Water Content in Food

The Wonders of Water

By Kathleen M. Zelman, MPH, RD, LD
WebMD Feature

Reviewed by Louise Chang, MD

"Water is one of the most basic elements of life but figuring out how much we ought to drink hasn't always been so simple.

Most of us grew up thinking we needed to drink eight glasses of water each day, in addition to any other drinks we might choose. But the latest recommendations say that we no longer need to worry about drinking specific amounts of water. Instead, we can simply satisfy our thirst with any beverage. As it turns out, there really was no scientific evidence for the 64-ounce daily recommendation that was based on survey data of usual consumption.

Of course, water -- clean, refreshing, and calorie-free -- is an ideal beverage of choice...

To help make the facts about water crystal clear, WebMD asked experts for the skinny on just how much water we need...

The New Fluid Guidelines

A 2002 study published in the American Journal of Physiology questioned the old recommendation of 8 ounces of water, eight times a day. After a thorough review, researcher Heinz Valtin concluded there was inadequate evidence that healthy adults -- living in temperate climates and not engaged in rigorous activities -- need large amounts of water.

For normal, healthy adults, Valtin recommended simply drinking when thirsty. 

In February 2004, the Institute of Medicine (IOM) issued new recommendations that agree with Valtin's findings. The new guidelines remove the eight-glasses-a-day recommendation, and say healthy adults may use thirst to determine their fluid needs. Exceptions to this rule include anyone with a medical condition requiring fluid control; athletes; and people taking part in prolonged physical activities or whose living conditions are extreme.

How Much Is Enough?

The IOM report did not specify requirements for water but made general fluid intake recommendations based on survey data of 91 ounces (that's 11-plus cups a day) for women and 125 ounces (15-plus cups a day) for men. Remember, these guidelines are for total fluid intake, including fluid from all food and beverages.

Approximately 80% of our water intake comes from drinking water and other beverages, and the other 20% comes from food. Assuming these percentages are accurate for most of us, the recommended amount of beverages, including water, would be approximately 9 cups for women and 12.5 cups for men.

While 20% may seem like a lot of fluid to get from food, many common food items are mostly water.

 Here are some foods with high water content, according to the American Dietetic Association:

Food	Percentage Water
Lettuce (1½ cup)	95%
Watermelon (1½ cup)	92%
Broccoli (1½ cup)	91%
Grapefruit (1½ cup)	91%
Milk (1 cup)	89%
Orange juice (3/4 cup)	88%
Carrot (1½ cup)	87%
Yogurt (1 cup)	85%
Apple (one medium)	84%

When You Need More

Physical activity, heat, and humidity can increase our fluid needs. In these situations, keep water bottles close at hand and drink frequently to avoid dehydration. If you're going to be physically active for long periods, consider drinks that hydrate and provide easily usable sugar and electrolytes.

How Much Is Too Much?

Scientists on the IOM panel did not set an upper limit for water.

"Water intoxication is very rare, although it has been seen in fraternity pranks. That can be very serious and result in death" says David Perlow, MD, an Atlanta-based urologist.

One recent study of Boston Marathon runners showed that one in three marathon runners was drinking too much water during a race -- probably because they were following recent advice to drink as much as tolerated.

If you follow your thirst, you won't go wrong, Perlow says. He notes that pre-modern man never ran around sipping on a water bottle. A dry mouth indicated it was time to run to the stream for a drink.

"Trust your thirst instinct to make sure you get enough fluids and, of equal importance, void frequently," suggests Perlow."

Remember, fluid is only part of the hydration equation, balanced electrolytes are vital too.  And what do you do when you need INSTANT HYDRATION?...well that's a whole other question ...one only RevoH2O can solve.