What is Tryptophan? High and low values | Lab results explained

Tryptophan is an essential amino acid required for the production of the neurotransmitter serotonin.

Tryptophan is an essential, aromatic amino acid precursor to serotonin via 5-hydroxytryptophan (5-HTP). Serotonin is produced in the brain and the gut. It regulates gut motility, mood and helps induce sleep in those with insomnia.

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Tryptophan has special functions in brain chemistry and is the precursor to the brain chemical serotonin and the vitamin niacin in the body.
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High levels:

High levels may result from either excessive supplementation or poor metabolic utilization of tryptophan.

Required nutrients for this process include niacin and vitamin B6.

Low levels:

Low tryptophan may be the result of poor diet or elevated total body synthesis of serotonin, which depletes tryptophan.

Low levels are commonly correlated with depression, insomnia and schizophrenia. 

Supplementation with 5-Hydroxytryptophan (5-HTP) may help. 5-HTP is one enzymatic step away from serotonin.

Low levels of the three aromatic amino acids, tryptophan, phenylalanine and tyrosine, may indicate inadequate stomach acid.


The information on is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.

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