I talked nutrition with two groups at pre-retirement seminars today, and both groups wanted to know: "Should you really drink eight glasses of water when you're on a diet?"
And all the rest of the time, too.
Drinking plenty of water will help you control your weight, not because it's magic but because it helps you feel full.
A zero-calorie treat, water's helpful as a way to replace high-calorie drinks. Also, water is absorbed by the high fiber foods you eat, creating bulk, which helps you feel full and keeps your bowels functioning properly. That eliminates chronic constipation, along with the accompanying lethargy, headaches and crankiness. Regular bowel movement also reduces your risk of bowel and colon cancer.
Maybe we are bordering on magic here.
Your body is about 65 percent water. Every cell is filled with water. Every cell is surrounded by water. Your blood is mostly water. Despite all that water, there isn't any extra. You have to fill 'er up every day.
You lose about 1 1/2 quarts of water daily, through perspiration, breathing and urine. And you have to replace these losses constantly. In fact, although you could survive without eating for about five weeks, you cannot survive without water for more than five days.
Your kidneys help you out as best they can. When your fluid intake is low, they concentrate urine to minimize losses. But they can't overcome total neglect.
Water is also crucial for maintaining body temperature. When you sweat off as little as 1 percent of your body weight (about 2 pounds, or 4 cups of water), you begin to feel hot, tired and achy. The greater the losses, the worse you feel. If you lose enough, it can be life threatening.
Warm-weather athletes are at special risk and should assure the availability of water before, during and after long strenuous workouts.
Thirst is a warning sign that body fluids are low and need refilling. But for athletic events, thirst comes too late to be of value. Athletes have to train themselves to drink before they get thirsty.
Ice counts. So does milk, which is 87 percent water. Most fruits and vegetables are 80 to 90 percent water. Juices count, too, of course. But remember, milk and fruit and juice are not calorie free. They're good for you because they're full of the nutriients your body needs for good health. But if you're watching your weight, you can't drink them with impunity.
Coffee and tea and artificially sweetened soft drinks are calorie free and mostly water, but you do have to watch the caffeine, which is dehydrating.
Alcoholic beverages also have a diuretic effect, so although they're mostly water, the outcome is negative.
All told, it looks like water is still your best bet.
At least eight glasses every day.
Colleen Pierre, a registered dietitian, is the nutrition consultant to the Union Memorial Sports Medicine Center in Baltimore and national spokesperson for the American Dietetic Association.