Overconsumption of fluids by athletes

In the article “Overconsumption of fluids by athletes” BMJ Volume
327, 19 July 2003(1), Dr. Noakes argues correctly that excessive intake of
water or drinks low in sodium chloride before, during, and after exercises
in heat can be dangerous leading to water intoxication, seizures, and
death (1). He also implies that “ … the most dehydrated won those 32 (? 42
km) km races, as is usually the case.” Fortunately, he recommends in the
end that thirst is the best guide for anyone as to how much to drink
during and after exertion. As a general rule of physiology and medicine
replacement of the volume lost is important, but solutes (especially
sodium chloride) must be replaced as well.

Exercise by unacclimatized individuals under conditions of high
ambient temperature increase sweat volume as well as its content of sodium
chloride(2). Current sports drinks have low sodium concentration relative
to sweat losses at maximum sweat gland function. Thus, it may be safer to
increase the salt content of sports drinks to protect athletes performing
under high heat rather than discouraging adequate replacement of losses.
An added benefit would be that less serious athletes performing under
lower ambient heat would not over consume beverages with a higher
electrolyte content. Normally hydrated individuals would find the brackish
taste of more salty drinks less palatable. Such an idea obviously works
against the thrust of the beverage industry that seek to cajole us all to
drink as much as possible of any fluid they produce.

1. Noakes, TD. Overconsumption of fluids by athletes. BMJ. 2003 Jul
19;327(7407):113-4.

2. Gordon, RS Jr and Cage, GW. Mechanism of water and electrolyte
secretion by the eccrine sweat gland. Lancet. 1966 Jun 4;1(7449):1246-
1250.

Competing interests:  
None declared