Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: TUESDAY, July 25, 1995 TAG: 9507250042
SECTION: EXTRA PAGE: 1 EDITION: METRO
SOURCE: By SALLY SQUIRES THE WASHINGTON POST
DATELINE: LENGTH: Medium
A typical adult loses about one to two liters of fluid per hour working or exercising outdoors in the kind of weather that gripped the East Coast lately. Even easy activities like gardening mean losing a gallon of fluid within a couple of hours when it's scorching out.
That's why experts recommend drinking copious amounts of liquid when the mercury soars, whether or not you feel thirsty. For people who are out in the heat, that means consuming ``about a glass of water every 10 minutes,'' said Harvey Meislin, director of the Arizona Emergency Medicine Research Center at the University of Arizona College of Medicine in Tuscon.
Studies show that humans have ``notoriously poor thirst sensation,'' said Kevin Kregel, a physiologist at the University of Iowa in Iowa City. By the time you feel thirsty, he said, ``you have already started to become dehydrated.''
Cool water is the best bet for most people. ``The colder the better, because colder solutions get absorbed more readily,'' said Kregel. Cold water is also ``more palatable'' he said, so more of it is consumed.
In recent years, experts also have stressed the importance of drinking plenty of water before going outdoors. A draft of new exercise guidelines from the American College of Sports Medicine recommends consuming at least 18 ounces of fluid two hours before any outdoor activity in hot weather.
Whether there is any benefit to quenching thirst with Gatorade and other special drinks that are loaded with electrolytes such as sodium and potassium is a matter of debate. Most experts say that there's no harm in drinking these sports drinks, but they also emphasize that they are not necessary for everyone.
The people who may benefit the most are those who work or exercise outdoors. ``They ought to think about drinking commercially available electrolyte drinks,'' said W. Larry Kenney, professor of applied physiology at Pennsylvania State University in University Park.
Studies suggest, he said, that these fluids ``are maintained in the body longer than plain water,'' explained Kenney. ``That does help on a long-term basis.''
The elderly and children may also be helped by these drinks. Both groups are susceptible to the heat's effects and need to stay well hydrated. The young, for example, have undeveloped sweating mechanisms. ``They can't dissipate heat the same way you or I could,'' Kregel said.
In older people, thirst sensation declines and kidney function declines, ``making the elderly less able to retain fluid once it's in the body,'' Kenney said.
During a heat wave, many people like to quench their thirst by sipping iced tea, iced coffee or soft drinks containing caffeine. But caffeinated drinks, as well as alcoholic beverages, actually accelerate water loss.
Sugary soft drinks and full-strength fruit juices also have drawbacks. They are so loaded with carbohydrates and sugar that they concentrate fluid in the stomach and intestines rather than boosting its absorption and transfer to the rest of the body.
``Diet drinks are probably OK from the point of view that they don't have a lot of calories,'' Kregel said. So are diluted fruit juices, which have a lower sugar content, making absorption easier.
``You can also advise people to eat more foods high in water content,'' said Kenney. ``Things like fruit, watermelon, soups, even though it seems odd to drink hot soups on a hot day, they are so high in water content that they can really rehydrate people.''
by CNB