5-HTP (5-hydroxytryptophan)

Mechanism of action

After absorption, 5-HTP can cross the blood-brain barrier and be converted into serotonin (5-HT) via AADC. The increase in serotonin in the CNS can modulate circuits involved in sleep (architecture and latency), mood, and nociception. A portion can be converted into serotonin in the periphery (intestine and other tissues), contributing to nausea/diarrhea and other peripheral serotonergic effects. The increase in serotonin can also enhance melatonin synthesis (via N-acetylation and O-methylation), potentially influencing the sleep-wake rhythm. The final effect depends on dose, nutritional status (cofactors), genetics/enzymes, and above all on the concurrent use of drugs that increase serotonin.

Supported benefits

• Improvement in some sleep parameters (e.g., sleep onset latency and/or perceived quality) in specific clinical contexts (limited)
• Reduction of depressive symptoms in some studies (often dated, with small samples and variable methodological quality) (limited)
• Reduction in migraine frequency/intensity in some trials (limited)
• Possible reduction in appetite/caloric intake through serotonergic modulation (emerging)

Safety & side effects

• Nausea, abdominal cramps, diarrhea (common, dose-dependent)
• Drowsiness, vivid dreams
• Headache, dizziness
• Agitation/restlessness
• Palpitations or blood pressure changes in sensitive individuals (rare)
• Possible worsening of anxiety or insomnia in some individuals (interindividual variability)

FAQ

Is 5-HTP the same thing as melatonin?

No. 5-HTP is a precursor of serotonin; melatonin is a hormone derived from serotonin. 5-HTP can indirectly influence melatonin, but it is not equivalent and has a different profile of effects and risks.

Why can 5-HTP cause nausea or diarrhea?

Part of 5-HTP is converted into serotonin in the periphery, especially in the intestine, where serotonin regulates motility and secretions. This can increase gastrointestinal disturbances, often in a dose-dependent manner.

Is it suitable for chronic insomnia?

Evidence regarding sleep is limited and does not replace evaluation of the causes of insomnia (stress, sleep apnea, medications, circadian rhythms, medical conditions). In cases of persistent insomnia, clinical evaluation and interventions with established efficacy (e.g., CBT-I) are indicated.

What is the main risk if taken with antidepressants?

The combined increase in serotonin can lead to serotonin syndrome, a potentially serious condition. For this reason, combinations with serotonergic drugs require medical supervision.

Does 5-HTP always increase serotonin in the brain?

Not necessarily in a predictable way. It depends on absorption, transport into the CNS, enzymatic activity, competition with other amino acids, and concurrent use of medications. In addition, the peripheral increase may predominate in some individuals.