Fermented foods and the gut microbiome: yogurt, kefir, sauerkraut

Updated November 14, 2026 Well Day Media Editorial Team

A grandmother and granddaughter fermenting cabbage, jars of pickles on a shelf

The short answerFermented foods such as kefir, plain yogurt, sauerkraut and kimchi may support the gut microbiome. In a 10-week randomized trial at Stanford, a diet high in fermented foods increased microbiome diversity and lowered 19 inflammatory markers. The study was small, so the findings are preliminary.

Key points

In a randomized trial, fermented foods increased gut microbiome diversity.
Levels of 19 inflammatory proteins went down.
The study was small (36 people) and needs confirmation.
Choose unsweetened products and refrigerated sauerkraut or kimchi with live cultures.

What the study showed

Researchers at Stanford randomly assigned 36 healthy adults to a diet high in either fermented foods or fiber for 10 weeks. The fermented-food group gradually increased to about six servings a day of yogurt, kefir, cottage cheese, kombucha, sauerkraut, kimchi and similar foods.

In the fermented-food group, gut microbiome diversity increased steadily, and levels of 19 inflammatory proteins in the blood, including interleukin-6, went down. In the high-fiber group, microbiome diversity did not change over 10 weeks (Wastyk et al., 2021).

The study was small and short, so the findings are preliminary. We do not yet know whether these changes lead to fewer diseases.

Fiber still matters

Fiber feeds the microbes already living in your gut, and high fiber intake has strong evidence for lower risk of chronic disease (Reynolds et al., 2019). The two approaches complement each other.

In practice

Plain yogurt or kefir with fruit at breakfast.
A forkful of refrigerated sauerkraut or kimchi with lunch or dinner.
Choose products without added sugar.
Watch the sodium in pickled vegetables; a Cochrane review links lower salt to lower blood pressure (He et al., 2013).

Frequently asked questions

Are fermented foods the same as probiotics?

Not exactly. Some fermented foods contain live microbes, but the types and amounts vary and are rarely listed. Probiotic supplements contain specific strains in defined doses.

Does shelf-stable sauerkraut count?

Shelf-stable sauerkraut is usually pasteurized, which kills the live microbes. Look for refrigerated products labeled as containing live cultures.

Sources

Wastyk et al. (2021). Gut-microbiota-targeted diets modulate human immune status. Cell 184(16):4137-4153.e14. doi:10.1016/j.cell.2021.06.019
Reynolds et al. (2019). Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet 393(10170):434-445. doi:10.1016/S0140-6736(18)31809-9
He et al. (2013). Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ 346(apr03 3):f1325-f1325. doi:10.1136/bmj.f1325

Prepared according to our evidence methodology and the principles of lifestyle medicine. For education only; it does not replace advice from your doctor.

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Fermented foods and the gut microbiome: yogurt, kefir, sauerkraut

Key points

What the study showed

Fiber still matters

In practice

Frequently asked questions

Sources

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