There is one aspect of this question which it might be well to touch upon in this place. The air that we breathe, as we know, contains a large percentage of nitrogen. Might it not be possible for the system to utilise some of this nitrogen, when the body is in a state of nitrogen starvation? Dr De Lacy Evans, surgeon to St Saviour’s Hospital, in London, contended that this might be the case, and in his “How to Prolong Life,” pp. 76-80, wrote:
“It has been argued that fruits will not sustain life, because they do not contain sufficient nitrogen; this argument is founded upon a theory which is demonstrably incorrect, and it is an ascertained fact that fruits alone will support life and good bodily health.... By experiments on ourselves, on friends, and on natives of tropical regions, we find a comparatively small quantity of nitrogen necessary to sustain life; in fact, fruits, taken as a class, contain sufficient nitrogen to sustain human life.... Now fruits will sustain life, and all fruits contain carbon, hydrogen and oxygen, and most of them a small quantity of nitrogen; and if these fruits which will sustain life do not contain sufficient nitrogen, may not man, who breathes and is in contact with an atmosphere (four-fifths of which is nitrogen), by means of his lungs, the surface of which is supposed to be more than twenty times that of the whole body, absorb the necessary nitrogen directly from the atmosphere? From careful observation of the diet of natives in tropical regions, and from direct experiments in England, we may state that this is positively the case. This is often observed in the herbivora: their natural food contains little nitrogen, still it is found in their flesh in about the same ratio as in the carnivora. Further, the carnivora live on food rich in nitrogen—yet one is as well nourished as the other.... Man may live entirely upon fruits, in better health than the majority of mankind now enjoy. Good, sound, ripe fruits are never a cause of disease; but the vegetable acids, as we have before stated, lower the temperature of the body, decrease the process of combustion and oxidation—therefore the waste of the system—less sleep is required, activity is increased, fatigue or thirst hardly experienced: still the body is well nourished, and as a comparatively small quantity of earthy salts are taken into the system, the cause of ‘old age’ is in some degree removed, the effect is delayed, and life is prolonged to a period far beyond our ‘three score years and ten.’”[17]
The consensus of modern opinion, however, seems to be against any such supposition. Chittenden, for example, writes:[18]
“Man lives in an atmosphere of oxygen and nitrogen. He can and does absorb and utilise the free oxygen of the air he breathes; indeed, it is absolutely essential for his existence, but free nitrogen likewise drawn into the lungs at each inspiration is of no avail for the needs of the body.”
As, however, all bodies contain more or less nitrogen in excess, there would be no need to call upon the air for its supply. It would be interesting to note the effects in cases of nitrogen starvation; but the simple fact that animals do die when sufficient nitrogen is subtracted from their food, would seem to indicate that but little nitrogen, if any, can be extracted from the air, even under these circumstances.
After the above lengthy argument, which endeavours to show that sufficient proteid can be supplied the body from vegetable foods, it is somewhat amusing to find that, as a matter of fact, far too much proteid has invariably been eaten by practically all civilised peoples—and that so far from there being any danger of nitrogen starvation, or lack of sufficient proteid, the danger is all the other way, and four-fifths of all the maladies from which mankind suffers are due to the very fact that an excess of proteid has been eaten! All physiologists agree that the majority of people eat far more, not only of proteid, but of all kinds of food, than is required, according to their tables; and Professor Chittenden has recently shown, as the result of an elaborate series of experiments conducted at Yale, that the average proteid standard set by physiologists, as being necessary for the maintenance of health, is at least three times too high! That is, the majority of persons eat considerably more than three times too much proteid! In view of these facts, it is amusing to find so much fear exhibited on all hands in case the proteid supply should not be sufficient in quantity.
These Yale nutrition investigations are now so widely known that it would be useless to do more than refer to them in this place. As the results of experiments upon University professors, upon athletes, and upon a squad chosen from the United States army, it was definitely proved that the proteid standards were far too high: the men flourishing, improving in every direction, and even doing a greater amount of physical work than usual on a diet averaging, in proteid value, about a third said to be necessary by the physiologists. When we take into account the fact that most people eat far more proteid than the physiologists said was necessary, it will be seen at once the tremendous disproportion which exists between the amount actually consumed, and the amount really needed by the body; and how absurd it is, in face of these facts, to persist in demanding an excess of those foods which contain such high proteid percentages! Chittenden says: