What Is Tryptophan?
Is eating turkey responsible for the lethargy and drowsiness that often occur after a Thanksgiving feast? Many people believe that consuming turkey can make you sleepy, since turkey meat contains high levels of an amino acid known as tryptophan, one of the so-called essential amino acids (that are essential for protein formation but cannot be manufactured by the body) in our diet. Tryptophan is an important precursor for the production of the neurotransmitter serotonin, which has a calming, sleep-inducing effect on the brain.
Tryptophan supplements were used as a popular sleeping aid until 1990, when the substance was banned by the U.S. FDA after a batch of contaminated product manufactured in Japan was associated with many cases of a rare and potentially fatal condition known as eosinophilic myalgia.
A Thanksgiving Myth
But the fact that the turkey is responsible for the Thanksgiving evening slump is a myth. For tryptophan to have a sedative effect, it must be taken on an empty stomach. After a "modest" Thanksgiving meal of turkey, stuffing, vegetables, sweet potatoes, gravy, rolls, cranberry sauce, and pumpkin pie with whipped cream, you aren't going to experience any sedative effects of tryptophan in the turkey. It's worth noting that turkey isn't the only food rich in tryptophan. Pork, chicken, and cheese also contain tryptophan, yet these foods are not associated with unusual or increased sleepiness after consumption.
Why Does Thanksgiving Dinner Make You Sleepy?
Then why are you drowsy after the Thanksgiving meal? Feeling sleepy after consuming large quantities of food is normal, especially after a high-carbohydrate feast containing sweets, potatoes, and bread. Alcohol consumption can also have a sedative effect, so a glass of wine with your meal, particularly for those who may not drink alcohol regularly, might also contribute to your lethargy.
Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care
MedscapeReference.com. Eosinophilia-Myalgia Syndrome.