"Clinically proven"
"Clinically proven" has no formal definition under UK MHRA or ASA rules. In regulatory usage "clinical" means studied in humans, and work in animals or cell cultures is "preclinical", but because the marketing phrase carries no legal definition it does not by itself guarantee the evidence came from people at all. The ASA CAP Code requires any "clinically proven" claim to be substantiated.
Full definition
The phrase "clinically proven" is widely used in hair-loss marketing for both POMs and supplements. The ASA CAP Code (rule 3.7) requires marketers to hold documentary evidence to substantiate efficacy claims, and that evidence has to be relevant to the claim actually made. This is where the word "clinical" does more work than most readers realise. In medicines regulation a "clinical" study is one conducted in human participants; work in animals, tissue samples or cell cultures is "preclinical" or "non-clinical", and it sits earlier in the development pathway precisely because it does not yet show what a substance does in people. A great many compounds that improve hair growth in mice have gone on to do nothing measurable in humans. Because "clinically proven" is a marketing phrase rather than a regulatory category, however, nothing about the words themselves guarantees the underlying evidence was generated in humans, and preclinical or in-vitro findings are sometimes presented in support of it. For UK-licensed POMs (e.g. finasteride 1 mg, topical minoxidil 2 and 5 percent solutions), the claim is supportable because the products carry an MHRA marketing authorisation based on phase III trials in people. For supplements, "clinically proven" frequently appears alongside small studies, in-house testing, animal or laboratory work, or studies conducted on a different formulation than the product sold; the claim is not invalid per se, but must be substantiated specifically and may attract ASA scrutiny.
What it does not mean
"Clinically proven" does NOT mean MHRA-approved as a medicine; does NOT guarantee the evidence came from humans rather than from animal, tissue or cell-culture studies; does NOT necessarily mean the product itself has been trialled; does NOT mean the claim has been independently reviewed. It is a marketing phrase, not a regulatory category. A result in mice is a reason to run a human trial, not a substitute for one.
Examples in use
Honest use
"Finasteride 1 mg is licensed in the UK for male pattern hair loss with efficacy demonstrated in randomised controlled trials (Kaufman 1998)."
Common misuse
"Our hair-growth supplement is clinically proven." (This is the pattern that attracts ASA substantiation challenges, particularly where the underlying study was conducted in mice or on cell cultures rather than in people.)
UK regulatory source
ASA CAP Code 3.7 (substantiation); MHRA Blue Guide on medicines advertising