Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. These microorganisms, including bacteria and yeasts, can be naturally present in fermented foods, added to other food products, or taken as dietary supplements. However, not all products labeled as “probiotics” have proven health benefits.
The mechanisms of action of probiotics primarily occur in the gastrointestinal tract, where they can influence the composition and activity of the gut microbiota. Probiotics exert their effects through various mechanisms, including inhibition of the growth of pathogenic microorganisms, production of bioactive metabolites, and reduction of luminal pH in the colon. The specific mechanisms vary depending on the probiotic strain, species, or genera.
Scientific research has focused on exploring the potential health benefits of probiotics in various conditions. Some of the conditions that have been extensively studied include atopic dermatitis, pediatric acute infectious diarrhea, antibiotic-associated diarrhea, inflammatory bowel disease, irritable bowel syndrome, hypercholesterolemia, and obesity.
Medical Evidence for Effectiveness of Probiotics Against Common Problems
- Probiotics have been studied for their effects on improving lipid profiles and reducing cholesterol levels in the blood.
- The mechanisms by which probiotics may affect cholesterol concentrations include increasing bile salt hydrolase activity, binding cholesterol in the small intestine, assimilation and incorporation of cholesterol into bacteria, and production of short-chain fatty acids.
- A meta-analysis of 30 randomized controlled trials (RCTs) involving 1,624 participants showed that probiotic treatment for 3 to 12 weeks resulted in lower total cholesterol and LDL cholesterol concentrations compared to placebo.
- Subgroup analyses indicated that longer-duration studies and participants with higher baseline cholesterol levels experienced slightly greater benefits.
- Specific strains such as Lactobacillus acidophilus, a mixture of Lactobacillus acidophilus and Bifidobacterium lactis, and Lactobacillus plantarum were associated with significant reductions in cholesterol levels, while Lactobacillus helveticus and Enterococcus faecium did not show the same effect.
- The gut microbiota are believed to play a role in nutrient and energy extraction from food, which may impact energy expenditure and storage.
- Clinical trials assessing the effects of probiotics on obesity-related endpoints have produced inconsistent results.
- One 12-week trial involving 210 healthy adults with large amounts of visceral fat found that consuming fermented milk containing specific strains of Lactobacillus gasseri resulted in significant reductions in visceral fat area, body mass index, waist and hip circumference, and body fat mass compared to the control group.
- Another trial involving 125 adults with obesity found that supplementation with Lactobacillus rhamnosus combined with an energy-restricted diet did not significantly affect weight loss compared to placebo, but did lead to reductions in body weight after 12 and 24 weeks in female participants.
- Systematic reviews of multiple clinical trials have shown mixed results, with some studies demonstrating significant decreases in body weight and/or body fat with probiotic supplementation, while others showed no effect or even increased body weight.
- The overall effects of probiotics on weight and body composition have been described as small and of questionable clinical significance.
- Exposure to probiotics during pregnancy and early infancy has been shown to potentially reduce the risk of developing atopic dermatitis in children.
- Meta-analyses of randomized controlled trials (RCTs) have demonstrated that probiotic treatment with specific strains significantly reduces the risk of atopic dermatitis.
Pediatric Acute Infectious Diarrhea
- Probiotics have been found to shorten the duration of diarrhea and decrease the risk of it lasting for more than four days in pediatric acute infectious diarrhea.
- Certain strains of probiotics, such as Lactobacillus rhamnosus GG and Saccharomyces boulardii, have shown efficacy in treating infectious diarrhea.
- Antibiotic-associated diarrhea, a common side effect of antibiotic treatment, can be reduced by the use of specific species and strains of probiotics.
- Meta-analyses have indicated that probiotics might reduce the risk of antibiotic-associated diarrhea, although the effectiveness can depend on factors such as the type of antibiotic, the strain of probiotic used, and the age and care setting of the individual.
Inflammatory Bowel Disease
- Inflammatory bowel disease, including ulcerative colitis and Crohn’s disease, has been the subject of research exploring the effects of probiotics.
- Some probiotics have shown modestly beneficial effects on ulcerative colitis but not Crohn’s disease.
- The evidence suggests that probiotics might help manage ulcerative colitis when used in combination with conventional therapies.
Irritable Bowel Syndrome
- Probiotics have shown a positive, albeit modest, beneficial effect in the case of irritable bowel syndrome (IBS).
- Meta-analyses have demonstrated that probiotics can reduce the risk of persistent or unimproved IBS symptoms.
- Various species and strains of probiotics have been found to have beneficial effects on symptoms such as abdominal pain, bloating, and flatulence.
In case you are conducting research on the scientific/medical proof of probiotics. The above conditions are a good starting point. Overall, scientific research has shown promising results regarding the use of probiotics in various health conditions, including atopic dermatitis, pediatric acute infectious diarrhea, antibiotic-associated diarrhea, inflammatory bowel disease, and irritable bowel syndrome. However, it is essential to consider the specific strains, dosages, and individual factors when determining the effectiveness of probiotic interventions.
Further research is needed to fully understand the mechanisms of action and optimize the use of probiotics for different health conditions. For instance, there is scientific evidence supporting the potential benefits of probiotics in reducing cholesterol levels in individuals with hypercholesterolemia. However, when it comes to the effects of probiotics on obesity-related endpoints, the evidence is inconsistent, with some studies showing positive effects and others showing no significant impact. Further research is needed to fully understand the role of probiotics in these areas.