Effects of Saccharomyces cerevisiae NK-1 on stool frequency and volume in healthy individuals with infrequent bowel movements: a randomized, placebo, placebo controlled, double-blind study

Abstract

Background: Constipation and other symptoms of gastrointestinal discomfort, such as abdominal swelling, are common among healthy individuals and have a significant impact on quality of life. Despite the known contribution of gut microbiomes to this pathology, little is known regarding which groups of microorganisms play a key role. Yeasts have been used for fermenting foods since ancient times. Saccharomyces cerevisiae is a type of yeast used for industrial and pharmaceutical purposes in the genetic and medical fields because it is unicellular with a simple biological structure. Yeast also helps improve the intestinal environment. The present study aimed to investigate the effect of foods containing Saccharomyces cerevisiae on bowel movement and to validate the safety of its long-term usage. Stool frequency and consistency were also assessed.

Methods: This was a randomized, double-blind, parallel-group study. The test food contained S. cerevisiae NK-1 powder (1 × 10¹⁰ cells), whereas the placebo did not contain it. The food was made into sticks and provided to healthy individuals with infrequent bowel movements (3–5 movements a week), three times a day for 12 weeks. Then we investigated the changes in stool frequency, volume, and other adverse events. 

Results: The number of days with bowel movement significantly increased in the test group compared with the placebo group after 8–12 weeks of consuming the test food (p < 0.05). Based on the blood test results, there were no adverse events associated with the consumption of the test food observed.

Conclusions: Consumption of the test food regulated intestinal function by promoting defecation in healthy individuals prone to constipation. Thus, S. cerevisiae NK-1 helps facilitate smoother defecation.

Keywords: Saccharomyces cerevisiae NK-1, bowel movement, stool frequency volume, gastrointestinal discomfort