by Reuven Bruner, Ph.D .

Amid today’s sports-drink craze, some thirsty exercisers and athletes have forgotten about the basic, old-fashioned fluid replacement: water. Generations of active people have quenched their thirst with H20, but today’s high-tech beverages are making inroads.

Yet water is worth remembering. Here is a reminder of just how important water is in today’s sports and exercise diet, and in fact, for non-active men and women as well.

What to know about H20

Water is a basic nutrient, essential for the maintenance of life and for proper body function. You can survive for weeks without food, but only a few days without water.

Water makes up about 60-70% of your body weight. Muscle tissue is actually 70-75% water. Fat, in comparison, contains only about 10-15% water.

Water performs very important functions in your body. In saliva and stomach secretions, it helps digest food. In body fluids, it lubricates the joints and cushions organs and tissues. In blood, it transports carbohydrates, fats, proteins, hormones, and oxygen to the working muscles. It also carries away waste products such as carbon dioxide, ammonia, and lactic acid.

In sweat, water removes the body heat you generate during exercise or other activity. Water helps regulate body temperature by absorbing the heat from the muscles and transporting it to the skin’s surface. Loss of a pound of sweat (about a pint) equals about 250 calories of weight loss.

It is quite evident that dehydration — a clinically severe lack of water — is likely to play havoc with your body’s ability to function at its peak. During the first few hours of water deprivation, the fluid is lost primarily from blood volume. Because about ninety percent of your blood should be water, one danger of dehydrating during exercise is that it takes longer for nutrients to be transported to and from your muscles. Your exercise and sports performance will suffer.

With dehydration, our cells lose water. When cells become overheated, they experience changes that can impair how they work. Water loss of nine percent to twelve percent of one’s total body weight can be fatal. It is therefore essential for us to prevent dehydration.

Thirst is your body’s way of telling you it needs liquids. Under normal resting conditions, thirst does an adequate job of helping maintain your water balance. If your body fluids become abnormally concentrated because you lack water, your brain receives a signal that makes you feel thirsty. But this happens late — after you are already a little dehydrated.

In some circumstances, the thirst mechanism is not reliable. Among athletes especially, thirst can be blunted by exercise and overridden by the mind. This is why extremely active exercisers and athletes should drink more than required to satisfy their thirst. The thirst mechanism in young children and older adults may also lack the sensitivity needed to match their fluid needs. They may not feel thirsty even though their bodies need fluid.

How much is enough?

Water is fundamental for survival, and you need to drink enough every day to replace the amount you lose through urine, sweat, feces, and breathing. Even if you don’t exercise, you lose about twelve ounces of water per day with simple breathing. You lose an additional twenty-four ounces through the skin, by way of perspiration that you don’t even notice. Add strenuous exercise to your daily routine, and you may lose up to three pounds of water (almost two quarts) per hour.

How much water you require per day is determined by how many calories you burn. If you are active and burn 4,000-5,000 calories per day, you need to take in four to five quarts of water or fluid daily. If you are an inactive person, you may burn 1,500 calories, requiring about one and a half quarts of water.

A simpler way to determine water requirements is to weigh yourself before and after you exercise. If you have lost a pound of body weight, you need to replace it with at least sixteen fluid ounces (two cups) of water. Or better yet, plan to drink at least sixteen ounces of water during your next workout, in order to preempt dehydration.

Another way to see if you get enough water is to monitor your urine. If you urinate a significant amount regularly and your urine is clear-colored, you are drinking enough. For athletes, this may mean drinking twelve to sixteen glasses of water. Others will need to drink less. Urinating about every two to four hours is fine. If you have to visit the bathroom every hour, you are drinking more than required. (For some quick tips on how to add more water to your day, see the sidebar on the previous page.)

Beyond the basics

For some people, water seems boring. Research by the makers of sports drinks has shown that active people tend to drink more fluids if they taste good. Given the choice between a tasty sports drink and plain water, the sports drink will disappear faster. A sports drink can, if you are an endurance athlete/exerciser, mean better hydration not only because you drink more fluid but also because your body absorbs sports drinks slightly faster than water. And sports drinks replace carbohydrates that help fuel your muscles. But you need the benefits of a sports drink only during endurance exercise that lasts over an hour.

So remember: the taste of water may be simple, but its function isn’t. Water is 100% natural, 100% pure, low-sodium, calorie-free, fat-free, and cholesterol-free — a practically perfect nutrient. Make sure you drink enough to stay hydrated for health.

Dr. Reuven Bruner is a health, fitness, nutrition, and total lifestyle consultant in private practice in Jerusalem. For more information, he can be reached at 972-2-566-2921, or by e-mail at dr_bruner@hotmail.com

Wet Your Whistle

If you want to make sure you are getting enough liquids, increase your water intake. Here are some helpful tips:

If you are hot, cold water will cool your body better than room temperature water.

If your tap water tastes bad, try a water filter or bottled water for a consistently pleasant flavor.

Keep a filled water bottle by your side at work and take water breaks instead of (or in addition to) coffee breaks.

Stock your refrigerator with a pitcher of tap water so it will be ready for fluid breaks. To keep the water cold and refreshing, wrap the pitcher in a towel or keep it in a small cooler.

If you work out in hot weather — for example, if you bicycle — you can drink from a water bottle that has been stored in the freezer. Water will thaw in the heat at about the same rate you want to drink it during exercise.