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Is Eight Enough?

Por Leslie Rodríguez, RD, LD* -

You’ve been told over and over again to drink 8 8-ounce glasses (2 liters) of water/other liquids each day. Does this really apply to everyone?

The 8 cups a day rule is a general guideline. This quantity was established as a result of past research indicating that you should drink 1 ml of water/other liquids for each calorie consumed. On a 2,000-calorie diet, that amounts to about 64 ounces of water/other liquids. However, to calculate fluid needs more precisely, you need to take into account many factors, such as body size, activity level, gender, and air temperature. For example, you may need more fluids when the temperature is very high or very low, and when performing strenuous activity. Men may need more water than women because they typically have more muscle mass.

About 55-75% of your body weight is water. Losing only 1-2% of your body’s water can affect your physical activity. If you lose more than 10% of your body’s water weight, you could have a heatstroke and possibly die! Maintaining fluid balance is essential, especially among athletes.

Water: important for many functions

Water is one of the most essential components of the human body. It works to regulate body temperature, cushions and protects vital organs, and aids in the digestive process. Water makes up 75% of all muscle tissue and 25% of fat tissue. It transports nutrients and dispels wastes. You can’t survive without water for more than a week.

Each day you must replenish the water you have lost. To regulate body temperature during exercise, you must stay well hydrated. Heat evaporates from the body in the form of sweat. Depending on air temperature and how intense the exercise is, one hour of exercise could potentially cause a loss of more than a liter (4 cups) of water in the form of perspiration. When you are not sufficiently hydrated, your body cannot cool itself properly, and you will begin to experience the effects of dehydration. This can happen even more quickly on a humid day, because the moisture in the air does not allow your sweat to evaporate as quickly.

Dehydration dangers

When dehydrated, your body cannot cool itself. The symptoms of dehydration are progressive and they begin with thirst. That’s why people say that by the time you are thirsty, it is too late; you’re already dehydrated. The next symptom is fatigue and possibly cramps, followed by loss of coordination, weakness, delirium (heat exhaustion and/or heatstroke) and finally, death.

To prevent dehydration, follow these general guidelines.

  • The 8-cups-a-day rule is a good place to start.
  • Add 1-3 cups, depending on your activity level.
  • Monitor the color of your urine. When you are well hydrated, it should be light to clear unless you are taking supplements (which will darken the color for several hours after consumption).

Hints for proper hydration for exercise:

  • Drink 1 to 2 cups of fluid at least 1 hour before the start of exercise.
  • Drink 8 ounces of fluid 20 to 30 minutes prior to exercising.
  • Drink 4 to 8 ounces of fluid every 10 to 15 minutes or so during exercise.
  • Drink an additional 8 ounces of fluid within 30 minutes after exercising.
  • Weigh yourself before and after you exercise. Drink 8 ounces of water for every pound you have lost.

Alternate water sources

Let’s face it. Drinking water all of the time can get pretty boring. Not all fluid has to come from pure water. Some other choices include fruits, juices, soups, and vegetables. Half a cup of lettuce, for example, is 95% water by weight. Broccoli is 91% water, and a baked potato is 71% water. Even tuna, rice, pasta, and chicken are 70, 69, 66, and 65% water by weight, respectively.

If you want to quench your thirst with something different, try decaffeinated drinks. Caffeine acts as a diuretic, causing you to lose water. If you are not concerned about calories, drink 100% fruit juice (dilute it for less calories) or unsweetened flavored waters, or sugar-free beverages. Alcoholic beverages also have a diuretic effect. Alternate these options with water to maintain your hydration status.

Do I need sports drinks?

The research surrounding whether drinking sports drinks is beneficial or not, is not conclusive. There are still varying opinions on this topic.  We provide here some general information that may guide your decision on whether to drink them or not.

Sports drinks can be helpful to athletes who are exercising at a high intensity for 60 minutes or more. Fluids supplying 60 to 100 calories per 8 ounces help to supply the needed calories required for continuous performance. It's really not necessary to replace losses of sodium, potassium and other electrolytes during exercise since you're unlikely to deplete your body's stores of these minerals during normal training. If, however, you find yourself exercising in extreme conditions over 3 or 5 hours (a marathon, Ironman or ultra marathon, for example) you may likely want to add a complex sports drink with electrolytes.

Find a balance

Though it is necessary to be well hydrated, over hydrating is also possible. Athletes who participate in long endurance events, such as marathons and triathlons, may be at risk of drinking too much water. This can result in diluted or low blood sodium levels. This condition is called hyponatremia. It is very rare but serious.

When athletes compete for a long period of time, they lose a great deal of salt through their sweat. Combine that with drinking water along the way, and the result is too much water and not enough sodium. Even more frightening is that the symptoms are very similar to those of dehydration: nausea, fatigue, vomiting, weakness, sleepiness, and death, in severe cases.

The best way to avoid hyponatremia but stay well hydrated is to follow some simple steps.

  • Don’t restrict your salt intake a few days before an endurance event, unless instructed by your doctor.
  • Drink sports drinks with sodium when you are competing for more than an hour, especially if the weather is hot and humid.
  • Some research has shown that using non-steroidal anti-inflammatory drugs, and ibuprofen before a race could predispose you to hyponatremia. Acetaminophen, however, is safe to take on the day of an event. It is best to consult your doctor before taking any medicines.
  • It may be difficult to drink sufficient water at first, but if you can stick it out for a few weeks, it will become it a habit. Carry a water bottle with you everywhere you go so that fluid is always close at hand.

As you increase your fluid intake, you will likely have to go to the bathroom several more times a day. Eventually, your bladder will adapt. Most importantly, you could greatly improve your energy and physical activity level as well as prevent the consequences of dehydration. That’s worth going to the bathroom a little more frequently, don’t you think?

*Specialist in sports nutrition and physical activity with MyDiet TM

Sources: Sports Medicine

Exercise and Fluid Replacement , ACSM Position Stand, American College Of Sports Medicine, Medicine and Science In Sports & Exercise, 2007.

Institute of Medicine. Water. In: Dietary Reference Intakes for Water, Sodium, Chloride, Potassium and Sulfate, Washington, D.C: National Academy Press, pp. 73–185, 2005.


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