Probiotics are live microorganisms that, when consumed in adequate amounts, provide health benefits. They're not all the same. Different strains do different things. Picking the right one matters.
How Probiotics Work
Your gut contains trillions of bacteria (the microbiome). Probiotics are beneficial bacteria that:
Compete with bad bacteria for space and resources
Produce helpful substances like short-chain fatty acids and vitamins
Support immune function (70% of your immune system is in your gut)
Influence the gut-brain axis, potentially affecting mood
They don't permanently colonize your gut. Think of them as temporary beneficial visitors that do good work while passing through.
Strain Specificity Matters
"Probiotic" is like saying "medication." Which one?
Lactobacillus rhamnosus GG - Best studied for diarrhea, especially antibiotic-associated
Saccharomyces boulardii - A yeast (not bacteria) specifically for travelers' diarrhea and C. diff
Bifidobacterium longum - Some evidence for anxiety and IBS
Lactobacillus acidophilus - General digestive support, vaginal health
VSL#3 - High-dose multi-strain, studied for IBD
The strain (that last part after the species name) determines the effect. A product that just says "Lactobacillus acidophilus" without a strain designation is making you guess.
CFU Count: More Isn't Always Better
CFU = Colony Forming Units (live bacteria count)
Marketing says: 50 billion! 100 billion! More is better!
Research says: Effective doses range from 1 billion to 100 billion depending on the strain and purpose. More isn't necessarily better.
What matters: - Survival to the gut (enteric coating or inherently acid-resistant strains) - Strain-specific research at the dose you're taking - Quality manufacturing ensuring viability at expiration, not just at manufacture
When to Consider Probiotics
Good evidence: - After antibiotics (L. rhamnosus GG, S. boulardii) - IBS symptoms (specific strains) - Travelers' diarrhea prevention (S. boulardii)
Moderate evidence: - General digestive discomfort - Immune support during cold season - Eczema in children (specific strains)
Emerging/Limited: - Mood and anxiety - Weight management - Vaginal health
Food vs Supplements: Fermented foods (yogurt, kefir, sauerkraut, kimchi) provide probiotics plus other benefits. They're a good baseline. Supplements offer higher doses of specific strains.