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.
Fasting is nature's own method of ridding the body of "diseased" tissues, excess nutriment and accumulations of waste and toxins. Nothing else will increase elimination through every channel of excretion as fasting will. Nothing else affords the organs of elimination the same opportunity to catch up with the work they are behind on and thus bring their work up to date.
At the start of the fast there occurs a temporary increase in elimination over the amounts usually thrown out, after which there follows a very rapid drop to lower levels. The fasting body strikes a new balance of excretion, one which represents a closer approach to the true wastes of the daily activities of life. Much of the larger amounts eliminated daily previous to the fast was due to the daily intake of much more food than the body required. As soon as this surplus is excreted, elimination seeks a lower level.
As the fast progresses, the blood and lymph (lymph makes up from 25 per cent to 35 per cent of the body weight; blood only amounts to about 5 per cent of body weight) becomes purified; pent-up excretions are expelled from the body; the nervous system and all the vital organs rest. As the nervous system secures relief, body and mind become rested and the bodily irritations that have caused the mental irritations and the mental bad conduct cease; indeed, the individual is "made over." Ridding the cells and fluids of accumulated toxins accounts for most of the benefits derived from fasting. The benefits last until the toxins reaccumulate and in most cases, this takes place quite rapidly due to subsequent return to a toxogenic mode of living.
One great source of toxins is decomposing food in the digestive tract. Fasting soon eliminates this completely. The alimentary canal becomes practically free of bacteria. Only a week of fasting is required to result in the complete disappearance of all germs from the stomach. The small intestine becomes sterile. The hibernating bear and other hibernating animals lose all their colon bacilli during hibernation. Typhoid cases that fast through their illness are free of "typhoid bacilli" at the end of the acute stage and are not "dangerous" as "carriers."