Water, The Rodney Dangerfield Of Nutrients: It Gets No Respect
It covers over half our planet, makes up most of our body weight and is the most essential nutrient for life. Yet water is still little more than an afterthought in our diets. Most of us don't drink nearly enough of it. Here's why you need to start paying more attention to this nutrient, especially as you get older.
Water plays a role in virtually every function of the body from breathing to batting an eyelash to flexing your biceps. Its main functions include regulating body temperature, carrying oxygen and nutrients to cells, adding moisture to the air we breathe so lungs can process it, cushioning organs and joints, absorbing nutrients, converting food into energy and removing waste.
Eight May Not Be Enough
We need 8 to 10 eight-ounce glasses of water a day just for the basic functions of life, explains W. Larry Kenney, PH.D., professor of physiology and kinesiology at Penn State University. Yet a normal, healthy adult excretes almost six cups of water a day in urine alone, according to Lawrence Armstrong, Ph.D., professor of environmental medicine and exercise physiology at the University of Connecticut in Storrs. And that doesn't take into consideration fluid losses from daily activity or hot weather
Your actual water requirements are based on the number of calories you burn. For each calorie burned, you need one milliliter of water. An active man who burns 3,000 calories a day needs more than three quarts of water, while a sedentary woman might require half that. Those of us who don't drink our quota live in a constant state of mild dehydration, notes Kenney.
Although little has been published about the cumulative effects of mild dehydration, there have been reports linking a low intake of water or fluids with certain cancers. In addition, new research indicates that fluid consumption in general and water consumption in particular can decrease the risk of kidney stones and enhance salivary gland function. And a new study from Loma Linda University of more that 20,000 people found that men and women who drank more that five eight-ounce glasses of water a day were about 50% less likely to suffer a fatal heart attack than those who drank two or fewer glasses of water, according to Jacqueline Chan, Dr. P.H., the study's principle investigator.
Based on our study, and Chan, drinking five or more glasses of water a day may be even better for the heart that alcohol or aspirin.
Most of all, water is essential for the production of perspiration, the body's way of cooling itself. Both while you're at rest and during exercise, evaporation of sweat helps keep the body's core temperature in check. When it rises above normal (98.6 F), the result can be heat illness, either mild (heat stroke) even deadly, if body temperature rises above 105 F. About 300 Americans die from heat-related illness every year.
Although clear symptoms of dehydration may not occur until you've lost more than 3% of your body weight in fluids, a fluid loss of just 1% to 2% of weight strains the heart and entire cardiovascular system.
The Influence of Age
The thirst mechanism that prompts us to drink doesn't work as well when we're older. In essence, there's no dipstick to tell us when we're a quart low.
"Even at the same level of dehydration, older people do not feel as thirsty as younger adults," says Kenney. This puts them at risk for dehydration. Older people need to be particularly conscious of water intake and drink regularly, whether or not they are thirsty.
Dehydration can also increase a drug's potency, resulting in more powerful effects than intended. Several medications (including beta-blockers, tranquilizers, antidepressants and over-the counter sleeping pills) can further dehydrate the body or impair its ability to regulate temperature, making it doubly important to get enough water. Ask your pharmacist.
Activity Ups Fluid Requirements
On a brisk walk, you can sweat as much as one quart per hour. Intense exercise causes even more sweating, of course. If the body can't sweat enough for example, because the humidity is high its forces the heart to beat harder and faster to pump the already decreased blood volume to exercising muscles.
Must It Be Water?
The question everyone wants to know is must you drink water or do other fluids work just as well? Although other liquids count (because most of them contain water), there's evidence drinking plain water is better. The Loma Linda study found that women and men who drank beverages other that water increased their risk of heart attack, perhaps because caloric drinks due to their concentration require water to be pulled from the bloodstream for digestion, thickening the blood. Moreover, sugary fluids like soft drinks and fruit juices can increase triglyceride levels, which cause clotting factors to increase, notes Chan.
How To Tell If You're Dehydrated - Here are some classic signs that you need to drink more water.
Dry lips and tongue.
Weakness, dizziness or exhaustion.
Nausea or headache.
Thirst - If you're thirsty, you're already slightly dehydrated. Thirst is triggered only when the body has lost 1% to 2% of its body weight (more in older people).
Cramps - Muscle cramps, especially in the legs, have been linked to dehydration or low levels of electrolytes (sodium, potassium, chloride and calcium), which help regulate muscle contractions.
Low urine volume - A decreased volume of urine, though not necessarily less frequent urination, is a definite indication you're running dry.
Deeply colored urine - Urine that's deep yellow, tan, light brown or has a greenish tint means you're dehydrated. Urine should be clear, pale yellow or straw colored. The lighter in color, the better.
Guide To Hydrating For Activity
This is good advice no matter what type of exercise you're doing, even simply walking, jogging or gardening or swimming, when sweating is not apparent.
Start exercise well-hydrated. Drink about two eight-ounce glasses of water two to three hours before exercise and another glass 10 to 20 minutes before exercising.
Drink eight ounces of water every 10 to 20 minutes during exercise.
Choose sports drinks if you're exercising for over an hour or at high intensity. The carbohydrates in them provide fuel to muscles, while the electrolytes (sodium, potassium, chloride) help blood hold onto more water. They also make you thirsty, so you'll drink more.
To re-hydrate after exercise, drink more than you lost in sweat. (Weigh yourself before and after exercise.) Drink 20 ounces for each pound lost.
Sports drinks are recommended for re-hydrating after long-duration or intense exercise, when several liters of fluid are lost.
The Bottom Line
Drink more water. Pure and simple. If you you're drinking enough, you won't get thirsty. Yet the older you get, the less you can trust your body to tell you you're in trouble. So aim for eight to ten glasses a day of water more if you exercise. Other fluids can provide the extra, but don't count on them to meet you basic needs.