In spite of hyponatremia being understood well for a couple of decades now, the lie that it is caused by lack of salt/electrolyte intake will just not die — hyponatremia is caused by, and only by, excessive fluid intake, the principal indicator being weight gain during exercise. No amount of ‘electrolytes’ you add to your drink will prevent it if you drink too much.

It is incredibly frustrating to see life-threatening misinformation on this subject aped again and again in various popular sport and, not least, outdoors articles; this is undoubtedly to do with the vested interests of the multibillion sports drink industry, which has sought to burry the early research into the condition, and continues to peddle misinformation on this subject.

The short of it is that electrolyte supplements are snake oil; the salinity of human blood is reliably regulated by the gut, and the salinity of your drink has no bearing on it; all that’s required is for your diet to contain the requisite daily salt intake, which happens to be pretty low, only around 3g per day (so well below the typical salt intake in a western diet).

Oh, and the salt maps on your clothing? That’s not your body loosing salt it desperately needs, that’s it shifting the excess that it doesn’t require.

If you want to know more about this, Tim Noakes’ Waterlogged is I think still the definitive text on the subject, worth plodding through not just for understanding the condition, but also the the history of research suppression around it.