Fermented foods (kefir, raw sauerkraut, kimchi)
The cleanest trial on the microbiome was on foods, not capsules. So start there.
The short version
What it does Ten weeks of fermented foods increases gut bacterial diversity and lowers inflammatory markers. It is the only “microbiome” intervention on this site resting on a clean trial — and it costs the price of a jar.
What it does not do It is not a treatment: not for irritable bowel, not for inflammatory bowel disease. And if you already bloat, start very gently or skip it — fermentation can make things worse before better.
What the studies say
Wastyk’s trial, published in Cell, allocated participants between a high-fibre diet and a diet rich in fermented foods, over ten weeks. Only the “fermented foods” group showed an increase in microbial diversity and a fall in nineteen inflammatory markers. It is an unusually clean result for this field.
Modest numbers, ten weeks, and an effect measured on biological markers — not on an illness avoided. The trial does not say which fermented food counts most, or how long the effect lasts if you stop. And it says nothing about probiotic capsules, which were not tested.
Before buying a probiotic, try ten weeks of kefir and lacto-fermented vegetables. That is what was tested, it costs ten times less, and it feeds you.
How to take it
Relevant for just about everyone, and particularly if your diet is low in plants. TO BE RULED OUT in severe immunosuppression, and to be introduced very cautiously if you already bloat or have irritable bowel.
Two portions a day is the target. One portion = a glass of kefir, two spoonfuls of raw sauerkraut, a small serving of kimchi. Start with one spoonful a day for a week and build up gradually: a sudden introduction produces gas and makes everyone stop.
Allow six to ten weeks, as in the trial. The useful sign is not an immediate sensation but more regular transit and less bloating by the end of the period. Gas in the first days is expected; if it persists beyond two weeks, drop the dose.
What is inside
Milk or water kefir, raw sauerkraut, kimchi, plain yoghurt, kombucha, unpasteurised miso. What they share is the presence of LIVE bacteria, which pasteurisation destroys.
One criterion decides: the product must be in the CHILLED AISLE and carry “unpasteurised” or “live cultures”. Sterilised tinned sauerkraut is an acidic vegetable, nothing more. Look at the salt too: lacto-fermented vegetables are high in it, which matters if you watch your blood pressure.
Anything pasteurised, sterilised or tinned. Very sugary kombuchas, which mostly deliver sugar. And large quantities from the start, which guarantee you give up after three days.
Cautions
- Severe immunosuppression: medical advice
- Irritable bowel: very gradual introduction
- High salt content of lacto-fermented vegetables
The three options
Farmhouse milk kefir, live cultures
No link: Amazon does not do fresh
A farmhouse milk kefir with live cultures is found at the producer, in an organic shop or in the supermarket chiller. Never in a parcel.
For whom — Anyone who wants the product closest to what was tested in the trial.
Nothing to buy here — the text above explains why.
Lacto-fermented cabbage in a jar
3 in stock, and “unpasteurised” is not stated
That is the whole question: pasteurisation preserves the jar and kills the ferments. The page says “lacto-fermented” without specifying. For the rest: organic white cabbage, 380 g, 20 reviews, the only one in the aisle claiming fermentation rather than cooking. If it fizzes and tastes sour on opening, the ferments are alive.
For whom — To start with fermented foods without making anything yourself.
Make your own kefir
Fresh, neither powdered nor dried
40 g of milk kefir grains, 2,158 reviews. The difference matters: fresh grains get back to work within a day, while freeze-dried sachets last one or two batches and then give out. These multiply: one purchase, and you produce your own kefir indefinitely.
For whom — The cost tends towards zero, and it is the most ancestral thing in this whole catalogue.
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