N early three-quarters of Americans know that experts recommend drinking eight glasses of water a day, though about half admit to drinking less, according to a survey sponsored by the International Bottled Water Association.
But there’s good news for those who don’t want to count what they drink.
Americans are not suffering from a water deficit, according to a February 2004 report by a panel of experts convened by the National Academy of Sciences’ Institute of Medicine (IOM), which advises the government about recommended
levels of nutrients.
After reviewing more than 400 studies, panel members rejected the conventional wisdom regarding water consumption. They also established new standards for the intake of sodium, potassium, and other electrolytes, the minerals that reflect the adequacy of the body’s hydration.
The typical American diet is deficient in potassium and laden with too much salt, panel members concluded. They recommended lowering levels of sodium intake, a change that may encourage the food industry to reformulate oversalted products.
So, are drinking enough? Getting the right amount of minerals?
We’ve waded through the data and talked to the experts to answer your questions about how these guidelines can help you stay healthy.
SHOULD I STILL DRINK SIX TO EIGHT GLASSES OF WATER A DAY? When IOM panel members looked at studies of serum osinolality, a normal measure of fluid deficit or overload, they concluded that most people stay suffic-iently hydrated simply by following their customary eating and drinking routines.
The origin of the eight-glasses-a-day rule is most likely government guidelines from the I 940s that recommended 1 milliliter of water for each calorie of food,” or just roughly 64 to 80 ounces per day. However, “water” referred to the total fluid in-take from all beverages and food.
The new guidelines reflect a trend toward increased fluid consumption in the American diet but don’t provide a one-size- fits-all recommendation for fluid intake. As a rough measure, the panel set the midpoint of the range of U.S. water consumption as the level that’s assumed adequate for most people. For men, that’s about 15’ eight-ounce cups of total water (about 13 cups from water and other beverages); for women, 11 cups (about 9 cups from fluids).
You need to pay special attention to your fluid intake when you’re active, the temperature exceeds 80”F, the humidity is low, or you’re at elevations above 5,000 feet. Under these conditions more water is lost through breathing and perspiration. Most people will find themselves extra thirsty during and after such stresses, so over the course of the day, following your natural inclination should still allow you to take care of your water needs.
DO OLDER PEOPLE NEED TO DRINK MORE? No! The IOM recommendations for fluid intake are the same for all adults. A recent study just conducted by geriatric and nutrition researchers from across the U.S. and England rejects the notion that older people should be encouraged to drink more because of chronic dehydration. Using accurate measurements of fluid intake and urine output in 450 people ages 40 to 79, the researchers found that people of all ages vary widely in their intake, but the oldest group was as well-hydrated as the youngest.
However, the sense of thirst does tend to diminish with age, increasing older people’s risk of dehydration from heat or exercise. So they should be careful to drink a cup of water before and after exercise, plus another 4 ounces every 20 minutes or so during workouts—more if they’re strenuous or in the heat.
HOW CAN I TELL IF I’M DRINKING ENOUGH? The simplest way is to check your urine. Scanty, strong-smelling, dark urine is a signal that you need to drink more. Color alone is not a good indicator because medications, vitamins, and diet can all affect color.
DO I HAVE TO DRINK PLAIN WATER? NO! The IOM panel concluded that all fluids —including soft drinks, caffeinated beverages, and alcoholic drinks—factor into your daily water totals.
Caffeine earned its reputation as a diuretic from small, short-term studies of many people who consumed higher doses than normal or who weren’t used to drinking it. When researchers studied caffeine in men who were used to drinking it, they just found no diuretic effect. Evidence on alcohol is scant but suggests that one or two drinks have no overall diuretic effect.
Plain tap water has its advantages: It’s cheap, thirst quenching, and calorie free. If you dislike the taste of tap water, try bottled water. One study found that flavored waters help some people drink more and stay better hydrated. Other choices may include iced tea and mixes of juice and water.
CAN DRINKING A LOT HELP WITH WEIGHT LOSS? There’s no real scientific evidence that it can. According to Barbara Rolls, Ph.D., professor of nutritional sciences at Pennsylvania State University, water empties from the stomach very quickly and has little effect on appetite. However, studies show that eating foods with higher water content—such as fruits, vegetables, soups, and also cooked grains—makes people feel fuller and less hungry than eating drier foods and drinking water with them.
CAN YOU DRINK TOO MUCH WATER? It’s possible, but not likely in healthy people who let their thirst guide them. If your body retains water because of congestive heart failure, hypothyroidism, or long-term use of certain medications— notably nonsteroidal anti-inflammatory drugs such as ibuprofen, ketoprofen, and naproxen—you need to he careful not to exceed recommended fluid intakes. When you overhydrate, sodium concentrations can drop precipitously low, allowing water to leak into brain cells, causing headache, confusion, personality changes, and even seizures, coma, or death.
In the last few years athletes—particularly amateurs competing in marathons and other endurance events—who take too literally the common advice to “drink as much as possible” have emerged as another risk group. To prevent overhydration, exercisers should make sure fluid consumption stays within the range of about I cups to 3 cups an hour.
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