Fermented foods | What are fermented foods?

While fermented foods are nothing new – yoghurt, kimchi, sauerkraut and kombucha have long been dietary staples in many parts of the world – thanks to recent studies looking at the impact fermented foods might have on the gut and immune system, they’re back en vogue and having a bit of a moment. But jars and bottles of funky-looking liquids and preserves can seem intimidating. And not all fermented foods benefit your health in exactly the same way.

In fact, while many fermented foods — including kefir and kombucha — contain probiotics, not all of them do. So in order to find out more about the gut health-boosting benefits of these foods, we’ve consulted research and expert commentary from dieticians to pull together a complete guide to the world of fermented foods. You can thank us later.

What are fermented foods?

Fermented foods are foods that have undergone some kind of microbial growth and fermentation. During this process, microorganisms like yeasts and bacteria break down sugars like glucose into acids, gasses or alcohol. This is what gives fermented foods like yoghurt, kimchi and sauerkraut their distinctive sour flavour, and foods like kefir and kombucha their fizziness.

What are the benefits of fermented foods?

The main benefit of eating fermented foods lies in the live bacteria present in the produce. Dr Emily Leeming, a microbiome scientist, dietician, and creator of the Second Brain newsletter, says when you eat fermented foods, ‘the live bacteria can potentially survive the passage through your stomach to reach your gut microbiome in your lower intestines. They can then influence your gut microbiome and the diversity of your gut bacteria.’

Eating fermented foods can help you absorb some minerals and vitamins more easily, says Dr Leeming. ‘Live ferments like kimchi and kefir contain live bacteria that can potentially reach your gut and contribute to your gut microbiome.’

These types of fermented foods are more beneficial than most because the bacteria aren’t killed off through cooking, she adds. ‘Some ferments, like sourdough bread, pasteurised cheeses and coffee don’t contain live bacteria anymore as the bacteria are killed off when cooking or preserved through heat.’

How often should you be eating fermented foods?

If you’re not already eating fermented foods, it’s definitely worth considering. Dr Leeming says regularly eating fermented foods has been linked to better digestion, and immune and gut health.

‘A study last year by Stanford University found that six servings of fermented foods a day is linked to greater microbial diversity, so more different types of bacteria in your gut, and lower levels of inflammation. They particularly found that an inflammatory protein called IL-6 was reduced, which’s been previously linked to chronic stress, type 2 diabetes and rheumatoid arthritis,’ she says.

‘Even adding a few live fermented foods into your day can be a great way to support your gut bacteria.’

Still not quite sure what counts as fermented food? No stress, we’ve pulled together a list of the best ones to add to your meal plan below…

Top 8 fermented foods

fermented foods kombucha


1. Kombucha

Once relegated to the crammed shelves of kooky health food shops, you’ll now find kombucha in almost every major supermarket in the UK. It’s the ancient Chinese drink that’s taken the beverage world by storm, and it has a whole host of reported health benefits too.

It’s made using tea, sugar, and a symbiotic culture of bacteria and yeast known as a SCOBY. It’s then fermented for 7-14 days, the SCOBY is removed and more tea is usually added. The sugar in the tea acts as nutrients for the SCOBY to feed on, which then creates more live bacteria that make the drink probiotic. Kombucha has also been found to contain vitamins and minerals like magnesium, iron, vitamin B1, 6, 12 and vitamin C.

The bacterial properties of the sour, fizzy drink are thought to help maintain healthy microorganisms in the gut, which can in turn have a positive impact on your overall wellness. Kombucha comes in lots of lovely flavours, ranging from fiery ginger to sweet and sour raspberry.

kefir fermented foods


2. Kefir

Originating in the mountainous region between Europe and Asia, Kefir is a fermented milk drink that’s similar in texture to a thin yoghurt. It’s made by inoculating cow, goat or sheep’s milk with kefir grains, a mixture of bacteria and yeasts.

This process ferments the lactose in the milk, breaking it down and creating lactic acid that tastes sour, and producing carbon dioxide which gives the drink its slight fizz. This also decreases the amount of lactose in the drink by as much as 30%, which some studies have shown makes it more suitable for people who consume a lactose-free diet than unfermented milk.

Kefir also contains a diverse range of bacteria that produce bioactive compounds that are beneficial for gut health and cholesterol levels. Some research has shown that kefir also has properties that protect against infections like salmonella.

It’s also a source of calcium, which is beneficial for bone health, and a range of vitamins like vitamins A, B12, E and K2.

miso fermented foods


3. Miso

If there’s one fermented ingredient you’ve probably heard of, it’s miso. The flavour-bomb paste that’s behind some of our favourite Japanese dishes, it also has plenty of nutritional benefits.

Miso is by fermenting soybeans with salt and kōji, which is a fungus made with white rice. The soybeans can be fermented anywhere between five days and several years, and there are two main types of miso you’ll come across most often in the shops. White miso is a milder variety of miso, and red miso is much darker and richer, owing to its longer fermentation time.

