What the evidence actually says about fermented food and your gut

The study

Wastyk and colleagues, published in Cell in 2021, randomised 36 healthy adults to ten weeks of either a high fermented food diet or a high fibre diet. The fermented food group increased microbiome diversity and showed decreases across nineteen inflammatory markers. The high fibre group’s diversity did not move. Thirty-six people is a real finding and a small one, and both of those things are worth saying.

What that means in a kitchen

Servings, climbed slowly. Most people land somewhere around one a day and stop, and that is a perfectly good place to stop. Yoghurt with live cultures, kefir, kimchi, sauerkraut from the chilled section, miso, kombucha. Not a supplement, not a powder, and not a subscription.

Start at one serving a day

For a fortnight. If your gut objects, stay here longer. There is no prize for speed.

Then two

Usually easiest as one at breakfast and one at dinner.

Then four, if you want to

The trial’s higher end. Plenty of benefit sits below it.

Six is the ceiling used in the trial

Not a target, and not better for being higher.

Why we do not sell a microbiome test

The same stool sample sent to different vendors comes back with different verdicts, so the input is not reproducible, and a recommendation built on it inherits that. On top of which, in the trial above, the effect came from the arm that needed no test at all. We would rather tell you that than sell you a kit.