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

While we often blame our post-dinner drowsiness on the tryptophan in turkey, experts say that isn’t the full picture.

What is tryptophan?

Tryptophan is one of 20 essential, naturally-occurring amino acids, which are the building blocks of proteins, according to the nonprofit Center For Food As Medicine. 

When tryptophan reaches the brain, it is converted into the neurotransmitter serotonin and hormone melatonin, both of which are sleep-inducing, 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 not likely to cause someone to need an immediate snooze. 

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

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

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

What else could contribute to Thanksgiving fatigue?

Betz says multiple aspects of a Thanksgiving feast could add to the “food coma”-type tiredness many experience. 

“The sleepy feeling you feel after a turkey dinner is much more likely related to eating a large, delicious meal — and perhaps an extra glass of wine — than a surge of melatonin related to turkey,” she said, explaining that when you eat, “blood rushes to your intestines to pick up all of those wonderful nutrients from food, moving away from your brain, which can make you feel tired.”

And alcohol has a sedative or “downer” effect, she added, which can contribute to sleepiness on the holidays.