Probiotics

Most probiotic bacteria you swallow never make it to your colon alive—stomach acid kills up to 99.9% of them before they reach their destination. The few survivors must then compete with your existing 100 trillion gut residents, which typically outcompete and evict these temporary visitors within days. This is why fermented foods eaten regularly may outperform occasional supplement pills: you're playing a numbers game where consistent reinforcements matter more than one-time invasions.

Élie Metchnikoff, the Russian Nobel laureate who popularized probiotics, believed intestinal bacteria caused aging and that replacing "bad" microbes with Lactobacillus from yogurt could extend life to 150 years. He consumed sour milk daily and died at 71—ironically, we now know he had it backwards: gut diversity, not monoculture replacement, correlates with healthy aging. His flawed reasoning launched a billion-dollar industry that took a century to properly test.

Not all Lactobacillus rhamnosus are created equal—two bacteria with identical species names can have completely different effects depending on their specific strain designation. L. rhamnosus GG might reduce antibiotic-associated diarrhea while another L. rhamnosus strain does nothing, yet most commercial products don't specify strains or use proprietary blends that make replication studies impossible. You're essentially buying a product where the active ingredient's identity is treated like a trade secret rather than a testable medical claim.

That trendy kombucha or raw sauerkraut delivers live cultures to your mouth, but whether those specific strains colonize your gut or provide health benefits remains largely unproven for most fermented foods. Traditional cultures that ate fermented foods daily weren't supplementing—they were preserving food without refrigeration, and any health benefits likely came from the whole dietary pattern, fiber intake, and reduced processed foods. The irony: we've turned survival technology into wellness products while ignoring that pasteurized yogurt with added fiber might work just as well.

The most robust probiotic evidence exists for the most unglamorous condition: preventing diarrhea during antibiotic treatment, where external bacteria can temporarily fill niches that antibiotics cleared out. For most other marketed claims—weight loss, immunity boosting, mood enhancement—the effect sizes are either tiny, inconsistent across studies, or only work for specific disease states, not healthy populations. If your gut ecosystem is already stable, trying to improve it with probiotics is like trying to enhance a rainforest by dropping in random seeds: the established community usually maintains its own equilibrium.

Because probiotics are classified as dietary supplements rather than drugs in most countries, manufacturers can market them without proving they work—only that they're generally safe. This creates a peculiar situation where your doctor might recommend a specific strain with clinical evidence, but the product you buy off the shelf might contain different strains, dead bacteria, or concentrations wildly different from studied amounts. The gap between what research shows about particular strains in controlled trials and what consumers actually experience from commercial products may be wider than in almost any other health category.