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.
The chemical changes which occur in the fasting body are as remarkable as anything that we have described previously. It is quite natural that the fasting body loses some of its substances, but it does not lose all of its elements at the same rate and, what is most remarkable, there occurs a redistribution of some of these, due to the urgent need for preserving the integrity of the vital organs.
The fasting body does not lose its inorganic constituents--minerals--as rapidly as it loses the organic constituents--fats, carbohydrates and proteins. It hangs on to these precious minerals while throwing away its excess of acid-forming elements. The more valuable the material the less of it is lost.
The muscles and blood lose relatively much of their mineral constituents, especially is there a decrease in the percentage of sodium, while considerable mineral substances accumulate in the brain, spleen and liver. There is, then a mere shifting of mineral substances from one part of the body to another. While sulphur and phosphorus diminish in the fasting muscles about as rapidly as do the proteins, there is an increase in the amount of calcium in these organs. There occurs an increase in the percentage of potassium in the soft parts of the body taken as a whole, during the fast. These facts show that potassium salts and calcium salts are not lost as rapidly as some of the other of the body's elements. The excess of iron that may be contained in the diet is taken to the cells of the liver and stored by these. It is probable that the iron set free by the breaking down of the red cells is also stored in the liver and spleen, at least it is not excreted in any great amount. The body's iron reserve, in the form of hematogen, is relatively large.
That the body possesses considerable iron reserve, even in pernicious anemia, is shown by the great and rapid blood regeneration and great increase in hemoglobin and red cells during a fast in these cases. During the fast, the iron liberated by the breaking down of tissue is retained in the body and is not thrown away. Considerable iron and proportionately other necessary elements are consumed during the fast, although the body stores much of its iron in the spleen, liver, marrow cells and in the increased number of red blood cells. The fact that enforced fasting in non-hibernating animals produces the same variable results as those produced by abstinence during hibernation, shows that there is no more danger to the non-hibernating animal than to the hibernating kind. The chief difference is that the non-hibernating animal is likely to be more active while fasting but seldom as active as the Alaskan fur-seal bull during the mating season. The hibernating animal is also likely to possess a greater store of reserve food at the outset.