If you can stay awake long enough after your Thanksgiving meal, sit down and play a game of Trivial Pursuit.

You may be able to remember the answers better, and even if you can't, you might not feel that bad losing.

New research suggests that the same chemical in turkey that has been blamed for making us want to curl up on the couch after Thanksgiving dinner - tryptophan - may also play a role in maintaining good mood and memory.

Tryptophan is an essential amino acid, not produced by the body, that is known for causing sleepiness. But the new study in the journal Brain, Behavior and Immunity found something else about tryptophan: not getting enough of it appears to impair learning and memory and cause depressed moods.

Someone put a copy of the findings on the desk of Sherrie Rosenblatt, a spokeswoman for the National Turkey Federation, a few weeks ago. But she didn't pay them much mind. She's already convinced of turkey's benefits.

It's high in protein and low in fat. And, this year, it's cheap.

"I think, all in all, people feel good about eating turkey," she said. "It's food you can feel good about."

Help for depression

The study did not definitively conclude that ingesting more tryptophan - which is also found in milk, bread and cheese - will make you happier or help you remember things. But it suggests a possible connection.

Scientists at the Brain and Behavior Institute at Maastricht University in the Netherlands lowered tryptophan levels in 27 subjects, 16 with an immediate relative with major depression. That resulted in lower levels of serotonin, a chemical messenger in the brain. Memory tests showed that the subjects had trouble recalling and recognizing words they learned during the depletion period. Half the subjects with a family history of depression experienced low moods.

Wim J. Riedel, lead author of the study and an associate professor at Maastricht University, concedes that the findings do not have much immediate relevance to the general public, but hopes they could help in the search for safe, effective treatments for mood disorders.

Blame carbohydrates

As for tryptophan and sleepiness, Rosenblatt thinks turkeys get a bad rap for the post-Thanksgiving feast sluggishness many of us feel. And Bridget Nelson, a clinical dietitian with the Johns Hopkins Weight Management Center, says she's right: It's all the carbohydrates that make us sleepy.

According to the American Dietetic Association, the traditional Thanksgiving meal has about 3,000 calories - many of which come from the carbohydrates found in dishes like sweet potatoes, stuffing and dessert.

After eating a carbohydrate-rich meal, Nelson said, the body boosts its production of serotonin, which is what makes us feel tired.

"It's the serotonin that has a sedating effect," she said.

Peggy Yen, a nutrition consultant with the Maryland Department of Health and Mental Hygiene who has a weakness for stuffing, put it less delicately: We feel sluggish, she said, because we're "stuffed full of food."