Lapis, there are a great many scientists who understand that tobacco smoke causes cancer. However, that contributes nothing to the topic at hand. Perhaps you can provide an explaination of how the body knows when to stop producing specific enzymes. Garcia and I are in agreement that the body produces all the enzymes necessary for digestion and also that I can name then and the messenger systems that cause these digestive enzymes to be released. The gentleman that was quoted second handedly received his Noble prize in 1945..do you know the source of the quote...original source that is. Do you know why there is no mention of a feedback system for the control of digestive enzymes mentioned in ANY human physiology book? The previous question was in reference to the presence of food enzymes replacing human enzymes in digestion thus saving energy. If no one is capable of supplying some evidence outside of a quote stating " enzymes are released from food" I am going to have to believe that no one udnerstands this process and that there is no evidence to support this notion.