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Glenn D. Braunstein, M.D.

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Water, Water Everywhere, But How Many Drops to Drink? Hydration and Health

Posted: 09/27/10 05:39 PM ET

The members of the old (actually, ancient) rock group Earth, Wind and Fire obviously did not major in biology, since they left out the fourth classical element of the universe and the number one element in the universe of the human body: water. This was shortsighted, because water is the body's most important nutrient and its most abundant substance, making up 75 percent of all muscle tissue and approximately 10 percent of fatty tissue.

But water isn't only important for how much of it there is, but for what it does, namely transporting nutrients, dispensing of waste and converting food into energy through a process called hydrolysis. Even if this was all water did, it would have pretty much earned its living, but water is also the containing medium for electrolytes and all other ions throughout the human body.

An electrolyte is an electrically charged mineral that acts as a chemical messenger, carrying electrical impulses from nerves that control tissue function and movement. When electrolytes get out of balance, it can lead to serious physiological disruptions, including heart and nerve function, muscle coordination and control, and maintenance of the body's fluid levels. These important levels of electrolytes (like sodium and potassium, which are most prone to becoming out of balance) are controlled by certain hormones and by the kidneys, which are responsible for retaining or removing electrolytes to keep them in balance. This is why dehydration is so dangerous. It literally throws the body out of whack. Being even 2 percent dehydrated can seriously impair physical and mental functions. A level of 15 percent dehydration can cause critical damage. Unlike vitamin and mineral deficiencies, which can take weeks or months to become noticeable, water deficiency can kill within days or even hours. Which is why, if someone asks you what you would want most on a desert island, don't say your iPad.

Water is also critical for removing toxins. The body has four major ways of doing this: through the bowels, processing by the liver, by urination and by perspiration. When it's dehydrated, the body will try to save water by minimizing urination, perspiration and bowel function, while forcing the liver to do much of the work. But the liver has other functions to maintain. If it's overburdened with detoxification, it can't metabolize fat efficiently, causing the body to store it instead. Dehydration also reduces protein synthesis, the process that builds and repairs muscles.

The Goldilocks Solution: How Much Water is Just Right?
So you get the picture; you need to hydrate. But how much and how often? Women should have about 91 ounces a day, and men need 125 ounces, which is considerably more than the 64 ounces (eight cups) generally recommended. But not to worry, we get most of the water we need from food (about 20 to 35 percent) and other liquids we drink (about 40 to 45 percent). Vegetables and fruits are the most hydrating (lettuce is 95 percent water). Meat, soup, juice, soda and milk are also sources of hydration. Contrary to popular belief, coffee is not a diuretic and counts toward one's daily water intake as well. However, alcohol has been shown to dehydrate the body, causing it to excrete more fluid than what is taken in.

So rather than a fad diet or fast, you can see that food helps to hydrate your body, metabolize fat, get rid of waste, keep your energy up so you can exercise and burn more calories, and plump cells to keep your skin looking healthy.

How much fluids you should drink varies with your size and activity level. One way to know if you're getting the right amount is by the color of your urine. Typically, good health is indicated by lighter urine color, although clear urine can be a symptom of over hydration or water intoxication (water poisoning) or even diabetes. The ideal urine color is actually a straw yellow color.

If you have any kidney or adrenal problems, or your physician has recommended diuretics, discuss how much water you should be drinking a day. Also, don't drink your daily requirement all at once. Divide the amount throughout the day. This is especially important if you engage in heavy exercise. Infants should not be given water, only formula or breast milk, unless your pediatrician recommends otherwise. And if you exercise nonstop for more than an hour, you might want to replace electrolytes along with water in the form of a sports drink to prevent hyponatremia (depleted sodium) or other forms of severe electrolyte depletion.

Water and Weight Loss: The Holy Grail
There are many different kinds of metabolism going on in the body all the time, but the one everyone means with relation to weight loss is the metabolism of fat. As already mentioned, the liver takes a major role in this, but if it's busy with detoxification, it's going to sock away the fat it doesn't have time to metabolize. So you might want to get right to that water bottle.

People also ask if water is good for suppressing appetite. Well, there's no real evidence for it; however, it's easy to mistake thirst for hunger, which means you might be eating food when you simply need some water. Try having a tall glass of water when you feel a craving for a snack, then see if you still want those potato chips. Some research has indicated that eating soup and other liquid-based foods at the beginning of a meal can help reduce hunger.

Given that adequate hydration helps in maintaining proper organ function, electrolyte balance, more efficient fat burning and waste removal, not to mention healthier looking skin, how many more reasons do you need to hydrate correctly? Besides, if you're not hydrating, you won't be going to the water cooler to talk about last night's episode of Mad Men.