You are what you eat. More and more, scientists add that you are also what you feed your microbiome – the collective term for the billions of micro-organisms that live in your colon.
Much of your food is digested and absorbed in the stomach and small intestine, but some of it remains undigested, including some protein and fibrous fruit and vegetable matter. The bacteria in your colon live on these leftovers.
Increasingly, it is also thought that our gut bacteria communicate with our brain, through the language of different chemicals they – and we – produce, which can cross the blood-brain barrier.
The brain responds to what seems to be going on down there in what is often called the “gut-brain axis”. It’s a constant and complex feedback system. For example, the gut seems to be sensitive to our anxieties and emotional states; the microbiome changes in response to the stress hormone cortisol.
Evidence so far suggests that diversity in our microbiome is a good thing, enabling us to better handle physiological stresses, moderate mood, appetite, and help us fight off viruses and harmful bacteria.
For example, very overweight people, and the increasing numbers of people suffering from irritable bowel syndrome tend to have less diversity in their gut bacteria. But it’s early days, and we are only just beginning to understand the dynamics.
So how do we get our gut bacteria in the first place? And can we change it? By the time we are about 3 years old we have taken on board most of the bacteria that will colonise us for life. Probiotics in yoghurt and other foods have only a transient effect; they are with us only for as long as we keep consuming them.
PhD student Laura Payling, under the supervision of Professor Warren McNabb and other scientists, has begun the ambitious task of looking at how the whole microbiome functions, rather than singling out specific bacteria to study.
The bacteria in our guts are largely anaerobic, because they are adapted to the inside of our bodies where there is very little oxygen. Some use carbon dioxide to synthesise their energy, like plants do, but give off hydrogen, methane and hydrogen sulphide gases – not oxygen – when they are active.
There are two types of people in this world. A third of us host microbes that exhaust high levels of methane, as ruminants do. The other two thirds produce less methane and instead produce more acetate and/or hydrogen sulphide.
Payling is taking faecal samples from volunteers representing each group, and putting them into her laboratory machine, which simulates the human colon. She has to be careful not to let in any oxygen, which is toxic to the bacteria.
She feeds the bugs with porridge and potatoes. Using the highly specialised equipment and knowledge of scientists at AgResearch, Scion, and Massey and Victoria universities, Payling will analyse what’s happening at regular intervals between three and 48 hours after feeding time – what genes in the bacteria are switched on, what chemicals are made, and how the different bacteria are communicating. She will capture and measure the methane and other gases coming off.
In the meantime, feed your gut bacteria well. They flourish on variety and so do we.
by Professor Warren McNabb, deputy director of the Riddet Institute, Laura Payling (PhD student) and Glenda Lewis, science writer. This article was originally published by Stuff