Probiotics

What are probiotics?

Probiotic products contain live microorganisms, most commonly selected bacteria or yeasts. Names such as Lactobacillus, Bifidobacterium and Saccharomyces describe broad groups, but research is often specific to an exact strain — the letters and numbers after the species name can therefore matter. Evidence for one probiotic strain or use should not automatically be applied to another.

Why do people try probiotics?

Some defined probiotic strains and combinations have shown benefits in studies of antibiotic-associated diarrhoea and certain digestive symptoms. The effects are strain- and outcome-specific: findings for one preparation cannot be assumed for every probiotic.

Worth knowing

Evidence is not equally strong for every use. For example, some probiotic preparations have evidence in antibiotic-associated diarrhoea and some gastrointestinal conditions, while evidence for preventing traveller’s diarrhoea is less certain. A probiotic can therefore be reasonable to consider without assuming that every product will work in the same way.

“Probiotic” does not identify one ingredient

Products can contain different genera, species, strains and combinations. Evidence for one defined strain cannot automatically be transferred to another. The same applies to combinations: a blend that has been studied as a blend is not necessarily equivalent to each of its components used separately.

See which identified strains appear in the probiotic product comparison →

How strong is the evidence?

The EU Register contains many non-authorised claims involving microorganisms and proposed effects such as intestinal flora, digestive health or immune defence. Reasons vary: the microorganism may not have been sufficiently characterised, the claimed effect may not have been adequately defined, or the evidence assessed may not have established the proposed relationship strongly enough for that health claim to be authorised.

Live cultures and lactose digestion

EU law authorises a specific claim that live cultures in yoghurt or fermented milk improve lactose digestion of the product in people who have difficulty digesting lactose. The claim has defined culture and CFU conditions, so it should not be generalised into a claim that all probiotic supplements improve digestion.

What is Saccharomyces boulardii?

S. boulardii is a probiotic yeast rather than a bacterial strain. Products should identify it clearly and state the viable amount and storage conditions. Evidence and safety questions remain product-, strain- and use-specific, so its presence is not a general guarantee of benefit. The microorganism is used in both food supplements and medicinal products; classification belongs to the specific product in a specific country, not to the name of the microorganism alone. Check whether the specific product is sold as a food supplement or a medicine in your country.

More strains or more CFUs: is bigger better?

Not automatically. Clinical studies have tested very different probiotic designs. Some investigate a single strain at a particular dose; others investigate combinations of several strains, sometimes with a different total or per-strain dose. Both approaches can produce useful evidence. There is no general rule that a multi-strain product is better than a single-strain product, or that a larger CFU number makes a product more effective. The more useful question is whether the particular strain or combination — at a relevant dose — has human evidence for the outcome you care about.

What should you compare?