Why Does Turkey Make You Sleepy?


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Eating turkey makes you sleepy, right? It’s practically common knowledge that the tryptophan in turkey leads to that post-Thanksgiving meal coma, but this is simply a myth.

Thanksgiving dinner plate filled with turkey, gravy, green casserole, and stuffing

Stop blaming the turkey for your post-Thanksgiving dinner slump. It’s a myth that eating turkey puts you to sleep. Although turkey contains tryptophan, it’s more likely the carbs that put you to sleep.

In fact, when you eat a protein-rich meal, you reduce the amount of tryptophan that will cross the blood-brain barrier (BBB) compared to a carbohydrate-rich meal. Tryptophan will more easily cross the BBB after a high carbohydrate meal.

What is tryptophan (also called L-tryptophan)?

It is an essential amino acid. Amino acids are the building blocks of proteins. Tryptophan is called an “essential” amino acid because the body can’t make it on its own. We must get it through our diet from protein-containing foods, including turkey.

A typical diet provides 0.5-2 grams of tryptophan per day [source]. Tryptophan and its metabolites (products of metabolism) significantly contribute to our health by supporting protein synthesis, niacin (vitamin B-3) synthesis, mood, sleep, cognition, and gut health [source].

So, why do you feel sleepy after that Thanksgiving meal?

Large meal. If you’re like most people, you’re eating a lot more than turkey on Thanksgiving. Digesting the large meal(s) requires a lot of energy.

High sugar. People often eat a lot of carbs on Thanksgiving. As mentioned, high carbohydrate intake, especially carbohydrate foods with a high glycemic index and high glycemic load, can increase tryptophan availability in the brain [source].

Stress. Many people are under additional stress during the holidays. This often leads to fatigue. Stress can lead to poor sleep, diet changes, and altered exercise routines, which can also contribute to feeling tired.

Alcohol. Alcohol is a central nervous system depressant. It can slow brain activity leading to feelings of sleepiness.

What foods have tryptophan?

It may surprise you to know that turkey is not at the top of the list when it comes to tryptophan content. Meat, seafood, eggs, dairy products, chickpeas, nuts (walnuts, cashews) are all good sources of tryptophan. Tryptophan is also found in cereals and maize but in lower amounts [source].  

This may shock you, but 2 slices (2-oz.) of cheddar cheese provides more tryptophan than 3-oz. of roasted turkey breast. 3-oz. of cooked sockeye salmon has more tryptophan than 3-oz of roasted turkey. One cup of cooked oatmeal provides 33% of the tryptophan Dietary Reference Intake (DRI), and 2-oz. of cashews provides 58% of the DRI. Two tablespoons of chia seeds provide 124 mg (44% DRI).

Turkey recipes

5 Health benefits of tryptophan:

#1) Protein synthesis

After consuming tryptophan-containing foods, tryptophan gets absorbed in the gut, moves into the bloodstream, and gets transported to tissues (e.g., muscle, liver). Once in the tissues, tryptophan is taken up by the cells. It will be stored in an amino acid pool with other amino acids in the cell and used when it’s needed [source].   

The body will use tryptophan in combination with other amino acids to build proteins (protein synthesis). This is critically important to health and wellbeing. We need all our essential amino acids, including tryptophan, for adequate protein synthesis to occur. Without it, our physical and emotional well-being will suffer [source].

#2) Mood support

Several studies have shown a link between lower levels of tryptophan and mood disorders like depression and anxiety [source]. One study examined the participant’s mood, anxiety, and depression symptoms after eating a high tryptophan diet for four days and a low tryptophan diet for four days.

Consuming the higher tryptophan diet was associated with improved mood, reduced anxiety, and decreased depression symptoms [source]. This association was likely due to altered serotonin levels. Tryptophan boosts the chemical serotonin.

Serotonin regulates many reactions in the body. When it’s low, we feel lousy and make bad choices. Low levels are associated with depression, anxiety, impulsive behavior, irritability, suicide, violent crimes, alcoholism, carbohydrate cravings, poor memory, and insomnia. Healthy serotonin levels are associated with improved mood, impulse control, reduce food cravings, improved self-esteem, and improved sleep.

#3) Healthy sleeping 

Tryptophan is essential for optimal sleep. The tryptophan-serotonin pathway leads to the production of melatonin. Melatonin is sometimes called the “sleep hormone” or the “hormone of darkness”. Serotonin is converted to melatonin. As melatonin increases, serotonin levels typically decrease.

