Updated 27th March 2026
Are fermented foods bad for your heart?
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This morning, you might have noticed a flurry of headlines warning that "gut-friendly foods could harm heart health."
At first, our collective hearts skipped a beat. ZOE (and your gut microbiome) are huge fans of fermented foods and fiber-rich plants.
So, what’s going on?
The story comes from a British Heart Foundation (BHF) statement, but, thankfully, the message is much more measured than the headlines suggest. We are totally onboard with their point, and it’s an important one to share.
Gut health is everywhere
At ZOE, we are proud to be part of the gut health revolution. It is now well established that gut health is health.
A thriving population of gut bacteria is associated with a wide range of beneficial health outcomes and a reduced risk of developing certain conditions.
There’s also good evidence that supporting gut health can help keep your heart healthy.
However, there’s a downside to the meteoric rise of gut health: Its popularity means that it’s profitable, so shops are filled with “gut health” claims that are hiding the product's true impact.
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The BHF’s note of caution
As BHF points out, probiotic foods can be great for your gut, but to make them more palatable and profitable, manufacturers often add other ingredients that make them less healthy overall.
Some of these products contain high levels of salt or sugar, both of which can be bad for your heart if consumed in large amounts.
A salt- and sugar-rich diet can increase blood pressure, putting strain on your heart and blood vessels. Both sugar and salt also make foods easier to overeat, potentially encouraging weight gain, which can also affect heart health.
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Shopping guide to healthy ferments
Here are some tips to make sure you get the best probiotic foods to support your gut and heart:
Many shop-bought kombuchas and some kefirs sneak in added sugars. Look for low- or no-added-sugar varieties.
Fruit yogurts often contain added sugars, sweeteners, or colorants. So, opt for a natural or Greek yogurt with very few ingredients. And if you like a fruity twist, simply add some berries (frozen or fresh). ZOE has a guide to buying yogurt that could be useful.
Sauerkraut and kimchi are naturally high in salt, so if you are salt-sensitive, have high blood pressure, or are watching your sodium levels, stick to smaller portions or choose a different ferment. There are some low-salt versions available. With that said, some evidence suggests that kimchi doesn’t impact blood pressure and may even help lower it.
Some fermented products are pasteurized. As part of this process, both good and bad microbes are killed, reducing (though not completely eliminating) gut health benefits. So, look for “contains live cultures,” or similar on the label.
If you’re feeling adventurous, you could even try fermenting at home. ZOE has a super simple guide to get you started.
A note on smoothies
Smoothies are often sold as “gut healthy,” too. Although they’re not fermented, they can contain lots of plants, which should be a good thing. However, when they’re blended, much of the fibre is lost, meaning there’s less for your gut bacteria to eat.
This lack of fibre also means that any sugars (added or otherwise) can enter your blood more quickly, which causes damage to your blood vessels in the long run.
As with the other products we mentioned above, it’s a good idea to check smoothies for added sugars and other unnecessary additives.
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What should you do?
Fermented foods can support your gut health, and that’s great. Sadly, now that Big Food has caught onto the gut health craze, we have to be a little more discerning. Gut health washing is a real thing!
So, when you’re looking to buy a fermented product, check the label for ingredients. It’s best to avoid any with lots of names you can’t understand, and particularly look out for added sugar and salt.
We have a useful guide to common food additives if you’d like to dive a little deeper. Also, to get the most out of fermented foods, make sure that they contain live cultures.
Another thing to be wary of is that manufacturers often hide sugar on food labels by using different names, such as agave syrup or cane crystals. But it’s still sugar.
To help, we created a guide to avoiding added sugars, which includes 42(!) alternative names for sugar you might see in the store.
If you’d like to learn more about fermented foods, try these next:
Alternatively, watch this episode of the ZOE Science & Nutrition podcast with Prof. Tim Spector. It covers the latest research into fermented food and health.
