A unique make-up of gut bacteria may help you live to the grand age of 100, research suggests.
The extent to which humans are capable of defying death has long been debated. In the UK, the average life expectancy for men is 79 and for women it is 83. While it may sound farfetched, scientists from the University of Washington have predicted someone will live to 124 this century.
In March 2021, scientists from the Institute for Systems Biology in Seattle reported how our gut bacteria may influence how long we live.
Adding to the discussion, a team from the Keio University School of Medicine in Tokyo analysed the stool samples of 160 Japanese centenarians, with an average age of 107.
Compared to people aged 21 to 55 or 85 to 89, the centenarians had higher levels of bacterial species that regulate the immune system, warding off life-threatening infections.
"The ecological interaction between the host and different processes in bacteria really suggests the potential of these gut bugs for health maintenance," said study author Damian Plichta, from Harvard.
The number of centenarians has risen steadily over the past few decades, a trend that has largely been put down to improved healthcare, widespread vaccinations and superior public health measures.
As a result, nearly half a million people are said to be aged 100 or over worldwide.
To better understand what helps a person live to 100 or beyond, the Keio scientists studied the microbes in the stools of volunteers of a range of ages.
The centenarians specifically had higher levels of several bacterial species that produce so-called secondary bile acids in the large intestine, according to the study published in the journal Nature.
These bile acids are thought to help protect the intestines from infections by regulating the body's immune response.
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In the second half of the experiment, the scientists exposed common bacteria to these secondary bile acids in a laboratory.
One bile acid in particular, called isoalloLCA, strongly inhibited the growth of Clostridioides difficile – an antibiotic-resistant infection that can cause severe diarrhoea and intestine inflammation.
The World Health Organization has called antibiotic resistance "one of the biggest threats to human health". Infections that are currently considered to be almost harmless may one day be incurable, with once-effective drugs being rendered useless.
The Keio results have also revealed Odoribacteraceae bacterial strains in particular produce isoalloLCA, which also protects against a bacteria called Enterococcus faecium. E. faecium normally lives harmlessly in the intestines, but can be serious if it reaches other parts of the body.
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Mice that were infected with C. difficile and then fed a diet supplemented with isoalloLCA went on to similarly have suppressed levels of the harmful bacteria.
The Keio scientists concluded isoalloLCA helps to maintain the delicate equilibrium of microbial communities in a healthy gut.
Although further research is required, bile acids could one day be manipulated to treat antibiotic-resistant infections.
"Our collaborative work shows future studies focusing on microbial enzymes and metabolites [products of metabolism] can potentially help us identify starting points for therapeutics," added co-author Dr Ramnik Xavier, from Harvard.