Taking probiotics may help prevent the decline in memory and thinking that can accompany ageing, suggests a study that may pave the way for new, non-invasive treatments that leverage the gut microbiome to mitigate cognitive decline in the elderly.

Researchers found that when people with mild cognitive impairment received the probiotic Lactobacillus rhamnosus GG (LGG) for three months, their cognitive scores increased. This cognitive improvement was also associated with changes in their gut microbiome.

“The implication of this finding is quite exciting, as it means that modifying the gut microbiome through probiotics could potentially be a strategy to improve cognitive performance, particularly in individuals with mild cognitive impairment,” said Mashael Aljumaah, a microbiology doctoral candidate at the University of North Carolina at Chapel Hill and North Carolina State University.

“This adds a new layer to our understanding of the microbiome brain-gut connection and opens up new avenues for combating cognitive decline associated with ageing."

Aljumaah noted that while studies usually focus on severe forms of cognitive diseases such as Alzheimer's and dementia, the new study included people with mild cognitive impairment which can include problems with memory, language, or judgement

“Interventions at this stage of cognitive impairment could slow down or prevent the progression to more severe forms of dementia,” she said.

The study involved 169 participants between 52 and 75 years old who were divided into two groups depending on whether they had no neurological issues or mild cognitive impairment.

Within each group, participants either received the LGG probiotic or a placebo in a double-blind, randomised clinical trial lasting three months.

The researchers selected the LGG probiotic because prior research had shown its potential beneficial effects in experimental models.

To investigate the study participants’ gut microbiomes, the researchers used 16S rRNA gene sequencing to identify and compare bacteria present in stool samples.

They then used whole genome sequencing to gain insights into the functional roles of the bacteria identified.

The analysis revealed that microbes in the genus Prevotella were present in a higher relative abundance in participants with mild cognitive impairment than in those with no cognitive impairment.

This suggests that gut microbiome composition could serve as an early indicator for mild cognitive impairment, offering opportunities for earlier interventions to slow cognitive decline.

For study participants who had mild cognitive impairment and received the LGG probiotics, the Prevotella relative abundance decreased.

This change coincided with improved cognitive scores, suggesting that cognitive health in older adults could be improved by manipulating the gut microbiota.

“By identifying specific shifts in the gut microbiome associated with mild cognitive impairment, we're exploring a new frontier in preventive strategies in cognitive health,” said Aljumaah.

“If these findings are replicated in future studies, it suggests the feasibility of using gut microbiome-targeted strategies as a novel approach to support cognitive health.”

The study was presented at the ongoing NUTRITION 2023, the annual flagship meeting of the American Society for Nutrition held from July 22 to July 25 in Boston.