tryptophan (L-tryptophan) is an essential amino acid found in various foods, for example, turkey. Its molecular formula is C11H12N2O2, and within the human body it fulfils many functions.

In this article we will review its characteristics, its functions and the foods that contain it .

Characteristics of tryptophan

As stated, tryptophan is an essential amino acid. But what does this mean? Well, that the body itself cannot synthesize it and it has to be achieved through food . Fortunately, tryptophan is found in a wide variety of foods, including meat, nuts, eggs and dairy products.

The body uses tryptophan to synthesize proteins, the B vitamin niacin and the chemicals serotonin and melatonin. However, in order to acquire serotonin from niacin, it is necessary to consume iron, riboflavin and vitamin B6 in addition.

A good dietary supplement

In recent years, this amino acid has begun to be marketed as a dietary supplement for its alleged mood benefits . In any case, with respect to this type of products, it has not been demonstrated that they significantly affect the levels of tryptophan in the blood. Therefore, their results are more than questioned.

However, some studies claim that tryptophan supplements may be effective as a sleep aid and antidepressant. These findings are associated with its role as a synthesizer of serotonin and melatonin.

Excess stimulation of serotonin on the post-synaptic 5-HT1A and 5-HT2A receptors at the central and peripheral levels can have negative consequences for the body. This is known as serotoninergic syndrome and can be fatal. Although this syndrome can be caused by taking drugs (e.g. Prozac) or using drugs (e.g. LSD, MDMA, methylphenidate, bath salts…), it is unlikely to be caused by taking tryptophan supplements. However, special care should be taken when combining different substances.

  • Learn more about this topic in our article: “Serotonergic syndrome: causes, symptoms and treatment”

Is it possible to consume a lot of tryptophan through food?

Tryptophan is necessary to live, but some studies indicate that consuming too much can be counterproductive to health . For example, because it causes a decrease in life expectancy, organ damage and increased insulin resistance.

Functions

Below, we will learn about the main functions of tryptophan. This amino acid is intimately linked to the correct functioning of the brain and our neurons.

1. The role of this amino acid in the brain

The blood-brain barrier determines which substances found in the blood can reach the brain. At least nine amino acids, including tryptophan, compete with each other for access to the same support that carries them through this barrier.

Amino acids that are present in greater quantities in the blood are more likely to pass the barrier. In most foods, tryptophan is found in small amounts, so it has serious difficulty passing the blood-brain barrier. However, it is possible to increase the possibility of crossing the barrier if it is consumed together with carbohydrates . The latter cause the release of insulin, which reduces the amount of other amino acids in the blood without affecting the tryptophan levels.

2. The role of tryptophan in serotonin synthesis

Serotonin is a chemical that neurons communicate with, that is, a neurotransmitter. Although many think that serotonin is only found in the brain, the Central Nervous System (CNS) contains only 5% of 5-HT. It is in the small intestine that the rest is produced. This serotonin never reaches the brain, as it has other functions, such as regulating the contraction of the smooth muscles of the blood vessels.

In the brain, serotonin is essential. Once tryptophan reaches the brain, it is converted into serotonin . As a neurotransmitter, serotonin has an important role in memory, regulating mood or appetite. Low levels of this neurotransmitter are associated with different pathologies (depression, obsessive-compulsive disorder, etc.).

3. Its influence on sleep cycles

After being converted into serotonin, the body can use this chemical to produce the hormone melatonin . In this sense, tryptophan helps to regulate the sleep-wake cycle, because melatonin regulates the biological clock. The amount of melatonin produced is determined by ambient light: during the day, melatonin levels drop. During the day, melatonin levels go down, while at night, they go up.

Melatonin supplements help improve sleep problems, such as those caused by jetlag.

4. The role of tryptophan in niacin production

The body can transform tryptophan into niacin, also known as vitamin B3 , which is essential for converting food into energy and maintaining a healthy nervous system.

Another important vitamin, which helps convert tryptophan to serotonin, is vitamin B6. Vitamin B6 deficiency can cause confusion, depression, memory loss, a faster rate of brain degeneration, difficulty paying attention, fatigue, and insomnia.

  • Learn more about the relationship between vitamins and the brain in our article: “6 vitamins for brain health”

Bibliographic references:

  • Afifi, A.K. and Bergman, R.A. (1999). Functional Neuroanatomy. McGraw Hill.
  • Hammond. (2001). Cellular and Molecular Neurobiology (with CD-ROM). Academic Press.
  • Rodriguez, F.; López, J.C.; Vargas, J.P. and Salas, C. (1998). Fundamentals of Psychobiology. Laboratory manual. Seville: Kronos.
  • Streit, W.J. and Kincaid-Colton, C.A. (1996). The brain’s immune system. Research and Science. January. 16-21.