How Much Is Enough?

Just how much water do you need?
Martha Filipic

Your question:
A friend told me about new recommendations on how much water we should drink. Isn't it still eight cups a day?

The expert answers:
Well, it never really was eight cups of plain water a day, although drinking that much water certainly wouldn't harm you.

Your friend was likely referring to the report, "Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate," issued by the Institutes of Medicine in February 2004.

Although the "adequate intake" of water varies person to person, almost all healthy people get enough from the water and other beverages they drink, as well as from water in foods. Most people get about 80 percent of water from beverages. The remaining 20 percent comes from foods, including iceberg lettuce (96 percent water), other fruits and vegetables (raw bananas are 75 percent water) and even foods like roasted chicken (64 percent water) and whole-wheat bread (38 percent water).

The report set the adequate intake of water from all sources for adults at 3.7 liters (about 16 cups) for men, and 2.7 liters (about 11 cups) for women. Although researchers note that "body water deficits" can occur over the course of a day because you're exercising, or because it's hot, or because you're just not consuming enough fluid, simply drinking a beverage at meals or just when you're thirsty is almost always enough for your body to maintain normal hydration.

Of course, during periods of heavy exercise, especially when it's hot, it's important to consume plenty of fluids. If your body gets dehydrated, it loses some of its ability to tolerate heat stress from exercise. That can be downright dangerous.

Also, thirst and other water-balance mechanisms are often impaired in older people. So, it's not unusual for health professionals to encourage older clients to drink water or another beverage even when they're not thirsty, just to make sure they're getting enough fluids for normal bodily needs.

One item of note: A lot of people have thought that you can't really "count" coffee or other caffeinated drinks in your daily water intake, because of caffeine's diuretic effect. But in reviewing the research, this report found inconsistent data to support that idea, and the scientists concluded that caffeinated beverages can contribute to your daily total water intake just like other


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