Sleepy after eating turkey? Actually, blame the carbs

Was it the turkey? More specifically, was it the tryptophan in the turkey?

Well, yes and no. Turkey does contain a large amino acid called tryptophan. So eating turkey puts some tryptophan into your bloodstream. But there are lots of other large amino acids riding around in there too. And, of course, turkey isn't all you gobble up at Thanksgiving. There's a lot of other stuff on the Thanksgiving plate, and a lot of it is carbohydrates.

When you eat carbohydrates, the pancreas releases insulin, and one effect of that is to lower the levels of all the large amino acids in your blood -- except for tryptophan. The upshot? You have relatively high levels of tryptophan in your blood, and in your brain that's converted into the neurotransmitter serotonin, and that can make you sleepy.

But many experts downplay the role of tryptophan in post-dinner nod-offs.

"You eat a ton of other food, and that makes you tired," says Jamie Davis, a registered dietitian and professor of nutrition at the Keck School of Medicine at USC. "Your body has to focus more on digestion, and that takes away from some of your energy."

Also note that eating protein has the opposite effect from eating carbohydrates -- it raises the blood levels of all large amino acids. If all you ate were turkey, you'd have relatively low levels of tryptophan -- and, if anything, you'd have some extra get-up-and-go, instead of all that extra lie-down-and-snooze.

"So turkey is really the good guy in all this," says James Hill, director of the Center for Human Nutrition at the University of Colorado in Denver. If you find yourself dozing off, it might be the carbs that did you in -- the seconds of mashed potatoes, that third helping of yams.

-- Karen Ravn