Tryptophan ChemistryTryptophan 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.
Tryptophan in the BodyTryptophan 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 misperception that vegetarians are at risk for insufficient tryptophan intake, but there are several excellent plant sources for 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, in order to make niacin and serotonin, you also need to have sufficient iron, riboflavin and vitamin B6. 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.
Tryptophan as a Dietary Supplement and DrugTryptophan 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. 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. A metabolite of tryptophan, 5-hydroxytryptophan (5-HTP), may have application in the treatment of depression and epilepsy.
Can You Eat Too Much Tryptophan?While you need tryptophan to live, animal research indicates eating too much too much of it may be bad for your health. Studies in rats correlate a diet low in tryptophan with an extended lifespan. Research in pigs shows too much tryptophan may lead to organ damage and increased insulin resistance. Although L-tryptophan and its metabolites are available for sale as supplements and prescription medications, the FDA 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.
ReferencesDietary Guidelines for Americans - 2005. Washington, DC. US Dept of Health and Human Services and US Dept of Agriculture: 2005.
Ooka H, Segall PE, Timiras PS (January 1978). "Neural and endocrine development after chronic tryptophan deficiency in rats: II. Pituitary-thyroid axis". Mech. Ageing Dev. 7 (1): 19–24.
Koopmans SJ, Ruis M, Dekker R, Korte M (October 2009). "Surplus dietary tryptophan inhibits stress hormone kinetics and induces insulin resistance in pigs". Physiology & Behavior 98 (4): 402–410.
Learn MoreDoes Eating Turkey Make You Sleepy?
Amino Acid Structures
Foods High in Tryptophan