Probiotics, colds and immunity in men
For colds, the class-level result is the only thing anyone can buy into, and by construction it points at no product. Cochrane 2022, 24 RCTs and 6,950 participants: at least one URTI episode RR 0.76 (95% CI 0.67–0.87), low certainty; antibiotic use RR 0.58 (0.42–0.81), moderate certainty. Cochrane's own authors' conclusion must be carried: "Overall, we found that probiotics were better than placebo or no treatment in preventing acute URTIs." And then the caveats, which are substantial: I²=71%, only 7 of 24 trials had adequate allocation concealment, contour-enhanced funnel asymmetry, roughly 10 of 24 manufacturer-funded, and no strain-level stratification whatsoever (PMID 36001877 (opens in a new tab)). A larger, newer, adults-only, independently funded network meta-analysis of 107 trials and 101,751 adults reports multi-strain RR 0.90 (0.82–0.98) — weaker than Cochrane's 0.76 — with no sex/gender subgroup analysis (PMID 40969681 (opens in a new tab)). Both flagship strain-pair trials in this domain missed their pre-registered primaries (PMID 33296464 (opens in a new tab); PMID 34927036 (opens in a new tab)), and the EU refused the L. casei Shirota immune claim outright (Commission Regulation (EU) No 1171/2011, Annex, claim 1; EFSA reference Q-2010-00137).
Colds and upper-respiratory infection, in one paragraph, with the caveats in the same block as the claim and the row this outcome holds in the 22-row table reproduced below it.
Where this outcome sits in the 22-row table
The grade is assigned on the hub’s 22-row table and argued above. The row is reproduced here unchanged, so the grade a reader quotes from this page is the same grade the table carries. What a grade measures is set out under how the grades work: it is a statement about the strength of the evidence for a named strain, never a statement that a product does anything.
| # | Outcome | Best grade at strain level | The strain, and the trial behind it | Buyable at the dose that was studied? |
|---|---|---|---|---|
| 10 | Colds, and antibiotic use for colds | Grade D for Colds, and antibiotic use for colds — class-level pooled evidence only | Class-level only — RR 0.76 (0.67–0.87); antibiotic use RR 0.58 (0.42–0.81) (PMID 36001877 (opens in a new tab)) | N/A — a class effect points at no product |
The strains named above, and the labels in this audit that print them
Every row below is a line on a printed supplement panel, read off that product’s own teardown. A panel printing a designator is a fact about the panel. It is not evidence that the product was tested, that it delivers the amount that was studied, or that the strain does anything — several of the paragraphs above say in terms that it does not, and the dose is unknowable wherever the panel gives no per-organism quantity.
- L. casei Shirota
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Not printed on any panel this audit has transcribed.
- L. fermentum VRI-003 (PCC)
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Not printed on any panel this audit has transcribed.
Read next
- Probiotics with antibiotics: diarrhoea, and the one strong reason The strongest evidence-backed reason a man might take a probiotic — and the strain that earns it is not in any men’s product at a knowable dose.
- Probiotics for IBS in men: the trial record, strain by strain No human RCT of any named strain, in men only, with an IBS endpoint. What exists: one null sex comparison, two failed primaries, strain by strain.
- Probiotic safety, and who should not take them The pooled safety data are genuinely reassuring, and the literature that produced those nulls did not systematically look. Both halves, with the scope.
- The evidence hub All 22 outcomes in one table, the strain × outcome table, and every other outcome page.
- What to buy, and what not to The verdict, the five reasons a man arrives here, and the products ranked by how much their labels disclose. Two of the five reasons end in nothing.