How Much Water Do You Need?

Water Is Essential

Water is one of the most important elements of the human body. It makes up approximately 70 percent of our muscles, and about 75 percent of our brains. It is also an essential part of a healthy diet and plays a vital role in the proper functioning of the body. Some of water's many benefits:

• Transports essential nutrients throughout the body and rids the body of waste
• Acts as a lubricant for the body, moistening eyes, mouth, nose, and skin
• Helps maintain adequate blood volume
• Helps regulate body temperature, especially in warm weather
• Helps prevent constipation
• Helps medications to work
• Helps prevent urinary tract infections
• Acts as an appetite suppressant
• Is calorie-free
• Boosts metabolism when drunk cold (we burn 2 calories per glass as we warm it up to body temperature)

Drinking water also forces fat to be used as fuel. How does this work? Without water, the kidneys are unable to function properly, so the liver picks up the slack. But the liver cannot properly metabolize stored fat as energy. The result is a decrease in fat metabolism, leading to more fat stored in the body. So, drinking lots of water helps avoid extra fat deposits.

How Much Do You Need?

The standard advice from nutritionists is to get at least 64 ounces of water daily. This is called the 8 x 8 rule (eight 8-ounce glasses). If you are trying to lose weight, it is especially important to stay hydrated. A good rule of thumb, experts say, is to drink half your daily water consumption between the time you wake up and lunch, and the other half between lunch and bedtime.

If you are exercising, you might want to drink a bit more. Drink 8-10 ounces approximately 30 minutes before exercising. You should also drink some water while exercising; about 3-4 ounces every 15 minutes. Finally, when you're through exercising, drink another 8-10 ounces to make up for the water you lose through prespiration.

Healthy adults of all ages need at least 8 cups of water every day. Children should have 6-8 servings, but the serving size depends upon the child's age. For children age 2 and under, a serving is half a cup; for kids age 3-5, it's 3/4 cup. For kids 6 and up, a serving is one cup.

Sneaky Ways to Drink More

Here are some easy ways to work in more water each day:

• Take frequent water breaks throughout the day
• Start lunch and dinner with a cup of soup
• Drink 100 percent juice at breakfast. (Dieter's caution: while juice and other beverages count toward your fluid intake, they are often high in calories.)
• Never pass a water fountain without drinking
• Take a bottle of water with you wherever you go
• Remember that only decaffeinated beverages count toward your goal

Dehydration Signs

In addition to using water, the body also expends it. In fact, just in everyday breathing we lose about 2 cups of water. We also lose body water through sweating and urinating. If we fail to replenish these losses, we set ourselves up to become dehydrated.

Thirst is the most recognizable cue that you need to drink more water. Another is the "pinch test." Gently pinch the skin on top of your hand and see if it holds the "pinched" position. If it holds, you need to drink more water. Other signs that you may be dehydrated:

• Dry mouth
• Flushed skin
• Fatigue
• Headache
• Rapid pulse
• High body temperature
• Increased breathing rate
• Dizziness, weakness
• Muscle spasms
• Swollen tongue
• Delirium

Tips to Avoid Dehydration

Luckily, dehydration is 100 percent preventable. Here are some practical tips to staying hydrated.

• Drink plenty of fluids: See the suggestions in this article regarding recommended fluid intake.
• Avoid caffeinated beverages and alcohol; both may cause dehydration
• Avoid carbonated beverages; the carbonation may cause bloating or a feeling of fullness and prevent adequate consumption of fluids
• Wear light-colored, absorbent, loose-fitting clothes
• Stay in cool, shaded areas and protect your skin with sunscreen

The Eight Glasses Controversy

If you have trouble drinking this amount of water, you may already be getting enough liquids in the foods you eat and other beverages you drink.

"People think they have to drink 8 eight-ounce glasses of water a day, when this has actually been the recommended amount of fluids," explains Jo Ann Heslin, RD. "Fluid intake can include water, mineral water, non-fat milk, or juice."

Any drink that does not contain caffeine counts toward daily intake, explains Heslin, who in addition adds: "We get a good amount of fluid in the foods we eat."

Other experts allow caffeinated and alcoholic beverages toward the count.

In a controversial report in the American Journal of Physiology, researcher Heinz Valtin, MD, a kidney specialist and author of two widely-used textbooks on the kidney and water balance, writes that he finds it "difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake."

Dr. Valtin believes the notion began as a misinterpretation of the recommendation by the Food and Nutrition Board of the National Research Council, which suggested "1 milliliter of water for each calorie of food" (about 60 to 80 ounces). Although the Board added that "most of this quantity is contained in prepared foods," he points out this qualifier seemed to be overlooked, and thus the 8 x 8 rule was perpetuated.

"I have found no scientific proof that absolutely every person must drink at least eight glasses of water a day," says Dr. Valtin. On the contrary, he says, some studies have shown that caffeinated drinks, such as most coffee, tea, and soft drinks -- and, to a lesser extent, even alcoholic beverages such as beer, if taken in moderation -- could count toward the daily total.

Can Water Harm You?

While Dr. Valtin's research casts doubt on the 8 x 8 rule, you may wonder if there's any harm in it.

"Potentially, there is harm, even in water," says Dr. Valtin. Even modest increases in fluid intake can result in "water intoxication" if the kidneys are unable to excrete enough. And he lists other disadvantages of a high water intake:

• Frequent urination, which can be both inconvenient and embarrassing
• Expense, for those who drink bottled water
• Possible exposure to pollutants, for those whose water source is questionable
• Feelings of guilt, for those who find the daily 8 x 8 impossible to achieve

So, what are we to make of the water debate?

"If you've been drinking 8 x 8 and you are comfortable with that," says Heslin, "there's no reason to make a change now until more is known." But if you've felt the pressure to guzzle this amount, this may be reason enough to ease up until greater evidence brings new recommendations.