When I meet Dr Megan Rossi, she makes me feel instantly at ease, which lends the old adage “trust your gut” a reasonable weight. Despite the fact that we’re discussing what many people might consider taboo subjects – gas, bowel movements and depression – Dr Rossi is unabashed and incredibly generous with her extensive knowledge. So much so that I’m enjoying this conversation about bloating after eating more than I anticipated.
Known as The Gut Health Doctor, Rossi has become one of the most trusted voices in nutrition science. With her research, books, Smart Strain probiotics and snack brand Bio&Me, her mission is to spotlight what she calls “a pretty unglamorous organ” and show us how it could be the secret to feeling better, looking better and even living longer.
“The gut isn’t just about digestion,” she tells me, leaning forward with conviction. “We now have research linking it with almost every organ in the body. Your metabolism, your hormones, your skin, your brain – your gut talks to all of them.”
“People are suddenly understanding why they're being told to eat healthily. The gut is not just about digestion and bloating, there's a mental health element, hormones, skin and metabolism. Technology has allowed us to understand exactly how powerful our gut microbes are. And I think ultimately, everyone wants to feel better, that also results in looking better.”
She tells me: “I was a dietitian first, working in a hospital, and what fascinated me was the patients who didn’t respond the way we expected. The more I looked into it, the more I realised the gut microbiome was the missing piece of the puzzle. We were underestimating its role in disease, in mental health, even in immunity.”
The more I write about gut health, the more I see the phrase “food as medicine”. It’s divisive, especially among medical experts, but Rossi doesn’t shy away from its complexity. “I think food is absolutely powerful. But it’s not a silver bullet,” she says. “Medicine has its place – antibiotics save lives. But what we’re learning is that food can be used as prevention, and in some cases, treatment.”
She adds: “We now have evidence that dietary changes can reverse type-2 diabetes in some people. That doesn’t mean food replaces medicine. It shows the potential of diet to reduce our reliance on drugs.”
30 plants a week
There’s something else I want to ask her about – the 30 plants a week rule. In a world filled with influencers peddling organ meat supplements and telling us not to eat vegetables, I’m keen to hear one of the leading microbiome researcher’s thoughts on one of the most influential arguments for eating more plants.
“The American Gut Study showed people who ate 30 or more different plants a week had much more diverse gut bacteria than those who ate fewer than ten,” she explains. “It wasn’t about being vegan or vegetarian. It was about diversity. Herbs, spices, nuts, seeds, they all count.” She laughs when I ask if thirty is a hard rule. “It’s not a cut-off point where you suddenly become healthy. It’s a guideline that makes it fun. People tell me they get competitive in the supermarket, hunting for a new bean or herb just to hit their thirty.”
But, she explains, the American Gut Study wasn’t a perfect study. Rossi believes we can do better. “People got behind it from a social media perspective very early on and were enjoying this plant point system. I contacted the researchers of that observational study and I quizzed them about which categories of plants they included and what they didn't include.
This 30 number is not some magical thing – it was based on one quite low level evidence study. So I would say, we do generally want to see more different types of plants because they've got all the different biochemicals we need for improved health and nutrition, but don't necessarily stop at 30. We need to do more clinical trials which, I am very pleased to say we've got the funding for to investigate specifically at Kings College.”
Right now, Dr Rossi is testing several theses – such as whether diversity matters more than fibre alone. “We’ve designed a study where people are eating the same amount of fibre, but one group gets it from just a few sources and the other from a wide variety. We want to see if it’s diversity itself that drives gut health. That’s what excites me, answering these questions properly.”
Read more: I’ve been drinking kombucha for years and it’s transformed my gut health – here’s how
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Gut worriers
Rossi has seen first-hand the impact of different diets on healthy people and those with chronic diseases, gut issues and debilitating inflammation levels. She suggests that the additives in our food are one of the most significant disruptors of the gut, yet this is something we rarely consider when we shop.
