The essential amino acid L-tryptophan, first discovered in the early 1900s, is considered essential because it cannot be synthesized by the human body and must be acquired through the diet or dietary supplements. While L-tryptophan has several important mechanisms of action in the body, its role in serotonin synthesis is its most significant and researched function. (8)

Continue reading to learn more about L-tryptophan, including its benefits and best dietary sources.

L-tryptophan benefits

Because of L-tryptophan’s key role in brain serotonin production, it can positively influence cognition, mood, and sleep.

L-tryptophan for sleep

Scientific literature supports the myriad health benefits of adequate, good quality sleep. Conversely, lack of sleep can lead to a variety of health issues including weight gain, reduced immunity, blood sugar imbalance, and increased inflammation. That’s why getting enough sleep is an important health goal for most individuals. And yet, according to the American Sleep Association, 40% of adults are not getting the recommended seven to nine hours of sleep required to maintain good health. (1)

That’s where L-tryptophan can help. Research shows that L-tryptophan obtained through food and dietary supplements can improve both sleep quantity and quality, and it can also help people fall asleep faster. (9) A study of volunteers between the ages 55 and 75 demonstrated that the consumption of a tryptophan-enriched cereal not only improved nocturnal sleep, but also enhanced levels of serotonin, melatonin, and anti-oxidants. (4)

L-tryptophan may help improve sleep quantity and quality.

L-tryptophan for anxiety

The most common mental health issues in the United States are anxiety disorders, and the Anxiety and Depression Association of America estimates that nearly 50% of people diagnosed with depression also have an anxiety disorder. (2) In addition to diet and lifestyle, some nutrients can help ease anxiety, including L-tryptophan.

A 2015 randomized crossover study featuring healthy college students demonstrated that a diet high in L-tryptophan foods resulted in significant improvements in mood compared to a diet low in L-tryptophan. Specifically, the participants who ate the diet high in L-tryptophan experienced fewer symptoms of anxiety, irritability, and depression. (7)

Other L-tryptophan benefits

L-tryptophan benefits go beyond sleep and anxiety. Preliminary research shows that L-tryptophan depletion can significantly aggravate symptoms of premenstrual syndrome (PMS). (8)

Early research also shows that L-tryptophan can be used adjunctively with a high-carbohydrate diet to reduce symptoms of nicotine withdrawal as a part of a comprehensive smoking cessation program. (3)

L-tryptophan foods

Looking to increase your L-tryptophan intake? Your diet is a great place to start. Perhaps the most well-known tryptophan-containing food is turkey, which contains about 300 mg per three-ounce serving; however, this amino acid can be found in many other dietary sources. In addition to turkey, other meats such as chicken and lamb contain about 400 mg of L-tryptophan per four-ounce serving. Other L-tryptophan foods, include: (8)

  • Fish (e.g., tuna, halibut, salmon, cod) = 250 mg to 400 mg per serving
  • Shrimp = 330 mg per 4-ounce serving
  • Cheese = 300 mg per ½ cup
  • Pumpkin seeds = 110 mg per ¼ cup
  • Milk = 100 mg per cup
  • Eggs = 100 mg each
  • Nuts (almonds, walnuts, peanuts, cashews) = 50 mg per ¼ cup (8)

In addition to food, certain dietary supplements also contain L-tryptophan, either alone or in combination with other calming nutrients and botanicals.

L-tryptophan vs 5-HTP

L-tryptophan is sometimes confused with 5-Hydroxytryptophan (5-HTP). The fact is, L-tryptophan is a precursor needed to make 5-HTP. 5-HTP can not be obtained from the diet, and adequate intake of L-tryptophan is necessary for the production of 5-HTP in the body. 5-HTP made from the plant Griffonia simplicifolia can also be found as a dietary supplement.

Both L-tryptophan and 5-HTP are precursors of serotonin production and both can be effective in supporting mood, cognition, and sleep. L-tryptophan is also a precursor to melatonin, a sleep-regulating hormone produced by the pineal gland, via the serotonin pathway. (6)

L-tryptophan is a precursor to serotonin and melatonin.

The bottom line

L-tryptophan can positively influence sound sleep, while also helping to alleviate symptoms of anxiety. The good news is that through a combination of diet and dietary supplements, it’s easy to get the L-tryptophan needed to support optimal health. For additional guidance or to discuss how to safely use L-tryptophan as a supplement, consult with your integrative healthcare provider.

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  1. American Sleep Association. (Accessed 2020, May 8). Sleep and Sleep Disorder Statistics. https://www.sleepassociation.org/about-sleep/sleep-statistics/
  2. Anxiety and Depression Association of America. (Accessed 2020, May 8). Facts & Statistics. https://adaa.org/about-adaa/press-room/facts-statistics
  3. Bowen, D.J., Spring, B., & Fox, E. (1991). Tryptophan and high-carbohydrate diets as adjuncts to smoking cessation therapy. J Behav Med, 14(2), 97-110. https://www.ncbi.nlm.nih.gov/pubmed/1880796
  4. Bravo, R., Matito, S., Cubero, J., Paredes, S.D., Franco, L., Rivero, M., Rodriguez, A.B., & Barriga, C. (2013). Tryptophan-enriched cereal intake improves nocturnal sleep, melatonin, serotonin, and total antioxidant capacity levels and mood in elderly humans. AGE, 35, 1277–1285. https://doi.org/10.1007/s11357-012-9419-5
  5. Jenkins, T. A., Nguyen, J. C., Polglaze, K. E., & Bertrand, P. P. (2016). Influence of Tryptophan and Serotonin on Mood and Cognition with a Possible Role of the Gut-Brain Axis. Nutrients, 8(1), 56. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728667/
  6. Lindseth, G., Helland, B., & Caspers, J. (2015). The effects of dietary tryptophan on affective disorders. Archives of psychiatric nursing, 29(2), 102–107. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4393508/
  7. Menkes, D.B., Coates, D.C., & Fawcett, J.P. (1994). Acute tryptophan depletion aggravates premenstrual syndrome. Journal of Affective Disorders, 32(1), 37-44. https://www.sciencedirect.com/science/article/abs/pii/0165032794900590
  8. Richard, D. M., Dawes, M. A., Mathias, C. W., Acheson, A., Hill-Kapturczak, N., & Dougherty, D. M. (2009). L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications. International journal of tryptophan research: IJTR, 2, 45–60. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908021/#!po=3.33333
  9. Yurcheshen, M., Seehuus, M., & Pigeon, W. (2015). Update on nutraceutical sleep therapeutics and investigational research. Evidence-Based Complementary and Alternative Medicine. 2015. https://pubmed.ncbi.nlm.nih.gov/26265921/