Meta-analysis: Insufficient evidence for probiotic, synbiotic use in dementia

Despite an extensive literature on the possible mechanisms involved in gut microbiota modulation and the pathophysiology of dementia, current evidence does not support clinical application of supplementation with probiotics and synbiotics to boost cognitive function in individuals with dementia, according to a meta-analysis.

Researchers searched multiple online databases for randomized clinical trials (RCTs) that addressed dementias and assessed the effect of probiotics and synbiotics on the following outcomes: inflammatory, oxidative stress and metabolic markers, cognitive function, nutritional status, and intestinal microbiota composition.

The search yielded 5,212 articles, of which three RCTs were included in the meta-analysis. The population comprised 187 elderly individuals with Alzheimer’s disease receiving probiotics with Lactobacillus and Bifidobacterium strains over a 12-week intervention. None of the trials included synbiotic supplementation or assessed microbiota composition.

Pooled data showed that compared with placebo, probiotic supplementation had a null effect on cognitive function (standardized mean difference [SMD], 0.56, 95 percent confidence interval [CI], −0.06 to 1.18), with very low certainty of evidence.

However, there were improvements observed in plasma triglycerides (mean difference [MD], 19.22 mg/dL, 95 percent CI, 29.79–8.64; p=0.0004), very-low-density lipoprotein cholesterol (MD, 3.37 mg/dL, 95 percent CI, 5.94–0.80; p=0.01), insulin resistance (MD, 0.32, 95 percent CI, 0.51–0.13; p=0.001), and plasma malondialdehyde (oxidative stress; MD, 0.39 µmol/L, 95 percent CI, 0.73–0.06; p=0.02; I², 87 percent).

The researchers pointed out that the evidence obtained from the RCTs was heterogeneous, of very low quality, and with high risk of bias.