The ‘Five K’s’ are considered key for optimal gut health – here's what a nutritionist wants you to know

Jul 18

Since gut health entered the chat we’ve been on a mission to improve ours. Here, a nutritionist explains the role that fermented foods – specifically, the five k’s – has to play.

While nutrition has long dominated the health space, gut health is a fairly new discovery to the many of us who don’t have a background in science. And yet, it’s quickly become a core focus.

The online grocery store Ocado recently shared that there has been a 247% uptick in searches for ‘gut health’ on its website since 2021. It makes complete sense – gut health has been associated with many of the body’s essential processes, from breaking down food to absorbing nutrients.

“The gut plays a significant role in our overall health; it’s a primary barrier for preventing unwanted viruses, pathogens and bacteria to pass into our bloodstream,” explains nutritionist Jenna Hope. “It’s important for supporting digestion and nutrient absorption, and plays a vital role in supporting immune health, brain health and heart health.” According to Hope, having a healthy gut can contribute to improved sleep health, mental health and cognitive function along with better digestion and energy.

There are still many unknowns about the gut, its many roles within the body and the ways in which it can be nurtured. One popular theory, however, is that gut health can be improved with the help of the ‘five K’s’ – a group of fermented foods said to have a host of nutritional benefits. Is it worth working them into your diet for a healthy gut? We asked Hope for a full debrief.

What are the Ks of gut health?

In short, the K’s are five fermented foods that are believed to have a positive influence on the gut, each beginning with the letter k. Food fermentation – the process of changing the properties of ingredients – has been around for thousands of years with the purpose of preserving perishable food and drink and making some unpleasant-tasting produce, such as olives, more palatable. Now, because fermentation facilitates the growth of bacteria, we also use it to make foods that are rich in probiotics which research suggests are beneficial for digestive health.

“The five K’s can be a great way to incorporate foods containing live cultures and fibre into your diet,” says Hope. “There is evidence to support fermented foods and their role in promoting a healthier gut profile.” So, what are they?

Kefir

A tangy, creamy drink that resembles a thin yoghurt, kefir is shoppable at most major supermarkets in the UK, and comes in a variety of flavours if the zing isn’t quite to your taste. “It contains a wider range of live bacteria species than yoghurt, making it a perfect option for supporting a healthy gut,” says Hope. “It’s also high in key nutrients such as vitamin D, calcium and protein.”

If you follow a vegan diet, or you can’t tolerate dairy, there are a growing number of water kefir alternatives available. They don’t quite have the same nutritional profile as milk-based kefir, but they’re still packed full of probiotics.

Kimchi

Kimchi is a Korean dish made from salted vegetables, often including cabbage, commonly seasoned with chilli, garlic and ginger, among other delicious flavourings. It tastes sour and savoury, and sometimes fizzy from the fermentation.

“Much like many fermented foods, kimchi is great for delivering live beneficial bacteria to the gut,” says Hope. “It’s also high in fibre, which is important for optimising bowel habits and feeding the beneficial bacteria.”

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Kraut

“Otherwise known as sauerkraut, kraut is fermented cabbage which provides similar benefits to the gut as kimchi does,” says Hope.

It has a crunchy texture and a sour flavour like pickle. “It’s a great source of live bacteria to help sow the seeds for a beneficial gut Microbiome,” Hope adds.

Khorasan sourdough

Khorasan is an ancient variety of wheat with a higher protein content than many varieties of wheat we often eat. “Khorasan sourdough is rich in fibre and contains live bacteria – it’s also often tolerated better than regular bread for those who find gluten difficult to digest (though, not for those with coeliac disease),” says Hope. This is due to the fermentation process breaking down some of the gluten meaning there’s less gluten in the bread by the time you consume it.

Typically, sourdough is made using white or whole wheat flour, so Khorasan sourdough isn’t easy to come by. You may find it in an independent bakery or, if you’re into baking, you can purchase the flour online. Not a problem if you can’t locate it, though – all sourdough has health benefits. A 2021 study found that consumption of sourdough bread facilitates better food digestion, promotes better nutritional uptake of minerals and vitamins and also improves gut health.

Kombucha

You may already be a fan of this zingy, sparkling drink. “Kombucha is a fermented tea which, when well made, can provide an array of live bacteria to support and optimise a healthy gut,” says Hope. She caveats that not all kombucha is created equal – particularly now it’s so popular. “Many will have added sweeteners, and in some cases the live cultures may not survive the stomach acid to reach the gut,” she warns.

Do fermented foods help gut health?

Fermented food contains beneficial live bacteria which is essential for obtaining a healthy gut, according to Hope. “When we consume fermented foods, the live bacteria can embed themselves into the gut. Eating plenty of plant foods can help these bacteria to grow, thrive and survive. The bacteria produces byproducts known as short chain fatty acids (SCFAs) – it’s these SCFAs which can communicate with other parts of the body in order to optimise health.”

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Research supports Hope’s enthusiasm for fermented foods. One 2022 study concluded that kefir, specifically, may create alterations in the gut microbiota composition (in short: microorganisms, including bacteria, fungi, and viruses that live in the digestive tracts).

Basically: a big yes to fermented foods – including the five K’s – for gut health.

How do I improve my gut health?

If you’re keen to incorporate the five K’s into your diet, Hope recommends doing this slowly over time. “Ensure you’re starting off by adding one very small serving – one to two teaspoons – to your daily diet, and then gradually increase this over time to a few servings of one to two tablespoons per day,” she says. Any more, and you may experience gas and bloating as your body hasn’t adjusted.

Of course, fermented foods aren’t necessarily for everyone – nor are they always easily accessible (or within budget!), and Hope assures that you can still have a healthy gut without eating the five K’s.

“I recommend increasing your fibre intake very gradually as it’s a great place to start when it comes to improving your gut health,” she says. She also advises limiting your intake of artificial sweeteners, which can be detrimental to gut health.

“Along with diet, lifestyle factors play an important role too. Try to focus on ensuring you’re getting eight hours of sleep per night where possible, and limiting stress or engaging in mindfulness activities regularly where you can.”

Wade Brimage