Tryptophan’s Possible Effects for Your Health

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By Dr. Mercola


Amino acids are key components in the body’s optimal function, as they serve as building blocks of protein and aid as intermediates in metabolism.1 There are around 20 types of amino acids that can help the body, and one in particular that has been gaining popularity is tryptophan, also called l-tryptophan, l-tryptophane, l-triptofano, l-2-amino-3-(indole-3-yl) propionic acid or l-trypt.2

Continue reading to learn what tryptophan is, how it works and what the best food sources of this amino acid are. Find out what existing studies say about it, and the possible side effects of taking tryptophan supplements.

What Is Tryptophan?

Tryptophan is needed by the body to make protein and promote normal growth in infants and nitrogen balance in adults.3 It’s one of nine essential amino acids that the body cannot produce, and must be obtained through the diet,4 from various plant and animal sources.5 Tryptophan and l-tryptophan are available as supplements, capsules or tablets.6

Ensuring that the body has enough tryptophan levels to prevent a tryptophan deficiency is crucial. Low tryptophan levels can significantly affect the body’s levels of serotonin, a neurotransmitter. Reduced serotonin levels can cause a person to be overwhelmed by stress and/or food cravings, and may find it difficult to focus. Emotional imbalances, diminished neural health and a higher risk of developing depression and anxiety symptoms are other negative effects of low serotonin levels.7

How Much Tryptophan Is in Turkey and Chicken?

As mentioned earlier, you have to get this amino acid from food sources.8 Organic grass fed turkey and chicken are ideal tryptophan-rich foods you can eat to increase your body’s tryptophan stores.

According to writer Sandi Busch, a 3-ounce serving of turkey contains between 250 to 310 milligrams (mg), although this amount is lower compared to chicken. In general, dark meats contain less tryptophan than light meats. Dark-meat turkey contains 250 mg of tryptophan, compared to dark-meat chicken’s 270 mg. On the other hand, light-meat turkey has 270 mg of tryptophan, and light-meat chicken has around 310 mg.9

What Other Foods Are High in Tryptophan?

Aside from turkey and chicken meat, here are other foods containing tryptophan that you can eat:10

Pumpkin seeds

Sesame seeds

Organic, free-range eggs

Raw, grass fed milk and dairy

Dark chocolates (eaten in moderation) or cacao nibs

Fish like wild-caught Alaskan salmon, anchovies, sardines, mackerel and herring

Despite their tryptophan content, I advise you to avoid consuming unfermented soy and its byproducts, such as tofu. The vast majority of soy grown in the U.S. is genetically engineered and is usually contaminated with herbicides. Furthermore, soybeans often undergo acid washing in aluminum tanks, possibly leaching aluminum into the final soy product and containing unsafe levels of manganese too.

Health Benefits of Tryptophan

Different health benefits have been linked to tryptophan supplements. L-tryptophan’s benefits begin with the body changing this amino acid into serotonin, which helps with controlling mood and sleep. Low l-tryptophan levels are often seen in people with depression. Because of this, researchers have claimed that taking l-tryptophan can help improve mood or address mental health disorders like depression, bipolar disorder or obsessive-compulsive disorder.11

It’s also said that l-tryptophan supplements may help with regulating mood swings caused by premenstrual syndrome (PMS) or premenstrual dysphoric disorder (PMDD). There’s a theory that PMS or PMDD is linked to a problem involving serotonin processing in the body, and this is where l-tryptophan can help. Still, further research must be conducted to confirm this purported benefit.12

Meanwhile, 5-hydroxytryptophan (5-HTP) that the body produces from tryptophan is considered a natural alternative to traditional antidepressants. When the body creates serotonin, it first makes 5-HTP. Taking a 5-HTP supplement may benefit the brain and central nervous system. 5-HTP can reach the brain by travelling through the bloodstream and crossing the brain barrier. Once 5-HTP reaches the brain, it gets converted into serotonin, and is stored in the neurons until a trigger prompts serotonin to be released.13

Activated serotonin binds with receptors to produce a calming response to stress. A serotonin release in the brain causes feelings of happiness, contentment and fulfillment, helps diminish the patient’s appetite (helpful for anyone trying to lose weight) and assists in boosting the mood and enhancing sleep.

