When you start to grow your own food for sustainability, you start to consider the volume and types of crops. You start to evaluate the ease of production and the nutrient content of the crops you are growing. You become aware of the necessity to grow food that is not going to poison you or make you sick from eating too much of it.
All food has medicinal qualities. Eat a proper diet and you will be less likely to get sick. You have to figure out what the proper diet really is for yourself, because everyone has his own products to sell. Canada Food Rules do not promote things like coconuts because no Canadian grows coconuts.
Consuming too much of anything will ultimately kill you. Anything that your body does not need as food for the health of individual cells has to be expelled from your body, so too much of anything is toxic. You overload your liver or kidneys or your immune system, lymph system, circulatory system, digestive system ....and inevitably one system will eventually fail. When any one system stops working it takes down the rest because your body is composed of many symbiotic systems, everything depends on something else.
Removing a cancerous tumour is only worth doing if what caused the cancer has been corrected. Deprive a healthy cell of oxygen and it dies. Reduce its oxygen supply gradually and it will morph into an anaerobic cell. Cells that don't need oxygen produce acid waste and offspring that don't need oxygen. The only thing they remember to do is how to reproduce.
If you wish to function truly independently, your little sustainable community will need a medicine garden, like the old Victorian estates that grew their own medicines before the advent of Big Pharma with their version of many of the natural substances found in plants, and their influence in the system to make the natural sources, or distribution of natural substances, illegal.
My latest discovery in medicine is that all vitamins carry an enzyme, which is a very small molecule that can not successfully be manufactured by man, so there is no patented version. You have to go to the source for your enzymes and that is fresh fruit and uncooked vegetables. I believe it is the reason why many patients experience cancer cure from drinking vegetable juices.