This may be my favorite medical myth, and it’s totally appropriate for the upcoming holiday. Happy Thanksgiving!
While not everyone stoops to the level of Seinfeld’s Jerry and George, who used tryptophan in turkey to lull a girl asleep so that they could play with her toys, the supposed sleep-inducing effects of tryptophan in turkey are commonly recounted at American Thanksgiving feasts and in the popular media around the holidays.
Scientific evidence does support a connection between tryptophan and sleep. L-tryptophan has been marketed as a dietary supplement to aid with sleep. Tryptophan also may have an effect on the immune system, with possible benefits for autoimmune disorders such as multiple sclerosis.
The truth is, turkey is not to blame for your sleepiness. Chicken and ground beef contain almost the same amount of tryptophan as turkey — about 350 milligrams per 4 ounce serving. While you might have heard someone claim that turkey made them drowsy, you have probably never heard someone say that chicken, ground beef, or any other meat made them sleepy. Swiss cheese and pork actually contain more tryptophan per gram than turkey, and yet the American classic, a ham and cheese sandwich, somehow escapes blame.
The amount of tryptophan in a single 4 ounce serving of turkey (about 350 milligrams) is also lower than the amount typically used to induce sleep. The recommendations for tryptophan supplements to help you sleep are 500 to 1000 milligrams. Many scientists also think the limited amount of tryptophan in turkey would be offset by the fact that it is generally eaten in combination with other foods and not on an empty stomach. While one clinical trial found comparable results for tryptophan from a food protein-source and pharmaceutical grade tryptophan, this study also used an extremely rich source of tryptophan, deoiled gourd seeds, which have twice the tryptophan content of turkey. In this trial, and in general use of supplements, tryptophan is taken on an empty stomach to aid absorption. Although it’s difficult to locate any experimental evidence to support this claim, many believe that the presence of other proteins and food in the stomach during a huge Thanksgiving meal would limit the absorption of the tryptophan in the turkey.
So not only is turkey not especially high in tryptophan content, ingesting that tryptophan in a large meal would also potentially be the least effective way to get its sleep inducing effects.
There are other elements of the holiday feasts that can induce drowsiness. Large meals have been shown to cause sleepiness regardless of what is eaten because the body increases blood flow to the stomach, and decreases blood flow and oxygenation to the brain. And don’t forget about the booze. One or two glasses of wine, especially for people who only drink occasionally, can make you drowsy, too.
Have a happy Thanksgiving, everyone. Stop blaming the turkey for your sleepiness.
Adapted from DON’T SWALLOW YOUR GUM! by Aaron Carroll, MD and Rachel Vreeman, MD copyright © 2009 by the author and reprinted with permission from St. Martin’s Griffin, an imprint of St. Martin’s Press, LLC