Which foods are really good for our gut health?

There is no shortage of supplements and gut shots, online memberships and apps, and it can be difficult to know what’s worth your money. Yet good gut health needn’t cost a lot. Dietician Dr Megan Rossi (aka the Gut Heath Doctor) has been outspoken against the marketing of probiotic capsules as a general cure-all.

Probiotics, she says, should be prescribed for specific problems eg. IBS: “Specific strains of bacteria for specific therapeutic benefits, but that's not the way they've been marketed. Instead, they've been marketed as a pill you should take every day and you'll have good gut health. But for general gut health, you don't take a probiotic, you need to eat a balanced diet with good plant diversity.”

Which foods can help improve gut health?

Bacteria are present throughout our digestive system, from mouth to colon, but the greatest concentration is in the large intestine. Achieving good diversity and a healthy balance with these bacteria can be encouraged in two main ways.

Firstly, it’s essential to eat plenty of plant fibre. This falls into two categories: roughage, which we need to keep the gut moving, and soluble fibre, which feeds the microbes. This soluble fibre is often called “prebiotics”.

Secondly we can introduce new microorganisms into the mix. These are probiotics, defined as “live bacteria that, when administered in suitable proportions, provide health benefits to the host”.

So, if you’re not taking a supplement, this is where fermented foods come in as they are full of probiotics. Examples include the “four Ks”: kraut, kimchi, kefir and kombucha. But also yogurt, miso, water kefir, kvass and various pickles.

Your balance of gut bacteria is as individual to you as your fingerprint, but unlike your fingerprint it can change over time. A study published last year showed that people who ate six portions of fermented foods a day saw decreased inflammatory markers after 10 weeks.

Dr Maria Valdivia-Garcia of the Faculty of Medicine, Department of Metabolism, Digestion and Reproduction at Imperial College London, says that the wider health benefits of fermented food only become apparent after six months of incorporating them regularly into your diet but the digestive benefits will be felt much sooner: “You can see a difference in as little as a week.”

However, not all fermented foods are created equal.

Mistakes to avoid when buying fermented food

• Kraut and kimchi: Make sure you’re buying them from the fridge. Anything that is shelf stable will have been pasteurised, killing the probiotics.
• Yogurt and kefir: Kefir contains more bacterial strains than yogurt but both are great sources of probiotics. Look for wording on the label like “live” or “active cultures”. Avoid artificially sweetened versions and check for ultra-processed ingredients such as modified starches, emulsifiers and preservatives which can have a negative effect on the gut microbiota.
• Kombucha: 'Kombucha' is not currently a protected term. Dr Rossi says, “It’s very difficult to make real, traditionally fermented kombucha at scale. So a lot of what you can buy is not really fermented.” Look for small, independent producers and don’t buy anything that is stable at ambient temperatures.
• Miso, tempeh, tofu: These products are created by fermentation but either usually pasteurised before sale (tofu and tempeh unless you are buying artisanal, small batch stuff) or you will kill the probiotics with heat during cooking.
• There is also confusion around sourdough bread. Sourdough bread is a fermented food and can have health benefits, but the baking process kills off any bacteria present so it doesn’t contain probiotics. Many gluten intolerant people find slow-rise, naturally fermented sourdough more digestible than the ‘Chorleywood method’ that makes up the majority of supermarket bread. These chemically enhanced, quick-mixed loaves have added fats, so are quick to produce but lacking in nutrients.

Shop-bought vs homemade

Dr Valdivia-Garcia says that shop-bought krauts, kimchis, yogurts and kefirs can be more consistent from batch to batch but tend to contain fewer different strains of bacteria than those made at home.

Shop-bought is a good place to start, but homemade is usually tastier. It’s easy to tweak homemade to your own personal taste – and not just by adjusting the recipe. A live ferment will be constantly converting sugar into lactic acid and the flavour changes accordingly. If you’re in control of the ferment, you can taste regularly and choose to stop the ferment (usually by moving your jar to the fridge) at the point at which you’re happiest with the flavour.

