Many of us feel sleepy after eating turkey and all fastenings on our Thanksgiving dinner table, but why?

While we often blame sleepiness after dinner Tryptophan in TurkeyExperts say that’s not the full picture.

What is tryptophan?

According to the nonprofit Center For Food As Medicine, tryptophan is one of 20 essential, naturally occurring amino acids that are the building blocks of proteins.

When tryptophan reaches the brain, it is converted into the neurotransmitter serotonin and the hormone melatonin, both of which promote sleep, according to the organization.

Does turkey really make you sleepy?

Research suggests that consuming tryptophan can help people fall asleep faster and improve sleep quality, according to the Sleep Foundation — but it’s unlikely anyone will need a nap right away.

“Turkey meat is reported to make us sleepy because it has a higher concentration of the amino acid tryptophan compared to some other meats,” registered dietitian Melanie Betz, founder and CEO of The Kidney Dietitian in Chicago, told CBS News. “In reality, brain chemistry is much more complicated. Turkey has many different amino acids, all of which are converted into different hormones and complement each other in all of these pathways.”

Turkey isn’t the only food that contains tryptophan either. It’s found in poultry, meat, cheese, fish, eggs, and seeds—some of which even contain more amino acids than the Thanksgiving staple it’s so often associated with.

“There are many foods, such as pumpkin seeds, ground pork, cheddar, Swiss cheese, provolone and mozzarella cheeses, and yellowfin tuna, that contain more tryptophan per 100 grams than turkey,” according to the Center For Food As Medicine.

What else could contribute to Thanksgiving fatigue?

Betz says several aspects of a Thanksgiving feast could contribute to the fatigue that many people experience is reminiscent of a “food coma.”

“The sleepy feeling you feel after eating turkey is much more related to eating a large, delicious meal — and perhaps an extra glass of wine — than to a turkey-related melatonin rush,” she said, explaining that while eating “Blood rushes to your intestines to absorb all those wonderful nutrients from food and moves away from your brain, which can make you feel tired.”

And alcohol has a sedative or “calming” effect, she added, which can contribute to holiday sleepiness.