There is no conspiracy to suppress a known cure. If any of the dietary, lifestyle, or thought manipulations being promoted actually were effective then that discoverer would have been awarded a Nobel Prize ten years in a row. Claims for the effectiveness of these types of treatments are never more than testimonials. A testimonial is nothing more than an unsubstantiated assertion of one's belief. It proves nothing, only what one believes.
Conventional treatment is the result of the scientific process.
A problem or phenomenon is studied. An hypothesis is made and experiments done to confirm or reject the hypothesis. The human body and its workings are incompletely understood. There is more unknown than known about it. But, even with this lack of knowledge the scientific process has yielded huge benefits to us.