The Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults: A Randomized Controlled Trial.

Objectives: Concurrent with global aging epidemics, cognitive decline has become an increasing public health concern. Dietary supplementation may offer neuroprotective benefits, and 5-hydroxytryptophan (5-HTP) has gained interest due to its role in serotonin synthesis, thereby regulating cognitive function and mood. However, there is limited evidence on its effect on cognitive function, especially among older Asian adults. Therefore, the study aimed to investigate the effects of 5-HTP supplementation on cognitive function and mood in Singaporean older adults. Methods: This was a single-blinded, 12-week randomized controlled trial, and 30 participants (66 ± 3 years) were randomly assigned to consume 100 mg of 5-HTP daily or not consume it. Cognitive function and mood were assessed via the Montreal Cognitive Assessment (MoCA), Geriatric Anxiety Inventory (GAI), and Geriatric Depression Scale (GDS). Cognitive function-related blood biomarkers, including amyloid beta (Aβ)40, Aβ42, gamma-aminobutyric acid, and serotonin, were also determined. Results: A significant time effect was observed in the MoCA score, which was mainly explained by a significant increase in the 5-HTP group (week 0 vs. week 12: 26.6 ± 1.4 a.u. vs. 27.6 ± 1.4 a.u., p < 0.05). Moreover, the 5-HTP group showed a significant increase in serum serotonin levels. Additionally, the GDS score improved in the 5-HTP group (week 0 vs. week 8: 1.2 ± 1.7 a.u. vs. 0.7 ± 1.2 a.u., p < 0.05). However, no effects on GAI and other biomarkers were observed. Conclusions: 5-HTP supplementation can enhance cognitive performance and reduce symptoms of depression in Singaporean older adults, potentially through serotonergic modulation. However, given the relatively small sample size (n = 30) and short-term (12-week) intervention, these findings should be interpreted cautiously, and further long-term studies with a larger sample size are warranted to confirm these preliminary results.