Could eating to feed your gut microbes be the key to better health? Our bodies are home to millions of microorganisms that, according to research, hold the key to how we fight off disease and metabolise food, and even impact how we feel. Studies suggest that a diverse diet is fundamental when it comes to maintaining a healthy digestive system, but not all foods are created equal – so we asked a scientist to give us the lowdown on which ones can really have an impact.

Click or scroll through our gallery for our A-Z of foods that can help improve your gut health.

This tender spring vegetable is another excellent source of inulin. "Consuming asparagus raw allows for the full intake of its prebiotic fibres, which are particularly effective at boosting levels of beneficial bacteria in the gut," says Miguel. "Cooking asparagus can break down some of its fibrous content; however, lightly steaming may preserve some of its prebiotic benefits while making it easier to digest for those with sensitive digestive systems."

Another source of gut-friendly fibre is avocado, which we know impact gut health thanks to a 2020 study by the University of Illinois. Researchers there found that people who eat an avocado every day have a more diverse gut population than those who don't – good news if your passion for guacamole knows no bounds. If you're not a fan of the fatty fruit, try it in a smoothie; adding fresh berries transforms the flavour and adds even more gut-healthy nutrients.

Is there anything bananas can't do? These sweet and nutritious fruits have long been celebrated for their slow-release energy and great potassium content – and they're good for your digestion, too. "Green bananas and plantains contain resistant starch, which acts similarly to fibre, resisting digestion and becoming food for our microbial friends," points out Miguel.

Whether cannellini, kidney, borlotti or haricot, we could all do with getting more beans in our diets. "Legumes are packed with fibres and resistant starches, which are key prebiotics," says Miguel. "Cooking them increases the bioavailability of their prebiotic components, breaking down some of the fibres and making them more accessible to gut bacteria." Besides eating them in stews or on toast, try your beans cooled in a salad – this way, their resistant starch content will be even higher.

Did you know that those gorgeously salty Greek black olives that pop up on pizzas and in salads are fermented? They're also incredibly high in polyphenols – plant micronutrients that, according to a Canadian review of existing studies, interact with our gut microbes to reduce our risk of chronic disease. In fact, all naturally processed olives (and good quality olive oils) are good sources of polyphenols, a contributing factor to the overall benefits of a Mediterranean diet.

When you consider how many of the world's heritage cheeses are made from cultured raw milk, it's not surprising that they're packed with diverse microbiota, ideal for expanding our own gut populations. French research has proven that raw milk cheeses can significantly improve populations of gut microbes following a dose of antibiotics. Hard, aged cheeses, such as Cheddar, Gruyère and Parmesan, may be particularly potent – and artisan or farmhouse cheeses are also more likely to be made using wild cultures, too.

This powerhouse of flavour is great for your microbiome. "Raw garlic is a rich source of inulin and fructooligosaccharides (FOS), potent prebiotics that stimulate the growth of beneficial gut bacteria," says Miguel. "Cooking garlic can diminish its prebiotic value, as heat can degrade these sensitive compounds, but adding it towards the end of the cooking process will help maximise the amount of allicin – a compound with notable health benefits – and minimise the degradation of the prebiotics."

Enjoy fizzy drinks or squash? "Sugar and artificial sweetener can disrupt our microbiota, leading to dysbiosis," says Miguel. This imbalance of the microbiome is bad news, as it can cause troublesome bacteria to flourish. "Seeking alternatives is wise, and while water is the gold standard for hydration, it doesn't have to be bland. Herbal teas offer a flavourful alternative without the sweeteners, providing hydration and variety. Or you can infuse cold water with slices of cucumber, lemon, orange and/or herbs to make drinking water more appealing."

Knobbly Jerusalem artichoke tubers are really worth seeking out because of their prebiotic content: fibre that we can't digest, but that our microbes thrive on. "Jerusalem artichokes are an excellent source of inulin, a type of prebiotic fibre that supports gut health by stimulating the growth of beneficial bacteria, particularly Bifidobacterium," says Dr Miguel Toribio-Mateas, a clinical neuroscientist, nutritionist and gut microbiome scientist specialising in the connection between the gut and mental health. Crunchy and sweet, they're great served raw in a salad or cooked into a tasty soup.

This ancient, fermented drink – made by adding jelly-like grains of living cultures to fresh milk – can have up to five times more live microbes than live yogurt. A slightly fizzy, soured milk isn't to everyone's taste, but you can easily work it into your favourite recipes. "Adding kefir to overnight oats or using it in a yogurt dip is fantastic," says Miguel. "Not just for its culinary creativity, but for its probiotic punch."

If you're yet to sample this mouth-watering Korean side dish, this is your call to action. Kimchi is made by fermenting vegetables – primarily Chinese leaf, but often white radish, carrot and spring onions, too – in a piquant paste of garlic, ginger, fish sauce, soy, sugar and Korean chilli flakes. It's easy to make at home, and your reward will be a potent probiotic food that's as packed with flavour as it is fibre.

To the uninitiated, kombucha is a slightly strange concept. It's made via an ancient Chinese process that sees very sweet black tea transformed into a sour sparkling drink thanks to the addition of a SCOBY (symbiotic culture of bacteria and yeast) – a floating culture that combines yeasts and bacteria into one rubbery disc. In recent years, kombucha has gained a cult following thanks to its natural fizz, complex flavours and live, probiotic benefits, which a systematic review of research, conducted in 2020, suggests help to support a healthy gut.

