Writing in the Japanese Journal of Pharmaceutical Health Care and Sciences, researchers said that healthy adults prone to loose stools experienced a significant decrease in defecation frequency and the number of defecation days after taking the probiotic drink for eight weeks.
Taking the probiotic drink also led to significant changes in the gut microbiota, such as a significant increase in the Lachnospiraceae family, which is involved in the production of the beneficial short-chain fatty acid butyrate. Butyrate inhibits the growth of harmful bacteria and serves as a nutrient source for other intestinal bacteria.
The probiotic strain used in the study was Lactiplantibacillus plantarum 299v (LP299V) supplied by Swedish probiotic firm Probi.
A total of 68 healthy adults with a high bowel movement frequency of 10 to 20 times per week and “slightly soft stool” or “mushy stool” based on the Bristol Scale participated in the study.
They were randomized to either the intervention or placebo group, which took a 100ml drink containing 10 billion CFU of LP299V or a placebo, respectively, daily for eight weeks.
To assess the impact of the probiotic intervention, participants kept a bowel movement diary and took gut microbiota and peripheral blood tests to examine changes in the gut microbiome and blood parameters.
Key findings
Findings showed that the intervention group had a significantly lower bowel movement frequency, also the primary endpoint of this study, as compared to the placebo group.
Specifically, the intervention group reported a bowel movement frequency of 6.7 ± 2.4 times per week by the end of the study, significantly lower than 8.1 ± 3.0 times reported in the placebo group.
The intervention group also reported a significantly lower number of days with bowel movement at 5.3 ± 1.3 days per week, while that of the placebo group was 6.2 ± 1.2 days per week.
“Since the participants in this study had a frequency of bowel movements between 10 to 20 times per week in the seven days prior to pre-intervention testing, which was higher than in the typical Japanese population, the finding that the intake of a beverage containing LP299V brought the frequency of bowel movements closer to that of the typical Japanese population can be considered a medically significant change,” the researchers wrote.
Citing an online questionnaire involving 5,155 Japanese males and females aged 20 to 79, the researchers said that the mean frequency of bowel movements among Japanese was 6.9 ± 4.2 times per week.
On the other hand, no significant differences were observed between the two groups in the number of participants who reported improvements in stool shape, color and odor by the end of the study.
Also, no significant differences were seen between the two groups in peripheral blood testing results. An exception was seen in uric acid levels, which were significantly higher in the intervention group. Nonetheless, the researchers reported no medically significant changes associated with the consumption of the probiotic drink.
Source: Japanese Journal of Pharmaceutical Health Care and Sciences, 2025; 82(10): 429-448. "Effects of Lactiplantibacillus plantarum 299v on bowel movements in healthy adults with a tendency for loose stools: a randomized, placebo-controlled, double-blind, parallel-group comparison study." Authors: Yamakawa Chiaki et al
