What Is the Gut Microbiome?
The human gut contains approximately 38 trillion microorganisms — bacteria, fungi, and viruses — collectively referred to as the gut microbiome. This community influences digestion, immune function, mood, skin health, and metabolic processes. Disruption of the microbiome (dysbiosis) has been associated with conditions ranging from inflammatory bowel disease and irritable bowel syndrome to depression, obesity, and type 2 diabetes.
Where Probiotics Actually Work
The clinical evidence for probiotics is strongest in specific areas:
- Antibiotic-associated diarrhoea — Lactobacillus rhamnosus GG and Saccharomyces boulardii have strong evidence for preventing diarrhoea during and after antibiotic treatment.
- Irritable Bowel Syndrome (IBS) — Multiple strains show benefit for bloating, pain, and altered bowel habits, though responses are highly individual.
- Clostridium difficile infection — Particularly in preventing recurrence when combined with antibiotic treatment.
- Infant colic and eczema prevention — Emerging evidence supports probiotic use in early life for reducing atopic disease risk.
Choosing the Right Probiotic
Not all probiotics are equivalent. The strain, dose (measured in CFU — colony-forming units), and formulation all matter. A probiotic that works for IBS may not address antibiotic-associated diarrhoea. Look for products with specific strain designations (not just “Lactobacillus acidophilus” but the full strain identifier), a dose of at least 1 billion CFU, and viability guaranteed through the expiry date — not just at time of manufacture.
