This section is from the book "The Hygienic System: Fasting And Sun Bathing", by Herbert M. Shelton. Also available from Amazon: The Hygienic System Vol III Fasting and Sun Bathing.
Throughout most of the fast, the fasting individual is annoyed by a very bad taste in the mouth. This may be alleviated somewhat by a daily scrubbing of the tongue with a toothbrush. This should not be done, however, until after the tongue has been examined by. the doctor who is conducting the fast. Mouth washes, lemon juice, etc., are not to be recommended. Gargling the throat is certainly of no value. As the fast progresses and the tongue clears up, the taste becomes less and less offensive, until, when the fast should be broken, the taste in the mouth is very pleasant.
It has been determined experimentally, that the chewing of gum occasions an inhibition of gastric secretion. This, instead of enhancing digestion, as gum chewing is popularly and professionally supposed to do, actually retards the digestion of protein foods. As there is no digestion going on during a fast, it may seem unimportant if the faster chews gum, but this is far from true. I have permitted fasters to chew gum and I have noted a tendency to chew it in large quantities, the faster chewing three or four packages of gum a day. I am inclined to think that he chews it until he extracts all the sugar from it, then takes fresh gum, doing the same with this.
Gum chewing serves no useful purpose. It is an evidence of weakness, the foundation for which is laid in infancy and early childhood. Mothers give their babies bottles, nipples, crackers or cookies to keep them quiet. Later in life these perpetual sucklings trade their nipples or their cookies for chewing gum or the cigarette. Gum chewing is a mental habit that is needless and foolish, as well as a wasteful practice under any and all circumstances. It is not the innocent practice it is commonly regarded. There can be no doubt that it exhausts the salivary glands. It does not seem probable that any useless habit can be regularly indulged by anybody with impunity. Gum chewing is certainly wasteful of the patient's energy and the energy wasted in this useless practice may be, at least in very low states of health, just enough to mean the difference between recovery and death. It is particularly essential in all serious states of disease, and in fasting, that all nerve-leaks and all sources of enervation be discontinued. Energy must be conserved in every possible way. The faster should certainly refrain from chewing gum.