Fermented Foods

•RCT evidence— Wastyk/Sonnenburg Stanford 2021 trial

The landmark Stanford trial

Wastyk et al. (2021) randomised adults to a high-fibre or a high- fermented-food diet for 10 weeks. The fermented-food arm:

• Increased gut microbiome diversity (the high-fibre arm did not).
• Decreased 19 inflammatory markers including IL-6.
• Reduced four immune-cell activation markers.

This was unexpected because fibre was the historical "feed the microbiome" strategy. Both probably matter; the trial suggests fermented foods add something independent.

What "fermented" means here

Live-culture, traditionally fermented foods — not vinegar pickles or heat-treated products that kill the microbes. Refrigerated and label- indicating "live cultures" or "unpasteurised" are the cues.

Practical

• Daily small portions of multiple fermented foods is more useful than one big serving of one.
• Start small if unaccustomed (some get bloating).
• Sugar-loaded "yoghurt drinks" don’t count as functional ferments.
• Sodium content of some ferments (kimchi, sauerkraut, miso) is meaningful; portion sensibly with hypertension.

Caveats

• SIBO and IBS flare in some individuals.
• Histamine intolerance: aged ferments may worsen symptoms.
• Pregnancy: avoid unpasteurised raw-milk products.

Related entries

Dysbiosis, Probiotics, Fiber and the microbiome.