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Released:  August 8,  2000

Fluids Key to Managing Heat

MANHATTAN, Kan. – It’s a good thing water bottles have become ‘cool’– the contents of the stylish containers can make coping with high heat and humidity easier. They also can protect outdoor workers, athletes, exercise enthusiasts, older adults, and children at play from summertime health risks that can be deadly, said Mary Higgins, K-State Research and Extension nutrition specialist.

Fifty-five to 75 percent of the body’s weight is water; the brain is 70 percent water; blood is 82 percent water; and the lungs are nearly 90 percent water. The refreshing liquid carries nutrients and oxygen to cells; cushions organs, tissue, bones and joints; removes wastes; and also regulates body temperature.

Excessive water loss (dehydration) can impair body function and lead to heat exhaustion and/or heat stroke that can be life threatening, she said. Water is lost through perspiration and elimination. In high heat, humidity, or times of high activity – like working outdoors or participating in athletic activities – perspiration (which cools the body through evaporation of fluids) increases. Exposure to the sun or a sunburn can speed fluid loss; so can beverages with caffeine, which acts as a diuretic.

"Fluid replacement is essential, but it’s best not to wait until you’re thirsty. People often become slightly dehydrated before they become thirsty," Higgins said.

Checking to see if your body is well hydrated is easy – just look at your urine. If urine is pale yellow in color, fluids would appear to be adequate. If urine is dark yellow or appears concentrated, more fluids are needed, she said.

Eight to 12 cups of fluid are recommended each day to replenish essential body fluids. Water is recommended as a majority of the fluid replacement because it is readily absorbed. Cool water is preferred because it is absorbed more readily than warm, hot or ice water.

"Some fluid replacement can come from other sources, such as milk; 100 percent fruit juice; low-sodium vegetable juice; foods that have a high water content, like fruits (melons) and vegetables (celery or tomatoes); or foods made with fluids (milk, fruit juices or soup broths, for example), such as puddings, gelatin salads or soups," the nutrition specialist said.

Beverages that contain caffeine (like coffee, tea and some soft drinks) or alcohol (which act as a diuretic that speeds fluid loss) are not recommended as essential fluid replacements. Higgins suggests that only half of the amounts of these beverages be counted towards total fluid replacement.

Sports beverages may be helpful to some athletes who are exercising more than one hour and in need of quick energy, but Higgins recommends diluting them with an equal part of water to help replenish fluids and reduce calories. Sugary beverages like sports drinks or carbonated beverages can add unnecessary calories, she cautioned.

Replenishing fluids is recommended for everyone. Before working in the heat, exercising or participating in athletics, Higgins recommends drinking 14-22 ounces of cool water. She also recommends drinking 1-1 ½ cups of water every 15-20 minutes during exertion. Children should be encouraged to take frequent water breaks (one-half cup after each 15 minutes of activity).

In order to make sure that people who work outdoors, athletes and/or active children get enough fluids to replenish fluid loss, Higgins suggests weighing before and after an activity and drinking 16-24 ounces of water for each pound lost.

Older adults also need to drink fluids, even if they are not thirsty. The ability to sense thirst declines over the years, so older people cannot rely on their thirst to prompt them to drink enough fluids. The ability to regulate body temperature easily also declines with age.

If a care giver is thirsty, a dependent older adult, infant or small child probably is, too. Hold a glass of water or other nourishing liquid up to them when offering a drink, Higgins said.

"Parents are encouraged to monitor their children’s (including toddlers and infants) fluids. Water is recommended for infants who have started on solid foods. Weighing children before and after play or participation in an athletic event can be helpful to parents in gauging their child’s fluid loss and replacement needed," she said.

In addition to replacing fluids, Higgins also recommends wearing a hat with a brim; choosing loose, comfortable clothes that breathe; using sun screen; and taking occasional breaks to help minimize the effects of heat and humidity.

For more information on nutrition and health, contact the local extension office.

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Sidebar or box: Children do not tolerate the heat as well as adults. Their bodies generate more heat relative to their size than adults do. They also lose more fluids because they have a greater proportion of skin surface in relation to their size. Since children do not always recognize their thirst, parents are encouraged to offer them a drink of water frequently – each time they pass through the kitchen and before, during and after play.

– Mary Higgins, K-State Research and Extension nutrition specialist.

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan. 


Nancy B. Peterson 
Communications Specialist 

K-State Research & Extension News

Contact Mike Bradshaw at 785-532-5773
Contact Mary Higgins at 785-532-1671