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Young Fish Poop Is a Fountain of Youth for Older Fish

Turquoise killifish

Story at-a-glance -

  • Middle-aged killifish exposed to young fish’s gut microbes had a microbiome that resembled that of 6-week-old fish, with longevity benefits to match
  • The fish exposed to younger microbes were more active than typical fish of their age and behaved more like young fish
  • After exposure to young fish’s poop, the older fish also enjoyed a 41 percent longer median lifespan compared to fish exposed to older fish’s microbes and a 37 percent longer lifespan than the control group of fish

By Dr. Karen Shaw Becker

The African turquoise killifish is one of the shortest-lived vertebrates, with a lifespan of just 4 to 6 months (and that's in a laboratory setting). Native to Zimbabwe, turquoise killifish live in seasonal water ponds that only appear during the rainy season, hence their unusually short life cycle. Their quick progression from egg to adulthood has also made them popular for scientists studying aging and age-related diseases, including helping to identify what factors influence the rate of aging.1

Meanwhile, gut bacteria have emerged as major players in health and longevity, such that fecal transplants — transferring poop from a healthy individual into an unhealthy individual for purposes of restoring the microbiome — have become a thing, both in dogs and in people. In a recent study published in eLife, a novel form of fecal transplant was explored, in which poop from young killifish was transplanted into older killifish to see its effect on life expectancy — with very intriguing results.2

Poop From Young Fish Extends Life in Older Fish

Dario Valenzano, Ph.D., a geneticist at the Max Planck Institute for Biology of Ageing in Cologne, Germany, and colleagues carried out the study by transferring gut microbes (aka, poop) from young 6-week-old killifish to middle-aged (9.5-week-old) killifish.

This was done by first wiping out the gut flora in the older fish by giving them antibiotics, then placing them into an otherwise sterile aquarium that contained poop from the young fish. "Killifish don't usually eat feces," Nature reported, "but they would probe and bite at the gut contents to see whether it was food, ingesting microbes in the process."3

The results were dramatic. At the senior age of 16 weeks, killifish exposed to the young fish's gut microbes had a microbiome that resembled that of 6-week-old fish, with longevity benefits to match. Not only were they more active than typical fish of their age and behaving more like young fish, but they had a 41 percent longer median lifespan compared to fish exposed to older fish's microbes and a 37 percent longer lifespan than the control group of fish.4

It's already known that microbial diversity is a harbinger of health, and diversity in gut microbes is greatest in young, healthy individuals. As people age, their microbes tend to become less diverse and more concentrated with disease-causing microbes. This is also the case with killifish, which have diverse microbial communities in their youth and much less diversity in their microbes as they age. As the study revealed, it appears that manipulating these microbes may have a significant effect on the aging process:5

"When the guts of middle-aged fish were colonized with microbes transferred from younger fish, the older fish lived longer and were more active later in life. These fish also maintained a more diverse microbial community throughout their adulthood and shared key microbes with young fish — possibly associated with the improved health benefits.

These results suggest that controlling the composition of the gut microbes can improve health and increase life span … Manipulating gut microbes to resemble a community found in young individuals could be a strategy to delay the onset of age-related diseases."

Fecal Transplants May Improve the Health of Sick Dogs and Cats

The use of fecal transplants for longevity purposes is still in its infancy, the use of this technique to treat illnesses is already underway in some areas, including in the Boston area by Dr. Margo Roman, a fellow integrative veterinarian and owner of Main Street Animal Services of Hopkinton (MASH).

Roman has used fecal transplants to successfully treat dogs and cats with a wide variety of conditions, including severe gastrointestinal disease, behavioral issues, atopic dermatitis and coprophagia (poop eating).

Here is a picture of my friend's dog, who suffered from terrible atopic dermatitis for most of his life. I finally convinced her to try this strange, cheap and possible highly therapeutic treatment on her dog, as she had nothing to lose by trying. The most impressive thing about her dog's recovery is that a year later his skin remains healthy; he has not regressed.

One of my clients also had success using a fecal transplant to save the life of their yellow Labrador retriever, who was very ill with parvovirus. While fecal transplants aren't yet widely used, they are growing in popularity with more integrative veterinarians. In Israel, the first case report of fecal transplant in a cat with ulcerative colitis was recently published, with researchers reporting "an immediate improvement after the procedure" and describing it as a "safe, beneficial and promising novel therapeutic procedure."6

Although there aren't many published studies on the use of fecal transplants in dogs and cats, there are many anecdotal reports of its success (Roman's clinic alone has performed more than 5,000 such procedures).7

Further, in 2016 a group of veterinarians, noting that "there are no published peer-reviewed studies with regard to the use of FMT [fecal microbiota transplantation] in dogs and cats" released a commentary on the procedure to help answer the many unanswered questions, such as when and how to administer it.

"In dogs and cats, FMT may have the potential to improve health in any disease associated with an alteration or dysbiosis of intestinal microbial ecology such as acute and chronic GI inflammation and idiopathic diarrhea as well as IBD," they wrote,8 adding:

"The mechanisms by which FMT confers health benefits to patients are not well understood but appear to be related to a restoration or restructuring of the gut microbiota. This hypothesis is supported by evidence on the beneficial effects that gut microorganisms exert on health and also by the observation, in humans, that an FMT recipient can adopt and maintain the transplanted microbiota.

It is also possible that FMT acts as a form of immunotherapy with multiple host–microbiota mechanisms likely contributing to improved gut homeostasis and host health."

If you're interested in a fecal transplant for your dog or cat, it's important you have a screened, "clean," approved donor. Ask your veterinarian if they perform microbiome restorative therapy or contact an integrative or holistic veterinarian in your area. This is an emerging field in both human and animal medicine but one that's likely to be game-changing, not only for its disease-fighting promise but its anti-aging potential as well.