A key to preventing memory loss in old age may lie with probiotics and the ‘gut-brain axis’.
Probiotic supplements are already known to help with gut health and conditions such as irritable bowel syndrome (IBS) and gastrointestinal problems after a course of antibiotics, by helping to rebalance the good bacteria in the gut.
But probiotics can also slow cognitive decline and dementia as you age, says 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 believed that the brain and gut are closely linked. This means that as 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 iIt is the sixth leading cause of death in the US.
Probiotics may also slow cognitive decline as you age, says 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 harmful bacteria that can lead to disease.
They can be found in foods such as yogurt, cottage cheese, buttermilk, kimchi, soybeans, kombucha, sauerkraut, tempeh and miso. Supplements of various types are also sold without a prescription.
Probiotics have been shown to relieve digestive problems such as diarrhea, constipation and bloating. They can also help improve immune health by balancing the good bacteria in the gut.
Good bacteria help boost immune function, regulate appetite and weight, improve depression and reduce inflammation.
Bad bacteria are bacteria that cause infections such as strep throat, staph and food poisoning. Probiotics help establish a balance between good and bad bacteria.
A study presented at the American Society for Nutrition meeting in July found that older adults who took a probiotic had better cognitive function than those who took a placebo.
Ms Eastwood and her team published a review in 2021 finding that a daily probiotic could reduce cognitive decline in otherwise healthy older adults.
The researchers looked at 30 articles with participants of different ages, from fetuses at 27 weeks old to seniors at 82 years old. Various tasks were used to measure cognition, such as tests of attention, memory and processing.
She said Insider: ‘Taking a probiotic supplement can be particularly helpful in mitigating that natural decline and maintaining cognitive function for longer.’
The review found that taking a daily probiotic could improve cognitive function in older adults with mild cognitive impairment or people with Alzheimer’s disease.
But larger and more in-depth studies are needed, Ms. Eastwood said, before researchers can determine the exact link.
However, it may be related to the ‘gut-brain axis.’ This is the communication network that connects the central nervous system and the enteric system, the system of cells that regulate the function of the gastrointestinal tract.
Anything that affects the brain can also affect the gut, Ms Eastwood said, which explains why you might get the feeling of butterflies in your stomach when you’re anxious.
But how the two systems interact is still not fully known.
Ms Eastwood said: ‘It’s still a bit unknown how exactly these bugs in your gut affect your brain.’
She added that probiotics typically don’t affect cognitive functioning in younger people because “they are already at peak performance.”
However, if you are stressed, you may see an effect.
Stress can cause people’s cognitive performance to decline, she said, but “when you take probiotics, you get a kind of buffering effect, so it reduces that decline.”
The majority of studies on probiotics involve people who have taken them daily for one to six months, Ms. Eastwood said.
A study published in 2019 found that women between the ages of 18 and 40 who took probiotics every day for 28 days performed better than those who took a placebo on a stressful task.
Researchers have yet to figure out which types of probiotics may be best for improving cognitive function.
Ms Eastwood recommends people take a multi-strain probiotic with a mixture of the most researched strains, such as lactobacillus, bifidobacterium and lactococcus species.