Every supplement featured on LeanBiome Reviews follows a structured five-step research process. This process is designed to produce honest, evidence-based assessments that serve readers rather than just generating affiliate revenue. Here is exactly how it works and why each step matters.
We search PubMed — the US National Library of Medicine’s database of over 36 million biomedical literature citations — for clinical studies on each ingredient. We use structured search terms combining the ingredient name, strain designation (where applicable), and outcome measures (“weight loss,” “body fat,” “gut microbiome”). We prioritise randomised controlled trials, then systematic reviews, then meta-analyses, then observational studies. We record study design, sample size, primary outcomes, and PMID for every citation we include.
We assess each study on four criteria: study design (RCT is gold standard), sample size (larger samples reduce bias and increase statistical power), relevance (is the dose and population comparable to the supplement’s use case), and publication quality (peer-reviewed indexed journals score higher). We rate ingredient evidence as Strong (human RCT with statistically significant outcomes), Moderate (human trials with positive trends but limitations), or Limited (animal data or in-vitro studies only). We do not cite animal-only evidence as if it were human evidence — a common misrepresentation in supplement marketing.
We compare manufacturer marketing claims against the clinical evidence we independently located. Claims directly supported by human RCTs are labelled evidence-backed. Claims that extrapolate from animal studies or cite trials with different strain designations, doses, or study populations are flagged. We verify manufacturing certifications (FDA registration status, GMP certification) independently where possible. We check whether “FDA-registered” is being confused with “FDA-approved” — a common misleading claim in the industry.
We analyse verified purchaser reviews systematically, looking for consistent patterns in both positive and negative feedback. We specifically examine timing (how long before results emerge), result type (what changes users actually report), frequency of complaints, and whether the refund policy functions as described. We look for signs of fake review patterns — unusual five-star clustering with no critical reviews — and note when feedback distributions are authentic vs potentially manipulated.
We compare each product against 3-4 direct competitors on ingredient evidence quality, probiotic strain count and specificity, delivery technology, price per month, and guarantee terms. We use neutral language and specifically require that our affiliate product does not win every comparison category — accurate neutral comparison is more useful to readers and ultimately more trustworthy than promotional comparisons. The comparison for LeanBiome is available on our vs competitors page.
When we write PMID: followed by a number and link to PubMed, it means the study is registered in the US National Library of Medicine, is peer-reviewed, and we have read the abstract and verified that the finding cited matches the study’s actual reported outcomes. We never cite a study based solely on a secondary source or a manufacturer’s summary. If a study is behind a paywall and we cannot access the full text, we cite only what is verifiable from the abstract and note this. This standard means our citation count is lower than some review sites, but every citation is independently verifiable by any reader with internet access.
Our Transparency sub-score assesses whether individual ingredient dosages are disclosed, whether manufacturing claims are independently verifiable, and whether affiliate relationships are clearly disclosed. Products using proprietary blends receive a Transparency cap of 3.5/5 because individual dose verification against clinical benchmarks is impossible. This applies to LeanBiome and is stated clearly in our review — see the full LeanBiome review for the complete scoring breakdown.
Our primary sources are PubMed, the Cochrane Library, and peer-reviewed journals accessible through open-access or institutional access. For gut health specifically, we also consult the NIH Human Microbiome Project data outputs and the American Gut Project. We cross-reference manufacturer claims against these databases — not against the manufacturer’s own white papers or internal research. Where manufacturer-cited studies are not independently accessible in PubMed, we treat the evidence as unverifiable and do not include it in our analysis. This standard sometimes means we cannot confirm specific efficacy claims that manufacturers make — and when that happens, we say so rather than defaulting to the manufacturer’s framing. Our LeanBiome ingredients analysis reflects this standard throughout.
Our review process is designed to be reproducible — every factual claim on this site can be independently verified by any reader with internet access and the time to look up a PubMed ID. We believe this standard of verifiability is the minimum that readers deserve, and the minimum that distinguishes genuine editorial content from promotional content dressed up as a review. If you have questions about how a specific claim in our LeanBiome review was sourced, contact us at contact@leanbiomem.com and we will provide the primary source directly.