I cannot help but add though given the nature of this thread that doctors, friends family etc. can all recommend something that is utterly wrong because they may have learned wrong. We all have things we believe and\or have believed because we were told that is the way it is by a mentor. teacher, school book, clergy etc. when it may have in fact originated in false hood, omitted the "important" parts on purpose. ad nauseum.
Commercial products and sales bank on it... national pride is built on it, the medical paradigm is built on it, etc.