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Scientists already know that probiotic supplements show promise in helping treat gut health conditions like IBS and gastrointestinal upset after taking antibiotics.
Now, scientists think that they might also slow down cognitive decline as we age, according to Jessica Eastwood, a nutritional psychology researcher in the department of psychology and clinical language sciences at the University of Reading in England.
In younger people, Eastwood told Insider, probiotics might even help people perform better when they're stressed.
"The microbes in your gut can affect your health in so many different ways," Eastwood said.
Here's some of what we know about probiotics and brain health.
Your gut and brain are closely connected, a partnership that's known as the "gut-brain axis."
What affects the brain can affect the gut too, and vice-versa. That's why you might have butterflies in your stomach when you're nervous, Eastwood said.
The connection is so strong that flares of GI conditions like IBS or Crohn's disease can set off mental health issues like depression or anxiety, according to Harvard Health.
Scientists aren't exactly sure yet how these two systems work together. "Understanding exactly how these bugs in your gut are affecting your brain is still a little bit unknown," Eastwood said.
As we age, our cognitive functioning, which includes memory and executive functioning, naturally declines.
Eastwood and her team published a 2021 review which found that taking a daily probiotic might reduce cognitive decline in otherwise healthy older adults.
"Taking a probiotic supplement might be particularly helpful in just helping to mitigate that natural decline and maintaining cognitive function for longer," Eastwood said. Eastwood said that this might be especially beneficial as people continue to live longer.
The review also found that a daily probiotic might help improve cognitive performance in older adults who have a mild cognitive impairment or have Alzheimer's disease.
While these findings are exciting, Eastwood said that bigger and better research trials are needed.
More recently, a study presented at the American Society for Nutrition meeting in July of this year that found that older adults who took a probiotic had cognitive improvement compared to those that took a placebo.
Probiotics won't usually boost cognitive functioning in younger people since "they're already performing at ceiling," Eastwood said. But "where you do see an effect in younger adults is if they are stressed."
Sometimes, Eastwood said, if you're stressed, your cognitive performance goes down. But in the same 2021 review, "we find that if you take probiotics, you get this sort of buffering effect — so it reduces that decline."
In other words, taking a probiotic may help maintain normal cognitive functioning despite stress.
"In young adults that are doing exams or going through a particularly stressful period, that's maybe where there could be some use," Eastwood said.
Most studies on probiotics have had people take them daily for four weeks to six months, Eastwood said. In a 2019 study, women ages 18 to 40 who took probiotics daily for 28 days performed better on a stressful task than those who took a placebo.
Since probiotic research is still in its early stages, we don't yet know which strains of probiotics might be the most helpful for cognitive function.
If you're interested in trying a probiotic, Eastwood recommends a multi-strain probiotic that contains a combination of the most researched strains including lactobacillus, bifidobacterium, and lactococcus species.
And as with any new supplement, you should check with your doctor first to make sure it's safe for you to take.
