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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.

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Why do people take L-tryptophan?

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. But research does not show that L-tryptophan supplements are a good or safe treatment for long-term insomnia.

Low levels of L-tryptophan have been seen in people with depression. Some claim that 1 to 3 grams of L-tryptophan daily may help improve your mood or ward off mental health disorders such as:

There is limited research to back up 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:

Can you get L-tryptophan naturally from foods?

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.

What are the risks of taking L-tryptophan?

L-tryptophan has been linked to a dangerous, even deadly condition called eosinophilia-myalgia syndrome (EMS). The FDA recalled tryptophan supplements in 1989 after tens of thousands of people who took them became sick, and some died. 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.

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