Simply put, your body must be able to take something from the outside world, break it down into its smallest parts, and absorb those parts to be able to build and repair. It is at the very moment that your body stops doing this that disease or illness begins. Secondary to that, if there is a backup in the sewage system of your body than digestion can not work properly. Your stomach actually has two parts. While sitting there enzymes that are in the food begin to break the food down.
All foods coming directly from nature come equipped with the proper enzymes to break itself down.
Leave a piece of raw meat out on the counter and it will start to degrade part of that process is caused by the enzymes going to work. Once the food has sat in the upper stomach for a period of time, then it drops to the lower part where the body then does the rest of the digestion work, mostly from the work of the liver and the pancreas. Ideally, this process is a fifty-fifty proposition. Half of digestion is done by your body and half is done by the enzymes that are in the food. Zero percent gets done by the enzymes and we expect our bodies to do all of the digestion work.