 100, which leaves barely any unsupplemented group at all, so this says more salt did not protect rather than that salt does nothing. Self-selected ultramarathon fields, single races.

Whether deliberately taking salt changes the risk of low blood sodium in endurance races is untested. Nobody has randomised runners to salt or none, because in these races almost everyone already takes it.

The finish-time result is a single p-value of 0.04 among eight reported outcomes, the shape of finding that most often fails to repeat. The abstract never says how many minutes faster, so the size of the advantage is not on the record anywhere. The trial's registry entry declared 40 participants against the 26 analysed, unexplained. Four to six hours of racing by trained triathletes says nothing about an hour in a gym.

One randomised trial found salt capsules got triathletes to the finish sooner, on a single borderline result in 26 people. Whether that holds up is open, because nobody has repeated it.