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.
It is quite true that many individuals reach middle life (or what is usually-called that) habitually using bread and cereals, and in apparent good health; but the race must be run before anything is proven. In my childhood I knew a neighbouring farmer who used to make daily trips, in the severely cold winters of northern Pennsylvania, to a village a half-dozen miles away, without any coat and without other clothing than the shirt he wore in summer time. The team which he drove hauled heavy loads of wood, and this necessitated a slow pace, and the teamster followed at a slow walk. He laughed at the foolishness of his neighbours who coddled themselves in coats; and, strangely enough, he got on for years in seeming good health. Ultimately he lost his health, and died in middle life; but, while in seeming vigour, his case was no proof that his habit was not injurious; it was proof only that the powers of his system were able for a time to overcome, and not at once die from exposure. During the civil war in America, it was found that farmers' sons did not make as tough and enduring soldiers as the young men about the towns, who had been clerks in stores, and like employments, where there was less strain, and less exposure to the extremes of weather, than had fallen to the lot of the farmers. This was a great surprise; most persons would have supposed that the fresh air and out-door work of the young farmer were more favourable to health and endurance than the coddled life of the town boy. When it came to the test, the only explanation of the failure of the farmer is in the supposition that the daily struggle with trying winter weather gradually undermines the vital powers of the system. Just so, I think, it is with starch foods; they are, like the inclement weather of our northern winters, an unnatural and health destroying strain upon the vital powers; and, while the vigour of youth and middle life is sufficient to overcome the strain for a time, it is only for a time; broken health and premature decrepitude are sure to follow.
This explains the phenomenon of the milk and water diet. When a person is stricken with illness, and vitality at a low ebb, it has been found by most physicians of all schools that milk is the best food, and that cereals - and especially bread - must be left off. When the usual vigour of the system has been established, the patient is again able (apparently) to endure the accustomed strain of starch foods. When my Pennsylvanian farmer was taken ill, his common sense forbade his exposure, in insufficient clothing, to the strain of severe winter; after the usual vigour had been re-established, he was again able (apparently) to endure the strain of his accustomed exposure.
When I began the Vegetarian life, some eight years since, I had neuralgic headaches, coming on periodically about every three weeks, of so severe a nature that I was compelled to take to my bed for a day; and the headache was not appeased until after several paroxysms of severe vomiting. I had inflammatory rheumatism, which sometimes sent me to bed for a week or two at a time. I had lumbago, of such a nature that I could stoop only with great difficulty at my best, and was sometimes unable to walk for days at a time. I inherited a tendency to skin cancer; and my face was habitually inflamed and pimpled. Have had chronic sore eyes since boyhood; and for twenty years preceding the adoption of Vegetarianism my eye-balls and eye-lids were at all times inflamed; and I usually felt an impulse to screen their lamentable condition from the gaze of others. Upon the adoption of Vegetarianism my health greatly and rapidly improved; the redness disappeared from the eye-balls and largely from the eye-lids; the rheumatism greatly improved; I was in every way better. But one serious difficulty from which I all my life have suffered (since the age of twelve) was not appreciably improved. I quite universally experienced a heaviness from one to three hours after meals; an inability to work and repugnance for any needed labour, and especially for mental work. I suffered much from heaviness and drowsiness, and could only with great difficulty bear a dull discourse; and in the evening, after my usual dinner, it was often quite impossible to keep awake. I have often, at such times, pulled hairs from my head (and I have none to spare!) in an attempt to pay some regard to the decencies required by the situation.
Some three years ago I was loth to discover, but forced to admit, that no progress was being made; indeed, I perceived that I was losing ground, and came to the conclusion that the roseate view I entertained as to a virtual restoration to health was doomed to disappointment. I was in this condition and this frame of mind, like many others, when I concluded (in September, 1889) to try what a non-starch dietary would do for me. I sensibly improved from the first week's trial. I had often noticed, previously to the trial of the non-starch diet, knowing I was to be called upon for mental work soon after a meal, that if I took a slice of brown bread - a tenth or a fifth of what the needs of my system required - I escaped the hateful heaviness, while at the same time the small amount taken was sufficient to appease hunger; and I had often for years wished that I might be able to eat as much food as the needs of my body required, and at the same time feel as delightfully free from the dreaded drowsiness as when eating only a sandwich. I had not gone a week on the new diet, until I discovered I could eat a full meal, and if desirable proceed at once to the transaction of business, or the writing of an essay, without any sense of having eaten, and without the slightest heaviness or drowsiness. I now average about seven and one-half hours of sleep in the twenty-four, as against about eight and one-half on my former cereal diet; and whereas then I was quite given to feel dull in the evening, and very apt to fall asleep if subjected to the infliction of a dull discourse; now I am wide awake until midnight, or later if occasion requires; and I am entirely freed from any fear of the somnolent effect of the dullest discourse. It was the freedom from the heaviness resulting from sluggish digestion that was noticed at the outset. As weeks and months wore on, I found distinct improvement in the rheumatism that had not - under the Vegetarian diet - entirely disappeared; now for some months I have been wholly free.