A small, carefully run study found that fermented foods changed the gut and lowered markers of inflammation. Here is what it showed, and what it did not.
Andrew Huberman, a neuroscientist at Stanford, has discussed gut health at length on his podcast, including a long conversation with the Stanford microbiologist Justin Sonnenburg. One study from that conversation is worth understanding on its own, because it is often cited and easy to overstate.
The study
In 2021, researchers led by Justin and Erica Sonnenburg and Christopher Gardner published a trial in the journal Cell. They randomly assigned 36 healthy adults to one of two diets for ten weeks. One group increased high-fibre foods such as legumes, whole grains, seeds, nuts, vegetables and fruit. The other increased fermented foods such as yogurt, kefir, kimchi and other fermented vegetables, vegetable brine drinks and kombucha.
What changed
The fermented-food group showed an increase in the diversity of their gut microbes, and the effect was stronger with larger servings. Blood tests also showed that 19 inflammatory proteins went down, and four types of immune cells were less activated.
The high-fibre group did not see the same drop in inflammatory markers, and on average their microbial diversity stayed stable. The researchers had expected fibre to do more, and suggested that some people’s gut microbes may not yet be equipped to make use of a sudden increase in fibre.
Participants in the fermented-food arm worked up to about six servings a day. Huberman has noted that going beyond that amount did not appear to bring further benefit in the study.
Why it matters to us
Fermentation is not a new idea in Thailand or across Asia. Many traditional foods are fermented, and fermented products are one of the categories we look for. This study does not prove that any single product is healthy. It does suggest that regular fermented food can shift the gut in a measurable way over a few weeks.
In a randomised trial, a diet high in fermented foods increased gut microbiome diversity and reduced a set of inflammatory markers over ten weeks.
The trial was small (36 people), short (ten weeks) and in healthy adults. It measured markers in the blood and gut, not long-term health outcomes. Fermented foods vary widely in salt, sugar and live cultures.
Sources
- Stanford Medicine. Fermented-food diet increases microbiome diversity, decreases inflammatory proteins
- Huberman Lab. Dr. Justin Sonnenburg: How to Build, Maintain & Repair Gut Health
- Huberman Lab. 6 Key Tools to Improve Your Gut Microbiome Health
A study is not a product claim. This note summarises published work in plain language and is not medical advice. Andrew Huberman, PhD is not affiliated with LIFTR and does not endorse our products. We link to this work because we learn from it.