Effect of Daily Consumption of a Fermented Milk Containing Lacticaseibacillus paracasei Strain Shirota (LcS) on Stool Consistency in United States Adults with Hard or Lumpy Stools: A Randomized Controlled Trial

Background

Lacticaseibacillus paracasei strain Shirota (LcS) has shown benefits for stool consistency in populations with certain bowel complaints (e.g., constipation), but data in a United States population are limited.

Objectives

This study evaluated the effects of LcS on hard or lumpy stools (HLS) in an otherwise healthy population that generally represents the United States adult demographic.

Methods

In this randomized, controlled, open-label study, 50 participants (41 females, 9 males) with HLS in ≥25% of bowel movements (BMs) during a 14-d run-in period were randomly assigned to receive either 80 mL fermented milk containing 8.0 × 10⁹ colony forming units LcS/mL for 28 d (active group) or no intervention (control group) followed by a 14-d postintervention period. Bowel habits were recorded daily using a novel smartphone application. The primary endpoint was the presence of HLS in ≥25% of the participant-rated BMs using the Bristol Stool Form Scale over the 28-d intervention. Secondary endpoints included the presence of reduced frequency of BMs with HLS from baseline, stool frequency, straining, incomplete evacuation, artificial intelligence-derived stool image scores, and Patient Assessment of Constipation Quality of Life (PAC-QOL) scores.

Results

The active group showed a significantly lower proportion of participants with HLS in ≥25% of BMs [odds ratio: 0.34; 95% confidence interval (CI): 0.14, 0.80; P = 0.014] along with a higher proportion of participants with a reduced frequency of BMs with HLS from baseline (odds ratio: 2.86; 95% CI: 1.03, 7.92; P = 0.043). The active group also demonstrated positive improvements in total PAC-QOL scores (P = 0.003).

Conclusions

Daily consumption of LcS-containing fermented milk significantly reduced constipation symptoms and improved quality of life in an otherwise generally healthy United States adult population with a history of intermittent BMs producing HLS. The intervention was well tolerated, with no serious adverse events related to the product, suggesting its safety and potential as a dietary strategy for managing constipation.

Trial registration number

This trial was registered at clinicaltrials.gov as NCT06014008 (https://clinicaltrials.gov/study/NCT06014008).