Probiotics for improving cognition in mild cognitive impairment and Alzheimer’s disease Original paper

In this meta-analysis of randomized controlled trials, supplementing with probiotics improved cognitive function in participants with mild cognitive impairment or Alzheimer’s disease.

Whether supplementing with probiotics improves cognitive function in people with mild cognitive impairment (MCI) or Alzheimer’s disease (AD).

In addition to global cognitive function, attention, delayed memory, immediate memory, language, orientation, and visuospatial/constructional function (needed for things such as depth perception and movement) were assessed.

A total of 852 participants (average ages of 62–82) with MCI (573) or AD (279).

A meta-analysis of 11 randomized controlled trials (with 12 intervention groups) was performed. The studies were conducted in Iran (4 trials), Japan (4 trials), China (1 trial), Korea (1 trial), and the United States (1 trial).

All of the probiotics used were from the Lactobacillus or Bifidobacterium genus. Eight of the interventions used a single probiotic strain, and the other 4 used a combination of probiotic strains. The duration of the intervention ranged from about 9 to 24 weeks.

Cognitive function was measured using different questionnaires, the most common of which was the Mini–Mental State Examination.

Compared with the placebos, probiotics improved delayed memory (medium effect size), global cognitive function (medium effect size), attention (small effect size), and visuospatial/constructional function (small effect size). There were no differences between the groups in immediate memory, language, or orientation.

One study had a high risk of bias, 4 had some concerns, and 6 had a low risk of bias.

The effects of probiotics are strain specific,^[1] so the effects of one probiotic supplement cannot be generalized to another. Consequently, because different probiotic supplements were studied, it remains to be determined which probiotic strain or combination of strains is most effective for improving cognitive function in the context of MCI or AD.