From kombuca to kimchi (that’s fizzy tea and pickled vegetables) fermented foods have earned themselves a gut-friendly following, but do they really benefit our bellies?
What are fermented foods?
Though they’ve only become trendy in recent years, fermented foods are nothing new. In fact, they’ve been part of our diets for thousands of years, because prior to refrigeration, fermentation was used to preserve and store food.
So what is fermentation? Fermentation takes place when harmless bacteria consume the natural sugars in foods (like vegetables, fruit and milk), converting them to organic acids and carbon dioxide.
This process gives the food a slightly sour, tangy taste but also prevents harmful bacteria from growing, making fermentation the ideal way to prevent food from spoiling, as well as giving an entirely different flavour and texture.
Fermented foods come in many forms, including sourdough bread, yoghurt, kefir (a fermented milk drink), cheese, chutneys, pickles, miso and tempeh.
Why are fermented foods linked with gut health?
The gut-friendly benefits of fermented foods are down to the lactic acid bacteria that convert natural sugars to lactic acid during fermentation.
Lactic acid bacteria are a large family of helpful bacteria that have been found to have probiotic (i.e. beneficial) effects in the body. Lactic acid bacteria include two groups known as Lactobacillus and Bifidobacterium. These helpful warriors are found in huge amounts in our colons (large intestines), where they help digest food, regulate inflammation and prevent the growth of harmful bacteria.
Experts think if the helpful bacteria in fermented foods can survive the journey to our colon, they could benefit our health. The difficulty is, the journey from mouth to colon is a long one, and requires these helpful bacteria to survive very strong stomach acid. So which (if any) fermented foods actually go the distance?
A fermented experiment
To answer this question, researchers from the UK TV series Trust Me I’m a Doctor carried out an experiment involving 30 volunteers who were split into three groups. The first group was asked to drink a daily probiotic yoghurt drink; the second group was asked to drink a daily dose of kefir, and the third group was asked to eat plenty of foods rich in prebiotics – sugars bacteria like to feed on.
Stool samples were sent off and changes in gut bacteria were mapped over a period of 4 weeks. At the end of the study, the kefir group experienced the largest rise in the numbers of lactic acid bacteria, the type that can benefit gut health.
So far so promising. However, this doesn’t mean all fermented foods pass the test. In another experiment by the same team, various fermented foods were tested for levels of lactic acid bacteria. The foods included soft cheese, sauerkraut (fermented cabbage), kimchi (fermented vegetables), kefir and kombucha (fermented tea). In this experiment, the researchers looked at both homemade versions, and shop bought samples.
Results showed that the shop bought sauerkraut, kimchi and soft cheese didn’t contain any of the helpful bacteria, probably because they were pasteurised (heat treated) which kills off both helpful and harmful bacteria. The unpasteurized shop-bought kefir and kombucha did contain helpful bacteria from the lactobacillus family, as did all the homemade fermented foods.
Are fermented foods for everyone?
Humans have been eating fermented foods safely for thousands of years, and you’ve probably eaten your fair share (olives, yoghurt, wine) already. Although there’s good reason to think fermented foods can big up the levels of helpful bacteria in your gut, there’s not enough research to show what difference this makes to our long-term health. As for claims that fermented foods can cure certain diseases… well, that’s just hype.
Fermented foods might not be helpful for everyone either. For people with IBS (irritable bowel syndrome) some types of fermented foods (sauerkraut, kefir and pickled vegetables) may actually make symptoms like gas, bloating and pain worse, because they can contain high levels of FODMAPs, a group of sugars that can aggravate symptoms.
The bottom line is that we need more research into fermented foods, but for most of us, there’s no harm in trying them. Just remember, they’re no magic potion, although they can be mighty tasty.
Fermented foods figured out
| Fermented food | What is it? | Try it… |
| Kombucha | Fizzy fermented tea | Instead of a fizzy drink – it has lower levels of sugar! |
| Sauerkraut | Pickled cabbage | As a topping in sandwiches |
| Kimchi | Pickled vegetables | Fried with rice and topped with an egg |
| Sourdough | A traditionally leavened bread | Toasted with avocado or a bowl of soup |
| Miso | A fermented soy bean paste | As a marinade for fish, or as a base for a noodle soup |
| Tempeh | Fermented soy beans, similar to tofu | Marinated in a sesame noodle stir fry |
| Kefir | A fermented milk drink | In smoothies, soda bread or as a drink! |
