Probiotics are popular, but the evidence is mixed and the benefit depends on the exact strain. Here is when they may help, and when to save your money.
What probiotics are
Probiotics are live bacteria or yeasts taken as capsules, powders or drinks, intended to benefit the gut. The bowel already contains trillions of bacteria, and a supplement adds only a small number, which mostly pass through.
Where they may help
- Reducing the chance of diarrhoea during a course of antibiotics, for some strains
- Some people with IBS find certain probiotics help bloating or bowel habit, but results vary from person to person
- As part of specialist treatment for some specific conditions
What to know before buying
- The effect depends on the specific strain, not just the species. A study showing one product works does not mean another will.
- Healthy people with no gut symptoms are unlikely to benefit
- If you try one, give it about four weeks. If there is no clear improvement, stop.
- Probiotics are generally safe, but people with a weakened immune system or who are seriously ill should check with their doctor first
Feeding your own gut bacteria
A varied diet with plenty of fibre from vegetables, fruit, whole grains and beans feeds the bacteria you already have. Fermented foods such as yoghurt, kimchi and tempeh can be part of a healthy diet.
Probiotics do not replace seeing a doctor for symptoms such as ongoing diarrhoea, blood in the stool, weight loss or pain.
General information only. Reviewed by Dr Chia Chung King, 2026-11-13. Book a consultation.