Another over-hyped fad? Not quite. There is some good science behind the fever for fermented food

Kimchi made of Young Radish in Glass Bootle.

Fermented foods have been part of our diet for thousands of years. Beer and wine are classic examples of fermented foods where yeast converts sugars to alcohol. Other types of fermented foods use bacteria, such as Lactobacillus, to make foods like yoghurt, sauerkraut, and kimchi. And when you start talking about bacteria, you move into the realm of probiotics which come with a long list of health claims.

Probiotics and health

Probiotics are live micro-organisms which, when consumed in adequate amounts, offer some form of a health benefit. The clinical evidence for probiotics places treatment of diarrhoea (especially caused by antibiotics) at the top of the list. A potential benefit in treating irritable bowel syndrome looks possible too.

Inflammatory bowel disease, prevention of some infant allergies such as atopic dermatitis, and an overall general protection against infection deserves considering, but the science is still evolving. Researchers are now even looking at direct links between gut bacteria and obesity and metabolic disorders such as diabetes.

Fermented foods in the spotlight

Sauerkraut and kimchi

Two well-known fermented foods with strong cultural ties are the German staple of sauerkraut and the traditional Korean dish of kimchi. Both these cabbage-based dishes are made by lactic acid bacteria fermentation.

Several studies have found that kimchi may be a potent food for its ability to lower cholesterol and control blood glucose. A 2013 study published in the Journal of Medicinal Food found kimchi eaten over seven days had beneficial effects on fasting blood glucose, total glucose, total cholesterol and LDL-cholesterol.


Kefir is an interesting probiotic food, because on the surface it appears similar to yoghurt. Kefir can be made from the milk of any ruminant animal, but is fermented with a different variety of bacteria to yoghurt and uses a starter culture that contains yeast. A scientific review published in 2013 found good evidence for its antimicrobial activity, improved gut health, anti-carcinogenic activity, control of blood glucose and cholesterol, improved lactose digestion and a stronger immune system. Quite an impressive list indeed.


Another popular non-dairy probiotic food is the Japanese staple of natto, which forms the base of miso soup. It is made by the fermentation of soybeans by the bacterium Bacillus subtillis. Natto offers some of the health benefits similar to soy foods, but with additional value coming from its probiotic properties.


Moving out of the realm of solid science, we have an emerging ‘star’ on the fermented food stage – kombucha. Kombucha is made from a sweet tea base that has been fermented with a symbiotic colony of bacteria and yeast. Popular in the health food, juice and detox scene, it is sometimes called ‘mushroom tea’ – getting its name from the brown slimy crust that forms on the surface of the beverage.

Claimed to be a super health elixir with a long list of health benefits, kombucha is one drink where science has yet to catch up, with no human clinical trials published so far. Considering its boutique price premium, unless you plan to make your own, I would be looking elsewhere for my probiotic hit.

The health low down

The long list of health claims made about fermented looks impressive, but the evidence for some of them is still lagging behind. We have been eating fermented foods for thousands of years and they certainly have a role to play in any diet. While not a silver health bullet, when added to a varied diet, fermented foods have the potential to make it even healthier.

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