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.
We often meet with the objection that a patient is too old to fast. I have conducted a number of fasts in patients from seventy years to over eighty-five years of age and I have found no reason to consider aged persons to be in a class by themselves. Adult animals of any species, including Homo Sapiens, can fast much longer than the young of the same species. Old people actually stand fasting best. Growing children stand it least, although they stand it well. Patients do not get too old to fast. The regenerating effects of fasting are especially apparent in the old.
I have conducted numerous fasts in both men and women whose ages ranged from sixty-five to eighty-five. Many of these patients have had long fasts of from thirty to over forty days. Dewey reported several cases of elderly people who fasted under his care with positive benefit. Carrington says that he has observed several such cases.
I agree with Carrington, however, when he says: "Notwithstanding, I should recommend fasting with great caution in persons over sixty years of age," but not for the same reasons he adduces. I do not hesitate to place old people upon a fast, but I watch them more closely than I do younger people, not because they do not stand fasting well, but because they are often possessed of hidden weaknesses that render it inadvisable to carry the fast to great lengths.