As most Americans prepare to gorge ourselves tomorrow, I'd like to set the record straight about the sedative effect of the amino acid tryptophan found in turkey: IT'S A MYTH.

Tryptophan is the key ingredient in making serotonin; without it, serotonin won't be produced. Because the body can't make it's own tryptophan, it must be taken in as part of the diet; for this reason tryptophan is known as an "essential" amino acid. Typtophan achieves its effects by way of serotonin which promotes feelings of calm, relaxation, and sleepiness. Lack of serotonin, on the other hand, is associated with depression. Many of today's antidepressant drugs work to increase the level of available serotonin in the brain.

However, eating turkey with lots of other foods on a day like Thanksgiving will actually lower your tryptophan. That's because tryptophan uses the same means of transport into the brain as other amino acids, and has to compete against them to cross the blood-brain barrier. As it happens, tryptophan is the least abundant amino acid in protein. Forced to fight for access against the more common amino acids, tryptophan is left waiting at the gate: the amount of tryptophan entering the brain actually decreases.

Why, then, the post-turkey torpor? It's more likely due to the combination of drinking alcohol and overeating - not just turkey, but also mashed potatoes, ham, creamed onions, cranberries, sweet potatoes, peas, stuffing (or dressing, if you prefer), carrots, bread, pies, and whipped cream - all of which have the effect of puling the blood away from your brain to help your digestive tract do its work, and the sugar/insulin effect. Put simply, you've stuffed yourself.

Gobble, gobble.

ABOUT THE AUTHOR

Zack Lynch, managing director of NeuroInsights, is an economic and social forecaster advising global organizations on the impact of neurotechnology on business, government and society. He serves on the advisory boards of the McGovern Institute for Brain Research at MIT,Center for Cognitive Liberty & Ethics, Global Neuroscience Initiative, the Center for Neuroeconomic Studies and SocialText, a social software company. He is currently finishing his book on Neurosociety: How Brain Science Is Shaping the Future of Business, Politics and Culture.