A key to preventing memory loss in old age could lie with probiotics and the ‘gut-brain axis.’
Probiotic supplements are already known to help with gut health and conditions like irritable bowel syndrome (IBS) and gastrointestinal issues after a course of antibiotics by helping to rebalance the good bacteria in the gut.
But probiotics may also stall cognitive decline and dementia as you age, said Jessica Eastwood, a nutritional psychology researcher at the University of Reading in England.
Exactly how this works is not fully understood by researchers, but it is thought the brain and gut are intimately linked, meaning if your gut health improves, so will your brain health.
More than six million Americans are diagnosed with Alzheimer’s disease, the most common form of dementia. The condition is the sixth leading cause of death in the US.
Probiotics may also stall cognitive decline as you age, said Jessica Eastwood, a nutritional psychology researcher at the University of Reading in England
Probiotics are considered ‘good bacteria’ in the digestive system and can help fight off harmful bacteria that can lead to illnesses.
They can be found in foods like yogurt, cottage cheese, buttermilk, kimchi, soybeans, kombucha, sauerkraut, tempeh, and miso. Supplements containing different strains are also sold over the counter.
Probiotics have been shown to alleviate digestive distress, such as diarrhea, constipation, and bloating. They can also help boost immune health by balancing the gut’s good bacteria.
Good bacteria help boost immune function, regulate appetite and weight, improve depression, and lower inflammation.
Bad bacteria are those that cause infections like strep throat, staph, and food poisoning. Probiotics help establish a balance between the good and bad bacteria.
A study presented at the American Society for Nutrition meeting in July found older adults who took a probiotic had better cognitive function than those who took a placebo.
Ms Eastwood and her team published a 2021 review that found a daily probiotic might reduce cognitive decline in otherwise healthy older adults.
The researchers looked at 30 papers with participants of various ages, from 27-week-old fetuses to seniors 82 years old. Different tasks were used to measure cognition, such as tests for attention, memory and processing.
She told Insider: ‘Taking a probiotic supplement might be particularly helpful in just helping to mitigate that natural decline and maintaining cognitive function for longer.’
The review found taking a probiotic every day might enhance cognitive function in older people with mild cognitive impairment or those with Alzheimer’s disease.
But larger and more in-depth trials are needed, Ms Eastwood said, for researchers to determine the exact association.
However, it could be related to the ‘gut-brain axis.’ This is the communication network that links the central nervous system and the enteric system, which is the system of cells that controls the function of the gastrointestinal tract.
Anything that affects the brain can impact the gut too, Ms Eastwood said, which explains why you might get the feeling of butterflies in your stomach when you are anxious.
But how the two systems interact is still not completely known.
Ms Eastwood said: ‘Understanding exactly how these bugs in your gut are affecting your brain is still a little bit unknown.’
She added probiotics typically will not affect cognitive functioning in younger people because ‘they’re already performing at ceiling.’
However, if you are stressed, you may see an effect.
Stress can cause people’s cognitive performance to drop, she said, but ‘if you take probiotics, you get this sort of buffering effect — so it reduces that decline.’
The majority of studies on probiotics include people who have taken them daily for one to six months, Ms Eastwood said.
In one study published in 2019, women aged between 18 and 40 who took probiotics every day for 28 days outperformed those who took a placebo on a stressful task.
Researchers are yet to work out which strains of probiotics might be best for improving cognitive function.
Ms Eastwood advises that people take a multi-strain probiotic with a mixture of the most researched strains, such as lactobacillus, bifidobacterium, and lactococcus species.