The proteinogenic amino acid L-tryptophan is essential for the human body and has an aromatic structure.
Like phenylalanine, histidine and tyrosine, its structure contains an indole functional group, which means it cannot be synthesised and must be ingested as part of the diet. Foods which are high in protein, like soybeans or oats, are particularly suitable for this purpose, though peas and walnuts can also be used to ensure the daily requirement is met.
As L-tryptophan isn’t soluble in water, and it possesses a marked resistance to heat, only a small amount is lost during the cooking process. The daily requirement for L-tryptophan differs from person to person, so it is hard to estimate how many people actually manage to regularly meet their own daily needs through nutrition alone.
Today, however, it is highly probable that unhealthy eating habits, as well as too much stress and too little time, mean that few people are able to meet their body’s requirement for L-tryptophan and therefore really ought to supplement their intake of this amino acid.
A deficiency in this essential amino acid can lead to erratic mood swings and occasionally even depression, as L-tryptophan performs important functions in the nervous system as a producer of messengers. For this reason, it is now possible to use this vital substance in the form of a dietary supplement to combat mental illnesses, which several studies have already demonstrated.
Foods with Lots of L-tryptophan
A healthy adult consumes around 3.5mg to 6mg of L-tryptophan per kilogram of body weight through food every day. There can, however, be large differences in the actual needs of individuals. 1 This means it is advisable to include as many different sources of L-tryptophan as possible in your diet, to prevent the danger of a deficiency as early as possible. A shortage is above all likely in cases of inflammatory gastrointestinal disorders or liver damage, where the natural capacity to absorb is disrupted; shortages in these cases can lead to the risk of complications.
Food doesn’t contain L-tryptophan in free form; it is instead bound up in protein. In every 100g of food, the following amounts of total protein and L-tryptophan respectively are to be found:
|Food||Total Protein||L-tryptophan||L-tryptophan % of Protein|
|Soybeans||36.5 %||590 mg||1.6 %|
|Cocoa powder (without sugar)||19.6 %||293 mg||1.5 %|
|Cashew nuts||18.2 %||287 mg||1.6 %|
|Chicken breast (raw)||21,2 %||267 mg||1.3 %|
|Peas (dried)||24.6 %||266 mg||1.1 %|
|Pork (raw)||21.0 %||220 mg||1.1 %|
|Salmon (raw)||20.4 %||209 mg||1.0 %|
|Oats||13.2 %||182 mg||1.4 %|
|Walnuts||15.2 %||170 mg||1.1 %|
|Chicken egg||12.6 %||167 mg||1.3 %|
|Brown rice||7.9 %||101 mg||1.3 %|
|Corn flour||6.9 g||49 mg||0.7 %|
|Cow’s milk (3.8% fat)||3.3 g||46 mg||1.4 %|
As the L-tryptophan contained in these foods is chemically bonded, only a fraction is absorbed by the body. The effect of these foods in the diet is therefore not the same as the effect of nutritional supplements containing L-tryptophan.
L-tryptophan – a resistant amino acid
No special precautions are necessary during the preparation of food containing L-tryptophan, as it is both heat and water resistant. However, the respective L-tryptophan contents of these various foods can differ and are influenced by factors such as where the food has been kept, conditions during production and other external factors.
As L-tryptophan is an amino acid, especially high amounts can be found in foods containing protein of a plant or animal origin. Soybeans, for example, contain a particularly large amount of L-tryptophan (around 590mg per 100g), though the amounts contained within cashew nut kernels (around 280mg per 100g) and unsweetened cocoa powder (approximately 290mg per 100g) are also worth noting.
For the purpose of a balanced and varied diet, oats (with a content of around 180mg per 100g) and chicken eggs (approximately 167mg per 100g) can also be used as sources of L-tryptophan to ensure sufficient levels within the diet. Furthermore, dried peas (around 275mg per 100g) and raw salmon (approximately 209mg per 100g) contain large amounts of this vital substance and can also be adopted in the diet.
Functions of L-tryptophan
L-tryptophan occurs naturally in foods, but only in smaller amounts than most other amino acids. However, it performs many important functions in the human body and its metabolism. The mood-lifting effects of L-tryptophan are particularly worth noting. This stems from the conversion of the amino acid into the neurotransmitter serotonin. As a precursor for serotonin, L-tryptophan contributes significantly to the balancing of our state of mind and has particularly positive effects on our sense of wellbeing.
