Megan Rossi is a research fellow at King’s College London and a dietician and founder of the Gut Health Clinic at Harley Street in London. Her background as a clinical dietician and sports nutritionist in Australia helped her realise the depth of the link between what we eat, the bacteria in our gut and how we feel, subjects she now researches at King’s. Her book Eat Yourself Healthy is published on 19 September.
It made me laugh when you said in your book that “intimate kisses” can transfer bacteria between partners. Are there consequences?
There are millions of bacteria in our saliva, so we’d like to see if these impact our partners’ health in some way. In observational studies, there’s an increased risk of being obese if you have an obese partner. Of course, this may just be down to your shared eating environment, but there’s a theory that you might also be sharing bacteria that are associated with obesity.
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How did you become The Gut Health Doctor? It’s not the most glamorous specialism.
I’ve always had a huge passion for food. During my dietetic degree, my grandma passed away of bowel cancer. I had a very negative relationship with the gut, for making her go through all that pain. But when I was working as a clinical dietician, I realised all my patients were complaining of gut problems even though they actually had kidney disease. I couldn’t find any information that linked the kidneys and the gut, so I did a PhD to see if there was a way to improve the health of these patients by giving them prebiotics, which are dietary fibre that feed gut bacteria, and probiotics, which are the actual bacteria. My work showed that this decreased the toxins in their blood that were associated with kidney disease and helped their gut problems.
At the same time, I was the nutritionist for the Australian Olympic synchronised swimming team and I saw that the girls who had the most performance anxiety had the most gut issues. All these things showed me how essential the gut was to every organ in the body.
How is it that gut bacteria can affect our brain?
It has been known for ages that there is a connection between our gut and brain via nerves, but now there is a new player, gut bacteria. They communicate with the brain in three different ways: they send signals up the vagus nerve directly into the brain; they influence immune cells in the gut, which produce a range of chemicals that affect the brain; and they produce chemicals that travel in the blood. Some can get through the blood-brain barrier to the brain. And it works in both directions.
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What is the effect of this gut-brain communication?
This is an area that scientists are desperately trying to understand. There are that suggest that bacteria can affect hormones and neurotransmitters like GABA, which has a calming effect on some areas of the brain, but the exact mechanism is something we don’t quite understand. However, if we give just the right bacteria for six weeks, we can see an increase in activation in parts of the brain associated with mood and emotions, compared with a placebo group. Gut bacteria can influence symptoms of depression, too.
So should we all be taking prebiotics and probiotics regularly?
You don’t need to take a prebiotic supplement: prebiotics are found in thousands of foods we would normally eat. If you’re generally healthy, you don’t need any extra probiotics either, but there is really good evidence that people with certain conditions will benefit from taking a probiotic supplement. One example is when you’re taking antibiotics. Probiotics can significantly reduce your risk of antibiotic-associated diarrhoea, which affects about 30 per cent of people.
How do we make sure we’re feeding our gut bacteria the right kinds of foods?
It’s not about taking supplements, but about having a wide range of plant-based foods in our diet. Things like whole grains, nuts, seeds, legumes, fruit – all these things should be part of our daily diet. There are beneficial chemicals like polyphenols in plant-based foods too. They are found in nice things like dark chocolate and red wine.
What are the easiest dietary changes we can make?
We know that people who have at least 30 plant-based elements in their weekly diet have a more diverse range of bacteria in their gut, which is associated with better weight management, better heart health and better mental health. One easy change is to get a packet of mixed seeds and put a teaspoon on your breakfast – that’s four extra elements right there. Or get a packet of mixed leaf salad, rather than a single lettuce, because each different type of lettuce has different plant chemicals that feed different bacteria.
Do we need to keep an eye on what comes out of our bodies, as well as what goes in?
Yeah. You don’t need to talk about it at the dinner table, but listening in to our gut health, keeping an eye on our poop every few weeks and talking about what we’re eating to help our bowels are definitely things we should be more open about.
