Does your mother pile her Thanksgiving dinner plate with Brussels sprouts and mashed parsnips while you go for the sweet potatoes with marshmallows? Does she prefer the tart, homemade cranberry-and-orange sauce while you gobble sweet cranberry jelly that comes in a can? Does she happily drink fresh grapefruit juice that makes you wrinkle up your nose and say, "Yuck! It's so bitter!"?

Adam Drewnowski, director of the nutritional sciences program at the University of Washington in Seattle, thinks he may have learned why grown-ups and kids prefer different taste sensations. His research suggests that sensitivity to bitterness in food declines with age, making vegetables taste better as people grow older. A young eater may find broccoli, Brussels sprouts and mustard greens especially bitter. But to an older mouth, the vegetables actually taste better.

"Taste is the driving factor" in what people choose to eat, Drewnowski says. "Your preferences will change with age."

Drewnowski did his research by testing the taste preferences of 329 women, ages 21 through 84. The older women liked the taste of vegetables more than the younger ones did. The older women also gave higher marks to vegetables, sour fruits, and bitter beverages such as coffee and tea.

This isn't the first time Drewnowski has looked for the reasons behind people's food choices. In 1996, he conducted studies that indicated that some people are born with a "fat tooth"--a preference for fatty foods--that is even stronger than their so-called sweet tooth. He found that this preference for fatty foods was especially strong in adults.

Many factors influence what human beings think of as delicious. Some of it is related to our culture--what we're exposed to and eat often as we grow up. Some of it is related to our biology and our age--like the changes in taste preferences Drewnowski has studied. But no matter what your taste preferences may be, healthful eating means consuming a variety of foods every day.

Many nutritionists use a "food pyramid" chart designed by the U.S. Department of Agriculture (USDA) to help people select healthful foods. If you follow the food group guidelines, you end up eating a diet high in grains, fruits and vegetables, supplemented by smaller amounts of dairy products, meat and fish, and only a little bit of fat and sugar.

A good way to help yourself maintain a balanced diet might be to keep tabs on portion sizes when you eat. It's the portion, or serving size, that determines the number of calories you end up eating. Even low-fat foods make you put on too much weight if you eat too much of them.

As you get ready for your Thanksgiving feast this year, check out these guidelines from the American Dietetic Association (ADA) to figure out what counts as a single serving. You might be surprised!

For example:

* 1 serving (3 ounces) of meat, poultry or fish is about the size of a deck of playing cards.

* 1 serving (1 cup) of fruit or yogurt is the size of a baseball.

* 1 serving (1/2 cup) of vegetables, pasta, rice or fruit is about the size of half a baseball.

* 1 teaspoon (1 serving) of fat is about the size of the tip of your thumb.

If you're careful about the serving sizes you choose during dinner this Thanksgiving, you might have enough room left for a really big piece of pie--or even two of them. After all, this holiday feast only comes around once a year. Happy Thanksgiving!

Tips for Parents

The American Dietetic Association says that while the Thanksgiving holiday is a time to enjoy favorite foods with family and friends, it needn't be a time for abandoning healthful eating habits.

The ADA offers some simple substitutions that can help cut the fat content of your holiday feast:

* Instead of cream cheese, use low-fat cream cheese or low-fat ricotta cheese.

* Instead of sour cream, use low-fat yogurt or low-fat cottage cheese blended with lemon juice to taste.

* Instead of whipped cream, use whipped evaporated skim milk. (Chill well before whipping.)

* Instead of whole eggs, use an egg substitute or two egg whites for each whole egg.

* Instead of mayonnaise, use reduced-calorie or "light" mayonnaise.

For You to Do

Nutrition specialists at the American Dietetic Association like to remind Americans that simply eating a balanced diet isn't enough to keep you healthy: You need exercise, too. This Thanksgiving, put yourself in charge of organizing a brisk walk with the family and friends who arrive at your house for the holiday feast. Ask your parents to help you schedule the walk so that it doesn't conflict with dinner or other activities. Maybe you could do it before dinner, or perhaps at halftime of one of the football games.