The Yanomamo Indians eat about 100 times less salt than we do. It has been argued that their salt intake is the natural salt intake for all humans. Obviously, if the salt intake is this low, then there is no room for there to be much salt in the sweat. However, most guidelines will say that if you sweat a lot, you should replenish the salt lost via sweating. But if the natural salt intake is much lower, then we're only losing excess salt via sweat.

So, is our sweat salty only because we eat way too much salt, or are we really losing essential salt via our sweat that we must replenish?

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    $\begingroup$ I feel like the sentence "Obviously, if the salt intake is this low, then there is no room for there to be much salt in the sweat." isn't necessarily true. Is there data on Yanomamo sweat saltiness? $\endgroup$ – kmm Jul 30 '18 at 20:05
  • $\begingroup$ @kmm Yanomamo sweat saltiness cannot possibly be high, given their extremely low salt intake and the fact that in the tropic rainforest where they do very strenuous work, they are bound to sweat a lot. $\endgroup$ – Count Iblis Jul 30 '18 at 20:07
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    $\begingroup$ I think the question is Yanomamo sweat saltiness relative to western diet sweat saltiness. Your certainty that Yanomamo differ from western diet needs some justification, I think. $\endgroup$ – kmm Jul 30 '18 at 20:44

The article you reference is only referring to supplemental use of salt; many foods are naturally salty, and I don't see any evidence there that Yanomamo are actually low on salt, merely that they have adapted to a lower sodium diet. The authors are simply making a case that the contemporary diet is very high in salt.

When animals move water around their bodies, such as by excreting water to sweat, they do it by creating an osmotic gradient by pumping some ions: this is why sweat is salty.

Consolazio, C. F., Matoush, L. O., Nelson, R. A., Harding, R. S., & Canham, J. E. (1963). Excretion of sodium, potassium, magnesium and iron in human sweat and the relation of each to balance and requirements. The Journal of nutrition, 79(4), 407-415.

Schwartz, I. L., & Thaysen, J. H. (1956). Excretion of sodium and potassium in human sweat. The Journal of clinical investigation, 35(1), 114-120.

  • $\begingroup$ Human sweat is hypotonic and body fluid sodium content and osmolarity are regulated by the kidney, not the skin. I think these are two key misunderstandings in the OP (and the marketing of sports drinks ). $\endgroup$ – De Novo Jul 30 '18 at 22:51

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