Prevention of heat-related illness. Heatstroke is a medical emergency caused by dehydra-
tion resulting from the failure to replace fluids lost through excess perspiration. Drinking
adequate amounts of water while exercising or working in a hot environment reduces (but
does not entirely eliminate) the risk of heatstroke. NOTE: Alcoholic beverages and caffein-
ated beverages are mild diuretics; drinking them increases your loss of water.
Antacid, diuretic, and laxative effects. Mineral waters are natural mild diuretics and, because
they contain sodium bicarbonate, naturally antacid. Any kind of water, taken warm about
a half hour before breakfast, appears to be mildly laxative, perhaps because it stimulates
contractions of the muscles in the digestive tract.
Adverse Effects Associated with This Food
Contaminants. Drinking water may pick up a variety of chemical contaminants as it trav-
els through the ground or through pipes. To date, more than 300 chemical contaminants,
including arsenic, asbestos, nitrates and nitrites, pesticides, and lead, have been identified in
the water systems of various American cities. Even chlorine, which is added to the water
supply to eliminate potentially hazardous microorganisms, can be a problem. The free
chlorine generated during the purification process may react with organic compounds in the
water to produce trihalomethanes, such a chloroform, which are suspected carcinogens or
mutagens (substances that alter the structure of DNA). To prevent this, the Environmental
Protection Agency (EPA) monitors chlorinated water supplies to make sure that the level of
trihalomethanes remains below 0.10 mg/liter (100 parts per billion), a level currently consid-
ered safe for human consumption.
Water overload. On an average day, a healthy adult may lose 2,500 ml (milliliters) water
through breathing, perspiring, urinating, and defecating. An ounce is equal to 30 ml, so we
can replace the fluid we lose with eight 10-ounce glasses of water or any equivalent combina-
tion of water plus other liquids and/or foods with a high water content. However, in 2008,
an editorial in The Journal of the American Society of Nephrology, the professional publication
of the association of doctors specializing in kidney diseases, questioned the validity of the
“eight-glass-a-day” rule. They concluded that there is no clear evidence to support drinking
large quantities of water and that it is more sensible for healthy people to drink when thirsty
rather than to rely on a specific amount of water each day. Their reasoning was simple: If we
take in much more water than we need to replace what we lose, the excess water will dilute
the liquid inside our cells, lowering the normal concentration of electrolytes (sodium, potas-
sium, chloride). Because a proper ratio of electrolytes is vital to the transmission of impulses
from cell to cell, a continued excessive intake of fluid may cause water intoxication, a condi-
tion whose symptoms include lethargy, muscle spasms, convulsions, coma, and/or death.
Healthy people whose kidneys are able to eliminate a temporary water overload are unlikely
to suffer from water intoxication, but diets that require excessive water consumption may be
hazardous for epileptics and others at risk of seizures.
Water