What Is Tryptophan And Why Does It Make You Tired?

If you've ever been told that turkey makes you sleepy because it contains an amino acid called tryptophan, you may be wondering if there's any truth to this (via Well+Good). Although turkey does contain tryptophan, it's not responsible for making you feel tired after eating a large Thanksgiving meal.

"Tryptophan is an amino acid that increases serotonin levels in the body," Keri Glassman, a nutritionist and registered dietician, told Well+Good. "Serotonin is a precursor to melatonin, a hormone that helps regulate sleep." While tryptophan can help promote sleep, you would need to consume at least 1 gram of it in order to feel its effects.

This may not sound like a lot, but it's actually a pretty large quantity when it comes to tryptophan. To put this into perspective, you would need to eat 12 ounces, or four to six servings, of turkey in order to consume enough tryptophan to induce feelings of sleepiness. Even if you really like turkey, this would be difficult for most people to do.

So if tryptophan isn't the reason you feel sleepy after Thanksgiving dinner, then what is? Well, your increased feelings of sleepiness on Thanksgiving are most likely due to the size of the meal (via Healthline). Consuming a large amount of food, especially carbohydrates, can impact your energy levels. That's because eating a heavy, carb-rich meal can actually cause your blood sugar to spike and crash, which can make you drowsy and trigger feelings of fatigue.

According to a 2019 study published in the journal Neuroscience and Biobehavioral Reviews, carbs can decrease your alertness as soon as one hour after consumption. Eating a large meal can also lead to a change in circulation, which can redirect blood flow away from the brain and closer to the stomach, which can make it difficult to stay awake. If you're looking to avoid feeling drowsy or tired during the holidays, however, you can try taking smaller portions and eating more slowly. This will give your body more time to digest so you can feel yourself getting full more easily and avoid overeating.