Effect of Lactic Acid Bacteria-Fermented Soy Milk Extract (LEX) on Urinary 3-Indoxyl Sulfate in Japanese Healthy Adult Women: An Open-Label Pilot Study

Objective: For the general population, the intestinal microbiota and its environment, including its metabolites, are important not only for disease prevention but also for overall quality of life. A convenient method to monitor the intestinal environment is to measure levels of urinary 3-indoxyl sulfate (3-IS). This approach has been used for several years. This study aims to clarify the efficacy of a lactic acid bacteria (LAB) dietary supplement combined with multi-strain LAB-fermented soy milk (LEX) extract in healthy, adult women with high urinary 3-IS levels. Materials and Methods: Japanese women aged 30–50 years with high urinary 3-IS levels and a tendency toward constipation were enrolled in this study. Each of them received 10 mL of a LEX-containing dietary supplement daily for 4 weeks. The primary outcome was changes in urinary 3-IS levels, and the secondary ones included the amount of defecation and more subjective symptoms of their physical condition, such as the Constipation Assessment Scale (CAS). Results: Thirty participants were enrolled, and all completed the study. Every participant showed a statistically significant improvement in their level of urinary 3-IS after ingesting the test article for 4 weeks. Any changes in urinary 3-IS also showed a high correlation to initial 3-IS levels. Moreover, CAS scores and other subjective symptoms improved after ingestion of the LEX-containing dietary supplement. The level of urinary 3-IS showed a modest degree of correlation with the score of overall physical condition, including CAS (Pearson’s r = 0.21; p < 0.05). Conclusion: These findings suggest that orally ingested LEX improves urinary 3-IS levels as an index of the health of the intestinal environment and that monitoring urinary 3-IS levels is effective in assessing changes in the intestinal environment and overall physical condition.