THP

probiotic

Probiotics

Moderate Evidence
Last reviewed July 2026

Live bacteria that support gut health. Evidence varies enormously by strain — not all probiotics are equal.

Overview

Probiotics are live microorganisms that, when consumed in adequate amounts, confer a health benefit on the host. Different bacterial strains have entirely different effects. Buying a generic "probiotic" without knowing the strain is like buying "medicine" without knowing what it treats. Strain specificity matters enormously when evaluating probiotic evidence. The gut microbiome also responds more to dietary changes (fibre, fermented foods) than to supplementation alone.

Evidence rating

Moderate Evidence

Probiotics have moderate to strong evidence for antibiotic-associated diarrhoea prevention and IBS symptom management. Evidence for immune support and mental health (gut-brain axis) is early but mechanistically compelling. Strain selection and dose are the most critical factors in whether a probiotic will work.

Common uses

  • Strong Evidence
    Restoring gut flora after antibiotic use
  • Moderate Evidence
    IBS symptom management
  • Moderate Evidence
    Immune support
  • Early Evidence
    Supporting mood via the gut-brain axis

Safety & cautions

Worth checking with a pharmacist if you take medication.

Common forms

Multi-strain capsulesBest form

Look for strains with peer-reviewed evidence relevant to your goal. CFU count matters less than strain identity.

Single-strain targeted products

Best when a specific strain has evidence for your goal (e.g. Saccharomyces boulardii for antibiotic-associated diarrhoea).

Food sources

  • Live yoghurtLook for "live and active cultures" on the label
  • KefirHigher diversity of probiotic strains than yoghurt
  • Sauerkraut (unpasteurised)Must be refrigerated. Pasteurised versions contain no live bacteria.
  • KimchiFermented vegetables with live cultures
  • Miso pasteUse in soups but do not boil — high heat kills the cultures.