It is not logical to assume that all diseases begin because of nutrition, but many have already been linked to it. Not having the appropriate nutritional habits, together with genetic and environmental reasons can lead to disease. Furthermore, a number of chemicals found in nature have demonstrated positive effects in human health conditions.
Until the advent of the pharmaceutical industry in the mid-1800's, people used natural products and primarily botanicals as treatments. To-date, many of the drugs we use are analogues of naturally occuring compounds, a lot of them being phytochemicals. A publication by the National Cancer Institute in the US in 2012 demonstrated that just in the area of cancer, since the 1940s, approx. half of the 175 drugs developed and approved were derived from natural products. Some of the known drugs that come from plants include: aspirin (from willow bark), digoxin (from foxglove), quinine (from cinchona bark), and morphine (from the opium poppy).