Explainer 1 min read

What Are Probiotics, and Do You Need Them?

Probiotics are live bacteria, added from outside. Most of them don't survive the journey to where they'd need to work.

Reviewed by our gut-microbiome scientists Built on 10+ years of MIT research

The short answer

Probiotic supplements have to survive stomach acid, then compete with the trillions of bacteria already established in your gut. For most people, most of the time, that's a hard ask.

Stomach acid kills a large share of probiotics before they reach the gut.
Even successful strains tend to stop working once you stop taking them.
Probiotics work best for specific, evidence-backed uses, not as a general gut-health fix.

Why most probiotics don't stick around

To work, a probiotic has to survive stomach acid, then compete with the trillions of bacteria already living in your gut. Most don't manage it — which is why effects from probiotics tend to fade once you stop taking them, even when they worked in the moment.

Where probiotics genuinely help

The evidence is strongest for specific situations — recovering the gut after a course of antibiotics, for instance — rather than as a general everyday gut-health fix. For that, feeding the bacteria you already have tends to be the more dependable approach.

Probiotic

New bacteria, added from outside

Live cultures. Most pass through without settling, so effects tend to stop when you stop taking them.

Prebiotic

Food for the bacteria you already have

Fibre that feeds an established community, rather than trying to introduce a new one.

Probiotics and prebiotics aren't competing solutions. They just do different jobs, and one is easier to keep working at than the other.

Feeding what's already there

Rather than adding new bacteria and hoping some of it sticks, we focus on feeding the community your gut already has. Different fibres feed different microbes, so we blend several rather than relying on one. One spoonful, stirred into whatever you're already having.

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