The largest study of its kind has found a link between the bacteria found in your gut and your long-term mortality risk. Researchers in Finland analysed stool samples taken 20 years ago and tracked the health and mortality of 7,000 participants up until 2017.

They found that the presence of certain bacteria seems to have a role in ageing and a person's likelihood of developing common diseases. A large amount of enterobacteria – linked with everything from gastroenteritis to pneumonia – is a prime example.

"Many bacterial strains that are known to be harmful were among the enterobacteria predicting mortality, and our lifestyle choices can have an impact on their amount in the gut," said study author Prof Teemu Niiranen at the University of Turku. "By studying the composition of the gut microbiota, we could improve mortality prediction, even while taking into account other relevant risk factors, such as smoking and obesity."

A person's microbiome – which describes the vast amount of microscopic organisms that live in our bodies – is as individual as a fingerprint, and it's becoming increasingly clear that it affects a growing list of health factors, including mental health. However, this is the first population-level study to follow participants over two decades, examining the link between specific bacteria and long-term health.

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Researchers compared health records and billions of DNA strands retrieved from the the original samples.

"We developed a machine learning algorithm that screened the data for microbial species having a significant association with mortality among the research subjects," said Prof Leo Lahti, another researcher involved in the study.

The more we understand about how our microbiome affects our health, the more we can do to optimise it. To date, scientists have stressed the importance of a varied, nutritious diet, one that includes fermented foods like kefir and sauerkraut, as well as polyphenol-rich foods like dark chocolate and blueberries.


A former deputy editor at Science Focus, Ian once undertook a scientific ranking of the UK's best rollercoasters on behalf of the magazine. He is now a freelance writer, which is frankly a lot less fun.