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Health Options
Alan Titchenal |
Summer time is fluid time
to stay safeSummer heat increases the need for water. Severe dehydration certainly can lead to a medical emergency. Less severe chronic underhydration has fewer obvious signs but can lead to problems that people often do not relate to water.
Question: What health problems are related to chronic underhydration?
Answer: A lack of adequate water forces the body to reduce its blood volume and produce very concentrated urine. This can increase the risk of kidney stones and aggravate existing kidney problems. Chronic underhydration also can lead to blood pressure fluctuations, headaches and intestinal problems.
Question: How much water is enough?
Answer: The common recommendation is eight glasses a day. This is appropriate for those who require about 2,000 calories per day. A general rule of thumb is to consume a liter of water (about four 8-ounce cups) for every 1,000 calories expended. So the typical person who burns 2,000 to 2,500 calories per day needs eight to 10 cups of water per day.
Q: Must it be plain water?
A: No. Although drinking pure water is a good habit, it is not essential for meeting water needs. Foods such as fruits and vegetables provide appreciable amounts of water. Hydration research also indicates that water in coffee, tea and caffeinated sodas can be counted as water intake.
The value of alcoholic beverages is less clear. A University of Hawaii study found that female athletes retained four times as much water from nonalcoholic beer as they did when drinking regular beer to rehydrate after exercise.
Q: Can you rely on thirst?
A: No. Sense of thirst can be a poor indicator of adequate water need, especially when water is lost rapidly during hot weather or exercise. Also, as a person ages or when a person is taking certain prescribed drugs, the thirst mechanism might become faulty. Children also overlook their fluid needs.
Q: How does hot weather affect water needs?
A: An hour in hot weather can increase water needs by 2 to 4 cups beyond the norm.
Q: How does exercise affect water needs?
A: Exercise in hot weather can double water needs to 2 liters or more for every 1,000 calories expended. In an hour of jogging, adults commonly lose 1 1/2 to 2 liters of water in sweat. For the body to recover, the exerciser might need to drink 2 to 3 liters of fluids -- some during and some after exercise. Consuming carbohydrate, salty foods and protein can help the body hold onto the water being replaced. Otherwise, there is a tendency for much of the water to just go out in the urine.
Recovery from dehydration requires getting water back into body cells. This can take several hours when dehydration goes too far. Bottom line, anticipate water needs to prevent dehydration, and remember, summertime is fluid time!
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Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S. are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, UH-Manoa. Dr. Dobbs also works with the University Health Services and prepares the nutritional analyses marked with an asterisk in this section.