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L-Tryptophan is an essential amino acid, a protein building block that can be found in many plant and animal proteins. L-tryptophan is called an essential amino acid because the body can’t make it. It must be acquired from food. The body requires this essential amino acid to synthesize proteins and specialized molecules such as the neurotransmitter serotonin. Serotonin appears to play significant roles in sleep, emotional moods, pain control, inflammation, intestinal peristalsis, and other body functions. 

Also known as:  L-Triptofano, L-Trypt, L-Tryptophane, Tryptophan

Diseases and Conditions

Clinical studies have shown L-Tryptophan is possibly effective in the treatment of premenstrual dysphoric disorder (PMDD) as it decreases related mood swings and irritability. It has also been taken orally to aide in smoking cessation when combined with standard treatments.


L-tryptophan is POSSIBLY UNSAFE when taken by mouth, as it may lead to eosinophilia-myalgia syndrome or mortality.

Medication Interactions

Do not take l-tryptophan with CNS depressants, as it results in major drug interactions. Antidepressants, Benzodiazepines, dextromethorphan, meperidine, monoamine oxidase inhibitors (MAOIs), pentazocine, phenothiazines, and tramadol may have adverse interactions with L-Tryptophan.

Supplement and Food Interactions

Do not mix L-Tryptophan with St. John's wort or supplements or herbs that have sedative properties or increase serotonin levels.  Some of these herbs and supplements include:

  • 5-HTP
  • Calamus
  • California poppy
  • Catnip
  • Hops
  • Jamaican dogwood
  • Kava
  • St. John's wort
  • Skullcap
  • Valerian
  • Yerba mansa
  • 5-HTP
  • Hawaiian baby Woodrose 
  • S-adenosylmethionine (SAMe)


The appropriate dose of L-tryptophan depends on several factors such as the user's age, health, and several other conditions. At this time, there is not enough scientific information to determine an appropriate range of doses for L-tryptophan. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.


Tryptophan is present in dairy products, meats, brown rice, fish, and soybeans.

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  1. https://naturalmedicines.therapeuticresearch.com/databases/food,-herbs-supplements/professional.aspx?productid=326
  2. https://nutritiondata.self.com/foods-000079000000000000000.html
  3. https://pubchem.ncbi.nlm.nih.gov/compound/L-tryptophan#section=Top
  4. http://www.uofmhealth.org/health-library/hn-10006312
  5. https://medlineplus.gov/druginfo/natural/326.html

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