L-tryptophan is an essential amino acid that is required for protein synthesis. It is therefore part of the group of 21 proteinogenic amino acids. You have probably heard of tryptophan as it is the precursor to the important neurotransmitter serotonin and the hormone melatonin.
When sufficient levels of L-tryptophan are available in the body, the amino acid is also involved in the formation of vitamin B3 (niacin). However, this process is highly inefficient: the body requires approx. 60 mg tryptophan to build 1 mg of niacin.
Sleep Disorders and Tryptophan
Tryptophan, magnesium, and the vitamins B3 and B6 are used by the body to initially form 5 hydroxytryptophan (5 HTP) and subsequently serotonin. In turn, serotonin, with the addition of panthenic acid (vitamin B5), alpha lipoic acid, B6, B12, and folic acid is used to synthesize melatonin.
Melatonin regulates our sleep and is generated particularly at night. Approx. 50% of individuals taking tryptophan to alleviate sleep disorders report positive effects with tryptophan therapy 1.
You should take tryptophan on an empty stomach or together with carbohydrates. Eating a meal rich in protein in the evening should be avoided. This is because complex proteins suppress the absorption of tryptophan.
Scientists often cite the combination of L-tryptophan with protein-rich foods as a reason for the ineffectiveness of L-tryptophan therapy. Combining tryptophan with other free amino acids is perfectly fine and does not interfere with absorption.
For insomnia, it is recommended that tryptophan is taken on an empty stomach approx. 45 minutes before going to bed. The combination with B vitamins (niacin, B6, B12, pantothenic acid) is also recommended. The amino acid gamma-aminobutyric acid (GABA) may also contribute to a better mood and restful sleep.
Mood, Serotonin Deficiency, and Tryptophan
Serotonin is a tissue hormone and neurotransmitter that plays an important role in blood clotting, blood pressure, and digestive processes.
Additionally, it is specifically known as a mood regulator. Serotonin provides feelings of calm, relaxation, and satisfaction. Serotonin deficiency is often a cause of depression and mood disorders.
High levels of serotonin may also have the sometimes sought-after effect of suppressing appetite. The craving of carbohydrates, in particular, may be diminished by serotonin.
Serotonin itself is only rarely used as a medication. Generally speaking, the precursors to serotonin, substances that affect the building and breakdown of serotonin, are used.
The Correlation between Stress and Tryptophan
Several studies point to a correlation between stress and a deficiency in tryptophan 2, 3. Long-term stress leads to the release of cortisone and the activation of two enzymes, TDO and IDO, that increasingly break down tryptophan in the body 4. The direct result is a deficiency in serotonin.
This also explains the relationship between stress and depression. Taking tryptophan combinations is recommended in these cases.
Tryptophan Requirements and Dosage
Our bodies require approx. 5 mg of tryptophan per kilogram of body weight per day to replace amounts that were used. At a body weight of 70 kg, this translates to a daily amount of approx. 350 mg tryptophan.
As a nutritional supplement or medication to help regulate sleep-wake cycles, tryptophan is administered in doses of 200 mg up to a maximum of 5,000 mg. You should not take L-tryptophan with meals. The amino acid should be taken at least one hour before or after meals.
Foods Rich in Tryptophan
Cheese, nuts, seeds, and beef are good sources of tryptophan. 100 grams of each of these foods contain approx. 300 – 450 mg of tryptophan. Eggs contain 230 mg per 100 g, and oatmeal contains 190 mg per 100 g. New studies show that eating fruits like cranberries, blueberries, plums, or kiwis may also have positive effects on the body’s own production of tryptophan 5.
Tryptophan competes with the other amino acids phenylalanine and tyrosine, as well as the branched-chain amino acids (BCAA) leucine, isoleucine, and valine for absorption into the brain. Therefore, ingesting tryptophan in the form of complex proteins is only of limited value and eating foods rich in tryptophan-containing proteins has only limited effect. However, free-form tryptophan can easily cross the blood-brain barrier for further processing.
Pure L-tryptophan can generally be taken in doses of up to 2,500 mg daily without side effects. It is approved as a nutritional supplement in Europe and the US at these dosage levels. At a higher dose, it is approved only as a medication.
Taking more than 5,000 mg tryptophan per day can lead to increased oxidative stress. Such high amounts should thus be taken in combination with antioxidants. Recommendations include:
- N-acetyl-L-cysteine (NAC), since it contributes to the building of the water soluble glutathione (a tripeptide with powerful antioxidant properties) 6,
- Vitamin C, and
- Vitamin E.
Other possible side effects have not been clearly determined and have only been observed in small-scale trials with daily intakes of 4,000 mg per day or more over a long period of time. Dosages of 200 mg to 800 mg per day even longer term are generally harmless.
- Silber BY, Schmitt JAJ. Effects of tryptophan loading on human cognition, mood and sleep. Neurocience and Biobehavioural Reviews. 2010. 34(3):387-407 ↩
- Hirota T, Hirota K, Sanno Y, Tanaka T. A new glucocorticoid receptor species: relation to induction of tryptophan dioxygenase by glucocorticoids. Endocrinology. 1985. 117(5):1788-95 ↩
- Miura H, Ozaki N, Sawada M, Isobe K, Ohta T, Nagatsu T. A link between stress and depression: shifts in the balance between the kynurenine and serotonin pathways of tryptophan metabolism and the etiology and pathophysiology of depression. Stress. International Journal on the Biology of Stress. 2008. 11(3) ↩
- Kiank C, Zeden JP, Drude S, Domanska G, Fusch G, Otten W, Schuett C. Psychological stress-induced, IDO1-dependent tryptophan catabolism: implications on immunosuppression in mice and humans. PLoS One. 2010. 5(7):e11825 ↩
- Pero RW, Lund H, Leanderson T. Antioxidant metabolism induced by quinic acid. Increased urinary excretion of tryptophan and nicotinamide. Phytotherapy Research. 2009. 23(3):335-46 ↩
- Vats P, Singh VK, Singh SN, Singh SB. Glutathione metabolism under high-altitude stress and effect of antioxidant supplementation. Aviation Space and Environmental Medicine. 2008. 79(12):1106-11 ↩