True or false?
- Health and nutrition experts recommend drinking eight or more 8-ounce servings of water daily.
- You should not wait until you’re thirsty to drink water. By the time you feel thirsty, you have lost a significant amount of your total body water composition.
- Caffeinated beverages such as coffee, tea, and cola, along with alcoholic beverages, can cause dehydration by lowering the net total of hydrating beverages such as water.
- Because the thirst mechanism becomes blunted with age, older people, in particular, need to make a conscious effort to drink eight glasses of water daily.
- For men, an average of 16 cups of water a day is adequate; for women, an average of 11 cups.
The only statement that’s true is the last one. How can it be that people need more than 10 cups of water a day but that health experts aren’t even recommending drinking at least 8 cups?
It’s that water doesn’t only come from drinking water. It also comes from milk, juice, coffee, alcoholic drinks (that’s right, coffee and alcohol), other beverages, and the moisture content of solid foods. And people are, in fact, consuming enough water each day from all those sources without thinking a whit about how many glasses they’re drinking of water per se. With thirst as their guide, Americans are well hydrated.
Such are the findings of an Institute of Medicine panel of distinguished US and Canadian scientists, convened by the National Academy of Sciences for the purpose of setting water recommendations for the general public. The panel does say that there is an “extreme variability” in water needs based on climate and people’s physical activity levels. In other words, some men and women will need more, some less. But in just about all cases, “fluid intake, driven by thirst…allows maintenance of hydration status and total body water at normal levels.”
Regarding caffeine, the panel says, “as early as 1928, it was reported that caffeine-containing beverages did not significantly increase 24-hour urine output” and that any diuretic effects they have may be transient in nature. Alcohol is not a water robber, either, the panel reports. In fact, the new guidelines say that coffee, tea, colas, and (in moderation) alcoholic beverages “can contribute to total water intake,” particularly in habitual consumers of caffeinated beverages like coffee because there’s an adaptation mechanism. The more regularly you drink it, the more the body is able to hold onto the water it provides. In other words, the popular notion that for every cup of coffee you consume you need to drink a cup of water to replace lost fluid is false.
This holds true for older people as well as young and middle-aged adults. Their thirst mechanism is blunted compared to that of younger adults. But even older people, as long as they’re healthy, were not singled out with a “prescription” for a particular number of glasses of water per day.
Bottom line: You don’t have to remind yourself to drink water—or any other beverage. You can let your normal drinking and eating behaviors be your guide. (About 20 percent of our water comes from solid foods.) As for how the idea of eight glasses of water a day and the coffee-as-dehydrating notion ever got started, it’s not clear, since they were never based on any scientific evidence. (Even so, the International Bottled Water Association, the trade group for much of the bottled water industry both in the US and abroad, continues to promulgate those claims on its website.)
The Sodium/Potassium Seesaw
While the Institute of Medicine panel’s guidelines for water essentially say that no particular rules need to be followed, its guidelines for sodium and potassium amount to significant dietary changes that the average American should be making.
Consider that the new Adequate Intake for sodium, one of the constituents of salt, is 1,500 milligrams daily for young and middle-aged adults; 1,300 milligrams for those over 50; and 1,200 milligrams for people older than 70. But, says Lawrence J. Appel, MD, chair of the panel and a member of the Departments of Medicine, Epidemiology, and International Health at Johns Hopkins University in Baltimore, while those are important numbers, “that’s not where the public health problem is. So few people come close to” that low. “People don’t need to worry about” not having an adequate intake of sodium.
The problem, he says, is that most Americans exceed the newly set Upper Level of 2,300 milligrams, raising their risk for high blood pressure, one of the leading risk factors for heart disease and stroke. Only “about 25 percent of women come close” to staying inside the 2,300-milligram limit, he points out, and almost no men. Indeed, average sodium consumption figures for men range from 3,100 to 4,700 milligrams a day and for women, from 2,300 to 3,100 milligrams (because they tend to take in fewer calories, not because they limit the sodium content of their foods more carefully).
Making a substantial shift downward in sodium intake could be tough, given the current state of our food supply. So many foods in the supermarket—so many otherwise healthful foods—contain enormous amounts of sodium. A packet of instant oatmeal, for instance, has almost 300 milligrams; a Healthy Choice frozen herb baked fish dinner, almost 500 milligrams; five Nabisco Wheatsworth stoneground crackers, almost 200; a serving of Seven Seas Reduced-Calorie salad dressing with olive oil, 450.
Given that almost every aisle of the supermarket (and most restaurant and takeout items) are laden with sodium, how do you begin to cut down? Think fresh, and think unprocessed, or at least minimally processed. That is, think fruits, vegetables, beans, low- and nonfat dairy products, and lean cuts of meat and poultry.
Fitting those foods regularly into your dietary pattern confers a double benefit. Not only are they relatively low in sodium, they’re also high in potassium—a good thing because in addition to setting new recommendations to keep down sodium consumption, the Institute of Medicine has also raised the potassium bar, so to speak. While the Daily Value for that mineral is 3,500 milligrams (that’s the level food labels refer to, if they include potassium numbers, which are optional), the new Adequate Intake level is 4,700 milligrams.(It could be years before labels reflect the change.) The higher amount is what experts consider appropriate for potassium to best perform its functions in the body—keep down blood pressure (in part by blunting the effects of sodium), prevent bone loss, and reduce the risk for kidney stones.
Currently, Americans take in an average of only about 2,500 milligrams of potassium daily—roughly half the Adequate Intake. Edging vegetable and fruit consumption toward nine servings a day (five servings is just the minimum recommended) will help people reach the potassium threshold. Also contributing significant potassium are dairy products, beans, peanut butter, almonds, and coffee.
The only people who need to confer with their doctors before substantially increasing their potassium intake are those with type 1 diabetes and those taking ACE inhibitor drugs, certain diuretics, or nonsteroidal anti-inflammatory drugs (NSAIDs), including COX-2 inhibitors. “Speak to your doctor if you’re on one of these,” says Dr. Appel. “It doesn’t automatically mean you shouldn’t increase your potassium intake,” he says. For instance, “someone taking a COX-2 inhibitor for shoulder pain who is otherwise healthy” would most likely do well to consume more potassium. But some people taking those classes of drugs can’t handle a lot of that mineral.
