5 min read
Fermented foods and your gut
What the research says – and what it doesn't
Fermented foods get a lot of attention these days. We looked at what science knows about them, what it doesn't, and why we don't promise miracles from kimchi.
What is the gut microbiome?
Billions of bacteria, fungi and other microbes live in our gut: that's the gut flora, or microbiome. Its make-up differs from person to person and is shaped by many things, such as diet, lifestyle, medication and age.
Researchers are studying its links to health more and more, but many questions are still open.
A much-cited experiment
In 2021, researchers at Stanford University followed 36 healthy adults for 10 weeks. One group gradually ate more and more fermented foods: yogurt, kefir, kimchi, kombucha and fermented vegetables. The other group switched to a high-fibre diet.
In the fermented-food group, the diversity of the gut microbiome increased, and more so the larger the servings. Of the inflammatory proteins measured in the blood, 19 went down. The high-fibre group showed no such change over this period. The study was published in the scientific journal Cell.
What this means – and what it doesn't
It's an interesting result, but worth keeping in proportion:
- it involved few participants and lasted a short time;
- participants ate many different fermented foods, so we don't know how much each one mattered;
- the participants were healthy adults, so it says nothing about illnesses.
The researchers themselves call for further studies. Promises of dramatic changes within a few days don't come from the science.
Why we don't call it 'probiotic'
In the European Union, the word 'probiotic' counts as a health claim. So far the EU has not authorised such a claim for any food.
So we don't put it on kaSi kimchi either, and we don't promise any health effect. What we do promise: it's made with care, the traditional way, and it will taste good.
Who should take care?
- Kimchi is salty, so if you're on a low-salt diet, enjoy it in moderation.
- Fermented foods can contain histamine; if you're sensitive to it, take care.
- It's spicy, so with a sensitive stomach it's worth starting small.
- Traditional recipes may contain fish sauce or fermented shrimp, so always check the allergens.
If you have a medical condition or take medication, ask your doctor before changing your diet.
The bottom line
Fermented foods have been part of many cuisines for centuries, and science is only beginning to uncover what goes on inside them – and inside us. We love kimchi first and foremost for its flavour. The rest we leave to the researchers.
Sources
- Wastyk, H. C. et al. (2021): Gut-microbiota-targeted diets modulate human immune status. Cell
- Stanford Medicine (2021): Fermented-food diet increases microbiome diversity, decreases inflammatory proteins
- Food Safety Authority of Ireland (FSAI): Probiotic health claims
- Regulation (EC) No 1924/2006 on nutrition and health claims made on foods