Probiotics, male fertility and semen parameters
This is the only male-specific outcome in the whole corpus where a named product has repeated positive human data — and it is still Grade C, it is not sold in this market, and the guideline has already ruled against routine use.
Semen parameters are the one page here where the evidence runs positive, which is exactly why the reasons it stops at Grade C are set out at the same length as the trials themselves.
Male fertility and semen parameters
Three men-only randomised trials of FamiLact®, all in the same direction. Abbasi 2021 (n=47 analysed, 80 days): concentration p=0.01, motility p=0.04, normal morphology p=0.03 (PMID 33842820 (opens in a new tab)). Gholipour 2026 (n=110, triple-blind, Bonferroni-adjusted): concentration p=0.007, motility p=0.001, morphology p<0.001, beating an antioxidant comparator on morphology and motility but not concentration; semen volume was not met (Time×Group P=0.71), and those figures are adjusted marginal means ± SE from a mixed model, not mean±SD (PMID 41625341 (opens in a new tab)). Asadi 2023, post-varicocelectomy (n=78, 3 months): concentration p=0.046, morphology p=0.016 — with motility p=0.177 and volume p=0.897, both null (PMID 38152072 (opens in a new tab)).
Why it stops at C, and every one of these ships with it. The effect sizes are pharmacologically implausible for this class. Three of the trials test the same Iranian product, and FamiLact carries no ATCC/DSM/CECT/CNCM strain designators anywhere in the public record — so by the FTC's own Example 36 standard, nothing transfers to any other product. There is no independent Western replication. No published human trial of probiotics in men reports pregnancy, ongoing pregnancy or live birth — the one trial with live birth as its primary endpoint (L. rhamnosus CECT8361 + B. longum CECT7347, sponsor Fundación IVI with ADM Protexin and Biopolis) recruited 56 of a planned 280, completed 14 November 2024, and has posted no results and published nothing (NCT04585984 (opens in a new tab)). One trial in this literature cluster has been retracted for concerns about data integrity, with the authors failing to respond or provide original data — and it is still being pooled by two syntheses (PMID 32985280 (opens in a new tab), retracted 28 April 2026). And the DNA-integrity claim printed in one trial's title is null between groups: DNA fragmentation index p=0.55, lipid peroxidation p=0.80, CMA3 p=0.76, with the placebo arm also improving significantly on fragmentation (p=0.03) (PMID 33842820 (opens in a new tab)).
The guidelines have assessed exactly these trials. EAU 2025 added a dedicated section (11.5.1.3 Probiotic treatment), carries the evidence statement "No conclusive data is available regarding the beneficial treatment with prebiotic/probiotic in men with idiopathic infertility; although, they may improve semen parameters" at Level of Evidence 1b, and issues the recommendation, strength Weak: "Do not routinely treat patients with idiopathic infertility with antioxidants, prebiotic/probiotic, selective oestrogen receptor modulators (SERMs) or aromatase inhibitors (AIs)." The same 265-page guideline mentions microbiome, microbiota and Lactobacillus zero times. AUA/ASRM Statement 45 rates supplements "of questionable clinical utility" (Moderate Recommendation, Evidence Grade B) and does not mention probiotics at all (PMID 39145501 (opens in a new tab)).
The mechanism story has an untested step in the middle. No human study has ever shown that an oral probiotic changes the seminal microbiome. The underlying association review (55 observational studies, 51,299 subjects) concludes that "the evidence regarding the impact of the seminal microbiome on fertility is inconclusive" (PMID 32794312 (opens in a new tab)). And the "probiotics increase sperm motility up to sixfold" marketing claim comes from a 9-man, single-arm, non-randomised before/after study that PubMed does not index as an RCT (PMID 28343402 (opens in a new tab)).
One harm signal worth knowing. Postbiotics of L. rhamnosus PB01 (DSM 14870) at concentrations above 15% reduced progressively motile human sperm in vitro (PMID 38892713 (opens in a new tab)).
Products that deliver a qualifying strain at the studied dose: none in this market. FamiLact is an Iranian fertility-clinic product that names no strains. B21060 (Flortec, Bracco) is in none of the 27 teardowns in the frozen founding cohort and in none of the 166 SKUs whose labels we read, and none can be matched to FamiLact because FamiLact names nothing to match.
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? |
|---|---|---|---|---|
| 7 | Semen parameters in diagnosed male infertility | Grade C for Semen parameters in diagnosed male infertility — one positive trial with a material design defect | FamiLact® (no strain designators exist); L. paracasei B21060 in a four-ingredient synbiotic | No — neither is a US retail men's probiotic, and EAU 2025 recommends against routine use |
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. paracasei B21060
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Not printed on any panel this audit has transcribed.
- L. rhamnosus PB01 (DSM 14870)
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Not printed on any panel this audit has transcribed.
- L. rhamnosus CECT8361
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Not printed on any panel this audit has transcribed.
- B. longum CECT7347
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- Seed DS-01 Daily Synbiotic Panel prints “Bifidobacterium longum SD-CECT7347-SP” with no per-organism quantity — the amount is inside a blend total.
Read next
- Probiotics and testosterone in men: the whole chain, end to end The claim starts in one mouse study, and the same strain then failed in men in a trial run by the company that sells it. Every link in the chain.
- Probiotics and erectile function Not "no evidence exists" — the trials that exist are placebo-free, in the wrong populations, using unnamed strains, with unreported effect sizes.
- 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.