A recent study involving mice has brought new insights into the complex role of probiotics in gut health, revealing that not all probiotic strains are inherently beneficial. Two strains of Lactobacillus were examined: Lactobacillus acidophilus and Lactobacillus gasseri Lg-36. The study, published in the journal mBio, revealed contradictions in their effects—L. acidophilus made it easier for Clostridioides difficile, a potentially deadly pathogen, to establish itself in the guts of mice treated with antibiotics, while L. gasseri Lg-36 conferred resistance against this bacterium. This prompts a reevaluation of how we think about probiotic supplements.
The researchers, led by Matthew Foley from North Carolina State University, based their selection of these Lactobacillus strains on their known health benefits. They expected some differences in performance, but were surprised to find the effects to be almost contradictory. While L. gasseri Lg-36 appeared to possess an advantage, the mechanisms behind these effects were complex and highlighted that not all beneficial bacteria behave uniformly in the gut environment.
The significant difference identified was that L. gasseri Lg-36 possesses extra copies of genes responsible for synthesizing antibacterial peptides, which can effectively combat C. difficile. In contrast, L. acidophilus may inadvertently help fuel C. difficile’s growth by breaking down proteins into amino acids that the pathogen prefers. This unexpected finding underscores the importance of strain selection in probiotic formulations, as the specific genetic makeup can lead to vastly different outcomes in gut health.
Further, L. gasseri Lg-36 not only engages in active antibacterial actions but also facilitates a favorable gut environment by promoting the growth of beneficial Muribaculaceae bacteria. These bacteria seem to outcompete C. difficile for resources, essentially starving it of the nutrients it requires to proliferate. In stark contrast, L. acidophilus’s metabolic activities can inadvertently support the pathogen’s growth, leading to unintended health consequences for the host.
Interestingly, the researchers found that the benefits conferred by L. gasseri Lg-36 persisted even after the strain had been cleared from the gut, suggesting that certain beneficial microbes can have lasting impacts on gut microbiota composition and function. This challenges the common perception that only permanent residents exert a significant influence, pointing to the long-term potential benefits of short-term probiotics.
Despite these promising findings, the authors caution against generalizing the results to humans without further investigation. The variations in probiotic effects can be attributed to individual health conditions, the specific strains used, and the existing microbiota within each person’s gut. The study highlights that the effectiveness of probiotics isn’t uniform; not all probiotics yield the same results in all individuals or diseases. This nuance is vital for both consumers and healthcare providers when considering probiotic options for gut health.
