How Fermented Foods May Alter Your Microbiome and Improve Your Health - The New York Times:

1. Apologies if the source is paywalled, but in this case I'm not overly concerned because...
2. This isn't necessarily good science. 36 adults isn't enough to identify results well, and using 2 separate variables with no control group for either means and measuring for different outcomes makes this suspect.

For the study, the researchers recruited 36 healthy adults and randomly split them into groups. One group was assigned to increase their consumption of fiber-rich plant foods, while a second group was instructed to eat plenty of fermented foods, including yogurt, sauerkraut, kefir, kombucha and kimchi.

(Original Cell article summary)

I don’t mean to say that the outcomes aren’t useful per-se, but this isn’t enough data to make any kinds of decisions.