Are fermented foods worth the hype?

Fermented foods have become a bit of a buzz word recently with people wanting to improve their gut health, but the chances are you've been eating fermented foods your whole life! About one third of our daily diet is thought to rely on fermentation including bread, chocolate, cheese, yogurt, olives and alcohol.

Generally speaking, any food or drink that relies on microbes to convert simple ingredients into its final product can be classed as a fermented-food. During the fermentation process, microorganisms such as bacteria, yeast or fungi convert organic compounds (such as sugars and starch) into alcohol or acids. This results in a change of taste (often a sour, tangy flavour) and smell of food and preserves its shelf life.

Popular fermented foods that have been associated with gut health benefits include yogurt, kefir, miso, tempeh, sauerkraut, sourdough bread and kombucha.

However, just because something is fermented it doesn’t mean it’s good for you or that it contains live bacteria. This is because it can be killed off during the either heat process i.e. for bread and filtering i.e. wine.  Additionally, unless the bacteria specie has been identified with a documented health benefit, it cannot be termed a probiotic.

However, even without the bacteria, fermented foods may also contain beneficial compounds produced from the fermentation process! Including increased concentration of vitamins such as folate, riboflavin and B12, organic acids which can help improve blood pressure, improve blood sugar control and support the immune system. Fermentation may also remove or reduce toxins and antinutrients.

There have been few well-conducted clinical trials that have looked at the benefits of fermented foods. Several in vitro (outside the human body) and animal studies, using fermented foods such as sauerkraut and kombucha, report encouraging results.

The most widely investigated fermented food is kefir, with evidence suggesting beneficial use in those who struggle to digest lactose. When compared to milk, yogurt also shows more favourable health benefits including weight management.

Fermenting may also lower the gluten content in sourdough bread, making it easier to digest for some individuals. A small study also showed that when compared to wholemeal bread, sourdough bread had favourable effects on blood sugar levels.


In summary, there is very limited clinical evidence for the effectiveness of most fermented foods in gastrointestinal health and disease. However, anecdotal evidence suggests that it can be beneficial for health. It is worth noting the difficulty in undertaking and replicating fermented food studies given the significant variability of cultures and ingredients present. Hopefully, as the popularity of fermented food increases, so will the studies!

Although the evidence for specific health benefits is not currently convincing if you enjoy the taste it is something that should be encouraged as part of a healthy balanced diet. Plus, it cuts down on food waste!