Small Randomised Dietary Trial • 2021 • Wastyk and colleagues; Cell
Research Summary
This study compared diets rich in fermented foods or plant fibre and examined changes in gut microbes and immune measures. The 17-week investigation included 18 participants in each dietary arm. Fermented-food intake was associated with increased microbial diversity and reductions in several inflammatory markers. The high-fibre intervention produced different microbial changes, with immune responses varying according to participants’ starting microbiomes. This makes the study interesting for understanding the connection between diet, gut ecology and inflammation. However, it was small, relatively short and not designed specifically for an over-60 population. Changes in microbial diversity or laboratory markers are not equivalent to proven prevention of chronic disease. The findings also do not establish that any commercial probiotic, fermented-food product or supplement produces the same effects. It is a useful mechanistic lead, with substantial limits on clinical conclusions.
Evidence and limitations: Small mechanistic trial; biomarkers rather than disease outcomes
Catalogue reference: KL-019. Source reviewed: 27 September 2026. This summary is independent of the publisher.