Tryptophan: characteristics and functions of this amino acid

The 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 fulfills many functions.

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

Tryptophan characteristics

As said, tryptophan is an essential amino acid. But what does this mean? Well what the body itself cannot synthesize it and it must be achieved through food. Fortunately, tryptophan is found in a wide variety of foods, including meats, nuts, eggs, or 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 thanks to niacin, it is necessary to also consume iron, riboflavin and vitamin B6.

A good dietary supplement

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

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

Excessive stimulation of serotonin on the postsynaptic 5-HT1A and 5-HT2A receptors at the central and peripheral levels can have negative consequences for the body. This is known as serotonin syndrome and it can be deadly. Although this syndrome can be caused by taking drugs (for example, Prozac) or using drugs (for example, LSD, MDMA, methylphenidate, bath salts...), it is unlikely to happen from the consumption of tryptophan supplements. However, when combining different substances, special care must be taken.

• Learn more about this topic in our article: "Serotonin 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 an increase in insulin resistance.

Features

Next we are going to know what are the main functions of tryptophan. This amino acid is closely linked to the proper functioning of the brain and our neurons.

1. The role of this amino acid in the brain

The blood-brain barrier determines what substances in the blood can reach the brain. At least nine amino acids, including tryptophan, compete with each other to access the same support that transports them across this barrier.

The amino acids that are present in greater amounts in the blood are more likely to pass the barrier. In most foods, tryptophan is found in small amounts, so it has serious difficulties to pass 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 tryptophan levels.

2. The role of tryptophan in the synthesis of serotonin

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

In the brain, serotonin is essential. Once tryptophan reaches the brain, it is converted to serotonin. As a neurotransmitter, serotonin plays an important role in the memory, regulates 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 converting to serotonin, the body can use this chemical to make the hormone melatonin. In this sense, tryptophan helps 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. Instead, during the night, they increase.

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

4. The role of tryptophan in the production of niacin

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, trouble paying attention, fatigue, and insomnia.

• Learn more about the relationship between vitamins and the brain in our article: "6 vitamins to take care of 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. (nineteen ninety six). The immune system of the brain. Research and Science. January. 16-21.