Everyone's Health

Summer heat, heavy sweat, is water enough or do you need a manufactured hydration substance?

In hot weather the body can overheat, a condition called hyperthermia.

The production and evaporation of sweat is the body's way of cooling itself.

During hot-weather activities, it's important to drink plenty of fluids to replace the body water lost through sweating. Failure to replace the lost water can lead to dehydration, which increases the risk of hyperthermia.

Drinking plain water to replace that loss through sweating is OK during shorter periods of physical activity. However, those who sweat profusely over extended periods of time lose electrolytes (particularly sodium) along with body water. This group could include roofers and other workers, indoor and out.

In those cases, a commercial sports beverage such as Gatorade is more appropriate. In addition to water, it replaces sodium and potassium and provides some simple carbohydrates (the body's “fuel”).

If no sports drink is available, an alternative might be to drink plain water and eat a salt-containing snack such as saltine crackers. (Salt is sodium chloride.)

A bit of physiology helps explain why drinking plain water is less than ideal to replace prolonged, heavy sweat losses. With plain water, you're replacing the lost body water, but not the lost sodium. That leaves you with a normal amount of body water, but a less than normal amount of sodium.

Part of the water you drink goes into the blood, which dilutes the already lagging amounts of sodium in the blood. Because the blood's sodium concentration must be kept within strict limits, the body attempts to raise this concentration by shifting some of the water from the blood into cells.

This influx of extra water into cells causes them to swell. Brain cells are particularly vulnerable to damage. If they can't adapt quickly enough, the result in serious cases can be coma and death.

Drinking water in excessive amounts over a short period of time (overhydration) increases this risk.

A few years ago, a number of military recruits were hospitalized and some died from overhydration during strenuous marches and exercises.

In everyday circumstances, drinking plain water to replace minor sweat losses poses no problem if your kidneys and other body regulatory systems are working properly. But in more extreme cases, replacing sodium along with appropriate amounts of water is good insurance.

by Richard Harkness

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