Do You Need Electrolytes? The Cramp Claim Rests on 18 Case Reports and One Study of Ten.

The reason you have been told to drink electrolytes is cramp. Sweat out your salts, the story goes, and the muscle seizes.

The evidence for that is eighteen case reports and one study of ten people. [1]

Four prospective studies — the kind that follow athletes forward and see who actually cramps — did not support it. [1]

A review that graded its own sources, on purpose

The 2009 review this comes from says openly why it applied evidence-based medicine criteria: because “the quality of experimental methodology varies considerably among studies that are commonly cited”. [1] Somebody had noticed that the citations were being counted rather than read.

What survived the grading, in the author’s words, was “anecdotal clinical observations, case series totalling 18 cases, and one small (n = 10) case-control study”. [1]

A case report is one person, described after the fact, with nobody to compare them to. Eighteen of those is not eighteen times the evidence. It is eighteen stories.

There is a competing explanation, and it fits better

If cramp is not salt, what is it? The leading alternative is altered neuromuscular control — the nerve signals controlling a fatigued muscle going haywire, rather than anything in the blood running low.

The evidence there comes from lab models where cramp is induced deliberately, from studies following athletes who cramp, and from animal work. [1] The review also notes that this hypothesis needs more evidence too, and we are not going to oversell a replacement the author himself hedges.

What tipped the review against the salt explanation was not just the thin evidence for it. It was that the hypotheses “do not offer plausible pathophysiological mechanisms with supporting scientific evidence that could adequately explain the clinical presentation and management” of cramp. [1] In plainer terms: even if you accepted the studies, the story still would not account for how cramp actually behaves.

Now the part that is actually true

We are not going to pretend electrolytes do nothing, because one thing they do is measured and real.

Put sodium in a drink and you retain more of the fluid. There is a measure for this — the beverage hydration index, where plain water is set at 1.00 and everything else is scored against it. In a randomised crossover trial, the highest-sodium drink came out at 1.24 in young adults. [2]

So: roughly a quarter more fluid retained than water, four hours later. That is a genuine effect and the trial found it rose as the sodium content rose, “independent of glucose or AA content”. [2] It is the sodium doing it, not the sugar.

Two things to hold onto, though. That trial had 24 people in it, twelve young and twelve older. And retaining more fluid is only worth something if you are short of fluid — which is a question about your afternoon, not about the sachet.

The real sodium emergency is the opposite of the sales pitch

Here is where the marketing and the medicine actually diverge.

There is a documented, dangerous, well-studied sodium condition in sport. It is called exercise-associated hyponatremia, and it is blood sodium falling too low. A 2025 review screened 1,516 papers, read 345 in full, and pulled 220 cases out of 56 field studies. [3]

Those cases came from endurance events lasting 5 to 29.5 hours. [3] Running and hiking, mostly. It is real, it puts people in hospital, and the way you get it is taking on a lot of fluid over a very long day.

Which is worth sitting with. The condition that genuinely calls for sodium is a condition of ultramarathons, not of a commute. And the same review notes that the milder symptoms — nausea, dizziness, headache, feeling weak [3] — are precisely the everyday complaints an electrolyte packet is sold to fix.

The verdict

Unsupported, for the claim that you need them.

Be clear about which part that covers. The cramp story — the reason most people first bought a sachet — rests on eighteen case reports and a study of ten, with four prospective cohorts pointing the other way. That claim does not stand up.

The hydration claim does. Sodium helps you hold onto fluid, by about a quarter over water, in a trial of twenty-four people. What that does not establish is that a person who is not losing much sweat needs help holding onto fluid at all.

So the honest version is not “electrolytes are a scam”. It is that they solve a problem sized by how much you sweat — and they are sold to everyone, at a price, on a cramp claim the evidence stopped supporting at least as far back as 2009.

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