A randomised controlled trial from Stanford University published in Cell in 2021 compared the effects of a high-fibre diet versus a high-fermented-food diet on the gut microbiome and immune function over 10 weeks. The fermented food group showed significantly increased microbiome diversity and a reduction in 19 of the 22 measured immune markers of inflammation. The fibre group showed improved microbiome function but did not show the same immune modulation. Both are important. The findings do not suggest one is better than the other but confirm that fermented foods have specific and measurable immune effects.
How Fermented Foods Reduce Systemic Inflammation
The bacteria in fermented foods, and the short-chain fatty acids and bioactive peptides they produce, interact with immune cells in the gut-associated lymphoid tissue. They promote the activity of regulatory T cells that suppress excessive immune activation, reduce the production of pro-inflammatory cytokines, and improve gut barrier integrity which prevents bacterial products from entering systemic circulation and driving systemic inflammation. After 40, when immune dysregulation and inflammageing are increasing risks, these effects are particularly valuable.
Best Fermented Whole Foods
- Kefir: fermented dairy or coconut milk containing 30 to 50 distinct bacterial and yeast strains, with good evidence for both gut and immune effects
- Live Greek yoghurt: widely available and affordable, choose full-fat versions with active live cultures
- Sauerkraut: raw, unpasteurised sauerkraut; not the heat-treated jarred versions which contain no live bacteria
- Kimchi: fermented vegetables with diverse bacterial species; also provides prebiotic fibre to feed the bacteria
- Miso: fermented soy paste used in soups and marinades, rich in enzymes and bioactive peptides
- Aged cheese: particularly unpasteurised varieties that retain live bacterial cultures