With some products, you’ll need to weigh up the pros and cons of how much effort you’re prepared to put in, and what’s most important to you. For instance, yogurt is easy to make but requires being kept at a constant warm temperature whilst it ferments, which some people find a faff. Texturally, shop-bought kefir is more reliably even-textured but homemade will have a wider variety of bacteria and is easy to make.

Homemade is almost always going to be cheaper. A jar of kraut or kimchi can cost as much as £10, even though the ingredients are inexpensive. All you need to make your own are vegetables, salt, a jar and some patience – which will cost you far less!

Often the mistake isn’t buying something that is making misleading health claims, it’s just shelling out when you don’t need to. For instance, even though certain brands might be associated with expertise or be able to provide studies illustrating the effectiveness of their products, sometimes they are just based on relatively simple ingredients that you can make yourself. One example would be ‘gut shots’ and probiotic drinks, which are often based on kefir plus some prebiotic fibre and fruit. You can make something very similar yourself for far cheaper and that would cut down on plastic waste.

Try these DIY super-easy ferments (which just cost pennies)

Making your own kraut is super easy. Traditional white cabbage sauerkraut is a great way to get started, or try beetroot and red cabbage for something more colourful.

Once you are comfortable with the method, you can adapt it with any hard, shreddable vegetable.

Kimchi is a little more complicated but the theory is the same – try this recipe.

To make kombucha or kefir, you will need to get hold of a scoby (which stands for ‘symbiotic culture of bacteria and yeast’). A kombucha scoby is flat and gelatinous, while kefir scobys (also known as grains) are white and knobbly and resemble cauliflower florets. Ask a fermenting friend if they have some spare or buy them online. You can then make your own delicious fermented tea and kefir.

Including six portions a day of these things might seem daunting but it’s fairly easily done. A bowl of kefir counts for two portions and makes a great breakfast or snack with fruit and granola. You could also make your own bircher muesli by mixing oats with grated apple and kefir and leaving it overnight.

Try some kraut as a side dish, especially alongside rich foods where the acidity cuts through nicely. It’s also great in a sandwich or mixed into a salad. Some of my favourites include a carrot-based kraut with hummus and flatbread and a spiced red cabbage and beetroot kraut with cold meats, or on a cheeseboard instead of a chutney. Kimchi goes beautifully with eggs for breakfast, is the perfect accompaniment to a cheese toastie or makes a simple, tasty dinner with rice, veggies and a fried egg.

Cooking with these things destroys their probiotics so, although there are plenty of tasty ways to add krauts and kimchi to stews and stir fries, if you want the probiotic gut health benefits then keep them cool and eat them as a last-minute addition.

Add these budget gut-health goodies to your basket…

• Jerusalem artichokes – the knobbly tubers are full of inulin, a prebiotic fibre that feeds good gut bacteria and is often a key ingredient in plenty of pricy supplements. They’re delicious roasted or in soup. Leeks, asparagus, bananas, onions and garlic also contain high levels of inulin.
• Oats – a good source of beta-glucan, a soluble fibre great for gut health.
• Pulses and legumes – Dr Rossi says tinned beans are her top cheap and easy gut-health buy: “They're so versatile and they just take the flavour of whatever you're having.”
• Kiwi fruit – the fibre-packed favourite of gastroenterologist cookbook author Dr Saliha Mahmood-Ahmed. Studies suggest it can also boost the population of beneficial bacteria in the gut.

But, more than any one specific ingredient, the key to happy gut microbes is to eat a wide variety of vegetables, pulses, wholegrains and fermented foods. Adding these plant foods to meals will help ensure a healthy, balanced diet – and generally makes the best use of your shopping budget.

Clare Heal is a London-based chef and fermentation expert. She worked for 15 years on the features desk of a national newspaper, before following her passion for food and retraining as a chef. Clare now divides her time between cooking, teaching, writing and recipe development. She has a particular interest in researching the transformative power of fermentation and puts on supper club events and teaches workshops, sharing her passion for the “four Ks” - krauts, kimchis, kefir and kombucha – which she loves for their deliciousness as well as their contribution to good physical and mental health.

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