The Doctor Weighs In

By Dov Michaeli MD, Ph.D

Our first in the series of debunking medical myths dealt with the maxim that you must drink 8 glasses of water a day. I hope you stopped drowning yourself in H 2 O. And if you survived this personal drought, here is another food related myth.

The turkey made me sleepy

Remember this truism? It is false. It’s not the turkey—it’s more likely the company!

· The main “evidence” repeated ad nauseam with great conviction is that turkey contains the amino acid tryptophan. This amino acid serves as the metabolic precursor of the familiar serotonin. And serotonin makes you feel happy and drowsy. Q.E.D.

Not so fast. Does pork make you drowsy? How about Swiss cheese? Both of these contain significantly more tryptophan that turkey does. In fact, all meat, including chicken and hamburgers, contain large amounts of tryptophan. Have you avoided driving after a stop at McDonald’s because you suddenly became sleepy. Besides, in order to provide enough tryptophan to enter the brain and form there enough serotonin to make you drowsy, you’d need to finish a couple of whole turkeys. Care to try it?

· What is true is that a large meal would tend to make you drowsy. But it has nothing to do with tryptophan or turkeys. What happens is that when a meal makes its way to the small intestine, where digestion takes place, blood is diverted to the GI tract, to better absorb the digested food in the form of sugars, triglycerides and amino acids, and deliver it to the appropriate organs. Since our total blood volume is constant, this diversion comes at the expense of blood flow to the brain and muscles. If the blood supply to the cardiac muscle is pretty low to begin with, additional reduction due to a heavy meal could be quite catastrophic. But in normal circumstances, the worst that can happen is that you will feel sleepy because of reduced blood flow to your brain.

So next time you sit down to a Thanksgiving, or Christmas, or a Seder meal—don’t fret. Eat to your heart’s content, and let the turkeys who worry about drowsiness leave their portions for you to have seconds and thirds.

Bon appetit!