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The facts on fermented foods

With a rise in popularity for fermented foods in recent years comes a look at their impact on health. Here, Gillian gets clear on what fermented foods are and if they actually have a positive effect on health.

What are they?

Fermented foods/drinks have become very popular over recent years even though they have been consumed worldwide for over 13,000 years! Fermentation is the bacterial (or yeast) conversion of sugar and starch to acids and other by-products, including ethanol. The acidity not only prevents growth of bacteria in food that can spoil food and drink but also creates foods with an interesting sour, tangy flavour.

Fermented local products include yogurt, beer and bread. Across the world fermented products include: Sauerkraut (‘sour cabbage’) from Germany, kimchi from Korea, kombucha from China and kefir from the Caucasian mountains.

Any benefits?

You can’t escape the supposed benefits of fermented foods as they have been touted all over the media. The main area of focus: probiotic content and gut health. A probiotic is defined as live microorganisms that can establish within the gut and provide a benefit to the host. With this interest has come an increased recognition for the importance of looking after our gut microbiota, both for gut and non-gut health outcomes.

At present, there is only a limited evidence base for fermented foods and health in humans as studies to date have produced inconclusive reports.

This is not a negative, just that research has uncovered so many variables that could be at play the outcomes are not clear-cut. Some other interesting areas of research ongoing include: the possibility that fermentation can increase the iron bioavailability from cereals by reducing phytic acid content, which can stop your body absorbing iron. Certain bacteria can also synthesise nutritive compounds, including particular B vitamins all very interesting.


Fermented foods can be included as part of a balanced, healthy diet, although it should be recognised that some have a high salt content such as sauerkraut and kimchi. Fermentation is popular at home and if you do wish to commence this ensure you follow safe food hygiene practices and that you use the correct ingredients, conditions and storage for that particular ferment. Although the evidence for specific health benefits is not currently available, the taste, saving on food waste are all positive!

Just remember if buying fermented foods in the supermarket that are processed by heat, baked or filtrated (e.g. pasteurised sauerkraut, sourdough) these are inactivate as this processing removes the microbes and will not contain live cultures.

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