Alzheimer’s disease is the most common type of dementia in the United States, affecting more than 6 million Trusted Sourcepeople.
The results of a meta-analysis suggest that probiotic supplementation may improve cognitive function in people with mild cognitive impairment.
The review adds extra information about the correlations between gut health and brain health.
Some studies hint that probiotics and prebiotics might slow the progression of some neurodegenerative diseases.
However, there are limited data on their effects in humans with Alzheimer’s disease or mild cognitive impairment (MCI).
Scientists from Jiangnan University in China collaborated to review the evidence to date. Their systematic review and meta-analysis appears in the journal Foods.
Overall, the authors report: “Consistently, our findings suggest that probiotic intervention at early stages of Alzheimer’s disease, such as MCI, could improve cognitive function and delay disease progression.”Probiotics, prebiotics, and synbiotics
The International Scientific Association for Probiotics and Prebiotics (ISAPP) is an international nonprofit established in 2002. It seeks to advance scientific research regarding probiotics, prebiotics, and synbiotics.
The ISAPP defines probiotics as living bacteria “which when administered in adequate amounts confer a health benefit on the host.”
Prebiotics are a group of nutrients, or substrates, that encourage the growth of gut microbiota. Synbiotics are a combination of probiotics and prebiotics.
Identifying relevant studies
The team explored several databases for studies published between 1984 and early 2021 involving subjects with Alzheimer’s or MCI.
Zhu and colleagues sifted through 294 studies, ultimately including just eight articles for the systematic review and seven for the meta-analysis.
Cognitive function was the primary outcome of all the studies, measured by Mini-Mental State Examination (MMSE) scoring. Secondary outcomes included nutritional status, inflammation biomarkers, metabolic profiles, and oxidative stress.Benefits revealed
The review’s authors found that probiotic supplements improved cognitive function in participants with MCI. However, the results were less impressive for participants with Alzheimer’s disease. Overall, the authors conclude:
“Compared with placebo or control interventions, probiotic supplementation considerably improved cognitive function in the participants with MCI, but it only caused a modest cognitive improvement in those with Alzheimer’s disease.”
The number of probiotic strains administered, their dosage, and the length of treatment played a role in the extent of cognitive improvement.
Probiotic supplementation also altered the structure and composition of fecal microbiota in people with Alzheimer’s.
The co-authors cite studiesTrusted Source that show a reduced fecal microbial diversity in Alzheimer’s. However, only one study in the review showed that probiotic supplementation altered the structure and composition of fecal microbiota in people with Alzheimer’s.Significant addition to research
Dr. David A. Merrill, Ph.D., is an adult and geriatric psychiatrist and director of the Pacific Neuroscience Institute’s Pacific Brain Health Center at Providence Saint John’s Health Center in Santa Monica, CA. He was not involved with this review.
In an interview with Medical News Today, Dr. Merrill explained:
“This meta-analysis — a study of studies — provides an important update about recent evidence showing that gut health may help brain function in older adults, especially those with mild cognitive impairment […] This is an important update on a topic which shows that our gut health impacts not only our systemic health but our emotional and cognitive well-being, as well.”
Dr. Merrill was intrigued by the review’s finding that prebiotics may enhance the production of brain-derived neurotrophic factor (BDNF):
“We know that BDNF levels decline in the brain of Alzheimer’s patients, and this loss of BDNF is thought to play a role in the increased death of neurons in the brain. So, perhaps indirectly, prebiotics may support the circulating levels of BDNF in the body, leading to greater cell survival in the brain.”
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