This site on FASTING has an MD describing what is happening when you have cleansing symptoms. It has quotes from 17 MDs on fasting. You can educate your friends on protein.
College textbooks on nutrition say that protein deficiency is rare in the world and it does not exist in this part of the world (America). The home page of site above is about losing weight. It tells how Americans eat 5 times the protein they need and how the excess is killing them. They may as well tell you that you need to smoke a cigarette. Or as the MDs used to say "you need a good blood letting or bleeding."