Does altering the gut microbiome improve motor symptoms in the context of neurodegenerative disease? Original paper

In this meta-analysis of clinical trials, interventions that altered the gut microbiome improved motor symptoms in participants with neurodegenerative disease, but many different interventions were used and the quality of evidence was poor.

The effect of interventions designed to alter the composition of the gut microbiome on motor symptoms and constipation in the context of neurodegenerative disease (NDD).

A total of 445 participants (average ages of 35 to 71) with a NDD.

Among the participants, 235 had Parkinson’s disease, 112 had multiple sclerosis, and 98 had Alzheimer’s disease.

A meta-analysis of 14 clinical trials (including 5 randomized controlled trials) was performed. The interventions included a rectal enema, fecal microbiota transplantation, a Mediterranean diet, a modified Mediterranean-ketogenic diet, a lacto-ovo vegetarian diet, alternate-day fasting + corticosteroid treatment, supplementation with probiotics or resistant starch, and antibiotics with or without other medications. The intervention duration ranged from 1 to 6 weeks and follow-up lasted up to 2 years. In 6 studies, there was no control group.

Motor symptoms were typically evaluated by having the participants complete a condition-specific questionnaire concerning their physical function.

Based on the results of 7 interventions (6 studies), interventions that altered the gut microbiome improved motor symptoms (medium effect size).

Based on the results of 3 studies, there was no effect on constipation.

Because the data from vastly different interventions in different populations were all lumped together in the same analysis, it remains unclear what the most effective gut-microbiome-altering intervention is for improving motor symptoms in participants with NDD.

All of the studies had at least some concerns of bias, and among the nonrandomized controlled trials, 6 of 9 studies had a serious risk of bias. For these reasons, the results should be considered exploratory.