This section is from the book "The Natural Food Of Man", by Emmet Densmore. Also available from Amazon: How Nature Cures Comprising a New System of Hygiene.
In the quoted extract, Mrs. Stuart tells us that she still considers Vegetarianism the ideal diet; but, she says, the trouble is we have not an ideal stomach with which to digest it. Here lies Dr. Salisbury's and Mrs. Stuart's mistake. It is necessary that we have foods adapted for stomach digestion, and fortunately it is not necessary to resort to animal flesh to obtain these foods. Dr. Salisbury taboos sweet fruits, because he says those foods ferment in the stomach; I freely grant that they ferment in pathological stomachs, but I am also prepared to affirm and to prove that they do not ferment in physiological stomachs; and, moreover, the sugar in those fruits is at once taken into the circulation, and at once becomes assimilable food. It will be found also that the banana is rich in nitrogenous element, and that this element is readily acted upon by the gastric-juice. Dr. Salisbury makes the great mistake of concluding that man's anatomical structure proves him to be a meat-eating animal, whereas comparative anatomy shows that the ape family are not only the most like the human animal, but their anatomy is in many ways scarcely distinguishable from the human, and the ape in his native wilds, filled with overflowing vigour and health, lives exclusively on fruits and nuts.
Sweet fruits, although well adapted to stomach digestion, are yet not adequate; nuts contain an important and indispensable element in man's food. It is quite true that many persons cannot eat nuts without suffering from digestive difficulty; but what is true of sweet fruits is also true of nuts - physiological, healthy stomachs find no difficulty in their digestion and assimilation; and it will one day be seen to be an indispensable element in our dietary. If man does not get this necessary food in that product which Nature has prepared for us, you will see him reaching after substitutes, and find him eating milk,butter, cheese, and the flesh of animals. Fortunately for Vegetarians, and all those food reformers who are glad to avoid excremental food and the sin of taking life, milk and its products, and eggs, are not excrementa; they are a secretion, and not an excretion, and may be used in substitution for nuts when these are not to be had in right varieties and condition; but man's nature will insist on having a substitute. And this is why Sylvester Graham and the Vegetarian Society, in a half-century of earnest work, have made so little headway. "Truth is mighty, and will prevail"; but the substitution of a food designed for cattle, and utterly unfit for a human stomach, for those foods which Nature designed for us, is not in accordance with truth, and the instinct of civilisation has cried out against it.
There remains to be considered another very important result caused by the laborious, protracted, and vital-force wasting digestion of starch and cereals. Constipation has always been recognised as destructive to the well-being of our physical condition. Dr. Abernethy, a hundred years ago, proclaimed three prime rules of health : "Keep the head cool, keep the feet warm, and keep the bowels open." When we eat such foods as are adapted to stomach digestion, the nutritive value of the food is largely assimilated while still in the stomach; and, when the residue is passed on to the intestines, what nourishing element still remains is soon absorbed into the circulation, and the remaining portion easily and quickly discharged from the bowels. There is a force or power controlling the vital processes of our organisms, that seems instinct with life, and to work with intelligent design. When foods are taken into the system which are difficult of digestion, and when this process is delayed hours beyond what is necessary or natural, this mysterious something, that watches over our animal economy, insists first and foremost that our bodies be furnished with nutrition; our very life depends upon it; and if food has been taken that gives up its nutrition tardily and with difficulty, this mysterious something (Nature) insists upon retaining such food until its nutriment is absorbed; and when this is accomplished there results lethargy, and a sluggish vitality unable to expel the residue from the body. I consider cereals and starch foods the father-and-mother of constipation.
I pray my brothers and sisters in food reform to spare themselves a resort to innuendo, sarcasm, or to personal epithets or anathema. I have but one aim - to know the Truth. Having retired from the practice of medicine, Mrs. Uensmore and I have no patients to seek, no books to sell, and through patients or books or this discussion not a shilling to gain; and I shall endeavour not to be deterred from the investigation of a Truth, however unpopular, and however severe the epithets that may be hurled at me.