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You should follow the diversity diet and eat 30 different plants a week to keep your digestive microbiota in best condition, says Dr Megan Rossi, known as the “gut health doctor”. Photo: Getty Images

Diversity diet: why a gut health doctor advises eating 30 different plants a week to keep your digestive microbiota in top condition

  • Organisms in our gut known as microbiota ‘do a lot for you on a daily basis’, Dr Megan Rossi says – from regulating our appetite to boosting the immune system
  • Plants have fibre, which gut bacteria breaks down, and myriad nutrients that can help protect against illness; an apple has 3,000 beneficial nutrients

Scientist and dietitian Dr Megan Rossi, known as the “gut health doctor”, regularly extols the benefits of plant-based food, which cultivates the trillions of beneficial microbiota in the gut.

In a recent talk for New Scientist magazine, titled “Eat More, Live Well: enjoy your favourite foods and boost your gut health with the diversity diet”, Rossi explained the workings of the digestive system and how a healthy gut safeguards whole-body health. Some highlights follow.

How what happens in your gut affects your overall health

What we eat has been known to affect overall health for some time, but it was originally thought to affect human metabolism in general. The recent landmark discovery has been “bacterial metabolism” – the way that our gut microbiota, the trillions of organisms that live in our gut, affect our health.

Scientist and dietitian Megan Rossi recommends eating 30 different types of plants – fruits, vegetables, seeds, nuts and so on – each week.

Microbiota, as these organisms are collectively known, are generally concentrated in the large intestine, and include bacteria, fungi, parasites and viruses. “Microbiota do a lot for you on a day-to-day basis,” Rossi said.

In her book Love Your Gut: Supercharge Your Digestive Health and Transform Your Well-Being from the Inside Out, Rossi lists how gut microbiota benefit their human hosts: they make vitamins, amino acids, hormones, and chemical messengers; they train our immune system to work effectively; they may help balance blood sugar, lower blood fats, regulate appetite and prevent diseases; and they communicate with our other vital organs, including our brain, liver and heart.

What is the gut microbiome? Five simple steps to keep yours healthy

“Microbiota produce chemicals that get into the blood and go to organs all over the body,” Rossi said. “They lower our risk of getting some illnesses, and can even lower our risk of getting things like the common cold. They can also produce vitamins and hormones.”

People who have been sent to hospital with Covid-19 seem to be missing some key gut bacteria, she noted.

Understanding the digestion process

The human digestive system. Illustration: Shutterstock

Digestion is all about getting the good stuff in the food into your blood, so it can be transported around the body to where it can be used.

According to Rossi, digestion happens in a few places. It begins in the mouth, with enzymes and chewing, which is why you should chew your food as much as 40 times, if you are patient enough.

The stomach comes next. “The stomach is actually like a washing machine, and it turns the food into a kind of purée. From there, it goes into the small intestine, where most of the food is absorbed,” said Rossi. “Anything that is not absorbed in the small intestine goes into the large intestine, which is where a lot of the gut bacteria live.”

The large intestine does focus on excretion – it makes faeces – but the existence of so many microbiota means that good things happen there, too.

The more varied your plant diet, the healthier your microbiota. Photo: Shutterstock

How to help gut microbiota to thrive

“Your gut microbiota are unique to you,” Rossi said, noting that even identical twins have different variations of microbiota.

“You can affect them,” she said. “What do they like? Fibre, which is the backbone of all plant-based food. Our bodies can’t break down fibre, so it travels into the large intestine, where most of the microbiota live, in an undigested form.

“The bacteria there can break it down … and that gets the nutrients into the blood.”

Gut feeling: everything you have to know about the stomach

There are about 100 types of fibre. “They are not all the same, and they do different things.

“For instance, 10 grams of wholegrain fibre a day may reduce the risk of colon cancer by 10 per cent. But the body does not have the same relationship with the fibre obtained from fruits and vegetables, as that fibre does different things.”

What to eat for optimum gut health

We should all be aiming for 50 grams of fibre a day, Rossi says, but diversity is as important as the total amount. “It’s best to have a diverse intake of plant-based food, over and above just the fibre – it’s not only about fibre,” she said.

The humble apple contains 3,000 beneficial chemicals, including melatonin, and a million bacteria. Photo: Shutterstock

“There is a range of other chemicals in plants which make a diversity of plant food important, like polyphenols. The humble apple contains 3,000 beneficial chemicals, including melatonin. There are a million bacteria in a single apple.

“To ensure good gut health, you should be aiming for 30 different plants a week. You don’t have to be a vegan. The foundation of the diet is plants, but what you eat on top of that is up to you. You don’t have to go to extremes. Animal-based foods, like oily fish, are beneficial for gut microbes, too.”

If you do eat meat, just replace some of it with plants, she said.

Processed plant food, like plant burgers, often has the fibre and nutrients stripped out of it. If you are not eating meat on ethical grounds, processed plant food is certainly an alternative, but it probably won’t do much for your microbiota, she said.

Those who don’t like the taste of plants may actually start to like them. According to Rossi, your taste buds are in a constant state of evolution, and regenerate every few weeks.

“You will get to like it, as your tastes change,” she said. So in time, you may find you start to enjoy the taste of healthy whole foods, and see your health improve, too.

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