Science, Tech, Math › Science The Effects of Tryptophan on Your Body How Long Does the Amino Acid Tryptophan Stay in Your System? Share Flipboard Email Print Pasieka / Getty Images Science Chemistry Chemistry In Everyday Life Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated November 24, 2019 Tryptophan is an amino acid that is found in many foods, such as turkey. L-tryptophan foods have a reputation for causing sleepiness. Here are some facts about what tryptophan is and the effects it has on your body. Tryptophan Chemistry Key Takeaways Tryptophan is one of the essential amino acids. Humans cannot make it and must obtain it from their diet.Tryptophan is used in the synthesis of the neurotransmitter serotonin.Some people take tryptophan supplements as a sleep aid or antidepressant. However, eating foods rich in tryptophan has not been shown to cause drowsiness. Chemistry in the Body Tryptophan is (2S)-2-amino-3-(1H-indol-3-yl)propanoic acid and is abbreviated as "Trp" or "W." Its molecular formula is C11H12N2O2. Tryptophan is one of the 22 amino acids and the only one with an indole functional group. Its genetic codon is UGC in the standard genetic code. Humans and other animals aren't the only organisms that use tryptophan. Plants use the amino acid to make auxins, which are a class of phytohormones, and some types of bacteria synthesize tryptophan. Tryptophan is an essential amino acid, meaning you need to get it from your diet because your body cannot produce it. Fortunately, tryptophan is found in many common foods, including meats, seeds, nuts, eggs, and dairy products. It is a common misconception that vegetarians are at risk for insufficient tryptophan intake, but there are several excellent plant sources of this amino acid. Foods that are naturally high in protein, either from plants or animals, typically contain the highest levels of tryptophan per serving. Your body uses tryptophan to make proteins, the B-vitamin niacin, and the neurotransmitters serotonin and melatonin. However, you also need to have sufficient iron, riboflavin and vitamin B6 to make niacin and serotonin. Together with tyrosine, tryptophan plays a role in anchoring membrane proteins in cells. Only the L-stereoisomer of tryptophan is used by the human body. The D-stereoisomer is much less common in nature, though it does occur, as in the marine venom contryphan. A Dietary Supplement and Drug Tryptophan is available as a dietary supplement, although its use has not been demonstrated to affect levels of tryptophan in the blood. Some studies have indicated tryptophan may be effective as a sleep aid and as an antidepressant. These effects may be related to the role of tryptophan in the synthesis of serotonin. Health conditions that lead to poor tryptophan absorption (like fructose malabsorption) may reduce blood serum levels of the amino acid and are associated with depression. A metabolite of tryptophan, 5-hydroxytryptophan (5-HTP), may have application in the treatment of depression and epilepsy. Can You Eat Too Much? Eating large amounts of foods high in tryptophan, such as turkey, has not been shown to cause drowsiness. This effect typically is associated with eating carbohydrates, which trigger the release of insulin. Even so, while you need tryptophan to live, animal research indicates eating too much of it may be bad for your health. Research in pigs shows excessive tryptophan may lead to organ damage and increased insulin resistance. Studies in rats correlate a diet low in tryptophan with an extended lifespan. Although L-tryptophan and its metabolites are available for sale as supplements and prescription medications, the Food and Drug Administration has warned that it is not categorically safe to take and may cause illness. Research into the health risks and benefits of tryptophan is ongoing. Foods High in Tryptophan Tryptophan is found in high-protein foods such as meat, fish, dairy, soy, nuts, and seeds. Baked goods often contain it, too, especially if they contain chocolate.Baking chocolateCheeseChickenEggsFishLambMilkNutsOatmealPeanut butterPeanutsPorkPumpkin seedsSesame seedsSoybeansSoy milkSpirulinaSunflower seedsTofuTurkeyWheat flour Resources and Further Reading Koopmans, Sietse Jan, et al. “Surplus Dietary Tryptophan Inhibits Stress Hormone Kinetics and Induces Insulin Resistance in Pigs.” Physiology & Behavior, vol. 98, no. 4, 19 Oct. 2009, pp. 402-410.Ooka, Hiroshi, et al. “Neural and Endocrine Development after Chronic Tryptophan Deficiency in Rats: II. Pituitary—Thyroid Axis.” Mechanisms of Ageing and Development, vol. 7, 1978, pp. 19-24.U.S. Department of Health and Human Services and U.S. Department of Agriculture. Dietary Guidelines for Americans. 6th ed., Government Printing Office, Jan. 2005, Office of Disease Prevention and Health Promotion.