Uses of Tryptophan

Tryptophan supplements are known to have a variety of uses:14,15,16

  • Assist with niacin (vitamin B3) production: Tryptophan or L-tryptophan is used by the body to produce niacin or vitamin B3, together with iron and vitamin B2 and B6. Vitamin B3 can assist with increasing good cholesterol levels and reducing bad cholesterol levels. The body also uses vitamin B3 to convert carbohydrates into energy, and aid in maintaining optimal health of the digestive system, skin, hair and eyes.
  • Improve sleep: For some people, tryptophan or l-tryptophan supplements can be useful in addressing sleep-related conditions like insomnia, sleep apnea and bruxism (teeth grinding).
  • Address certain conditions: Tryptophan or l-tryptophan may help relieve facial pain, assist a person in quitting smoking and aid patients with attention deficit-hyperactivity disorder (ADHD) and Tourette’s syndrome.
  • Enhance athletic performance: This amino acid may have potential in improving athletic performance, although more studies are needed to prove this.
  • Promote growth and development of infants: According to the National Institutes of Health, tryptophan can aid with brain maturation of the infant and play key roles in the neurobehavorial regulations of food intake, satiation and sleep-wake rhythm.

Studies on Tryptophan and L-Tryptophan Supplements

There are studies that examined what l-tryptophan and tryptophan supplements can be good for. Most of the research tackling l-tryptophan’s and tryptophan’s potential capabilities focused on its effects on mood and cognition. Here are a few examples:

A study published in the Archives of Psychiatric Nursing highlighted that increased dietary tryptophan intake can affect depression and mood scores of healthy participants. A diet wherein tryptophan was present led to less depressive symptoms and better mood states among people who ate it.17

In reverse, people who consumed less dietary tryptophan were more irritable and anxious compared to those who ate more tryptophan. The researchers noted, however, that consuming more tryptophan didn’t result in a significant effect on salivary cortisol levels.

A study in the International Journal of Neuropsychopharmacology found that tryptophan may have an effect on people who have at least one first-degree relative with depression. Participants who took tryptophan had better mood, although it was unexpected that tryptophan increased quarrelsome behavior and decreased agreeable behavior, especially during interactions at home.18

Negative social cognitions reduced when the tryptophan was given second, and lower during placebo when the placebo was given second.

Published in Psychopharmacology, another study found that l-tryptophan increased recognition of happy facial expressions while reducing the recognition of disgusted facial expressions in female (but not male) volunteers. L-tryptophan was also able to lessen attentional vigilance towards negative words and decrease baseline startle responsivity among females.19

These findings reveal that l-tryptophan supplements, when taken by females, can induce a positive bias in processing of emotional material similar to antidepressants. More studies, however, are needed to clarify l-tryptophan’s effects on these measures for men.

L-tryptophan supplements have also been studied for their effects on exercise performance. An International Journal of Sports Medicine study revealed that participants had a 49.4 percent higher increase in exercise time after taking l-tryptophan supplements. The researchers noted that this effect could be due to increased pain tolerance that occurred because of the supplement.20

However, the great margin of difference was only recorded for this parameter, and the differences from the control group weren’t statistically significant. No differences were observed in the other factors in the two trials in the study, namely perceived exertion rate, maximum heart rate, peak oxygen consumption, pulse recovery rate and post-exercise oxygen consumption.

On the other hand, a 2010 study published in the American Journal of Therapeutics studied the benefits of another type of tryptophan supplement, 5-hydroxytryptophan (5-HTP), in improving sleep quality. An amino acid preparation of Gabadone, composed of 5-HTP and GABA, and a placebo was given to 18 patients experiencing sleep disorders.

Results showed that Gabadone improved the persons’ ease of falling asleep, boosted awakenings and morning grogginess, reduced sleep latency, increased sleep duration and enhanced sleep quality.21

How Much Tryptophan Should You Take?