When the light goes down, melatonin is secreted into the blood by the pineal gland. As light increases, melatonin levels decrease, and serotonin levels rise. Melatonin is instrumental in your sleep-wake cycle. It is also involved in other circadian rhythms, seasonal rhythms, it’s an antioxidant, stimulates the immune system, and protects cells [source].

Researchers have shown an association between elevated tryptophan levels in the blood, increased melatonin levels, and improved sleep. One study found increased melatonin levels in the evening following a tryptophan-rich breakfast plus daytime light exposure. Another study found improved quality and quantity of sleep in older adults given a tryptophan enriched meal given at breakfast and dinner.

#4) Cognition and memory support

A diet enriched with tryptophan has been shown to support cognition and memory. The depletion of tryptophan has been shown to impair learning and memory in healthy people and those with serotonin abnormalities.

One study had healthy adults learn a list of words. When the participants were tested after learning the word list, there were no impairments. However, when participants were tested 30-minutes after peak tryptophan depletion both word recall and word recognition were impaired. The study researchers concluded that altered serotonin activity impaired memory [source].

Although more research is needed, there may be a link between tryptophan and cognitive decline seen with aging. Studies have shown a decline in an enzyme involved in converting tryptophan to serotonin called tryptophan hydroxylase with age. Changes in this enzyme’s activity may reduce the level of serotonin in the brain [source].

Cognitive decline is also associated with niacin (vitamin B-3) deficiency. Tryptophan can be used to create niacin in the body and tryptophan depletion is associated with niacin deficiency. If both niacin and tryptophan are deficient, serotonin production will suffer affecting cognitive health [source].

#5) Gut health

The gut is critically important to emotional and physical wellbeing, and tryptophan appears to be important to gut health. As we have discussed, tryptophan leads to the production of serotonin. Serotonin is found primarily in the digestive system, and it plays a key role in the gut-brain axis. The gut-brain axis is the two-way communication system between the gastrointestinal tract and the brain. The gut and brain communicate through the nervous system and the immune system. Fascinatingly, the microbes living in the gut direct much of this communication [source].

Tryptophan and/or its metabolites may play an important role in regulating inflammation and mood state in people with gut disorders like IBD.  Research has shown significantly lower levels of serum tryptophan in patients with IBD. Tryptophan deficiency may be contributing to the development and aggravation of the disease [source]. Scientists speculate that tryptophan provides protection against intestinal inflammation partially by regulating serotonin [source].

Recent research also shows a link between the bacterial species Lactobacillus reuteri, a normal part of the gut microbiome, and the development of immune cells that promote tolerance. Meaning they help balance cells capable of triggering inflammation. Studies in mice discovered these bacteria need tryptophan. If this is the case in people, it could mean less gut inflammation and relief for millions of people suffering from IBD [source].

How much tryptophan do you need?

It is important to consume the recommended amount of tryptophan to prevent deficiency and reap the rewards. The effects felt from tryptophan can vary depending on the person, their health status, and the source providing tryptophan. 

The dietary recommendation is 5 mg/kg body weight. Body weight in pounds divided by 2.2 will give you weight in kilograms. The dietary recommendation can be easily reached with food alone (e.g., 4 oz. turkey sandwich).  

Clinical trials have used varying amounts of tryptophan. The dosage is dependent on why the tryptophan is being used and the population. Some people will take doses up to 4-5 grams per day (60-70 mg/kg) to improve things like mood and sleep [source].

It is best to consult with your primary healthcare provider before adding dietary supplements. Supplements can cause unpleasant side effects and even health risks in some people.

Take-home message

There are likely a dozen reasons why you’re sleepy after that Thanksgiving Day meal. Although turkey contains tryptophan, it’s more likely the carbs that put you to sleep. Sleep is an important benefit of tryptophan via melatonin production, but this amazing essential amino acid supports our physical and mental health in many amazing ways.

It helps to build and repair our tissues, supports gut health, leads to the creation of our mighty mood-stabilizing neurotransmitter serotonin, and supports cognition. This naturally occurring amino acid is obtained easily through the diet. Simply eat a variety of foods – poultry, fish, meat, eggs, dairy, legumes, nuts – and you can meet your body’s need for tryptophan.

Jessica Gavin

I'm a culinary school graduate, cookbook author, and a mom who loves croissants! My passion is creating recipes and sharing the science behind cooking to help you gain confidence in the kitchen.

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  1. Dave says

    The real reason we’re sleepy after the Thanksgiving meal is that we usually eat enough in one sitting to hold us thru a winter of hibernation. Like you stated, the amino acid just adds to our health.

    Now, please pass the mashed potatoes and gravy boat!