5-HTP (5-hydroxytryptophan) is a naturally occurring amino acid and chemical precursor in the biosynthesis of serotonin, a neurotransmitter. The pineal gland is responsible for producing melatonin from serotonin, and thus, by increasing serotonin levels, 5-HTP could theoretically support melatonin synthesis and indirectly influence pineal gland function. There is some scientific evidence that 5-HTP supplementation increases brain serotonin levels and, by extension, may affect melatonin production and sleep regulation. Several small clinical studies have examined 5-HTP's effects on sleep and mood, with some positive findings for sleep onset and quality, suggesting a link to melatonin and thus pineal gland activity.

However, direct evidence specifically connecting 5-HTP supplementation to improved pineal gland function or health is limited. Most research focuses on 5-HTP’s effects on serotonin, mood, and sleep, rather than direct pineal gland outcomes. There is also a lack of large-scale, high-quality clinical trials validating its use specifically for supporting the pineal gland. Therefore, while there is a plausible scientific basis and some supporting evidence, it remains limited and indirect, reflected in a moderate evidence score.