Every year at Thanksgiving, most of us eat with our eyes, which are usually way bigger than our stomach is. So much so, that shortly afterwards, we find family and friends zonked out on the couch half way through the traditional Turkey Bowl football game.
Most of us have heard that post-meal ZZZ’s are caused by the bird itself. But is this long-held belief true? In part, the idea stems from the fact that turkey contains an amino acid called tryptophan that the body uses to produce serotonin—a neurotransmitter that helps to regulate sleep. But studies have shown that eating turkey doesn’t actually cause increased serotonin production in the brain. So what’s the science behind the turkey-makes-you-sleepy myth?
To make sense of things, we need to brush up on our biochemistry. To begin with, tryptophan is one of 20 amino acids that the body requires. These amino acids are like building blocks, linked together in different combinations to form proteins in the body like skin, hair, and muscle. Interestingly, the body cannot make tryptophan—we have to get it from the food we eat. Because of this, it is referred to as an “essential” amino acid.
Although turkey does contain tryptophan, many other protein-rich foods like eggs, cheddar cheese, fish, meats, and other poultry contain tryptophan too. In fact, ounce for ounce cheddar cheese has more tryptophan than turkey. BTW, just in case you’re wondering, no one food contains just tryptophan, other amino acids are present as well.
After digestion, amino acids are absorbed and circulate through the bloodstream. Like hurried passengers trying to find a seat on a crowded train, they look for specific transport proteins to carry them to their destination. Since tryptophan is biologically available in low amounts—and competes with five other amino acids for the same transporter, it has a tough time finding a seat. The result? Only part of the tryptophan that is circulating in the bloodstream actually makes it to the brain to produce serotonin. So… you can’t blame the bird.
Part of the post-turkey dinner food coma likely involves carbohydrates. When we eat carbs—like stuffing, mashed potatoes, creamed corn and pie—a hormone called insulin is released. Insulin helps move glucose and most amino acids into the body’s tissues, but interestingly has little effect on tryptophan. Because of this, tryptophan has less competition from other amino acids and can enter the brain more easily to form serotonin. Bottom line: eating a carbohydrate-rich meal actually increases brain serotonin in spite of the fact that there is no tryptophan in carbohydrate! Yet again, the bird is blame free.
Then there’s melatonin—a sleep-associated hormone that is elevated during sleep. Tryptophan is a precursor to melatonin. Does that explain the myth? Nope. It’s not that straightforward. Even though tryptophan is linked to melatonin production, simply eating turkey, or any other tryptophan-containing food, does not increase melatonin levels. A series of additional biochemical reactions involving specific enzymes are needed to make melatonin.
Another factor to consider is the fat content of Thanksgiving dinner. As the body redirects blood flow to digestion for the breakdown of food (and fat takes longer time to breakdown than protein or carbs), there is less going to the brain and skeletal muscle. This can leave us feeling sluggish and tired. But again, you can’t blame the turkey since it’s naturally low in fat. Without the crispy skin, of course. J
Finally, we are left with the most obvious reason that we feel tired after eating turkey dinner. We are eating a large meal—in a relatively short period of time—that contains lots of calories mainly from carbohydrate and fat. According to the Calorie Control Council, the average person will eat 4,500 calories on Thanksgiving. That’s 3,000 for dinner and another 1,500 for snacking. If you add alcohol into the mix it further increases the calories and the sedative effect.
My advice? Take time with family and friends to enjoy the meal—and your post-meal nap. And when someone says “it’s the turkey that makes you tired”, you can confidently exclaim “don’t blame the bird!” Armed with an understanding of the science of turkey dinner, you can tell them why.
Happy Thanksgiving! When it’s time for turkey leftovers, here are some delicious recipes for you to try!
Pair with sliced turkey. Or add chopped turkey and spinach and roll up into a wrap.
Suzy’s Simple Turkey Salad
I use leftover turkey for this quick, light salad. The raisins sweeten the salad and the chopped nuts and diced apples add crunch. You can place the salad over baby spinach leaves.
- 4 cups cooked turkey, cut into bite-size pieces
- 1/2 cup chopped almonds
- 1/2 cup raisins
- 1 large granny smith or honey crisp apple, cored and diced
- 1/4 cup shredded cheddar cheese
- 1/4 cup low-fat mayonnaise
- 1/2 lemon, juiced
- Sea salt to taste
- Other add-ins if desired: 1 tsp curry powder; ¼ cup cilantro
Combine the turkey, almonds, raisins, apples, cheese, mayonnaise, and lemon juice in a large bowl. Mix well. Refrigerate at least 1-2 hours to allow flavors to blend together. Enjoy!
Some Food Numbers that Make Thanksgiving (source: CNN)
2 — The maximum number of days the U.S. Department of Agriculture suggests keeping a fresh turkey before cooking it.
5-5.5 — The number of hours it takes to cook a stuffed 22-24 pound turkey at 325°F.
36 — The number of years it took magazine editor Sarah Josepha Hale to crusade for an annual Thanksgiving holiday. President Abraham Lincoln proclaimed the fourth Thursday in November Thanksgiving in 1863.
79 — Percentage of Americans surveyed who said eating Thanksgiving leftovers is more important than eating the Thanksgiving meal.
100,000-plus — Questions typically answered by the Butterball Turkey hotline every November and December.