# A Guide to Fermented Foods: What They Are and Why You Should Eat More of Them

> Fermented foods have been part of human diets for millennia. Here is what they are, how they are made and what the evidence says about their health effects.

*Section: Food — By Sofia Reyes (Culture & Entertainment Writer) — Published January 11, 2026 — 2 min read*

Canonical URL: https://dailyjunction.org/food/guide-to-fermented-foods
Tags: fermented foods, probiotics, gut health, kombucha, kimchi

## Key takeaways

- Fermentation uses microorganisms to convert carbohydrates to acids, gases or alcohol, preserving food and changing its nutritional profile
- Fermented foods are a natural source of probiotics (live beneficial bacteria) and prebiotics (food for beneficial bacteria)
- Research on gut microbiome diversity links fermented food consumption to better health markers
- Sourdough, kimchi, kefir, live yoghurt, sauerkraut, miso and kombucha are the most accessible fermented foods

## What fermentation is

Fermentation is the metabolic process by which microorganisms — bacteria, yeasts, moulds — convert carbohydrates into acids, gases or alcohol in the absence of oxygen. Humans have used fermentation for at least 13,000 years, initially as a preservation method. Fermented foods include bread (sourdough), dairy (yoghurt, kefir, cheese), vegetables (sauerkraut, kimchi), soy products (miso, tempeh), vinegar, tea (kombucha) and alcoholic drinks.

## Why fermented foods may be good for you

A landmark 2021 Stanford study found that a 10-week diet rich in fermented foods increased the diversity of gut microbiome species and reduced markers of immune activation (inflammation). The effects of fermented foods on gut microbiome diversity are more consistent in the research than those of probiotic supplements, possibly because they contain a wider range of microbial species and the food matrix facilitates their survival through the digestive system.

## The most accessible options

Live yoghurt (check the label for "live cultures" — pasteurised yoghurt after fermentation has had the bacteria killed): the most widely available and affordable fermented food, good evidence for gut health and calcium source. Kefir (fermented milk drink with a diverse microbial profile): growing evidence for lactose intolerance tolerance (kefir fermentation breaks down much of the lactose) and gut health. Sauerkraut and kimchi (fermented cabbage): rich in beneficial bacteria and fibre; can be made at home cheaply. Miso (fermented soybean paste): used in Japanese cuisine, a versatile ingredient with good probiotic content (add to dishes after cooking to preserve bacteria). Sourdough: the long fermentation breaks down some gluten and phytic acid, though most commercial "sourdough" is not genuinely fermented.

## Making your own

Fermented foods are among the more accessible DIY food projects. Sauerkraut requires only cabbage and salt (two to four weeks at room temperature). Sourdough requires flour and water. Kefir requires kefir grains and milk. The barrier to entry is mainly time and the willingness to have live cultures in your kitchen.

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## Sources

- [BBC Good Food](https://www.bbcgoodfood.com)
- [Delicious Magazine](https://www.deliciousmagazine.co.uk)

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