Fermentation is one of the oldest food preservation methods there is, and virtually every food culture in the world has its own version of it. Yoghurt, cheese, bread, vinegar, wine, beer, soy sauce, kimchi, miso, sauerkraut, kefir: these are all products of fermentation, meaning they've been transformed by the activity of bacteria, yeasts, or moulds in ways that change their flavour, texture, and nutritional profile.
The recent interest in fermented foods isn't purely about tradition. Research into the gut microbiome has given the scientific community a reason to look at these foods differently, and what they've found is reasonably consistent: regular consumption of fermented foods appears to support a more diverse and settled gut microbiome, and may have downstream effects on digestion, immune function, and mood.
What fermentation does to food
During fermentation, microorganisms consume sugars and starches in the food and produce acids, gases, and sometimes alcohol as byproducts. This process changes the food in several useful ways. It can increase the bioavailability of certain nutrients, making them easier for the body to absorb. It can reduce compounds that some people find digestively difficult, which is part of why sourdough bread and aged cheeses are better tolerated by many people than their conventional equivalents. And in the case of live fermented foods, it introduces beneficial bacteria directly into the digestive system.
The key distinction is between fermented foods that still contain live bacteria when you eat them and those that have been heat-treated after fermentation, which kills the bacteria. Pasteurised sauerkraut and most commercially produced yoghurts fall into the latter category. Products labelled as containing "live cultures" or unpasteurised versions are the ones where you'd expect to find active bacteria.
"Every traditional food culture has its own ferments. The gut microbiome didn't wait for modern research to tell it what was good for it."
The most accessible options
Natural live yoghurt is the easiest starting point. It's widely available, most people already eat it, and the research behind it is well-established. Greek yoghurt with live cultures, eaten a few times a week, is a reasonable foundation for anyone new to thinking about fermented foods.
Kefir is a fermented milk drink with a sharp, slightly fizzy quality that takes a little getting used to. It tends to contain a wider variety of bacterial strains than yoghurt and is available in most supermarkets. A small glass a day is the kind of habit many people find easy to sustain once they've adjusted to the flavour.
Kimchi and sauerkraut, the fermented cabbage preparations from Korean and Central European cooking respectively, are good options for those who prefer something savoury. A small spoonful alongside a meal, rather than as a main feature of it, is a low-commitment way to include them regularly.
Miso, the Japanese fermented soybean paste, is versatile and easy to use. Stirred into warm (not boiling) water with a little seaweed and tofu, it makes a quick broth. Added to dressings or marinades, it brings depth of flavour as well as its microbial content.
If you have a digestive condition, a history of gut sensitivity, or you're considering significantly increasing fermented foods in your diet, a nutritional therapist can help you approach this in a way that suits your particular situation. Some people with specific gut conditions need to introduce fermented foods gradually and with guidance. Welvow can help you find qualified practitioners in your area.
Find your practitioner →Fermented foods don't need to be eaten in large quantities or every day to be useful. A little, regularly, is generally where the value sits.