For the health-conscious person, they have been the golden rules that govern daily eating and exercise routines.

Drink eight glasses of water. Make carbohydrates the foundation of your diet. Eat five servings of fruits and vegetables.

Lately these and other rules have come under question -- or, in some cases, all-out attack. Some rules have turned out to be myths. Others do not go far enough. It's enough to send the well-intentioned reeling toward the couch with a tub of ice cream. But don't despair. Even as the experts dissect the latest findings, they stress that the No. 1 rule of food and fitness is to make moderation a habit.

"Few of us can stay with an extreme form of exercise or nutrition for a long period of time," said Steven Loy, professor of kinesiology at California State University, Northridge, and regional director for the American College of Sports Medicine.

RULE: Drink eight glasses of water daily. REALITY: Unsubstantiated.

Who hasn't been badgered by fitness instructors, nutritionists, beauticians and the like to drink eight eight-ounce glasses of water a day? Scientists aren't sure where the mandate originated and how it came to be perpetuated as fact.

The National Academies' Food and Nutrition Board, which sets the recommended daily allowances used for food labels in the United States, speculates the rule might have stemmed from one of its prior formulas that tied water intake to the number of calories expended. The board is studying water intake and plans to issue recommendations in the spring.

A Dartmouth Medical School study released earlier this year also found no scientific basis for the eight-glasses-a-day mandate.

"Water intake depends on whether you're male or female, child or adult, level of physical activity and climate," said Paula Trumbo, senior program officer for the Food and Nutrition Board.

Caffeinated beverages as well as food contribute to total water intake, Ms. Trumbo said. A half-cup of lettuce, for example, is 95 per cent water by weight. Even if Americans don't need to be toting bottled water all over the place, nutrition experts aren't likely to discourage a no-fat, no-calorie trend. In 2001, Americans drank five billion gallons (nearly 23 billion litres) of bottled water, according to the International Bottled Water Association.

However, consumers should read the labels and be aware of what they're buying, said Arthur von Wiesenberger, a consultant to the beverage industry.

OLD RULE: Load up on carbohydrates. NEW FAD: Load up on protein. REALITY: Load up on fruits and vegetables.

Carbohydrates -- in particular, refined carbs such as rice, pasta and bread -- have taken a drubbing in the past few years as protein diets have exploded in popularity.

Although refined carbs (fruits and vegetables also are carbohydrates, by the way) have been blamed for the bulging North American waistline, several Los Angeles-area nutritionists said the real culprit is serving size.

When it comes to serving sizes, most people underestimate. Two cups of pasta at dinner doesn't equal one serving, but four.

"It doesn't matter what you eat if you're eating too many calories," said Carol Koprowski, assistant professor in USC's department of preventive medicine.

Not only are people overdoing the refined carbs, they tend to eat about twice as much protein as they need, said Gail Frank, professor of nutrition at California State University, Long Beach, and spokeswoman for the American Dietetic Association.

Based on U.S. national dietary guidelines, a 120-pound person requires about 48 grams of protein a day. Prof. Frank shows how quickly the protein grams add up: A half-cup of low-fat granola with a cup of milk for breakfast, a 3-ounce hamburger patty with an ounce of cheese on a bun for lunch and 10 tortilla chips as a snack total 48 grams. If anything should knock the breads and cereals group from the foundation of the USDA food guide pyramid, it's not protein but fruits and vegetables, nutrition experts said.

RULE: Eat five servings of fruits and vegetables daily. REALITY: That's just the beginning.

For 13 years, Californians have heard the mantra to eat five servings of fruits and vegetables a day. Now the National Cancer Institute is raising the bar with a new slogan: "Eating Five to Nine and Feeling Fine."

"The range has always been there, but no one was talking about the higher end," said Lorelei DiSogra, director of the National Cancer Institute's Five a Day Program. "The importance that fruit and vegetables play in reducing the risk of cancer has grown stronger and stronger. It gives more evidence to the fact that people need to eat more fruits and vegetables."

Sure enough, the USDA food guide pyramid recommends two to four servings of fruit and three to five servings of vegetables -- a range of five to nine. According to Ms. DiSogra, five servings are plenty for children ages 2 to 6. But children age 7 and up, teenage girls and women should consume seven servings, while teenage boys and men should shoot for nine.

The National Cancer Institute estimates that 35 per cent of cancers in the United States can be attributed to diet. Research also shows a a diet rich in fruits and vegetables reduces the risk of heart disease and diabetes, Ms. DiSogra said.