Serotonin
Tryptophan → 5-HTP → serotonin — mood, sleep, gut motility (90% gut-made)
Serotonin is most famous as a 'mood neurotransmitter,' but 90% of the body's serotonin is actually made in the gut where it regulates motility and signals satiety. The brain makes its own pool independently. Synthesis starts with the amino acid tryptophan, which gets hydroxylated to 5-HTP and then decarboxylated to serotonin. Iron and vitamin B6 are the load-bearing cofactors; vitamin D modulates the enzyme. Serotonin gets converted to melatonin at night via methylation — which ties this pathway to sleep, methylation, and circadian rhythm.
The load-bearing nutrients — if these are deficient, this pathway slows down. Click any to see daily targets, food sources, and supplements that supply it.
Nutrients that contribute to this pathway but aren’t the single load-bearing inputs.
Pathways that share a load-bearing cofactor with this one.