during the last decades , there have been great advancements in the field of preventive medicine . research has demonstrated that nutrition plays a crucial role in the prevention of chronic diseases . it proposes to consider food not only vital to survive , but also a mean for mental and physical well - being , contributing to the prevention and reduction of risk factors for diseases . however , there is evidence that the concept was believed by ancient physicians as well . rhazes said ;  as long as a disease could be treated with food , medicine should be avoided we carried out a review of avicenna s canon of medicine and rhazes books for the definition of food and drug and similar concepts of functional food . rhazes has a book called  manafe al - aghziyeh , in which he writes about the medicinal benefits of different nutrition . five concepts ( food , drug , medicinal food , nutritional medicine and antidote or poison ) were noted in these books . there are many recommendations on food for the prevention and treatment of diseases in tpm books , which can be the basis for novel research studies .