L-tryptophan decreases appetite and reduces anxiety
If there is an insufficient amount of L-tryptophan in the body, serious anxiety disorders or even depression can develop as a result. Moreover, serotonin has a limiting effect on appetite, decreasing it, so a sufficient concentration can help obese people lose weight. Specially manufactured nutritional supplements can be used to this purpose, to support the effects of a diet. Competitive sportsmen also benefit from the consumption of supplements containing L-tryptophan, as these can increase physical fitness and thus improve training results.
A further important function of L-tryptophan is supporting the synthesis of niacin (vitamin B3) through its role as a provitamin. As niacin undertakes important tasks in the carbohydrate, protein and fat metabolisms and thus ensures an energy supply for the body, L-tryptophan is also of great importance for this process. Furthermore, vitamin B3 is necessary for the synthesis of some neurotransmitters and messengers, enabling the transmission of stimuli in the brain. As a component of many different proteins, L-tryptophan is also indirectly involved in many enzymatic reactions, enabling the building of different tissues through the so-called ‘structural proteins’.
L-tryptophan encourages a healthy sleep pattern
New findings have proven that L-tryptophan can also help with a good night’s sleep; it keeps the level of serotonin fairly constant during the day, allowing enough melatonin to be produced from this serotonin during the night. This hormone significantly influences our sleep cycle and is necessary for restful sleep. Low concentrations of L-tryptophan can therefore cause problems falling asleep and even insomnia, and can considerably worsen our general state of health.
The Medical Uses of L-tryptophan
As L-tryptophan has lots of positive effects on the human body, it can be used to combat certain medical conditions and contribute to recovery. Several studies have already been carried out in order to confirm these assumptions, and have convincingly proven the effectiveness of essential amino acids.
A study in 2010 examined, for example, to what extent L-tryptophan can halt the spread of a common liver condition (steatohepatitis). The study was based on the formation of oxidative stress and inflammatory reactions. After only four weeks, participants in the study who had received special supplements every day had a significantly improved level of triglyceride and the amount of available inflammatory cytokines. It could therefore be proven that L-tryptophan helps significantly to prevent the spread of steatohepatitis and can improve the general state of health of the patient. 2
Furthermore, this essential amino acid has positive effects on irritable bowel syndrome. 3
The less L-tryptophan there is in the body, the more serious the symptoms of this condition; L-tryptophan can therefore be used to relieve irritable bowel syndrome.
Finally, this protein substance has already been proven to be very effective in combating depression, and it has become the most important anti-depressant which does not have side effects. 4
An overdose of L-tryptophan is simply not possible, as L-tryptophan has no toxic effects on the body.
Despite this, L-tryptophan as an amino acid preparation is not legally available in Germany, as it is viewed as a pharmaceutical drug. It is available in Austria and Switzerland on prescription.
L-tryptophanis one of the most important mood-lifting substances found in nature and is involved in the synthesis of the so-called ‘happiness hormone’, serotonin. In contrast with many conventional anti-depressants, it does not cause any harmful side effects and can have astonishing effects even in cases were traditional treatment has failed.
Targeted supplements containing this essential amino acid can also encourage weight loss and help overcome sleep disorders. Moreover, L-tryptophan is necessary in the body for the production of various substances and plays a role in the metabolism and the production of energy. It has in recent years therefore been recognised as an important remedy in orthomolecular medicine.
- “G. Lazaris-Brunner, M. Rafii, R. O. Ball, P. B. Pencharz: Tryptophan requirement in young adult women as determined by indicator amino acid oxidation with L-(13C)phenylalanine. In: Am. J. Clin. Nutr. 68(2); Aug 1998: S. 303-10” ↩
- “Cichoz-Lach H. et al.: The effects of L-tryptophan and melatonin on selected biochemical parameters in patients with steatohepatits; J Physol Pharmacol 2010 Oct; 61(5): 577-580” ↩
- “Fitzgerald P et al.: Tryptophan catabolism in females with irritable bowel syndrome: relationship to interferon-gamma, severity of symptoms and psychiatric co-morbidity; Neurogastroenterol Motil 2008 Sep 17” ↩
- “Roiser JP, Levy J, Fromm SJ, Nugent AC, Talagala SL, Hasler G, Henn FA, Sahakian BJ, Drevets WC. The effects of tryptophan depletion on neural responses to emotional words in remitted depression. Biol Psychiatry. 2009 Sep 1;66(5):441-50. Epub 2009 Jun 17” ↩