Could other peoples' poop hold the secret of "eternal youth?" A new study has shown how swapping gut bacteria from young to old mice through a fecal transplant appears to help reverse some aspects of the aging process. It's yet to be demonstrated in humans, but the early research is yet another example of how our guts' own little hive of microorganisms is immensely influential in our health – and perhaps even the way we age.  

Scientists at the Quadram Institute and the University of East Anglia (UEA) in the UK transplanted fecal microbiota from young to old mice, finding that it reversed numerous inflammation-linked hallmarks of aging in their gut, eyes, and brain. Conversely, microbes from old mice transplanted into young mice resulted in inflammation in the brain and depleted a key protein required for normal vision.

Their results were reported in the journal Microbiome.

"This ground-breaking study provides tantalizing evidence for the direct involvement of gut microbes in aging and the functional decline of brain function and vision and offers a potential solution in the form of gut microbe replacement therapy," Professor Simon Carding, from UEA's Norwich Medical School and head of the Gut Microbes and Health Research Programme at the Quadram Institute, said in a statement.

The gut microbiome describes the trillions of bacteria, viruses, and other microorganisms living within our intestinal tract. Most of these gut-dwelling microorganisms are not our enemies – the huge majority of these tiny residents live in harmony with the body, helping us break down food and providing access to much-needed nutrients. 

The inner workings of this complex system are not fully understood, but it’s clear the make-up of a person's microbiome can profoundly influence a person’s immune system, metabolism, mood, and even behavior by altering brain chemistry. Gut bacteria have also been associated with age-related disorders including inflammatory bowel diseases, plus cardiovascular, autoimmune, metabolic, and neurodegenerative disorders.

This latest study adds further evidence that the gut microbiome changes with age, having a significant effect on metabolism and immunity. The team noted that the older microbiome results in a significant shift in lipid and vitamin metabolism, which may explain the changes seen in inflammatory cells in the eye and brain.

The researchers cautioned that more work is needed to see whether these results can be applied to humans. However, given that very similar pathways exist in the guts of both mice and humans, the study hints that we could potentially ward off impacts of aging through meddling with the gut microbiome, whether that's through poop transplants or simply just changes to diet.  

"We were excited to find that by changing the gut microbiota of elderly individuals, we could rescue indicators of age-associated decline commonly seen in degenerative conditions of the eye and brain,” explained Dr Aimee Parker, lead study author from the Quadram Institute.

"Our results provide more evidence of the important links between microbes in the gut and healthy ageing of tissues and organs around the body. We hope that our findings will contribute ultimately to understanding how we can manipulate our diet and our gut bacteria to maximise good health in later life."