Impact of 5-Hydroxytryptophan Supplementation on Gut Microbiota Composition of Older Adults With Different Sleep Status in Singapore: A Randomized Controlled Trial

OBJECTIVES: The gut and brain communicate bidirectionally through the gut brain axis. Lower microbial diversity has been observed in populations with sleep disturbances. 5-Hydroxytryptophan (5-HTP) is known as a potential modulator of sleep quality, while its impact on the gut remains unclear. The aim of this study was to assess the impact of 5-HTP on gut microbiota in older Singaporeans with different sleep status. METHODS: This study is a single-blinded, 12-week parallel randomized controlled trial. Thirty older adults (66 ± 3 years, mean ± SD) were randomly assigned to either consume or not consume 100 mg 5-HTP daily. Their baseline sleep status was evaluated using global sleep score (GSS): GSS ≤ 5 (good sleepers, n:17); GSS > 5 (poor sleepers: n:13). Characterization of the bacterial population from the stool samples collected at week 0 and 12 was analyzed through 16S metagenomic sequencing. Microbiota composition between GSS ≤ 5 and GSS > 5 was compared via MetaStat analysis. The main effect and interaction of 5-HTP on gut microbiota composition was evaluated by mixed analysis of variance (ANOVA). RESULTS: At baseline, poor sleepers have a significantly lower relative abundance of Firmicutes than good sleepers (GSS > 5: 3.78 × 10(−1) ± 5.43 × 10(−2); GSS ≤ 5: 4.33 × 10(−1) ± 9.32 × 10(−2); p-value: 0.048). After a 12-week consumption of 5-HTP, subjects with GSS > 5 showed an increase in α-diversity (Simpson(5-HTP) vs. Simpson(Control): 0.037 ± 0.032 vs. −0.007 ± 0.022; p(interaction): 0.013). 5-HTP supplementation also showed interaction effects on the relative abundance of Bacteroidota (Bacteroidota(5-HTP) vs. Bacteroidota(Control): −1.03 × 10(−1) ± 4.99 × 10(−2) vs. −3.06 × 10(−2) ± 4.39 × 10(−2); p(interaction): 0.019) and Firmicutes (Firmicutes(5-HTP) vs. Firmicutes(Control): 1.10 × 10(−1) ± 2.40 × 10(−2) vs. 2.02 × 10(−2) ± 7.82 × 10(−2); p(interaction): 0.031). No significant changes were observed for GSS ≤ 5 group. CONCLUSIONS: In older adults, 5-HTP consumption modulated gut microbiota composition in poor sleepers (GSS > 5). However, no influence to the gut microbiota was observed in good sleepers (GSS ≤ 5). FUNDING SOURCES: NUS iHealthtech Microbiome in Health, Disease and Ageing.