Got Water? Summer Heat Ignites Dehydration

A woman drinks bottled water.

hide captionDrinking helps replenish fluids lost through sweating.

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Heat-related dehydration is a big problem in summer. And if you're active — even if you're healthy — you're at risk. Thirst isn't always the best clue that it's time to take a drink.

Technically, dehydration sets in when a person has lost 2 percent of his or her body weight. How quickly that happens depends mainly on the conditions.

The American College of Sports Medicine recommends that athletes drink 16 ounces of fluids — two full glasses — a couple of hours before starting practice or exercise.

Duke University sports medicine expert Blake Boggess says the body needs that much time to absorb the fluid.

For most adults, thirst is a good guide that it's time to take in some fluids, he says. But research suggests that by the time we have reached our late 30s, our recognition of thirst has become a bit delayed.

That means weekend hikers or bikers should drink up before they venture out.

Everyday Hydration Tips

Dr. Douglas Casa, Director of Athletic Training Education in the University of Connecticut's Neag School of Education says people get into trouble when they try to follow set requirements for hydration. A magazine article that endorses eight glasses of water a day may not be right for you. Quench your thirst for information with Dr. Casa's tips on how to regulate your daily drinking.

Peek at Your Pee: Monitor its color. If it's light, like lemonade, you're doing pretty good. If it's darker, like apple juice, start gulping down liquids.

Step on the Scale: And do it both before and after exercising, to get a better sense of your individualized hydration needs. If you weigh more after a workout, chances are you drank too much while exercising. If you weigh much less, you may need to drink more. Experts recommend losing no more than 2 percent of your body weight during activity. Weighing the same before and after exercise, or slightly less, suggests you are an efficient hydrator.

Consider Sports Drinks: Because they replace some of the salts you lose when sweating, they're ideal for activities that last longer than an hour (for instance, hiking or biking treks) or even during very intense activities. Or if you're the kind of fanatic who's jogging in 110-degree heat.

Remember Chug Capacity: Recent studies show that coffee doesn't dehydrate, but Casa still doesn't recommend it for a workout; it's not the kind of fluid you can chug when you need to replace a lot of fluid in a short period of time.

(But Not for Beer!:) Alcohol does not leave you in the best possible state to recognize your fluid needs, prepare for the next bout of activity, or maximize fluid retention. Only use if stranded on an island with a case of beer, not for the purpose of fluid replacement.

Shun Sugar: Sodas, fruit juices and even beer have a higher level of sugar (which means more calories per serving) than most sports drinks or water. These drinks can rehydrate your body because they contain water, but their sugars give the stomach and intestines more to deal with; as a result, the fluids aren't absorbed into the body as quickly. It's fine to drink these beverages with meals and during leisure activities, but they won't keep you optimally hydrated during exercise.

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