For older fish, the Fountain of Youth might actually be more like the Poop of Youth. Nature News reports that scientists have found that eating poop from its younger brethren can extend the life of the turquoise killifish.

Nothobranchius furzeri, native to Zimbabwe and Mozambique, lives an incredibly short life—just a few months—which makes it the perfect model for studies on aging. Using these short-lived fish, researchers from the Max Planck Institute for Biology of Ageing in Germany recently discovered that microbes could play a role in staving off the effects of aging. Their study is posted in its pre-print version (meaning it hasn’t been peer-reviewed like a published paper would be) on bioRxiv.

They examined the gut bacteria of both 6-week-old and 16-week-old fish, discovering that the diversity of the fish’s gut microbiome declined over its lifespan. The older fish’s gut micobiomes were largely dominated by Proteobacteria, unlike the more diverse gut bacterial colonies seen in young fish.

Then, the researchers transplanted the gut bacteria of young fish into older ones. They wiped out the preexisting gut bacteria of 9.5-week-old fish—middle-aged—by giving them antibiotics, then introduced them into a tank with the gut contents of other middle-aged fish or young, 6-week-old fish. The fish that were exposed to youthful gut bacteria—by swimming around in a tank with young fish and their poop—lived significantly longer than the other fish. The fish exposed to young poop lived 41 percent longer than the fish that were swimming around in the gut bacteria of middle-aged fish and 37 percent longer than the control group. The fish rejuvenated with youthful gut bacteria were also more spry at the ripe age of 16 weeks than the other fish in the study.

Scientists are increasingly finding that the bacteria that live in our guts and on our skin have a profound impact on our lives. Different microbiome makeups are associated with obesity, anxiety levels, sexually transmitted diseases, and more. And the turquoise killifish isn’t all that different from us, gut-wise. The gene sequencing work performed by the Max Planck researchers found that the four most prevalent bacteria in the turquoise killifish’s gut are the same as in the human gut: Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes. Humans also lose some of the diversity of their gut bacteria as they age.

So while young blood might not be the way to rejuvenate aging bodies, young poop could very well be. (But maybe don't try this experiment on your own just yet.)

[h/t Nature News]