According to MedicineNet, adults might need to take 8 to 12 grams of l-tryptophan orally daily, in divided doses of three to four times a day. However, I advise that you consult your physician or doctor first, as there isn't enough scientific information to determine an appropriate range of doses for l-tryptophan. The patient’s age, health and other conditions are factors that can help the health professional identify the ideal l-tryptophan dose for a patient.22,23

Children and pregnant women aren’t advised to take tryptophan or l-tryptophan, as information is lacking regarding safety and effectiveness of tryptophan for these people. Breastfeeding women must not take l-tryptophan too to reduce risks for a newborn baby, since it’s not known whether this substance can end up in breast milk.24,25

Side Effects of Tryptophan

If you plan to take tryptophan supplements, be wary of these side effects:

Blurred vision




Head twitching



Loss of muscle coordination and muscle stiffness

Strong and pounding heartbeat (palpitations)




One of the most adverse side effects of tryptophan is a dangerous and potentially deadly condition called eosinophilia-myalgia syndrome (EMS), which can trigger symptoms like sudden and severe muscle pain, nerve damage and skin changes.

In 1989, the U.S. Food and Drug Administration (FDA) recalled tryptophan supplements after tens of thousands of people became sick, while some died. According to doctors who checked the patients, the number of people affected by EMS reduced after the recall. Research has suggested that this EMS outbreak was caused by contaminants that reached the supplements during manufacturing in a factory in Japan.26

Tryptophan supplements can also interact with certain medicines. It’s advised that patients who are taking antidepressants like citalopram (Celexa), desvenlafaxine (Pristiq), vilazodone, linezolid and phenelzine27 mustn’t take tryptophan supplements, because it can result in a life-threatening condition called serotonin syndrome that causes symptoms like:

Extreme anxiety

Tendency to be easily startled

Rapid heartbeats


Severe muscle spasms

Increased body temperature

Meanwhile, if you have cirrhosis (scarring of the liver) or a white blood cell disorder called eosinophilia, talk to your physician or doctor first to prevent potential complications.28 I recommend telling your physician or doctor about supplements that you are taking, including those that are natural and are bought without a prescription. This will allow the health professional to look for potential side effects or interactions with other medicines.

A Final Word Before Taking Tryptophan Supplements

The positive effects of amino acids like tryptophan towards the body are unparalleled, especially since it helps boost mental health and address conditions that cause pain and discomfort. While tryptophan supplements have made a good case for themselves, this doesn’t mean that you have the liberty to use these as freely as you can, because of their links to major side effects. Instead, try naturally boosting your intake of tryptophan from the food sources mentioned above, especially if you wish to address mental health disorders.

Frequently Asked Questions About Tryptophan

Q: What is a tryptophan supplement used for?

A: Tryptophan supplements may be recommended to help improve sleep, assist in relieving conditions like facial pain, aid patients with ADHD and/or Tourette's syndrome and help with serotonin and vitamin B3 or niacin production.29,30,31

Q: What does tryptophan do?

A: Tryptophan is an amino acid that plays a role in producing protein, serves as an intermediate in metabolism32 and assists in promoting normal growth for infants and nitrogen balance in adults.33 What tryptophan can be highly beneficial for, however, is its potential in regulating mood swings caused by PMS or PMDD and in producing serotonin that can promote a person's mood and enhance sleep.34,35

Q: Does tryptophan make you sleepy?

A: Yes. The body utilizes tryptophan to produce niacin or vitamin B3 that helps with creating the neurotransmitter serotonin. When the body has enough tryptophan, the serotonin levels increase, resulting in feelings of wellbeing and relaxation, and ultimately, even sleepiness.

According to Elizabeth Somer, author of the book “Eat Your Way to Happiness,” “When levels of serotonin are high, you’re in a better mood, sleep better, and have a higher pain tolerance.” Furthermore, serotonin is also used to create melatonin, a hormone that assists with controlling sleep and wake cycles.36

Q: Is tryptophan safe?

A: Adults can take tryptophan supplements safely, provided they follow the appropriate dosage (more on this to come later). However, the same cannot be said for children and pregnant and/or breastfeeding women, given the lack of scientific evidence highlighting its safety. It’s best that these groups avoid tryptophan.37,38

Tryptophan supplements, when taken in excess, can also trigger unwanted side effects such as hives, dizziness, drowsiness, nausea and palpitations. A patient can also experience eosinophilia-myalgia syndrome (EMS), characterized by indicators such as sudden and severe muscle pain, nerve damage and skin changes.39

Q: How much tryptophan is too much?

A: The suggested daily amount is 8 to 12 grams of tryptophan or l-tryptophan supplements, divided into three to four separate doses.40 Any amount higher than that may have the potential to cause side effects. However, I advise that you talk to a health professional first.

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