When it comes to the question, “Why are some people able to live past the age of 100?” there is plenty of debate.

Vegetarians argue for eliminating meat from the diet completely. Advocates of the Ketogenic diet urge cutting carbs in favor of fat. Followers of the Paleolithic diet take a third route and follow a diet that mimics that of hunter-gatherer peoples.

But, while none of these diet types represent the majority of centenarians, there is one longevity indicator that all people over the age of 100 share: they all have healthy guts with diverse bacterial colonization.

Two studies in 2023 add to the small, but solid, body of evidence highlighting this phenomenon.

Chinese centenarians

A study from China, published in Nature Aging in April 2023, found the gut microbiota of centenarians is populated by higher levels of beneficial bacteria. At the same time, the study also showed that people over 100 had lower levels of potential inflammatory bacteria.

To conduct the study, researchers at the Guangxi Academy of Sciences analyzed the gut microbiomes of 1,575 adults aged between 20 and 117. Of this group, 297 were centenarians—19% of the total.

The researchers reported that while people in their 40s to 60s saw a decline in gut diversity, the centenarians had microbiomes that were “enhanced throughout aging” and looked more like that of young people even into old age.

“Thus, we propose that the unique aging pattern of the gut microbiome in centenarians may confer positive effects on their health by reducing the senescence or chronic diseases that generally accompany aging,” the scientists wrote in the study summary.

The researchers also performed a longitudinal analysis across a 1.5-year period for 45 centenarians, and found that their healthy microbiome hallmarks continued to be maintained.

“The longitudinal analysis in this study revealed that long-lived individuals with higher microbiome diversity were prone to fewer microbiota changes during aging, suggesting that higher diversity or species evenness in centenarians (compared with that in other old adults) might protect the gut microbiome from instability,” wrote the researchers.

“Because the gut microbiome has a critical role in host health and diseases, we speculate that this unique gut microbial signature and aging pattern may contribute to longevity,” they added.

Will centenarians be “mined” for probiotics in the future?

In a 2021 study published in Frontiers in Immunology, researchers found​​ that a combination of probiotics derived from healthy centenarians was able to provide anti-aging potential in mice. The healthy “transfer” to the mice also provided protection against neuro-inflammation via the gut-brain axis.

Scientists say the findings continue to suggest that in the future the microbiomes of centenarians could be “mined” for novel probiotic strains to support health and longevity in other individuals.

 Sardinian and Japanese centenarians

A second study, published in Nature Microbiology in May 2023, came to similar conclusions when examining the microbiome’s of 195 centenarians from Japan and Sardinia.

The study, a cooperative effort by researchers in the USA, Japan, Denmark, and Finland, was not only designed to examine the gut microbiomes of centenarians, but also the viromes.

A virome refers to the hundreds of thousands of viruses, known as bacteriophages, that also normally inhabit the gut. The virome can also be referred to as phageome.

Just as in the earlier Chinese study, the examinations of the Sardinian and Japanese centenarians revealed they possessed gut microbiomes that were similar to that of younger people up to a maximum age of 55. But in this study, the examinations also revealed that the centenarians had young viromes.

Moreover, the data showed the centenarians not only had a greater diversity of bacteria and viruses, but more viruses were also in the lytic life cycle, a phase more associated with infants than adults.

The researchers noted that it is already known that bacterial composition of the gut of centenarians is associated with a healthier lifespan, but the new study demonstrated that the virome is also implicated in longer and better health.

“We speculate that in centenarians this translates to increased levels of microbially-derived sulfide, which may lead to health-promoting outcomes,” the scientists wrote in the study summary.

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Sources: Nature Aging, Nature Microbiology.