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Maximum sweat rates of an adult can be up to 2–4 litres (0.53–1.06 US gal) per hour[1]

Although the mineral content varies, some measured concentrations are: sodium (0.9 gram/litre), potassium (0.2 g/L)[2]

Suppose a situation you know you will be sweating profusely for hours e.g. climb significant elevation on a bicycle in 35°C; work masonry in the blasting sun protected only by a sombrero.

Knowing the volume of one's water bottle is it wise to drop some salt every time it is refilled? In contrast to consuming salt directly or not doing it at all. If so, how to dose properly?

References(I haven't personally verified those):

  1. Mack GW, Nadel ER (1996). "Body fluid balance during heat stress in humans". In Fregly MJ, Blatteis CM (eds.). Handbook of Physiology. Section 4: Environmental Physiology. New York: Oxford University Press. pp. 187–214. ISBN 978-0-19-507492-5.

  2. Montain SJ, Cheuvront SN, Lukaski HC (2007). "Sweat mineral-element responses during 7 h of exercise-heat stress". International Journal of Sport Nutrition and Exercise Metabolism. 17 (6): 574–582. doi:10.1123/ijsnem.17.6.574

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    We've discussed this before, but whether any of the old questions is closer enough to flag a duplicate is another matter. First though, are you talking about just table salt (sodium chloride) or electrolyte salts in general? The latter are harder to replace quickly from dietary sources.
    – Chris H
    Commented Jul 2 at 16:21
  • @ChrisH Looks like NaCl and K are the major constituents of sweat with everything else in the mg range so I guess I'm asking only about table salt.
    – Vorac
    Commented Jul 2 at 16:24
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    I would suggest either a drink with electrolytes, or salty snacks. Drinking salty water is not something I'm up for, and would probably lead to drinking less. However, the old advice from the 60's of eating salt tablets is really overboard. Your body happily modulates how much salt is released from sweat glands.
    – Jon Custer
    Commented Jul 2 at 18:32
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    Indeed, it is very interesting. Note also that the body prefers to try and hang on to Na (at the expense of K), which made sense from an evolutionary perspective. The ease of of obtaining NaCl salt in the store is quite modern.
    – Jon Custer
    Commented Jul 3 at 16:23
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    @Vorac although the others are present only at low levels in sweat, they do everything at low levels (daily intake, amount in the body) so you can't dismiss them out of hand. I think I'm going to have to research a full answer. My personal approach is to use electrolyte tablets - conscious of the roles of Mg (e.g. when it comes to cramp) and Ca - in some bottles but not all, drinking mainly plain water
    – Chris H
    Commented Jul 5 at 10:36

2 Answers 2

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Tim Noakes is the world authority on this type of thing. See this paper:

Noakes, Fluid and electrolyte disturbances in heat illness, Int J Sports Med. 1998 Jun:19 Suppl 2:S146-9. doi: 10.1055/s-2007-971982.

The idea that heat illness is caused by dehydration or electrolyte imbalance is folk wisdom that doesn't stand up to empirical testing.

Although hyponatremia (low sodium in the blood) is a well documented and sometimes deadly condition, deaths from that condition seem to be caused by people's exaggerated folk beliefs about how much water they need to drink. For example, there was a case where a military recruit was forced to drink 20 liters of water in one morning, and died as a result:

Garigan, T. P., & Ristedt, D. E. (1999). Death from Hyponatremia as a Result of Acute Water Intoxication in an Army Basic Trainee. Military Medicine, 164(3), 234–238. doi:10.1093/milmed/164.3.234

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  • Thanks! However my question is more in the lines of "I'm going to be sweating a lot for several days. Is it a good idea to add table salt to my water so that I stay in healthy and operational physical condition?"
    – Vorac
    Commented Jul 2 at 21:11
  • Drinking to thirst when exercising in hot conditions can get to 10 litres/day. You wouldn't want to do that for long without some intake, which may well come from food depending on what you eat.
    – Chris H
    Commented Jul 5 at 10:37
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Hell NO! High concentrations of salt only make you thirstier! This is the main reason seawater isn't drinkable. If you sweat too much salt, eating something that's salty is the safest bet.

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    I don’t think the OP ever mentioned “high concentrations” of salt. The concept isn’t unreasonable - I mean, see Gatorade for example. It’s not heavily salty but it absolutely contains some. The question seems to be asking along the lines of making their own version, just without all the sugar. Commented Jul 3 at 5:33
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    @fyrepenguin - indeed, and the folks who developed Gatorade but a lot of effort into making it something that the university football players actually wanted to drink.
    – Jon Custer
    Commented Jul 3 at 13:40
  • Drinking sea water does't just fail to quench thirst: it is toxic because it dyhydrates you very quickly. Commented Jul 3 at 20:48
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    Seawater sodium content averages 10g/kg of seawater while I'm proposing 0.9. This is hypotonic.
    – Vorac
    Commented Jul 4 at 2:24
  • Eating something salty also makes you thirsty. Thats why they sell snacks in pubs.
    – Chenmunka
    Commented Jul 5 at 9:15

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