They love your guts: microbes and what your diet does to them
Studies have uncovered links between particular foods and a healthy diversity in our intestinal ‘populations’
Gut bugs: a study of older people found that those who had less diverse diets tended to have less diverse populations of bacteria in their gut, and this was also linked with poorer health
Diversity is the spice of life. And it seems the same goes for your gut bugs – as we get on in years, at least. That’s the finding of the Eldermet study, which tracked 178 older people who were living in the community or in long-term care.
The study, which was led by Prof Paul O’Toole at University College Cork and the Alimentary Pharmabiotic Centre, found that people in care who had less diverse diets tended to have less diverse populations of bacteria in their gut, and this was also linked with poorer health.
The study, which was published in the journal Nature last year, was an eye- opener for co-author Fergus Shanahan, professor of medicine at UCC, who never expected to find such a strong correlation.
“It seems that for the elderly it’s not enough to have calories and nutrients, you have got to have diversity in the diet too,” he says. “And the prediction now is that there will be new foods for promoting this diversity in the microbiome [the ecological community of micro-organisms that share our body space], and that we may in the future be able to measure the gut bacteria as biomarkers of health in the elderly.”
The study draws attention to the goings-on deep in your gut, which is packed with trillions of bacterial cells – hundreds of different species – that far outnumber the cells in your own body.
And even though you can’t see those bacterial cells, what they are and what they are doing matters. If you have a lack of diversity, if the “wrong sort” is hanging around in there, or if there’s some unruly microbial behaviour, it could spell trouble.
In recent years studies have linked the gut microbiota with the risk of gut inflammation, colon cancer and obesity, and they might even have implications for mental health.
However, while we might be somewhat at the mercy of our gut bugs, it seems they in turn are at the mercy of what we feed them through our diet.
Antibiotics or illness can cause havoc, and gut microbes tend to be more malleable in children and the elderly, but overall diet is the main determinant of which microbes are in the gut and which are behaving, explains Shanahan, who directs the Science Foundation Ireland-funded Alimentary Pharmabiotic Centre in Cork.
“Over a lifetime, diet is the most important thing that influences your microbiome,” says Shanahan, who earlier this month scooped the award of SFI researcher of the year.
“The microbiota in health in adult life is relatively stable – although perhaps not as stable as we once thought – and with new molecular techniques we are finding that environmental and lifestyle factors, especially diet, are influencing the composition of the microbiota. Also, the bacteria are making and producing things, and depending on what you feed them, they will behave differently.”
So what should we be feeding them? It’s a quickly evolving area of study, but so far it seems that the old advice to eat fibre and a diversity of foods holds true.
Recent advances in genetic technology mean that we can now get a better handle on the bacteria in the gut by looking at their DNA – although typically the experiments are done in what comes out the other end, where faecal bacteria can give a good sense of the populations in the bowel.