What Effect Does Tryptophan Have On Your Body?

This is the molecular structure of the amino acid tryptophan.
This is the molecular structure of the amino acid tryptophan. Pasieka, Getty Images

Tryptophan is an amino acid that is found in many foods, such as turkey. Here are some facts about what tryptophan is and the effects it has on your body.

Tryptophan Chemistry

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.

Tryptophan in the Body

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, in order to make niacin and serotonin, you also need to have sufficient iron, riboflavin and vitamin B6. The amino acid, together with tyrosine, 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.

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. Some types of bacteria synthesize tryptophan.

Tryptophan as 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 (e.g., fructose malabsorption) may lead to reduce blood serum levels of the amino acid and are associated with depression.

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. Research in pigs shows too much 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 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.

Learn More About Tryptophan

Tryptophan is an amino acid with a reputation for causing sleepiness. Here's what you need to know:

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 chocolate
  • Cheese
  • Chicken
  • Eggs
  • Fish
  • Lamb
  • Milk
  • Nuts
  • Oatmeal
  • Peanut butter
  • Peanuts
  • Pork
  • Pumpkin seeds
  • Sesame seeds
  • Soybeans
  • Soy milk
  • Spirulina
  • Sunflower seeds
  • Tofu
  • Turkey
  • Wheat flour

Tryptophan Chemistry Key Takeaways

  • Tryptophan is an essential amino acid. 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.

References

  • Dietary 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.