In recent years, there has been growing evidence regarding the relationship between the gut and sleep.
Previous studies by a group of Japanese researchers found that YM, a water-soluble, indigestible carbohydrate derived from yeast cell wall, could have a positive impact on altering intestinal microflora.
To evaluate the effect of YM in improving bowel habits and sleep quality, the researchers conducted a double-blinded, randomised, placebo-controlled trial from May 2021 to November 2021.
The study was funded by Bio-oriented Technology Research Advanced Institution, NARO, and Asahi Group Holdings.
The participants included healthy Japanese adults aged between 20 and 64 years with a tendency for constipation. They were randomly allocated to either the YM group or placebo group, and directed to take five YM or placebo tablets once a day for four weeks.
The daily dose of five tablets contained 1.1g of YM prepared from yeast cell walls provided by Asahi.
Data from 37 participants were collected and used for efficacy analysis. These comprised information on bowel movements, tablet intake, menstrual status, physical condition, and the use of other medications.
Sleep electroencephalogram (EEG) was carried out and recorded, and faecal sampling were performed pre- and post-intervention.
The results showed that the YM group significantly increased defecation frequency compared to the placebo group during the treatment period.
While changes in stool volume were markedly higher in the YM group than the placebo group, the Bristol Stool Scale (BSS) scores indicated that stool forms of the two groups were not significantly different.
After four weeks of intervention, the non-REM sleep stage 3 (N3 deep sleep stage) duration in the YM group was significantly longer than that in the placebo group.
In addition, YM intake significantly shortened N3 latency, meaning the transition to N3 was accelerated, and significantly lengthened total time in bed (TIB), compared to placebo intake.
“N3, in which growth hormone is released in abundance, serves as an indicator of deep and restorative sleep. Our findings imply that YM may be a useful prebiotic for improving some aspects of bowel movement and sleep quality.
“Further studies are required to fully assess the beneficial effects of YM supplementation and clarify the underlying mechanism,” the authors wrote.
Sleep and gut environment
The metabolomics analysis found a total of 20 metabolite differences between the YM and placebo groups.
To explore the relationship between sleep quality and gut environment, forward stepwise linear regression analysis was applied.
According to the researchers, the extension of TIB could be explained by elevated propionate (short-chain fatty acids or SCFAs) levels in faeces (53%), while the shortened N3 latency could be attributed to increased gamma-aminobutyric acid (GABA) and deoxythymidine monophosphate (dTMP) levels (59.3%).
“Even GABA concentration alone could account for 33.3% of the change in N3 latency. Based on these findings, the effect of YM on sleep might be explained via at least two routes — gut-derived propionate and GABA.”
GABA is a key inhibitory neurotransmitter closely linked to sleep, and GABA receptors are pivotal targets for pharmaceuticals, such as benzodiazepine, to alleviate insomnia.
Food ingredients and products enriched with GABA have also been shown to enhance sleep quality in people with insomnia symptoms and healthy individuals.
Secondary bile acids and SCFAs could trigger secretion of gut hormones, such as peptide YY, glucagon-like peptide-1, and 5-hydroxytryptamine, from intestinal epithelial cells.
It is speculated that YM-degrading microorganisms produce propionate in the gut, and the subsequent increase in intestinal propionate levels enhances gut motility.
Chronic constipation is estimated to affect about 10% to 15% of the Japanese population.
“Multiple factors are essential for normal gut motility, such as the immune and nervous system, bile acid metabolism and mucus secretion, and the gut microbiota and metabolites.
“An imbalance or dysfunction in any of these factors can lead to abnormal gut motility and, consequently, constipation symptoms. One possible approach to actively modulate the gut environment is through a prebiotic.”
The clinical application of prebiotics has received increasing attention due to their low risk of serious side effects, ease of administration, and high potential to influence the composition and function of intestinal microbiota.
YM is a highly complex polysaccharide that is not assimilated by most organisms. Bacteroides thetaiotaomicron (B. thetaiotaomicron), one of the dominant bacterial species in the human gut microbiota, expresses specific α-mannan-degrading enzymes. Unlike other gut microbes, it can utilise YM as a carbon source.
In this study, the relative abundance of B. thetaiotaomicron in faeces was increased in the YM group, further underscoring the potential benefits of YM.
“Effects of Prebiotic Yeast Mannan on Gut Health and Sleep Quality in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Study”
Authors: Reiko Tanihiro, et al