Probiotics containing certain strains of Bifidobacterium may have neuroprotective effects, according to a large meta-analysis.
The research, published in Nutrients, suggests that Bifidobacterium infantis and Bifidobacterium breve may improve neuropsychiatric symptoms, enhance cognitive functions and reduce neuroinflammation and oxidative stress markers.
"Incorporating these probiotics into therapeutic protocols presents a promising avenue for enhancing the quality of life for individuals suffering from conditions such as Alzheimer's and Parkinson's disease," wrote researchers from Nebrija University in Spain.
Alzheimer's disease and Parkinson's disease are progressive neurological conditions with distinct disease characteristics. However, the two share many overlapping traits, with both characterized by oxidative stress and chronic inflammation.
Since gut microbiota is known to play a key role in the regulation of oxidative stress and inflammation, researchers in recent years have begun to analyze the link between the gut microbiome with the onset and progression of age-related neurodegeneration.
It has been observed that certain forms of dysbiosis are associated with these neurodegenerative conditions, leading researchers to assess probiotics as a potential intervention.
The most-studied probiotics are those comprised predominantly of Bifidobacterium and Lactobacillaceae which are found in the gut microbiota of humans and many animals. However, given the heterogeneity of microbiota profiles, the data on such interventions are diverse.
For their study, the researchers conducted an extensive literature search, identifying 17 human and animal studies that met the inclusion criteria.
Each of the studies analyzed the impact of administering Bifidobacterium infantis and Bifidobacterium breve, alone or in combination with other strains, in people with neurodegenerative diseases.
Collectively, the results suggest that these probiotics may improve motor symptoms and neuropsychiatric impairments and reduce neuronal damage.
In the context of Alzheimer's disease, both in humans and animals, probiotics containing Bifidobacterium appeared to provide neuroprotective effects. These effects were associated with significant changes in the serum profile and in outcomes related to memory and learning.
Bifidobacterium probiotics also demonstrated favorable outcomes in the two studies which focused on Parkinson's disease. The administration of Bifidobacterium breve showed protective effects by preventing a reduction in spine density, as well as improvements in motor symptomatology and the reduction of striatal TNF-α.
Tumor necrosis factor alpha is considered a marker of neuroinflammation in Parkinson's patients and is significantly implicated in the progression of the disease.
The researchers say the review emphasizes the "pivotal role" of the intestinal microbiota in the development and progression of neurodegenerative diseases. However, they warn that the results should be interpreted with caution.
"It is premature to consider these results as definitive support for specific therapeutic applications," they wrote. "Although dietary supplements containing these strains are commercially available, their effectiveness in clinical settings requires further scientific evidence."
"This evidence should be increased through longitudinal and controlled studies, including clinically relevant biomarkers and reproducible protocols," they concluded.