4. Discussion
Chronic constipation, insomnia, Constipation
REGRESSION, MINOR
This study aimed to assess whether supplementation with YM would confer health benefits to healthy adults experiencing discomfort in defecation. Recently, we reported that the regular intake of YM for eight weeks improved the bowel habits of healthy women aged 30–49 years [Constipation can occur in anyone as a minor discomfort that may result from altered gut motility. Chronic constipation is estimated to affect about 10–15% of the population and significantly impacts the quality of life [More importantly, we found that supplementation with YM as a prebiotic could alter sleep architecture and contribute to better sleep quality. Recent studies have focused on the interaction between gut microbiota and sleep disturbances, indicating that a healthy gut environment, including microbiota and metabolite composition, is increasingly important for host health [We hypothesized that changes in the levels of certain metabolites in the colon following changes in the gut microbiota composition due to YM intake would be responsible for the effects of YM on sleep quality. We also evaluated the impact of YM intake on fecal metabolites using a CE-TOFMS-based metabolomics approach. As a result, 20 differential metabolites between the YM and placebo groups were screened. This study represents the first report on the alteration of fecal metabolites following YM administration. To explore the metabolites associated with changes in objective sleep parameters—TIB or N3 latency, which were significantly altered by YM ingestion—stepwise linear regression was performed using these twenty differential metabolites as independent variables. Relationships between the changes in fecal metabolites and each sleep variable were found. The extension of TIB could be explained in 53.0% by elevated propionate levels in feces. However, the shortened N3 latency could be explained at 59.3% by increased GABA and dTMP levels. Even GABA concentration alone could also explain 33.3% of the change in N3 latency. Based on the above, the effect of YM on sleep might be explained via at least two routes: gut-derived propionate and GABA.First, regarding the association between sleep and fecal propionate level, a prior study in preschool-aged children found that the fecal propionate concentration was lower in children with long wake times after sleep onset, indicative of difficulty maintaining sleep [In addition, we consider the possible effects of gut-derived GABA on sleep quality. Our results found that fecal GABA levels were increased by YM administration. GABA is a key inhibitory neurotransmitter closely related to sleep, and GABA receptors are pivotal targets for pharmaceuticals, such as benzodiazepine, to alleviate insomnia [One limitation of this research is that the EEG data collection was partly incomplete. Incomplete EEG data due to inappropriate use of equipment reduced the sample size of the EEG data set, although this reduction is in line with the missing data observed in previous EEG studies. Although bowel habits may be affected by diet, we did not impose strict dietary restrictions on participants or provide uniform diets.