The flavour of miso can also vary depending on additional ingredients like barley or seaweed. It can taste super savoury and meaty, or even fruity and earthy.

Studies show that miso paste is bursting with gut-friendly bacteria and is high in vitamins E and K. Research also says that consuming miso may help to regulate cholesterol and even have anti-ageing effects.

kimchi fermented foods


4. Kimchi

This Korean ‘banchan’ (which means small side dish) is as much about the flavour as it is about the health benefits.

It’s bright red and has bags of spicy, sour flavour that makes it a brilliant addition to rice dishes. It’s made with salted and fermented vegetables, most commonly a type of cabbage called napa cabbage, radishes, carrots and spring onions. Gochujang, a fermented red chilli paste, is added for spice, and you’ll also often find ginger and garlic in jars of the Korean condiment.

The kimchi-making process usually involves salting the vegetables, adding the gochujang and other seasonings and sealing in a jar for a few days, leaving room at the top for carbonation. After fermentation, which takes a few days in the fridge, the kimchi will have a sour, pickly flavour as well as a whole load of nutritional benefits.

The fermentation in kimchi happens due to ‘wild cultures’ already present in the vegetables that reproduce and create probiotic bacteria that some research suggests can regulate and improve symptoms like bloating. Kimchi also contains vitamins A, B, C and K and minerals like iron and selenium.

sauerkraut fermented foods


5. Sauerkraut

You might know sauerkraut as a German Christmas market bratwurst accompaniment more than a health food, but it can actually be a brilliantly beneficial fridge staple.

German for ‘sour cabbage’ sauerkraut is made with finely sliced raw cabbage that’s then layered with salt, jarred and left to ferment. This method of fermentation is similar to making kimchi and makes use of the natural sugars in the cabbage leaves to create probiotic bacteria over the course of a few days in the fridge.

Sauerkraut has a distinctive, sour flavour caused by the lactic acid result of fermentation that works really well in meat dishes and salads to cut through rich flavours.

Sauerkraut is also a high source of vitamins C and K, which are more easily absorbed into the body than in normal cabbage due to the fermentation process. It’s also high in calcium and magnesium minerals, as well as containing that all-important probiotic bacteria that’s so beneficial for gut health and is found in all fermented foods.

yoghurt fermented foods


6. Yoghurt

With lots of exciting, flavourful fermented foods on the market, it can be easy to forget about old reliable probiotic yoghurt. Yoghurt is made from milk that’s been fermented, with bacteria in yoghurt cultures feeding on the sugar present in milk, creating lactic acid. This gives yoghurt its distinctive sour flavour.

It’s high in lots of good stuff, including calcium, potassium and vitamin B12. It’s also mega easy to incorporate into your diet, as it’s great dolloped on curries and spicy dishes, on your breakfast or even mixed into salad dressings or sauces to create a creamy, sour flavour.

When you’re looking for yoghurts with the most benefits in the shops, make sure to check the label for live cultures. This is the part of yoghurt that’s probiotic, and what helps create a lovely, diverse gut microbiome.

tempeh fermented foods


7. Tempeh

Tempeh is tofu’s protein-packed, funky cousin. Originating from Indonesia, it’s made from fermented, cooked soybeans and formed into blocks that are then sliced. Tempeh’s texture can be described as meaty, and you can often see whole beans in slices.

The fermentation of tempeh gives it an unusual taste that can be described as nutty, mushroomy or even a little cheesy. It’s usually used in vegetarian dishes as a meat substitute and can be fried, baked and marinated.

Tempeh is higher in calories than tofu, but it’s also higher in protein and is a brilliant source of fibre, B vitamins and iron, so if you’re following a plant-based diet it’s a winner. While uncooked tempeh has plenty of probiotic bacteria, most tempeh sold in the UK is already cooked, so it’s unlikely to retain the benefits of this good bacteria. However, tempeh is high in prebiotic fibre, which feeds good bacteria in the gut, helping them thrive.

apple cider vinegar fermented foods


8. Apple cider vinegar

If there’s anything you’ve probably already got in your cupboard, it’s this one. It’s the unexpected fermented store cupboard hero. Made from fermented apple juice, apples are crushed, squeezing out the juice, then bacteria and yeast are added to start the fermentation process. The sugars then convert into alcohol, then the alcohol is fermented into vinegar by acetic acid, creating vinegar’s sour taste.

The benefits of apple cider vinegar are widely disputed, but some research shows it may be beneficial for controlling blood sugar levels. Some studies also show that consuming apple cider vinegar may aid healthy weight loss, curbing excessing snacking habits by promoting satiety.

Apple cider vinegar also contains amino acids and antioxidants, which can help boost your immune system, support digestion and provide energy.

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