“Regulators have always assessed emulsifiers based on safety to human cells. But no one asked how they affect the microbiome,” she says. “In our trial, people with Crohn’s [disease] on a low-emulsifier diet not only felt better, but their disease severity actually reduced. This is the first time we’ve shown emulsifiers can impact gut health in humans.” She shakes her head. “That’s huge. And it means we need to rethink the way we regulate food.”
“Historically, there's 400 plus different types of food additives, which were generally regarded as safe because they did the safety tests, only on animal and test tube studies. But that was all before we understood the gut microbiome and the impact over years, not just weeks or months. So now, the European Food Safety Authority and groups all over the world are now starting to reassess the safety profile,” she explains.
She is just as fascinated by the placebo – and its counter, the “nocebo” – effect in her research, something she points out is on the rise due to the sheer volume of nutrition advice we see on social media. Essentially, we’re all being led to believe that certain foods will cause bloating, weight gain and inflammation – wheat and dairy being the top two supposed offenders.
Read more: The truth behind ex-vegan influencers now selling organ meat supplements
“If someone believes a food is bad for them, that belief alone can trigger symptoms,” she explains. “We see it with gluten all the time. People react when they think they’re eating gluten, even if the food is totally gluten-free.” Rossi doesn’t dismiss this. “It doesn’t mean the symptoms aren’t real. It means the gut and the brain are so closely connected that expectation itself can change how our body responds.”
“Sometimes people give up fruit, then they stop eating broccoli or chickpeas and pretty soon there's nothing left. And then what happens is in the short term they feel better and then they add them back into their diet but in too large an amount so they instantly get bad symptoms. That will reinforce that they've got an intolerance. No, you just need to train your gut. Like you would your muscles for a marathon.
“Underlying gut sensitivity affects 20 per cent of the population. Maybe it's because you've had a gut infection or an imbalance, or because of that chronic stress. You can definitely have more sensitivities to these foods and therefore, if you have a big amount of fibre and your gut's not trained for it, it will create loads of gas and therefore stretch your gut. And if you think about that gut brain connection, those enteric nerves, it's like these millions of live wires and that stretching it and it creates a lot of discomfort.”
Perhaps the most hopeful part of Rossi’s message is that the gut can be trained. “It’s like a muscle,” she says. “If you suddenly go from zero to 30 grams of fibre, you’ll get cramps, gas, discomfort. But if you build up gradually, your microbes adapt. They start producing the right enzymes and those symptoms improve.”
She explains the importance of fibre for a healthy gut but urges anyone incorporating more into their diet to go slow. “Spread fibre through the day. Add a little more each week. Be patient with your microbes. They want to help you, but you’ve got to give them time.”
Fighting misinformation
Dr Rossi does have plenty of compassion for those who tend to believe everything they see on social media – after all, misinformation and bizarre diet advice is rife online and we aren’t often taught about the needs of the gut specifically.
“I see a lot of teenagers who believe bloating means they’re intolerant, or that they should have a flat stomach 24/7,” she says. “That’s just not realistic. A bit of bloating after a high-fibre meal is actually normal, it’s a sign your microbes are working.
“It's a really vulnerable time, I think, for teenagers to be on social media because they don't necessarily have that baseline knowledge.
The pursuit of a certain body type, she warns, can lead to restriction. “Cutting out food groups without a clear reason can really harm your gut health long-term.”
One of her biggest frustrations is the rise of commercial food intolerance tests. “IgG tests do not diagnose intolerance,” she says firmly. “All they show is what you’ve eaten recently. Yet people spend hundreds of pounds, get a long list of so-called problem foods, and then cut them all out. That’s damaging, not empowering.”
So what does empower people when it comes to gut health? Rossi’s advice is actually fairly simple. “Focus on variety – plants in all their forms. Increase fibre slowly and consistently. Question your beliefs around food – could your symptoms be expectation, not the food itself? Don’t restrict unless there’s a clear medical reason. And if you suspect an allergy, see a professional. Please don’t rely on a commercial test.”
When our conversation comes to an end, Dr Rossi circles back to the bigger picture. “Your gut microbes are incredibly resilient. If you feed them variety, if you give them time, they’ll look after you.
Read more: From Marmite to Tabasco: the everyday foods experts say can improve gut health
