What is tryptophan and what is it for?

L-tryptophan is an amino acid, that is, one of the nitrogenous compounds that constitute the basic building blocks in the composition of proteins.

Among the known amino acids, a part of them can be synthesized by our metabolism, while others -among them tryptophan- must be compulsorily supplied through the diet we eat, since our body is unable to synthesize it from other precursors , then forming part of the so-called “essential amino acids”.

Now, let’s delve into what tryptophan really is and what is its specific utility in human metabolism.

Tryptophan vs L-tryptophan

Molecules with potential biological activity can sometimes occur in nature in various possible biochemical forms.

When a molecule has its functional group in the right-hand sense, it is called “D”, and the other, conversely, with the functional group to the left of the carbon, is called “L”. Out of these two possible molecular shapes, only the L forms have activity related to living beings. That is why L-tryptophan is the one that has the possibility of being incorporated into the internal synthesis of biologically active proteins in our body.

Once we obtain L-tryptophan through the intake of proteins of vegetable or animal origin, it is transformed inside our body into 5-HTP (5-hydroxytryptophan), to be later incorporated as part of the chain of amino acids of a series of fundamental proteins in the metabolic processes related to the health of our body.

What is it for?

Tryptophan results essential for the nervous and digestive systems and for proper skin care, from the first stages of the embryonic development of the fetus, our infantile and juvenile stages, as well as in the maintenance of the metabolic balance of nitrogen in adults.

L-tryptophan is a fundamental part of the composition of various biologically active substances, which regulate different biological functions of our body; between them:

  • Serotonin, called the “happiness hormone”, Because it induces states of relaxation and a feeling of fullness, modulating our behavior, moods and the development of the capacity for knowledge due to its physiological effect on the brain.
  • Melatonin, which is a hormone whose function is regulate wake and sleep cycles within circadian rhythms.
  • Vitamin B3, or niacin, essential for the synthesis of the coenzymes NAD and NADP, related to energy production metabolism in living cells and cellular communication. It also contributes to the regulation of cholesterol levels in the body.

Natural sources of L-tryptophan in food

As a consequence of the fact that it cannot be synthesized by our body, its intake must be supplied externally from foods rich in tryptophan. Among the extensive list that have it in its composition, there are both plant origin as animal. Among them we can highlight:

Of vegetable origin

  • The seeds of some oilseed plants, such as soybeans, peanuts, sesame or sesame, sunflower and pumpkin.
  • Nuts and their derivatives, such as almonds, walnuts, hazelnuts, pistachios and cashews, peanuts and peanut butter.
  • Fruits like banana, or plantain, and avocado.
  • Cereals, among them mainly oats, rice, amaranth, chia and quinoa.
  • Legumes in general (beans, lentils, chickpeas).

Of animal origin

  • The eggs; especially the yolk.
  • The birds; especially lean chicken and turkey.
  • Blue fish, such as sardines and salmon.
  • Dairy; either directly the milk, or its derivatives, such as cheese, yogurt, kefir.

To adequately process the natural source of tryptophan in the diet, the body requires simultaneously having adequate concentrations of some minerals that act as enzymatic cofactors, especially iron. On occasions, the intracellular presence of riboflavin and vitamin B6 may also be required to complete the synthesis of larger molecules of biological action with tryptophan in their composition.

L-tryptophan as a dietary supplement or medical treatment

When certain conditions related to a deficient synthesis of serotonin or melatonin occur, L-tryptophan can also be directly supplied as supplement
in clinical treatments based on other drugs.

As a precursor element for the synthesis of serotonin, L-tryptophan has shown its efficacy in the treatment of certain health disorders, especially psychiatric ones, such as:

  • Recurrent difficulty in falling asleep, insomnia, night apnea, and irritability and discouragement as a consequence of said lack of good rest.
  • Depressive and anxiety disorders, replacing or enhancing the effects of certain antidepressant and anxiolytic drugs.
  • Seasonal affective disorder (SAD), or seasonal depression, which affects certain people, including children, during the fall and winter.
  • Irritability derived from premenstrual dysphoric syndrome (PMDD).
  • As an aid in treatment to quit tobacco use.
  • To improve performance in certain sports disciplines.
  • To aid in the healing of ulcerative lesions caused by Helicobacter pylori infection.
  • Its possible therapeutic effects are being evaluated in the treatment of some neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Alzheimer’s.


The use of L-tryptophan carries risks that are eliminated or minimized under strict control of the doses used in medical treatment, as the excess intake of this amino acid has been blamed for the development of eosinophilia and myalgia syndrome (SEM), which causes a set of symptoms such as chronic fatigue, muscle weakness, intense muscle and nerve pain, pain and chronic inflammation of the tissue connective, articular and thoracic organs, skin rashes and alopecia. It can also cause minor conditions, such as stomach pain, heartburn, belching and flatulence, as well as nausea and dizziness, headache, diplopia, vomiting, diarrhea, dry mouth, lack of appetite and sexual dysfunctions.

The intake of L-tryptophan should also be carefully regulated in patients under treatment of synthetic and natural psychotropic medications, pregnant and nursing mothers, and people with liver or kidney dysfunction.

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