What is the Difference Between Tryptophan and Serotonin?

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  • Written By: Roon Obannon
  • Edited By: A. Joseph
  • Last Modified Date: 08 November 2019
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The connection between tryptophan and serotonin is fairly straightforward. At a simplistic level, it could be thought of as a parent-child relationship, with tryptophan being the parent. The primary difference between tryptophan and serotonin is that tryptophan is an essential amino acid and a building block of plant and animal protein, and serotonin is a neurotransmitter. Tryptophan is a precursor of serotonin and must be available for its organic production; it is the only known supply source. In addition to directly influencing the levels of serotonin in the brain, tryptophan exerts a mild tranquilizing effect and helps to combat headaches, anxiety, depression and insomnia.

Unlike serotonin, tryptophan cannot be synthesized in the body and must be obtained through foods or nutritional supplements. Dietary sources of tryptophan and serotonin include protein-rich meat, cottage cheese, milk, brown rice, soy protein, tuna, shrimp and peanuts. After the digestive process has occurred, some tryptophan is bound up in proteins for storage, and the rest is absorbed into the bloodstream and transported to the brain, where one of two things will occur.

Most of the tryptophan that reaches the brain will enter the kynurenine pathway, with the end result being vitamin B3, also known as niacin. The remaining tryptophan will travel the other pathway and will be processed into 5-hydroxytryptophan (5-HTP). This is an intermediate stage along the serotonin-melatonin route.


The next conversion that takes place produces the chemical messenger known as serotonin. This neurotransmitter is responsible for transferring information from one cell to another during normal nerve and brain function. Serotonin is most concentrated in the gastrointestinal tract, platelets and the central nervous system’s hypothalamus, mid-brain and nerve endings.

Finally, serotonin must pass through an N-acetyl stage before being converted by the pineal gland into a neurohormone called melatonin. This hormone is a free-radical scavenger that plays an important role in healthy aging. It also helps set the body’s circadian rhythm by synchronizing the secretion of other hormones. Melatonin levels decline with age.

Dietary tryptophan supplements were recalled and later banned in certain areas of the world after some deaths and illnesses attributed to contaminants in the late 1980s. In some countries, supplemental tryptophan is available by prescription. In places where it’s banned as a single supplement, it can usually be found as a component in sleep-aid formulas. There are over-the-counter synthetic versions of 5-HTP based on extracts from the seeds of the Griffonia simplicifolia plant that can help increase levels of tryptophan and serotonin. Melatonin supplements are also available and are typically used as a sleep aid or to reduce jet lag.


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Post 3

Oh, so trytophan is the precursor to serotonin. For some reason, I thought that tryptophan is a type of serotonin. Thank you for the article, it's very explanatory.

Post 2

@fBoyle-- Actually, I don't think that the tryptophan in food is enough to boost serotonin, not unless you are eating tons of turkey and cheese. Since tryptophan in food has to compete with other nutrients in food in order to get absorbed, all of it is not made use of by the body. Moreover, all of tryptophan is not used to make serotonin, some of it is made into vitamin B3 as the article said.

That's why I think that people with a tryptophan deficiency and consequently, a serotonin deficiency ought to take supplements. Supplements have more tryptophan than food, so more of the amino acid is likely to get converted into serotonin. I'm not a doctor or anything, it's just my opinion. But if your doctor approves and recommends a tryptophan supplement, it's probably worth a try. Make sure to use a high quality one from a reputable brand.

Post 1

I was wondering why my doctor recommended tryptophan supplements when I asked about an alternative to selective serotonin re-uptake inhibitor drugs. I have low serotonin levels which cause anxiety and depression but I'm not fond of medications that increase serotonin in the brain. They're addictive and cause side effects.

I'm actually not too fond of supplements either so I'm happy to know that tryptophan is available naturally in food. I'd much rather get my tryptophan that way.

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