Does Tryptophan Actually Make You Tired? Separating Fact from Myth

Despite the common belief that tryptophan in turkey makes you tired, the real cause of post-meal sleepiness is far more complex. The idea is a widespread myth, and the small amount of tryptophan in a typical meal is not enough to induce a food coma. This article explores whether tryptophan actually makes you tired by examining its role in the body and how it is affected by diet.

Quick Summary

Tryptophan is an amino acid that produces sleep-regulating hormones like serotonin and melatonin. The amount found in food rarely causes drowsiness due to competition for transport across the blood-brain barrier. Carbohydrates, large meals, and supplements have a greater impact.

Key Points

• Turkey and Tryptophan Myth: The belief that tryptophan in turkey causes drowsiness is a myth, as turkey does not contain exceptionally high levels of the amino acid.

• Role of Carbohydrates: The sleepiness following a large meal is primarily caused by the insulin response to high carbohydrate intake, which helps tryptophan cross the blood-brain barrier.

• Blood-Brain Barrier Competition: Dietary tryptophan from protein-rich foods must compete with other amino acids to enter the brain, which is an inefficient process.

• Diet vs. Supplements: While dietary tryptophan supports overall sleep health, high-dose supplements are more effective for inducing acute sleepiness due to reduced competition.

• Other Factors in Fatigue: Overeating, alcohol consumption, and high-fat or sugary foods are significant contributors to post-meal drowsiness.

• Tryptophan-Serotonin-Melatonin Pathway: The body converts tryptophan into serotonin and melatonin, hormones critical for mood and sleep regulation.

The Tryptophan-Turkey Myth

For years, the tryptophan found in turkey has been blamed for the sleepiness that follows Thanksgiving dinner. However, this is largely a myth. While turkey does contain tryptophan, it's not present in higher concentrations than in other common protein-rich foods like chicken or cheese. Furthermore, the quantity of tryptophan in a normal serving of turkey is insufficient to cause the significant drowsiness associated with a large holiday meal. The post-meal fatigue is more likely caused by other factors, including the sheer volume of food consumed and the high carbohydrate content of side dishes like mashed potatoes and stuffing.

Tryptophan’s Role in the Body

Tryptophan is an essential amino acid, meaning the human body cannot produce it and must obtain it from dietary sources. It plays a critical role as a precursor for several important compounds:

• Serotonin: This neurotransmitter is often called the “feel-good” hormone and is involved in regulating mood, appetite, and sleep.
• Melatonin: This hormone, synthesized from serotonin, controls the body's sleep-wake cycle (circadian rhythm).
• Niacin (Vitamin B3): The body can also use tryptophan to produce niacin, which is necessary for energy metabolism and DNA production.

The Blood-Brain Barrier Challenge

The primary reason that dietary tryptophan doesn't cause immediate sleepiness is the blood-brain barrier (BBB). This is a protective network of cells that controls what enters the brain. Tryptophan must compete with other larger, more abundant amino acids from a protein-heavy meal to get a “ride” across the BBB via specialized transport proteins. Because tryptophan is a relatively minor amino acid in most protein sources, its chances of successfully crossing the barrier are limited in the presence of more numerous competitors. This explains why eating a protein-rich food like turkey or chicken doesn't necessarily make you feel tired right away.

The Real Culprit: How Carbohydrates Boost Tryptophan

So, if the tryptophan in turkey doesn't make you sleepy, what’s going on during that post-holiday meal crash? The answer lies in the combination of protein and carbohydrates. When you consume a large, high-carbohydrate meal, your body releases insulin to manage blood sugar. Insulin’s job is to move sugar from the blood into the cells, but it also prompts the uptake of most amino acids from the blood, leaving tryptophan largely behind. With less competition, the tryptophan that is still in the bloodstream has an easier time crossing the blood-brain barrier and entering the brain. The increase in brain tryptophan can then boost serotonin and melatonin production, contributing to drowsiness. This effect, combined with the general sluggishness from a large caloric intake, is the real reason for the post-feast lethargy.

Dietary vs. Supplemental Tryptophan

There is a significant difference between consuming tryptophan naturally through food and taking it as a dietary supplement.

Supplemental Tryptophan

• Higher Doses: Supplements provide a much higher, concentrated dose of tryptophan than is possible through diet alone.
• Reduced Competition: The isolated nature of supplemental tryptophan means it doesn’t have to compete with a flood of other amino acids, making it more efficient at crossing the BBB.
• Evidence of Efficacy: Research has shown that supplemental doses of 1 gram or more can reduce wakefulness after sleep onset and decrease sleep latency in individuals with mild sleep disturbances.
• Potential Risks: High doses may have side effects and potential interactions with certain medications, such as antidepressants. A specific contamination issue in the past led to a temporary ban, though this has been resolved.