Lentils are absolute powerhouses of gut-friendly nutrients. "They're rich in fibre, which is not just any kind of nutrient; it's the feast upon which our gut microbes thrive," says Miguel. "This fibre promotes the growth of beneficial bacteria, leading to a healthier gut environment." Fabulously versatile, lentils are perfect for adding to soups, stews and pasta sauces, as well as putting centre stage in curries, burgers and salads.

This fermented soybean paste adds flavour to everything from broths and salad dressings to marinades and even ice cream (miso caramel is a winner) – so including it in your diet will be no hardship. It's worth the effort, because its natural probiotic content is proven to support healthy digestive function; one US study shows that miso can reduce side effects in people taking antibiotics. To get the best from your miso, always look for unpasteurised pastes. Darker miso is generally fermented for longer than lighter, sweeter varieties.

They're delicious, versatile and bring real benefits to our gut health. In all their diverse varieties, mushrooms are fundamental to so many delicious dishes. A Chinese review of scientific research conducted in 2017 found that the prebiotic components in mushrooms help healthy populations of microbiota to flourish in the gut, keeping toxic bacteria in check and making a significant impact on our health. So, whether you like stir-fried shiitakes or stuffed portobellos, your microbes are sure to thank you.

Natto is a Japanese dish made from soybeans – fibre-rich legumes – that have been fermented to bring out their slightly sour and cheesy umami flavours. The process creates a slightly bizarre texture; natto is stringy, rather like melted cheese, but also has the floury quality of well-cooked beans. It makes a great addition to rice, miso soup and steamed vegetables, but be sure to opt for live, unpasteurised beans to benefit from the probiotic qualities as well as the fibre.

These whole grains are such a wonder food that we shouldn't be surprised to discover they're great for our digestive health. Research conducted in 2021 proves that the particular forms of fibre found in oats are great at growing good bacteria in the gut, and improving symptoms of some digestive diseases. That's good news for porridge fans – but oats can also be used to up the fibre content in pancakes, cookies and traybakes, too. Fine oatmeal can even be used instead of refined wheat flour to thicken soups and sauces.

"While raw onions are a good source of inulin and FOS, cooking onions can actually transform their complex carbohydrates into simpler forms that might be more readily available to our gut bacteria," says Miguel. "Cooking can also soften the fibres, potentially making them easier to digest, and allowing for better absorption of the prebiotics." Some of us also find cooked onions much tastier. Slowly sweat them down with butter to bring out their very best caramelised qualities. 

Eastern Europe's fermented cabbage dish is a delicious Iive food that's often deployed alongside fatty meat dishes, as its sour crunch cuts through rich sauces. Classically made with white cabbage, sauerkraut can also incorporate red cabbage, carrot, apple and spices, all of which add to its digestive health benefits. "The gut thrives on variety," says Miguel. "Incorporating different fermented foods like sauerkraut introduces different strains of beneficial microbes, enriching our gut microbiome's diversity."

Sea vegetables are real culinary gems, adding delicious umami flavours and silky textures to everything from sushi rolls to salads – and even baked brownies. Not only does seaweed diversify our diets, bringing that variety our microbes love, but it also gets extra marks for content. "Seaweed might come as a surprise, but it's packed with unique polysaccharides that benefit our gut flora," says Miguel.

The industrial yeasts and additives in ultra-processed bread are no friends to our gut microbes, but traditionally leavened bread is a very different story. Sourdough is made when wild yeast cultures are added to a wet wheat or rye dough; these living microbes slowly eat the naturally occurring sugars from the flour, producing airy bubbles as they go. The growing population of microbes brings an addictive sour taste to the dough and pre-digests some of the acids, making this type of bread significantly gentler on our stomachs.

This peppery salad leaf has long been loved for its flavour but, as a study from 2021 confirms, it's also a powerhouse of flavonoids. That's good news for watercress fans, because the microbes in the gut set to work transforming these nutrients into compounds that regulate the immune system and fight disease. Enjoying fresh watercress in a tossed salad is the easiest way to access its nutrients, but a watercress soup, made with gut-boosting fresh green peas, is a real winner, too.

If you love kombucha but prefer to swerve caffeine, consider its cousin: water kefir. Also naturally sparkling thanks to the presence of live microbes, it's a milder, lighter drink that's easy (and very cheap) to make at home. Water kefir grains, which are distinct from those used to culture milk, are widely available online, and will transform a large jar of water, sugar, lemon and ginger into a delicious probiotic beverage. Caring for the grains can be a bit like attending a needy pet, though – so finding a local producer could be a real win.

"It's often demonised because of its gluten content, but whole grain pasta is a robust contender in the quest for gut health," says Miguel. "Its fibre content acts as a nurturing ground for the gut microbiome, offering a complex array of polysaccharides and resistant starches." In fact, cooled whole wheat pasta – maybe in a salad – is a source of resistant starch that encourages bacteria that produce butyrate, a potent anti-inflammatory.

The original live food, yogurt hails from ancient Mesopotamia, and humans have been eating it for around 7,000 years – for very good reason. Studies show its interaction with the microbes in our bodies improves everything from bad breath to yeast infections. Its impact on the gut can help to tackle problems as diverse as type 2 diabetes and high cholesterol. So, whether you're spooning it into a kebab, onto a curry or over some fresh berries, live yogurt is in your corner.

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