Use of Probiotics Linked to Slower Cognitive Decline

Taking probiotics for three months reduced the levels of specific gut bacteria, which coincided with improved cognition in patients with mild cognitive impairment, a study found.

Often called the "second brain," the gut is home to the enteric nervous system (ENS), consisting of more than 100 million nerve cells. Imbalance in the gut bacteria may play a role in developing many health conditions, including mental health and neurodegenerative diseases, as the ENS communicates with the big brain.

A new study presented at the annual meeting of the American Society for Nutrition (ASN) looked at how probiotics — the good, live bacteria — affect cognitive function.

The clinical trial enrolled 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, the participants were randomly assigned either Lactobacillus rhamnosus GG (LGG) probiotics or a placebo for three months. The probiotic was selected because previous research had shown its potential beneficial effects in animal models.

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

The analysis revealed that participants with mild cognitive impairment had higher levels of Prevotella bacteria compared to 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.

The participants with mild cognitive impairment who received the LGG probiotics saw the levels of Prevotella bacteria decrease. 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," says Mashael Aljumaah, a microbiology doctoral candidate at the University of North Carolina at Chapel Hill and North Carolina State University. "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."

Mild cognitive impairment (MCI) is defined as having minor problems with cognition, such as memory, thinking, or problem-solving. For example, a person with MCI may forget recent events, repeat the same question, struggle to judge distances or navigate stairs. Between 5 and 20% of people 65 and older have MCI, which is not a type of dementia but increases the risk of developing it.

A 2023 study from Japan identified three types of gut bacteria linked to dementia with Lewy bodies (DLB), the most common form of dementia. The patients with the condition had higher levels of Ruminococcus torques and Collinsella and decreased Bifidobacterium. The authors hope their findings could improve the diagnosis and treatment of DLB.

Although the new study does not prove that the use of LGG could improve cognitive function, it adds to the mounting evidence that gut microbiota may significantly impact overall health.