Tryptophan: Uses, Sources, Imbalances

Tryptophan is an essential amino acid. It is found in plant and animal foods and is not produced by the body. Tryptophan is converted into serotonin, melatonin, and vitamin B-3 (niacin). It is also needed for normal infant growth and the production and maintenance of proteins, muscles, enzymes, and neurotransmitters.

This article will discuss what tryptophan is, what it does, where it can be acquired, and what happens if there is an imbalance of tryptophan in the body.

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What Is Tryptophan?

Tryptophan is an essential amino acid, meaning the body cannot produce it. Tryptophan is necessary for vital bodily processes, so it must be acquired through plant and animal sources in our diet.

What Does Tryptophan Do?

The body uses tryptophan to produce:

  • Serotonin: A neurotransmitter involved in regulating mood, appetite, sleep, pain, sex drive, and digestion.
  • Melatonin: A hormone that helps regulate the circadian rhythm (sleep-wake cycle).
  • Vitamin B-3: Niacin is needed for energy metabolism and DNA production.

The body needs enough iron, riboflavin, and vitamin B-6 to change dietary tryptophan into niacin.

Tryptophan is also necessary for the production of the body’s:

  • Proteins
  • Enzymes
  • Muscle tissue

Does Turkey Make You Tired?

The notion that the tryptophan in turkey is responsible for post-Thanksgiving drowsiness is a myth.

Tryptophan does help support healthy sleep by playing a role in the production of serotonin and melatonin, but there is no more tryptophan in turkey than in other poultry. The amount of tryptophan we get from food doesn’t usually significantly impact our wakefulness.

Thanksgiving drowsiness is more likely caused by eating a large amount of rich foods in one sitting, whether or not that includes turkey.

Sources of Tryptophan

Tryptophan can be found in foods such as:

  • Chicken
  • Turkey
  • Fish
  • Egg whites
  • Cheese
  • Milk
  • Peanuts
  • Soybeans
  • Sunflower seeds
  • Sesame seeds
  • Pumpkin seeds
  • Other high-protein foods

Getting tryptophan into the brain can be tricky as it competes for entry with other amino acids.

Consuming carbohydrates with tryptophan-containing protein foods can help tryptophan get past the brain’s gatekeeper. When you consume carbohydrates, the body produces insulin. This sends other amino acids to muscle tissue, leaving tryptophan in the bloodstream with less competition for entry to the brain.

Should You Take Tryptophan Supplements?

Tryptophan is available as an herbal supplement, but its safety and efficacy are debated. Some experts advise against taking it. These supplements are not regulated and may contain harmful substances such as toxic metals or other drugs, mainly when purchased from Internet vendors, unreliable sources, or suppliers outside the United States.

Tryptophan supplements were banned by the Food and Drug Administration (FDA) from 1989 to 2005 because of a rare but serious side effect called eosinophilia-myalgia syndrome (EMS). There have been no published cases of EMS in the United States since the FDA allowed the reintroduction of tryptophan supplements.

Tryptophan supplements are considered unsafe to use during pregnancy and also may be unsafe to take while breastfeeding.

They may cause side effects such as blurred vision, dizziness, and fatigue.

Tryptophan Supplements Warning

Tryptophan supplements may worsen some health conditions and/or interact with some medications. Don’t take tryptophan supplements if you take:

  • Antidepressants/anxiolytics, such as tricyclics, monoamine oxidase inhibitors (MAOIs), and selective serotonin reuptake inhibitors (SSRIs)
  • Zyvox (linezolid), an antibiotic
  • Carbidopa, used in combination with levodopa to treat and manage Parkinson’s disease

For most people, a varied and balanced diet will provide adequate tryptophan without needing a supplement. If you are considering taking a tryptophan supplement, talk to your healthcare provider first.

What Happens if Your Tryptophan Is Out of Balance?

A tryptophan deficiency may cause symptoms such as:

  • Nausea
  • Heartburn
  • Muscle fatigue and pain
  • Swelling

Diets that lack enough tryptophan (or the body’s failure to absorb it) can lead to a condition called pellagra, caused by a niacin deficiency. Pellagra is rare in developed countries.

Symptoms of pellagra can include:

  • Skin lesions, such as dermatitis
  • Gastrointestinal problems, such as diarrhea
  • Neurological disturbances, such as dementia

Pellagra can be fatal if left untreated.

The body’s ability to effectively use tryptophan can also be affected by how it moves through the body. If we are sick or stressed, tryptophan may take a different route than the usual kynurenine pathway (also known as the tryptophan degradation pathway). When this pathway is overactive, tryptophan is led away from serotonin synthesis and eventually melatonin synthesis.

The kynurenine pathway is necessary for functions such as the synthesis of niacin. Still, in order to maintain health, there needs to be a balance between these functions and the production of serotonin and melatonin.

Researchers continue to explore the potential effects of imbalances related to tryptophan on the body.


Tryptophan is an essential amino acid. The body uses it to produce serotonin, melatonin, and niacin. It also helps to produce proteins, enzymes, and muscle tissue.

The body does not produce tryptophan. It must be acquired by eating high-protein foods that contain tryptophan, such as turkey, chicken, fish, egg whites, milk, cheese, peanuts, and some seeds. Pairing carbohydrates with these foods helps tryptophan enter the brain more readily.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Heather Jones

Heather M. Jones is a freelance writer with a strong focus on health, parenting, disability,
and feminism.