By Joseph E. Scherger, MD, MPH

Core Faculty, Eisenhower Health Family Medicine, Residency Program, Eisenhower Health Center, La Quinta, CA; Clinical Professor, Keck School of Medicine, University of Southern California, Los Angeles

SYNOPSIS: A diet rich in fermented foods from dairy and other sources reduced 19 inflammatory markers compared with a high-fiber diet.

SOURCE: Wastyk HC, Fragiadakis GK, Perelman D, et al. Gut-microbiota-targeted diets modulate human immune status. Cell 2021;184:4137-4153.e14.

Researchers from the Stanford Center for Human Microbiome Studies randomized 36 healthy adults to a high-fiber diet or a diet rich with fermented foods for 10 weeks. Their microbiomes were analyzed before and after the study, along with a variety of inflammatory markers. The high-fiber group ate mainly plant-based, fiber-rich foods. They doubled their fiber intake from 22 grams per day to 45 grams per day, roughly triple the average American intake. The fermented food group went from eating almost no fermented foods to six servings a day of yogurt, kefir, sauerkraut, kombucha, and kimchi. The small study size allowed for a meticulous review of the group compliance.

Those on the fermented food diet showed better diversity of the microbiome, with fewer inflammatory markers and improved immune profiling. These effects were dose-related to the amount of fermented foods. Those on the high-fiber diet showed stable microbiome diversity and no change in these markers. The authors concluded fermented foods may be valuable in improving microbiome diversity and countering the increased inflammation seen in industrialized society.


When I make food selections, I ask three questions: How healthy is the food? Do I like the food? How good will this food be for my microbiome? After all, we are completely responsible for the health and diversity of our “inner garden” that does so much to keep us healthy. For the second question, I remember a quote I read not long ago: There is no such thing as a food you do not like, there are only foods you do not like yet. Pickles and olives were two foods I avoided because of the taste, but now I eat them heartily when I found out how good they were for my microbiome.

High-fiber foods do produce proven health benefits, and Wastyk et al suggested a follow-up study of the combined effects of a high-fiber diet rich in fermented foods. Meanwhile, we should start recommending fermented foods to our patients as part of a healthy diet.