It's not, proving a medical effect and having a medical effect are orthogonal concepts. The world doesn't wait on medical science to keep turning.
A lot of medical recommendations are based on expert opinion, which means there is no proof of their effectiveness but there is a logical basis based on our current understanding of the human body.
New studies come out every day proving the effect of certain herbs, extracts or therapies for certain pathologies, yet these therapies were known to work long before the studies came out.
Even some synthetic drugs are approved without having been demonstrated to be effective at what they claim, for example osteoporosis drugs still haven't been proven to reduce fractures yet get prescribed every day for that very use.
A lot of medical recommendations are based on expert opinion, which means there is no proof of their effectiveness but there is a logical basis based on our current understanding of the human body.
New studies come out every day proving the effect of certain herbs, extracts or therapies for certain pathologies, yet these therapies were known to work long before the studies came out.
Even some synthetic drugs are approved without having been demonstrated to be effective at what they claim, for example osteoporosis drugs still haven't been proven to reduce fractures yet get prescribed every day for that very use.