Scientist who’s cracked the secret to great gut health

She wants us to all be eating 30 different types of plant a week, which she refers to as “plant points”, to ensure that different types of gut bacteria are nourished, multiply, and knock out unhealthy bacteria.

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“This is not about a boring diet,” she says. “The more variety we introduce, the tastier the meal, and ultimately the better we feel.”

She’s put her ideas in practice on her husband Rory, an NHS doctor who has been on the frontline of the Covid pandemic. He was a “massive meat eater” when they met, so she “upped the plant content of his food subtly – adding lentils and mushroom in his lasagne and reducing the mince for example – and he didn’t even notice, it was also much cheaper”. This recipe is one of more than 80 in her new book. “I am a foodie by nature. I’m not anti-meat, just passionate about plants.”

Dr Rossi isn’t pro-vegan either. “The science doesn’t support that being healthy, necessarily,” she says. “The processed mock meats and fake cheeses have the plants’ health benefits stamped out of them.”

The key point is that there is a hugely mutually symbiotic relationship between what we eat and the bacteria inside us that craves it. So if we eat herbs, certain bacteria will benefit from breaking them down in the microbiome, at the same time releasing chemicals from the herbs – such as polyphenols, which promote cell renewal – that otherwise we wouldn’t be able to absorb.

Fibrous foods are another example. Unless we have the right gut bacteria to digest fibre we can’t digest it properly. Fibre is particularly crucial to ensuring a healthy microbiome, which in turn is linked with better mental health, heart health, metabolism and so on.

It’s also crucial to the relationship between our gut and our metabolism, she explains. Gut bacteria and the chemicals they make when they digest the fibre we eat from plants can help us feel full, halting the production of hunger hormones such as ghrelin, and boosting the “I’m full” hormones such as leptin.

She is not a fan of commercial microbiome tests either – the ones that require a stool sample and send back lengthy analyses. “They can’t predict illness – not yet anyway – and there are thousands of gut bacteria that have not been identified yet… I don’t recommend people waste their money on these. We need to do more research.”

So how do we get this large variety of plants into the daily diet? “The goal is to enjoy something from each of what I call the super six categories: wholegrains, nuts and seeds, fruit, veg, legumes and beans, and herbs and spices. Note how many different varieties you eat in one week.”

Swapping more in is remarkably easy, she adds. “Have barley or oats rather than wheat, for example. Buy frozen or tinned legumes, vegetables and fruits to widen the variety.”

One of the benefits of plant-based eating, she says, is that you can easily reach your weight goals without dieting. But nuts and avocados are full of calories, so how does that square up?

“This is where the importance of diversity comes in,” Rossi says. “We need to move away from the idea of fixating on super foods and loading up your plate with one variety – for example, avocados. When you’re getting your 30 plant points you won’t have room to eat one in excess.”

The same holds true for fruit, she says. “There are so many myths and a lot of confusion about how much sugar there is in fruit. There is a world of difference in drinking refined fruit juice, which is high in added sugars and low in fibre (the part our guts love) and eating apples which not only contain fibre, and an array of plant chemicals, including the feel-good hormone, dopamine, but they also contain millions of bacteria.”

The benefits of fasting can also be confused for outweighing those of a varied microbiome, she says. “A long fast can make it hard to get 30 plant points in, so you could end up doing more harm than good. I don’t think it is the panacea some suggest.”

Hers is not a fad diet, she reinforces. “It’s about tapping into the latest scientific discoveries about how our bodies, and gut bacteria, work best.”

Eat More, Live Well is published by Penguin Life

The Telegraph, London