SEATTLE – How much water is enough? The answer is fluid.

It depends on your activity, age, diet, condition, even the climate you live in. Athletes exercising hard or long or both need more than walkers do, of course, and the hotter it gets and the more you perspire, the more you need to hydrate.

It also depends on whom you ask. Different agencies, companies and trainers have their own ideas. Considerable attention has been paid over the past few years to the problems that drinking too much can cause. So many convoluted formulas are floating around that I challenge any athlete to keep it straight during the heat of competition. The best policy is to incorporate planning, a sense of thirst and common sense.

The Institute of Medicine’s Food and Nutrition Board said in 2004 that most healthy people get enough daily hydration by following their thirst. Thirst isn’t always the best first sign that your body needs liquid, however. The older we get, the less we are able to sense thirst. Sometimes, we lose a significant amount of fluid reserves before thirst kicks in.

That’s where common sense enters the formula.

The Mayo Clinic recommends drinking two cups of water two hours before an endurance event or hard, short bouts of exercise. Replenish during the activity and at regular intervals. Drink after you’ve finished, too. If you sweat a lot, you might consider a sports drink to replace the sodium you lose.

The American College of Sports Medicine urges people to take the threat of dehydration seriously, especially older athletes pushing themselves in triathlons, marathons or other challenging events. Dehydration limits the body’s ability to regulate inner temperature and is an especial threat to those not used to strenuous activity in hot environments. Dehydration robs the body of its ability to cope with heat stress, such as heat cramps, heat exhaustion and heatstroke. If you wait until you’ve begun exercising to drink water, you’re too late.

That doesn’t mean you guzzle. While uncommon, there are cases when athletes over-hydrate, lose sodium levels, and suffer a condition known as hyponatremia, which happens when the body’s sodium levels are diluted.

The sports-medicine college also recommends drinking about two cups two hours before exercise. A quart and a half (6 cups) is the most you should drink per hour. The maximum amount to drink in 24 hours is 12 quarts, the group says.

Food in the average American’s diet provides about 20 percent of our daily water intake. That’s another reason to eat healthy. A balanced diet helps keep a good sodium level, and fruits and vegetables are full of water – 87 percent in oranges, 95 percent in cucumbers. Milk, juice and other beverages also have large amounts of water. Coffee and pop contribute some to the fluid bottom line. The well-worn guideline of eight 8-ounce glasses of fluid a day with a healthy diet should be sufficient for most of us, although it lacks scientific validation.

The sports-medicine college says water is usually all you need, but sports drinks containing sodium and carbohydrates should be used whenever doing heavy work for an hour or more in hot conditions.

Some experts say the bigger you are the more water intake you need. Some suggest you check your urine. If it is clear or pale yellow, you are drinking enough. If it’s dark yellow, perhaps you should hydrate more.

Then there is the “sweat rate.” Weigh yourself naked just before beginning an hour of moderate exercise. Don’t drink anything during or after the workout. Don’t shower. Towel-dry perspiration and then step on the scale again. How much weight did you lose? One to two pounds is normal. Lost one pound? Then you should replenish 16 ounces of water per hour while working out at a similar level. Lost two? Then double that. Of course, not everyone agrees with that, either. You can hydrate during this test if you factor how much you drink into the bottom line.

Added incentives to imbibe

The folks behind Propel Fitness Water have come up with another reason to drink their product: “Propel Calcium.”

Propel and other sports drinks can be a good alternative for some athletes because the slight flavoring entices people to drink more. Adding calcium to some of its products helps the company fill another niche. Almost 80 percent of us don’t get the daily level of calcium recommended by the U.S. Department of Agriculture.

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