Probiotics: allies or illusion?

#Probiotic #Inflammation #GutMicrobiota #ChronicDisease #GutHealth  


Non-communicable diseases (NCDs) such as type 2 diabetes, multiple sclerosis, cardiovascular disorders, and neurodegenerative diseases are now the leading causes of chronic illness and mortality worldwide. These persistent conditions are often associated with an unfavorable biological background marked by low-grade inflammation and sustained oxidative stress. Both mechanisms are now recognized as key drivers in the progression of NCDs, promoting metabolic dysregulation, cellular damage, and gradual loss of physiological function.  

In this context, the gut and its microbiota have emerged as major therapeutic targets. Gut microbiota imbalance (or dysbiosis), observed in many NCDs, can worsen intestinal permeability and trigger a systemic inflammatory response. Probiotics—defined as live microorganisms that confer health benefits to the host—have been proposed as a promising strategy to restore microbiota balance, reinforce the gut barrier, and positively modulate the gut-immune axis.  

However, clinical study results have been mixed. The effects vary depending on the probiotic strains used, the doses administered, the duration of treatment, and patient profiles. Some studies show improvement in inflammatory or antioxidant markers, while others show no effect. This variability makes it difficult to establish clear guidelines. Therefore, this study was initiated to clarify the actual impact of probiotic supplementation on key biomarkers of inflammation and oxidative stress in adults with NCDs.    

Do probiotics really make a difference?

Eighteen randomized controlled trials, selected according to PRISMA guidelines and the GRADE approach, were analyzed. Data were synthesized using a random-effects model and presented as standardized mean differences.  

Results showed that probiotic supplementation significantly reduced several key biomarkers of inflammation and oxidative stress. C-reactive protein (CRP) decreased notably, with a strong and consistent effect across subpopulations, providing a high level of evidence. Tumor necrosis factor-alpha (TNF-α) was also reduced, although the effect was more moderate and supported by a low level of evidence. Regarding oxidative stress, malondialdehyde (MDA)—a marker of lipid peroxidation—dropped sharply, especially in patients with Alzheimer’s disease and those over 50. Additionally, glutathione (GSH), a major antioxidant, increased significantly, particularly in diabetic patients and young adults.  

In contrast, no significant effect was observed on interleukin-6 (IL-6). Similarly, probiotics had no notable impact on total antioxidant capacity (TAC) or nitric oxide (NO) levels.  

Positive effects were generally more pronounced in studies with intervention durations of 12 weeks or longer, highlighting the importance of allowing sufficient time for meaningful gut microbiota modulation and sustained anti-inflammatory responses.    

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Microbes against inflammation: a successful bet?  

This meta-analysis suggests that probiotic supplementation may play a supportive role in reducing inflammation and oxidative stress in patients with NCDs—particularly diabetes, multiple sclerosis, and Alzheimer’s disease. Probiotics positively affect certain biomarkers (CRP, TNF-α, MDA, GSH), though their impact is limited on others (IL-6, NO, TAC), likely due to individual differences, strain selection, or treatment duration.  

Modulating the gut microbiota via probiotics appears to be a promising avenue but requires refinement through longer-term, standardized clinical trials. The lack of effect on some biomarkers highlights the need to personalize probiotic approaches according to each patient’s clinical and metabolic profile.    

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