Dietary Tryptophan

• Natural Intake: The tryptophan is part of a balanced protein source, which means it’s consumed with all other amino acids.
• Low Concentration: The amount of tryptophan is relatively low compared to other amino acids, leading to strong competition at the BBB.
• Subtle, Long-Term Benefits: Consistent dietary intake, particularly when paired with carbohydrates, contributes to overall healthy serotonin and melatonin production without causing acute drowsiness.

L-Tryptophan vs. 5-HTP

For those considering supplements, two common options are L-tryptophan and its metabolite, 5-hydroxytryptophan (5-HTP). Understanding the differences is key.

Feature	L-Tryptophan	5-HTP
Pathway	Precursor to 5-HTP, then to serotonin.	Direct precursor to serotonin, bypassing the first step.
BBB Competition	Must compete with other amino acids to cross the blood-brain barrier.	Easily crosses the blood-brain barrier without competition.
Speed of Action	More gradual, sustained effect.	Faster onset, but potentially shorter duration.
Long-Term Safety	Generally considered safer for consistent, long-term use.	Use needs caution; long-term use may affect dopamine levels.
Other Uses	Versatile; used for protein synthesis and niacin production.	Primary focus is on serotonin and mood/sleep support.

High-Tryptophan Foods

While food won't make you instantly sleepy, a balanced diet ensures a steady supply of this essential amino acid. Foods rich in tryptophan include:

• Poultry: Chicken and turkey.
• Dairy: Milk, cheese (like mozzarella and cheddar), and yogurt.
• Eggs: A good source of all essential amino acids.
• Soy Products: Tofu, soybeans, and soy milk.
• Nuts and Seeds: Pumpkin seeds, sesame seeds, almonds, and peanuts.
• Fish: Salmon, tuna, and other fish.
• Legumes: Lentils and beans.

Beyond Diet: Other Causes of Fatigue

If you regularly experience fatigue after meals, it's not just about tryptophan. Several other factors can contribute:

• Overeating: A large, calorie-dense meal requires a lot of energy for digestion, diverting blood flow to the digestive system and away from the brain.
• Fatigue-Inducing Nutrients: High-fat meals can cause a release of the hormone cholecystokinin (CCK), which has been linked to feelings of drowsiness.
• Alcohol: Consuming alcohol with a meal is known to induce drowsiness and can exacerbate post-meal fatigue.
• High Glycemic Index Foods: Refined carbohydrates and sugary foods can lead to a blood sugar crash, resulting in fatigue and sluggishness.

Conclusion

To answer the question, no, tryptophan in food does not actually make you tired in the immediate, food-coma-inducing sense. The widespread myth, particularly associated with turkey, fails to account for the competitive barrier that prevents most dietary tryptophan from reaching the brain quickly. The reality is more nuanced: the insulin response from a large, carbohydrate-rich meal is the key mechanism that facilitates tryptophan's entry into the brain, leading to increased serotonin and melatonin production. While consuming high-tryptophan foods as part of a balanced diet supports healthy sleep cycles over time, acute sleepiness is more likely caused by the meal's overall composition, size, and accompanying factors like alcohol consumption. For those seeking therapeutic benefits, supplemental tryptophan, taken at a sufficient dose and without the competition from a meal, is more effective, though it should be used with caution and under medical guidance.

For more comprehensive information on sleep health, consult the Sleep Foundation.

Frequently Asked Questions

Is it the tryptophan in turkey that makes people sleepy?

No, the idea that tryptophan in turkey is the sole cause of post-meal sleepiness is a myth. Turkey does not contain significantly more tryptophan than other meats. The food coma effect is more likely due to a large, carbohydrate-heavy meal.

How do carbohydrates affect tryptophan absorption?

When you eat a high-carbohydrate meal, your body releases insulin. This insulin helps clear other amino acids from the bloodstream, reducing competition and making it easier for tryptophan to cross the blood-brain barrier and enter the brain.

Can tryptophan supplements make you tired?

Yes, unlike dietary sources, high-dose tryptophan supplements can increase sleepiness. Studies show doses of 1 gram or more can reduce the time it takes to fall asleep in people with mild sleep disturbances.

What is the difference between L-tryptophan and 5-HTP?

L-tryptophan is an amino acid that first converts to 5-HTP, which then becomes serotonin. 5-HTP is a direct precursor to serotonin and can cross the blood-brain barrier more easily than tryptophan.

What are some foods that are high in tryptophan?

Foods rich in tryptophan include poultry, dairy products, eggs, soy products, nuts, and seeds. While a regular diet provides enough for normal function, it won't cause instant sleepiness.

Why do I feel tired after a big meal, if it's not the tryptophan?

Post-meal fatigue can be caused by the sheer volume of food, the body's energy expenditure on digestion, high carbohydrate intake causing a blood sugar spike and crash, or consuming alcohol.

Is taking tryptophan supplements safe?

Supplemental tryptophan should be used with caution and ideally under a healthcare provider's supervision, especially if you are on other medications. High doses can cause side effects or interact with certain drugs, particularly antidepressants.