The study was conducted by researchers from the Kanazawa University, University of Fukui, and KAGAMI INC.
Writing in PLoS One, the researchers said that sake lees - the by-product of sake or rice wine fermentation - has been shown to relieve constipation and improve the gut microbiome.
Sake lees, also known as sake kasu, are widely consumed in Japan for their rich dietary fibre content.
A study published in 2012 showed that daily consumption of 50g of sake lees could alleviate constipation in the general population.
Sake lees also contains high D-amino acid content, which is produced by microorganisms during fermentation.
D-amino acids, such as D-alanine and D-serine, have been associated with kidney-protective properties.
Eight healthy individuals - mostly women (75 per cent) with an average age of 46 years old and suffering from chronic constipation took part in this pilot study.
The study was aimed at finding out the effects of sake lees on kidney protection parameters.
These parameters include plasma D-alanine levels, as well as faecal uremic toxin levels. Uremic toxin amounts are measured as it accumulates in body fluids during the course of progressive chronic kidney disease.
The pilot study was also an open-label, single-arm study without a control group.
During the study, the eight participants were randomised to consuming either 25g or 50g of sake lees per day for six weeks. They could choose to cook the sake lees or prepare it in their preferred way.
The sake lees used in this study were sourced from the Japanese sake “Kakuma no Sato” and purchased directly from the manufacturer in Japan.
According to the manufacturer’s specifications, every 100g of sake lees contained 7.2g of protein, 0.6g of fat, 30.8g of carbohydrate, and 5.2g of dietary fibre.
Every 100g of sake lees also contained 12 µmol of D-alanine and 0.7 µmol of D-serine.
Functional foods or medications for improving gut health were not allowed during the six-week intervention period, as well as the two-week run-in period which happened before the intervention.
However, the participants were permitted to consume yogurt or other fermented foods during this period.
The constipation scoring system (CSS) score, the patient assessment of constipation quality of life (PAC-QOL) score, and faecal samples collections were some of the methods used to measure the changes in constipation, gut microbiome, and uremic toxin levels.
Improvements in constipation
Findings showed a significant improvement in secondary end-points of constipation, plasma D-alanine levels, but not with uremic toxin levels - which was the primary endpoint of the study.
Uremic toxin levels, in this case faecal indole, had increased from the baseline by 42 per cent and 52 per cent during week two and four of the pilot study.
It only saw a decrease of six per cent by the end of the six-week study.
Similarly, the faecal levels of another uremic toxin, faecal p-cresol, also went up by seven per cent in the first two weeks of the study.
A decline of 20 per cent was seen at both week four and week six of the study, however, the decline was not statistically significant.
Sake lees consumption, however, did lead to significant improvements in constipation, based on the constipation scoring system.
Constipation scoring system scores across both groups decreased significantly from the baseline of 9.3 to 6.8 at week two of the study, and the decrease continued until the end of the study.
“The CSS score at week two was 6.8, which represented a significant decrease compared to the baseline score and continued through week six,” said the researchers.
The improvement in constipation was also accompanied by faecal microbiome changes.
In this case, firmicutes - which are gram positive bacteria - had increased slightly from 53 per cent at baseline to 57 per cent by the end of the study.
The researchers said that the increase in firmicutes could be due to the dietary fibre content in sake lees.
“Sake lees is a fermented food that contains a variety of bacteria and may contribute to changes in the faecal microbiome. Although this study was a 6-week intervention, our findings indicate the possibility that longer-term interventions can sustain changes in the gut microbiome and provide lasting health benefits,” said the researchers.
Increase in plasma D-alanine
Third, there was a significant increase in plasma D-alanine levels from week two of the study. The increase in D-alanine was 39 per cent higher than baseline at week two and remained at 38 per cent higher than baseline at the end of the study.
In contrast, the levels of D-serine had remained unchanged.
Both are amino acids that come with kidney-protective properties.
The increase in plasma D-alanine levels was also more pronounced in the group taking the higher amount of sake lees.
The researchers said that this could be due to sake lees containing a higher amount of D-alanine than D-serine.
“Since sake lees contain more than 10 times as much D-alanine as D-serine, it is likely that D-alanine was absorbed, but D-serine did not show a change due to its lower content,” said the researchers.
Source: PLoS One
Effects of sake lees intake on fecal uremic toxins, plasma D-alanine, constipation, and gut microbiome in healthy adults: A single-arm clinical trial.
https://doi.org/10.1371/journal.pone.0325482
Authors: Tokumaru T, Toyama T, Nakade Y, Ogura H, Oshima M, Nakagawa S, et al.