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Keeping Your Cool Expert advice on everything you need to know about staying hydrated 
A reasonably healthy human might be able to make it eight weeks without food, but will likely only live three to five days without water. In extreme heat, the liquid-deprived could actually become dangerously dehydrated in only a few hours. Comprising approximately 65 percent of the human body, water is essential to both blood flow and organ and muscle function. But it can't be stored up, thus we need a fresh supply every day to replace the liquid lost through sweat, tears, urine, feces and breathing. So how much exactly do you need and what's the best way to get it? Quench your thirst for hydration knowledge with the following guide. Q: What are the best liquids for hydration? A: Water is, of course, the ideal source for hydrating; however, according to Holley Johnson Grainger, MS, RD, food editor for MyRecipes.com, one out of 10 American adults say they do not drink water daily. The problem is the lack of flavor. "Studies show that if you like the taste of a beverage, you're more likely to stay hydrated," says Liz Applegate, Ph.D, director of sports nutrition at the University of California Davis. "Luckily, all beverages hydrate with the exception of alcohol." Grainger recommends breaking the monotony of water with other drink options. One hundred percent fruit juices provide vitamins and minerals with naturally occurring sugar, while sports drinks can replace electrolytes (sodium and potassium) lost through exercise. But if you're concerned about the calories, consider fitness and flavored waters that may contain added nutrients or simply have a more appealing taste. That said, these bottled beverages can be costly so first try enhancing tap water with lemon slices or fresh herbs. Speaking of food, don't forget about the liquids you have to chew. "Twenty percent of fluid (roughly two to three cups) is taken in through food," Grainger says. Good examples include soups, salsas, fruits (like watermelon and grapes), veggies (like cucumbers and lettuce), grains cooked in water and meat, fish and poultry. As to coffee and cola, it might surprise you to hear you can have at it. "People used to throw a fuss," Applegate says. "You know, 'Uh-oh, caffeine's a diuretic; don't consume it at all.'" But while downing a couple pots of coffee might wreak havoc on your central nervous system, recent fluid balance studies have found that typical intakes of up to 200 or 300 milligrams (two or three cups of coffee) do not actually impact hydration. However, Grainger advises eschewing the energy drinks. Not only are they expensive and typically high in calories, some contain whopping doses of caffeine and unregulated stimulants such as guarana and ginseng - a controversial stimulant that has been compared to ephedrine. Q: Does it matter what temperature the liquid is? A: In terms of hydration, the liquid's temperature does not make a significant difference. According to Grainger, drinking ice water will actually burn a few extra calories because your body must use energy to raise the temperature of the water to the body's temperature; however, the numbers are pretty minor - roughly eight calories for an eight-ounce glass of cold water. For those who prefer it warm, new studies are finding that drinking a glass or two of hot water increases the body's internal temperature slightly, causing you to sweat out toxins and helping to purify your bloodstream. Drink it at whatever temp is most tempting to you. Q: How do you know if you are dehydrated? A: "True dehydration occurs when a person has lost more than two percent of their body weight," Grainger says. "But people will start to feel thirsty when they are about one percent dehydrated." Pay attention to signs that your fluid levels are too low, such as thirst, headache, fatigue, muscle ache, dry skin, dry mouth, light-headedness and chills. Q: How much liquid is enough? A: The Institute of Medicine suggests that men get 16 cups of fluid per day and women get 13 cups. These recommendations may vary slightly depending on your age, diet, muscle-mass, activity level and the climate, Grainger says. Q: How much do you need during heavy exercise? A: Most people will sweat about one liter for every hour of exercise, Applegate says. Make sure you are prepared by drinking two cups of liquid about 30 minutes prior to working out, and then consume another fourth to half cup every 20 minutes or so if you continue over an hour. Q: Should I be concerned about getting too much water? A: Hyponatremia or water intoxication happens when there is a low concentration of sodium in the blood, Grainger says. It is most common during high-endurance events such as marathons and Ironmans. Endurance athletes can prevent this by drinking beverages containing electrolytes and carbohydrates to replace what is lost in the sweat. |
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