Methodology

Who compiles this

Matt Crawford is the creator and curator of Supplement Engine. He is not a doctor, dietitian, or clinical researcher. Content here is compiled from publicly available research summaries, government and manufacturer reference material (such as NIH Office of Dietary Supplements fact sheets and NHS/gov.uk guidance), and publicly documented statements made by the health influencers featured on the site — then reviewed and edited for clarity. It reflects independent research and editorial judgement, not personalised clinical expertise, and it does not replace advice from a qualified healthcare professional.

We are not a clinic, and this site does not provide personalised medical advice, diagnosis, or treatment.

What evidence levels mean

• High — Multiple human clinical trials, systematic reviews, or meta-analyses support the primary use(s) described, with broadly consistent outcomes across studies.
• Medium — Some supportive human research exists, but studies are smaller, shorter, mixed in outcome, or the effect size is modest. More or better-quality evidence would raise our confidence.
• Low — Evidence is mostly preliminary, mechanistic, based on animal studies, or largely anecdotal for this specific use. Human data is limited, inconsistent, or absent.

Evidence levels describe the strength of research for common uses discussed on each page — not a guarantee of benefit for any individual, and not a ranking of product brands. Each rating is assigned per supplement page for its stated primary use(s); the same supplement can be well-supported for one use and speculative for another.

Sources we use

Supplement write-ups are compiled from publicly available research summaries and reference material — including government and institutional fact sheets (e.g. the NIH Office of Dietary Supplements, NHS/gov.uk guidance), peer-reviewed study abstracts, and reputable health publications. We don't invent doses, evidence ratings, or health claims, and we don't cite a specific study for every sentence on every page.

Influencer stacks are compiled from public statements (podcasts, books, interviews, published protocols). A general disclaimer is not a citation on its own — we run an ongoing, script-assisted sourcing audit to attach a specific citation (a podcast episode, article, or published protocol) to each individual claim, rather than relying on one blanket disclaimer per influencer. Items that don't yet have a verified citation are left unlabelled rather than guessed at; see the citation link under any sourced item on an influencer's page.

Cautions & interaction notes

Where the Stack Builder flags two supplements together (e.g. "space out iron and calcium" or "cumulative fat-soluble vitamin load"), that note reflects well-established, general nutrition-science facts — mineral absorption competition, cumulative stimulant or sedative load, and similar broadly documented effects. It is not a licensed drug-interaction database and does not check for interactions with medications. Always tell your doctor or pharmacist what supplements you take, especially alongside prescription medication.

What we do not do

• We do not invent doses, evidence ratings, or health claims.
• We do not invent or guess product identifiers (e.g. Amazon ASINs) or pick a specific brand on your behalf — buy links use a keyword search unless a real, verified product link has been added.
• We do not claim affiliation with, or endorsement by, the individuals whose public protocols are discussed.
• We do not sell supplements; some outbound links may be affiliates.
• Availability and legal status of products vary by country — always check local regulations before purchasing.