Medically Reviewed by Melinda Ratini, MS, DO on September 24, 2021
3 min read

L-tryptophan is an essential amino acid that helps the body make proteins and certain brain-signaling chemicals.

Your body changes L-tryptophan into a brain chemical called serotonin. Serotonin helps control your mood and sleep.

You can get all the L-tryptophan that your body needs by eating a healthy, balanced diet. Supplement doses depend on the health condition you are trying to prevent or treat.

Some people take L-tryptophan supplements to try to help them sleep

Low levels of L-tryptophan have been seen in people with depression. Some claim up to 60 milligrams of L-tryptophan daily may help improve your mood or ward off mental health disorders such as depression.

There is limited research to back these claims and studies show mixed results in supporting these claims.

Some women take L-tryptophan supplements to try to ease mood swings due to premenstrual syndrome (PMS), also called premenstrual dysphoric disorder (PMDD). The theory is that these conditions may be linked to a problem with serotonin processing in the body, and that L-tryptophan could help that. However, there is little evidence to show this really works.

Early research in people hints that L-tryptophan supplements may be helpful for:

L-tryptophan is found in meats such as turkey and chicken.

It is also found in:

  • Bananas
  • Cheese
  • Chocolate
  • Dried dates
  • Eggs
  • Milk
  • Fish
  • Oats
  • Pumpkin seeds and sesame seeds
  • Soy
  • Tofu
  • Tree nuts, including peanuts and peanut butter

The amount of L-tryptophan in these foods is small compared to supplements.

L-tryptophan has been linked to a dangerous, even deadly condition called eosinophilia-myalgia syndrome (EMS). The FDA recalled tryptophan supplements in 1989 after up to ten thousand people who took them became sick. EMS causes sudden and severe muscle pain, nerve damage, skin changes, and other debilitating symptoms. Doctors saw a lot fewer people with EMS after the ban. Some research suggests the sickness was due to contaminants that got into the supplements during manufacturing in a factory in Japan.

The supplements have since been re-introduced to the U.S. market.

Side effects of L-tryptophan may include:

L-tryptophan can interfere with many different medicines. Do not take L-tryptophan if you are on antidepressants known as selective serotonin reuptake inhibitors (SSRIs), MAO inhibitors, tricyclic antidepressants and atypical antidepressants. Doing so may lead to a life-threatening condition called serotonin syndrome. Symptoms of serotonin syndrome are:

  • Extreme anxiety
  • Easily startled
  • Rapid heart beats
  • Delirium
  • Severe muscle spasms
  • Increased body temperature

L-tryptophan supplements should be used with caution in pregnant women.

Talk to your doctors before taking this supplement if you have scarring of the liver (cirrhosis)

Always tell your doctor about any supplements you are taking, including natural ones and those bought without a prescription. That way, your doctor can check on any potential side effects or interactions with any medications.

Supplements are not regulated by the FDA the same way that foods and drugs are. Manufacturers are responsible for the safety and labeling of their own products.

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