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L-Tryptophan

L-tryptophan is an essential amino acid, most commonly known as the metabolic precursor of serotonin[1]. L-Tryptophan needs the co-factor B6 to convert to serotonin and this is an important clinical note when thinking about supplementing with this amino acid. Food sources of tryptophan include oats, bananas, milk, tuna, chicken, turkey, peanuts, chocolate, and cheese [2]. L-tryptophan can go down a couple of different pathways, one of which is where the tryptophan- is converted to 5-HTP, then serotonin, then melatonin. The second is tryptophan-kynurenine-quinolinic acid-NAD+ and the third is tryptophan-kynurenine-kynurenic acid. Tryptophan tends to be shunted down the kynurenine pathway when there is inflammation, high cortisol, genetic factors[3]
or if the body needs to make more niacin (if there isn’t enough in the diet). When the kynurenine pathway is optimized, this impacts upon the amount of serotonin and melatonin made.


Because of the link between low serotonin with depression and anxiety, tryptophan is often studied for its ability to elevate mood[4]. As discussed above, it is important to encourage l-tryptophan down the 5-HTP pathway rather than the kynurenine pathway to get the mood enhancing effects of tryptophan[5]. This pathway also relies on the presence of other nutrients, notably magnesium and vitamin B6. Tryptophan can also compete with other amino acids for absoprtion, it is therefore suggested to take tryptophan away from other proteins to maximise its serotonin potential.


Serotonin converts to melatonin, which is our sleep hormone and is important when it comes to getting a good quality night’s sleep. Traditionally, studies looking at tryptophan and sleep have typically used high doses of tryptophan and it has shown positive results. One study decided to test using low doses and the results were also positive. One gram of L-tryptophan significantly reduced sleep latency and lower doses produced a trend in the same direction. Stage IV sleep was significantly increased by using 1/4 g of L-tryptophan[6]. These are amounts which we can typically get from diet alone yet in the presence of some of the factors mentioned above including high stress, inflammation or genetic factors, sometimes supplementation may be helpful.

Recommended For

Sleep , Anxiety , Depression

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MoltiPro (180 caps)

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