Gut microbiome research has exploded in the last decade — and so has the marketing of expensive probiotics, prebiotics, and 'gut health' protocols that go far beyond what the science actually supports. The reality is more interesting and more boring than the marketing.
What we know with reasonable confidence
Microbiome diversity correlates with various health outcomes. Diet shapes the microbiome significantly. Fiber feeds beneficial bacteria. Fermented foods add live cultures (with variable but mostly positive effects). Antibiotics significantly disrupt the microbiome, sometimes for months.
What we don't know yet
Which specific bacteria are best for which outcomes (huge individual variation). Whether commercial probiotics actually colonise the gut (mostly they don't — they pass through). Whether expensive 'personalised' microbiome tests deliver clinically useful results (currently weak evidence). Whether supplementing specific strains delivers the benefits attributed to them in research.
What actually works dietarily
Diversity of plants
Aim for 30+ different plant foods weekly. Each plant feeds different bacteria. Adds far more microbiome diversity than any supplement.
Fermented foods
Kefir, sauerkraut, kimchi, miso, yoghurt with live cultures. Stanford study showed measurable microbiome diversity increase from regular fermented food consumption.
Fiber
30g+ daily from whole foods. Soluble fiber (oats, legumes, fruit) feeds beneficial bacteria specifically.
Reducing ultra-processed foods
Emulsifiers and certain additives in UPFs negatively affect microbiome — independent of other dietary factors.
Where commercial 'gut health' products fail
Single-strain probiotics for general 'gut health' (no clear evidence). Expensive prebiotic powders (a serving of beans does the same thing for £0.50). 'Detox' or 'reset' protocols (no evidence base; sometimes harmful). Microbiome testing without specific clinical indication (interesting curiosity, unclear actionability).
Where probiotics genuinely help
After antibiotic courses (specific strains: Lactobacillus rhamnosus GG, Saccharomyces boulardii) reduce antibiotic-associated diarrhoea. Specific strains for IBS (Bifidobacterium infantis 35624 — Align). Vaginal health (Lactobacillus crispatus oral or topical). These are targeted, evidence-based uses.
Gut health responds to diverse whole-food eating more than to expensive supplements. The marketing is decades ahead of the science.