Is all fermented food probiotic?

Last updated: 01-08-2025

When you take a sip of kombucha or taste a bite of kimchi, you might automatically think: “Great, another dose of probiotics!” But did you know that not every bacterium in fermented foods may officially be called a probiotic? Time to clear up that misunderstanding.

What do we actually mean by ‘probiotics’?

The scientific definition (Hill et al., 2014) states that a bacterial strain can only be called probiotic if it provides clinically proven health benefits in humans. In the United States, bodies such as the FDA and the International Probiotic Association actively monitor this.

In short, a probiotic must…

• Be alive at the moment of consumption
• Be identified down to the strain level
• Demonstrate a controlled human benefit
• Be taken in sufficient amounts

Europe still lacks such a clear quality mark. Want to know which strains are proven effective and in what amounts? Check the US Probiotic Chart.

Fermentation ≠ probiotics

Fermentation is a natural process in which microorganisms convert sugars in food into acids, gases and flavour compounds. Some of those bacteria can be probiotic, but most are simply “friendly household residents” without solid clinical data.

Still, you benefit: while they “eat” the vegetables, these microorganisms secrete various metabolites (such as short-chain fatty acids and vitamins) that your body can absorb. That makes fermented foods a genuine diversity booster for your own micro-zoo.

What can you do with this information?

1. Keep rotating: combine fermented favourites (kimchi, kefir, tempeh) with products that do contain a registered probiotic strain.
2. Read the label: besides listing live bacteria and their strain-level names, a good extra check is whether a product is pasteurised. If it is, it no longer contains live cultures and therefore has no probiotic effect.
3. Measure your microbiome: use the MyMicroZoo test to discover which residents already live in your gut and where there’s room for reinforcement. You might not need extra probiotics at all!

Sources:

Hill, C., Guarner, F., Reid, G., et al. (2014). Expert consensus document: The ISAPP consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews 

Gastroenterology & Hepatology, 11(8), 506-514. https://pubmed.ncbi.nlm.nih.gov/24912386/