Do all probiotics work the same way?

No. Effects are strain-specific. The precise strain and dose determine what a probiotic does; 'probiotics' as a general term says little.

Do probiotics keep living in my gut?

Usually not permanently. Much of the effect occurs while they pass through, so regular intake is generally needed.

Are probiotics also found in food?

Yes, in fermented products such as yoghurt, kefir, sauerkraut, kimchi and miso, although the species and amounts vary greatly.

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Probiotics

EN: probiotics · related terms: prebiotics, synbiotics, microbiome

Definition Probiotics are living micro-organisms that, taken in sufficient amounts, confer a health benefit on the host. They are often lactic acid bacteria (such as Lactobacillus and Bifidobacterium) or yeasts. Effects are strain-specific: not every strain does the same thing.

In plain language

Probiotics are living, beneficial micro-organisms that you take in through fermented food or supplements. You find them in yoghurt, kefir, sauerkraut, kimchi, miso and other fermented products. The idea is that you add useful 'team-mates' to your gut team. Important to know: probiotics work very specifically. One strain may help with traveller's diarrhoea, another with recovery after antibiotics, and yet another does something completely different — or nothing. 'Probiotics' as a general word therefore says little; it is about the precise strain and the dose. And they usually do not colonise your gut permanently: much of the effect is temporary, while they pass through. That is why they work best together with a good diet that keeps feeding your own microbes — and that is exactly where prebiotics and synbiotics come in.

The science behind

The recognised definition (Hill et al. 2014, ISAPP) reads: 'living micro-organisms that, administered in adequate amounts, confer a health benefit on the host'. Crucially, effects are strain-specific and cannot simply be generalised to the species or the genus.

• Mechanisms of action. Colonisation resistance against pathogens, strengthening of the barrier, production of bacteriocins and organic acids, modulation of the immune system and interaction with the existing microbiota.
• Transient versus colonising. Most probiotic strains do not settle permanently; the effect generally lasts as long as they are taken.
• Evidence. Strongest for specific indications (for example antibiotic-associated diarrhoea with certain strains); for many general 'wellness' claims the evidence is weaker.
• Quality. Viability until the end of shelf life, correct strain designation and dose are decisive.

In combination with a suitable substrate (prebiotics) we speak of synbiotics. Within holobiont thinking, probiotics are one lever alongside nutrition, sleep and lifestyle — not a miracle cure. My InnerSelfie places them in the context of the full gut environment. This reading is supportive and observational — not a medical diagnosis.

Related concepts

Prebiotics Synbiotics Microbiome Dysbiosis Holobiont

Where appropriate — support: if you opt for probiotic support, the right strain and dose matter; combine them with fibre for a lasting effect. Discover the My Key Nutrients range.

Scientific references

• Hill et al. (2014), ISAPP consensus on the definition of probiotics, Nature Reviews Gastroenterology & Hepatology.
• Prebiotics, Probiotics and Nutraceuticals.
• Emily Leeming, Genius Gut.

Frequently asked questions

What are probiotics?: Living beneficial micro-organisms that, taken in sufficient amounts, confer a health benefit.
Do all probiotics work the same way?: No. Effects are strain-specific. The precise strain and dose determine what a probiotic does; 'probiotics' as a general term says little.
Do probiotics keep living in my gut?: Usually not permanently. Much of the effect occurs while they pass through, so regular intake is generally needed.
Are probiotics also found in food?: Yes, in fermented products such as yoghurt, kefir, sauerkraut, kimchi and miso, although the species and amounts vary greatly.