There have been numerous explanations for how some people are able to live to extreme ages - including genetics and healthy living.
Centenarians themselves have revealed all kinds of oddball secrets, including eating raw eggs, chicken brains and ramen noodles, staying single and enjoying hot springs. (WILL LINK)
But scientists now say it could be all in the gut - specifically, the kinds of microbes you have living in there.
"Centenarians display decreased susceptibility to ageing-associated illness, chronic inflammation, and infectious disease," a new paper published in journal Nature says.
"Here we show that centenarians have a distinct gut microbiome enriched in microbes capable of generating unique secondary bile acids."
They studied three groups of Japanese people, known for the exceptional rate of centenarians. Some were over 100, others between 85 and 89, and a third group between 21 and 55.
Compared with the younger groups, centenarians' good gut bacteria had the ability to produce acid which killed bad bacteria which have been linked with a range of poor health conditions.
"The majority of centenarians were free of chronic diseases such as obesity, diabetes, hypertension, and cancer, and the prevalence of these diseases was not significantly increased as compared to the elderly group."
The scientists - from the Keio University School of Medicine in Japan - hope the finding leads to treatments that could "manipulate the bile acid pool for health benefits", but admit there's a lot more work to be done to verify the findings first.
Earlier this year a separate group of scientists said the absolute oldest a person could live is likely to be about 150. In 2020 a similar study came up with 138.
The world's oldest person on record was French woman Jeanne Calment, who was 122 when she died in 1997. The oldest living person right now is Kane Tanaka of Japan, who is 118, and credits her longevity to "eating good food and practicing math".
