We have seen the diet of the evolving man becoming epoch after epoch more and more concentrated. At the present time this process has reached its acme, so that a high degree of concentration is perhaps the most characteristic feature of the neo-man's diet.
How very condensed modern diet is does not seem to be adequately realized. Writers on treatment are constantly recommending a "highly nutritious diet," and the energy values of various foods are carefully estimated with a view to indicating their several nutritive values. Yet, as a matter of fact, it is no easy matter to prescribe an innutritious diet, unless it be one consisting of green vegetables or luscious fruits. That all kinds of animal food - milk, eggs, fish, game, and "meat" - are highly nutritious needs no insistence. The like is true of our most important source of vegetable food, the cereals, which contain a high percentage of protein and starch. Moreover, man has learnt to separate all the energy-yielding food-stuffs - protein, fat, starch, and sugar - from their natural combinations, and much of our modern food consists of these substances in what is practically the pure form. Thus fat is separated from milk as butter, and fat and casein in the form of cheese. Large quantities of starch, again, are extracted from vegetable substances, yielding such highly nutritious food as sago and tapioca, while enormous quantities of pure sugar are obtained from sugar-cane and beetroot, to say nothing of the large supply of vegetable fat and protein now placed on the market.
This extreme concentration of modern diet has three consequences : (a) It is chiefly responsible for the present prevalence of constipation, a prevalence so great that man has actually been defined as "the constipated animal." (b) It promotes over-eating: a concentrated diet - especially when at the same time it is soft, as so much modern vegetable food is, and thus slips easily into the stomach - is apt to be consumed in excess before the sense of satiety is produced. (It does not seem unlikely that a type of person is being evolved capable of coping with an excess of food.) (c) It is rendering some extent of the alimentary tube, notably of the larger bowel, redundant.