Major Research Findings

Probiotics are live microorganisms that, when consumed in adequate amounts, confer a health benefit to the host. 22 investigated the effects of Bifidobacterium animalis subsp. lactis BB-12® on the lipid/lipoprotein profile and short chain fatty acids (SCFAs) in healthy young adults. They found that BB-12® significantly increased fecal acetate, a type of SCFA, but had no effect on total cholesterol, LDL cholesterol, HDL cholesterol, or triglycerides. 19 conducted a systematic review with meta-analysis to evaluate the efficacy of Lactobacillus rhamnosus GG (LGG) in the prevention of antibiotic-associated diarrhea (AAD) in children and adults. The study found that LGG was effective in preventing AAD in both children and adults, but the quality of evidence was moderate to low. 14 conducted a randomized controlled trial to investigate the efficacy of Saccharomyces boulardii in preventing necrotizing enterocolitis (NEC) or sepsis in very low birth weight infants. The study found that S. boulardii did not decrease the incidence of NEC or sepsis. 13 conducted a meta-analysis of probiotic efficacy for gastrointestinal diseases. The study found that probiotics generally have positive effects on the prevention and treatment of specific gastrointestinal diseases. 12 conducted a study to elucidate the effects of oral bifid triple viable probiotics among patients with colorectal cancer. The study found that preoperative probiotics minimized the postoperative occurrence of infectious complications. 27 conducted a systematic review with meta-analysis to synthesize the published evidence on the effects of Bifidobacterium animalis subspecies lactis on gastrointestinal symptoms (GIS) in healthy adults. The study found that B. animalis subspecies lactis supplementation may increase defecation frequency and reduce colonic transit time (CTT) in healthy adults. 24 conducted a systematic review and meta-analysis to assess the effects of probiotics on stress in healthy subjects. The study found that probiotics can reduce subjective stress level in healthy volunteers. 26 conducted a systematic review of the effects of probiotics on depression and anxiety. The study concluded that the use of probiotics to alleviate depressive symptoms and anxiety is promising. 10 reviewed the evidence for probiotics for the induction of remission in Crohn's disease. The study concluded that there is some evidence that probiotics are effective in other conditions affecting the gastrointestinal tract, but their efficacy in Crohn's disease is undetermined. 29 conducted a systematic review and meta-analysis to investigate the effects of concurrent probiotic supplementation on gut microbiome composition during antibiotic therapy. The study found that probiotic supplementation during antibiotic therapy was not found to be influential on gut microbiome diversity indices. 7 conducted a study to investigate the mode of action of a multispecies probiotic consisting of Lactobacillus rhamnosus GG, Lactobacillus rhamnosus Lc705, Propionibacterium freudenreichii ssp. shermanii JS and Bifidobacterium breve Bb99 by monitoring its effects on intestinal microbiota and markers of microbial activity. The study found that factors other than the microbial groups and metabolites studied seem responsible for the alleviation of irritable bowel syndrome symptoms by the multispecies probiotic. 2 investigated the effects of orally ingested probiotic bacteria on the immune response to polio vaccination. The study found that probiotic bacteria stimulated virus-specific neutralizing antibodies following a booster polio vaccination.

Benefits and Risks

Benefit Summary

Probiotics have been shown to offer various health benefits, including improving gut health, boosting the immune system, and potentially aiding in the management of conditions such as antibiotic-associated diarrhea, inflammatory bowel disease, stress, depression, and anxiety. They may also contribute to maintaining a healthy gut microbiome and promoting a balanced immune response. 19 , 13 , 27 , 24 , 26 , 10

Risk Summary

While probiotics are generally considered safe, they can potentially cause side effects in some individuals. Common side effects may include digestive discomfort, gas, and bloating. Individuals with weakened immune systems or serious medical conditions should consult with their healthcare provider before taking probiotics. Pregnant or breastfeeding women should also consult their physician before taking probiotics. 15 , 11 , 18

Comparison of Studies

Commonalities of Studies

The studies reviewed demonstrate a consistent theme of probiotics potentially impacting gut health, immune function, and potentially contributing to the management of various health conditions. They also generally indicate that probiotics are well-tolerated and associated with minimal adverse effects.

Differences of Studies

The studies reviewed varied in the specific probiotic strains investigated, dosage, target conditions, study design, and outcomes assessed. These variations make direct comparisons between studies challenging. Some studies reported significant effects from probiotics, while others showed less pronounced or no effects. This underscores the possibility that the efficacy of probiotics may depend on factors like the specific strain, dosage, and individual characteristics.

Consistency and Contradictions of Results

While the studies generally suggest that probiotics may have various health benefits, the findings are not entirely consistent. Some studies demonstrate notable effects, while others show less definitive outcomes. The evidence suggests that the effectiveness of probiotics can vary based on factors like the specific strain, dosage, and individual characteristics. It's crucial to acknowledge that the field of probiotic research is still evolving, and further studies are required to clarify the specific benefits and limitations of probiotics.

Implications for Daily Life

Probiotics are widely available as dietary supplements, making them easily accessible. However, it's important to remember that probiotics are not a cure-all and should not be considered a replacement for medical treatments. Before incorporating probiotics into your diet, consult with your healthcare provider. They can help determine whether probiotics are appropriate for you based on your individual health needs and any potential interactions with medications or existing conditions.

Limitations of Current Research

Probiotic research is still a developing field, and many questions remain unanswered. Further research is needed to better understand the specific mechanisms of action, long-term safety, optimal strains and dosages, and the effectiveness of probiotics for various conditions.

Future Research Directions

Future research in the field of probiotics should focus on several key areas, including:

• Conducting larger-scale, well-designed clinical trials to assess the effectiveness of probiotics for specific diseases.
• Investigating the influence of factors such as strain, dosage, and individual characteristics on probiotic efficacy.
• Conducting long-term studies to evaluate the safety and long-term benefits of probiotics.
• Developing personalized approaches to probiotic use based on individual gut microbiome composition and health status.

Conclusion

Probiotics hold significant promise as potential health-enhancing agents, contributing to gut health, immune function, and the management of various conditions. However, their efficacy can be influenced by multiple factors. It is crucial to approach probiotics with a balanced perspective, seeking guidance from healthcare professionals before incorporating them into your diet. Continued research is essential to solidify our understanding of probiotics and guide their responsible use in the pursuit of optimal health.