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NEW YORK, Nov 20, 2003 (United Press International via COMTEX) -- Thanksgiving also is known as "Turkey Day" for the bird on which so many feast, but researchers have found that as meals change to reflect modern dietary trends, those changes can bring unexpected stress to holiday traditions.
"Meals are likely to be more complicated now, which can produce some consternation because during the holidays meals tend to be the same from one year to the next," psychologist Thomas Shipley of Temple University in Philadelphia told United Press International.
Sharing food is a tradition as old as cooking itself. By eating the same food, relationships form.
"Rules of what one can and cannot eat have historically served to keep groups together and separated from others. In part, that's because what one eats has moral implications about the eater," Shipley explained.
Following this line of thought, families during the holidays tend to consume the same meals from year to year.
"Holiday food -- and Thanksgiving in particular -- tends to have a very strong conservative character," Shipley said. "People want the same foods one year to the next. Woe be to the food preparer if they get bored and want to do something slightly different."
One reason foods remain the same is their aromas provide strong emotional links to past experiences.
"The memories of sights and sounds have a cold character to them, but memories associated with smells can evoke emotions in a way the other senses don't," Shipley continued. "A consequence is that if you have happy memories of childhood from good holiday meals, you're going to revisit those memories with foods that smell the same -- that taste the same as those."
Another reason holiday foods often are linked to happy memories is they are loaded with chemicals that alter moods for the better. For instance, turkey is rich with the amino acid tryptophan, a key ingredient of mood-related brain chemicals dopamine and serotonin. Tryptophan is responsible for the drowsiness Thanksgiving diners often feel after the main meal.
"There's a hypothesis that by raising levels of tryptophan, you indirectly raise the levels of dopamine and serotonin, and this provides a feeling of tranquility, a general good feeling," Shipley said.
As more people eschew eating meat for moral or health reasons, however, holiday meals have been changing, producing some unexpected and negative results. For example, in a well-known episode of the television sitcom, "Everybody Loves Raymond," the family's matriarch cooks a "tofu turkey" in an attempt to serve a healthier Thanksgiving dinner, only to spark a hilarious but catastrophic family conflict.
"This can produce a certain amount of consternation, as captured fairly nicely in the 'Raymond' episode," Shipley said, but added he did not think vegetarianism or other diversity in food choices would cause the disintegration of family holidays. To avoid such a prospect, he advised making alternative dishes available for vegetarian guests.
"Holidays can be fairly stressful as is when you have different people come together, not because they believe in the same thing, but because they have a common history, they're all part of the same family. So holidays may cause stress by people who already don't agree," Shipley said.
"One way of reducing that stress (by providing) a meal that everyone enjoys," he said. "As much as possible, accommodate everyone."
One consequence of the added selections is everybody could end up eating more.
"One of the things that regulates how much people eat is a phenomenon called sensory specific satiety, which means the more you eat of something, the less desirable it becomes," Shipley said. "If you have a single dish available, you can only eat so much before it becomes unpalatable. If you can eat new foods, people's interest will recover over the meal."
For vegetarians who still want a tryptophan fix, milk is chock-full of the compound. "That's why a warm glass of milk helps people sleep at night," Shipley said.
Charles Choi covers research for UPI Science News. E-mail firstname.lastname@example.org
Copyright 2003 by United Press International.