Researchers from Italy explored the potential impact of probiotics on restoring microbial balance and enhancing vaginal health using a fecal batch culture model.
Results published in the journal Food suggested that probiotic-enriched fermented soy beverages may positively influence gut microbiota, especially through encapsulated strains.
However, in vitro the effects varied across individuals, which the reachers said highlighted the complexity of the gut microbiota and the need for further research to understand the long-term effects of probiotics.
Probiotics may support vaginal health in post-menopausal women
Research has shown that post-menopausal women have lower gut microbial diversity and altered composition compared to pre-menopausal women. Additionally, 25% to 50% of post-menopausal women experience vulvovaginal symptoms—discomfort that affects the vulva or vagina.
This is linked to reduced estrogen levels during menopause which can decrease lactobacilli and increase intravaginal pH, creating conditions for harmful microorganisms to colonize the vagina.
Probiotics may offer a promising solution to maintain vaginal health or treat dysbiosis, with previous studies highlighting the potential of vaginal lactobacilli strains, such as Lactobacillus crispatus and Lactobacillus gasseri.
Study details
The researchers encapsulated Lactobacillus crispatus BC4 and Lactobacillus gasseri BC9, sourced from the University of Bologna.
They cultured the vaginal strains, and after centrifuging and washing, they resuspended the microbial pellets in a commercial soy beverage and spray-dried the suspensions to produce microcapsules.
For fermentation, they combined starter cultures provided by Sacco srl (L. delbrueckii subsp. bulgaricus and S. thermophilus) with encapsulated or non-encapsulated probiotics according to different formulations. The researchers then assessed microbial viability after one day of storage and subjected the fermented soy beverages to in vitro digestion, simulating oral, gastric and intestinal phases.
They then added predigested soy beverages to fecal batch cultures prepared from post-menopausal women’s fecal samples. Cultures fermented anaerobically for 24 hours before being measured for pH, gas production and short-chain fatty acids (SCFAs). The researchers then analyzed microbiota composition by extracting DNA from bacterial pellets.
After 24 hours results showed that pH changes varied by donor, with some cultures showing a decrease and others showing an increase.
Gas production data also showed physiological variability between donors but no significant differences between samples with different soy product formulations.
Acetate was found to be the most abundant SCFA, followed by butyrate and propionate. The results found that certain probiotic strains, especially when encapsulated, had a greater effect on SCFA production, suggesting that encapsulation enhances microbial survival and metabolic activity.
The researchers examined the levels of Bifidobacterium, Lactobacillus and Enterobacteriaceae in fecal cultures. Some donors showed increased Bifidobacterium and Lactobacillus levels after supplementation, while others exhibited a decrease.
Results showed that the addition of probiotics initially increased Lactobacillus bacteria in some cases but led to a greater decrease after 24 hours. The researchers noted that probiotics may promote beneficial microbes initially, but long-term effects can fluctuate.
They concluded that donor variability played a significant role in microbial diversity, and different probiotic treatments had varying impacts on microbial composition. For example, non-encapsulated probiotics increased Ruminococcaceae and Oscillospiraceae in one donor, while encapsulated probiotics increased Bacteroidaceae and Akkermansiaceae in other donors.
The complexity of the gut
The researchers wrote that the study underscored the complexity of the gut microbiota and the need for further research to understand the long-term effects of probiotics on health, especially in different populations.
“Although the mechanisms are not always clear, the presence of vaginal lactobacilli can, in certain conditions, increase the level of beneficial microbial population in fecal samples,” they said.
They added that further research should explore alternative dosages, such as increasing the intake of the functional product during its shelf life, or by boosting the cell load of vaginal strains in the original soy beverage.
“While the 24-hour incubation and small sample size limit long-term insights, the study provides valuable data on the immediate effects of these products, which could be useful for future human interventions,” the researchers wrote.
As regular probiotic intake is essential for their effectiveness, they proposed developing a food product containing functional vaginal strains to improve women’s health, using human intervention studies to confirm the beneficial effects of these fermented products.
Source: Foods 2025, 14(6), 1022. doi: 10.3390/foods14061022. “Impact of Fermented Soy Beverages Containing Selected Vaginal Probiotics on the In Vitro Fecal Microbiota of Post-Menopausal Women”. Authors: D’Alessandro, M. et al.