Fecal Transplants May Reverse Brain Aging in Mice

Older rodents showed improved cognition and behavior after receiving a microbiome refresh from younger rodents

Enterococcus bacteria under microscope
This photomicrograph reveals shows a type of Enterococcus bacteria. Strains of Enterococcus are commonly found in the gut. Photo by Smith Collection/Gado/Getty Images

Scientists may have found a crappy solution to winding back the clock. A new study reveals that transplanting the feces of younger mice into the gut of older mice can reverse cognitive declines associated with aging. The work, which was published Monday in the journal Nature Aging, is the first to suggest a link between gut health and age reversal in rodents.

“It’s almost like ... we could press the rewind button on the aging process,” study author John Cryan, a neuroscientist at University College Cork in Ireland, tells Rachel Fritts for Science.

A microbiome is a colony of trillions of bacteria that live together in a particular habitat. Ecosystems like oceans have their own microbiome, and so do plants, humans, and other animals, like mice. Scientists have known for decades that a healthy microbiome supports everything from digestive health to immune system function, but the link to aging is less clear. A team of researchers from University College Cork was curious if transplanting the robust microbiome of young mice could turn back the clock in older mice.

“The good thing about your microbiome—as opposed to your genome—is that you can change it,” Cryan tells Science.

To see if the microbiome had an influence on aging, scientists gave the rodents a special poo-fortified meal plan. They started by taking fecal samples from 3- to 4-month-old mice—young adult mice, by human standards—and fed the slurry to geriatric 20-month-old rodents using a feeding tube twice a week. After eight weeks of fecal transplants, the gut microbiome of the older mice started to resemble their younger counterparts. Bacteria, like Enterococcus, which is abundant in young mice, began to flourish in the guts of older mice.

The change in the geriatric rodents wasn’t limited to their guy bacteria. A region of the brain called the hippocampus, which is associate with learning and memory, became physically and chemically similar to younger mice. Older rodents that received poop transplants from young mice could navigate mazes faster and remember their layouts better than mice who didn’t get a microbiome upgrade.

“It was really great to see that full change in their microbiomes can really excel such effects on cognitive behavior, like almost resembling the learning performance of young mice, it was pretty mind-blowing,” study author Marcus Böhme, also a University College Cork neuroscientist, tells Inverse’s Elana Spivak.

Fecal microbial transplants aren’t new, but the science supporting their anti-aging ability has been sparse—until now. Other fecal transplant studies on mice have yielded mixed results, including one linked to cognitive declines. In humans, fecal transplants are already used to treat conditions like allergies and irritable bowel syndrome, but it will still be a long time before doctors prescribe a dose of feces to reverse aging.

“I'm not recommending that we should go into poo transplants ... because we have no evidence that that would work in humans,” Cryan tells Inverse. Still, he says the work suggests an important link between gut health and aging.

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