Probiotics

Probiotics are live microorganisms — primarily bacteria, but also some yeasts — that, when consumed in adequate amounts, confer a health benefit on the host. The most commonly used probiotic genera are Lactobacillus, Bifidobacterium, and Saccharomyces. Probiotics are found naturally in fermented foods like yogurt, kefir, sauerkraut, kimchi, miso, tempeh, and kombucha, and are also available as dietary supplements in capsule, powder, and liquid forms.

Probiotics work through several mechanisms: they compete with harmful microorganisms for nutrients and attachment sites in the gut, produce antimicrobial substances like lactic acid and bacteriocins, strengthen the intestinal barrier, modulate the immune system, and produce beneficial metabolites including short-chain fatty acids, vitamins, and neurotransmitters. Different probiotic strains have different effects — a Lactobacillus rhamnosus GG supplement does not provide the same benefits as a Bifidobacterium longum supplement, which is why strain-specific evidence matters.

The evidence for probiotics is strongest for antibiotic-associated diarrhea prevention, infectious diarrhea treatment, and certain forms of irritable bowel syndrome. Emerging research explores their potential benefits for mental health (psychobiotics), allergies, metabolic conditions, and inflammatory bowel disease. However, the probiotic supplement market is far ahead of the science, with many products making health claims that are not yet supported by rigorous clinical evidence.

If you're taking antibiotics, your healthcare provider may recommend a probiotic to reduce the risk of antibiotic-associated diarrhea. The most evidence-supported strains for this purpose include Saccharomyces boulardii and Lactobacillus rhamnosus GG, taken during and for 1-2 weeks after the antibiotic course.

For general gut health, incorporating naturally fermented foods into your diet may be more beneficial than supplements, as fermented foods provide a broader ecosystem of beneficial organisms and metabolites. If you're considering probiotic supplementation for a specific condition, look for products with strain-specific evidence and third-party quality testing.