In addition to proteins, carbohydrates, fats, mineral salts and vitamins, there are in food blood-forming substances, extractives, flavouring matter and pigments that have parts of greater or lesser importance to playing the nourishment of the body. The food must also contain a certain amount of innocuous, indigestible material, or roughage as it is called, to stimulate intestinal movements.
Besides all this, there is something in the freshness of food, especially vegetable food – some form of energy perhaps; it may be certain rays of light or electrical property – which gives to it a health – promoting influence. Certain it is that no synthetic diet that I have been able to devise has equalled in health-sustaining qualities one composed of the fresh foodstuffs as nature provides them.
Further, the quality of vegetable foods depends on the manner of their cultivation : on conditions of soil, manure, rainfall, irrigation. Thus, we found in India that foodstuffs grown on soil manured with farmyard manure were of higher nutritive quality than those grown on the same soil when manured with chemical manure. Rice grown in standing water – the common practice in India – was less nutritious than when grown on the same soil under conditions of natural rainfall. spinach grown in a well-tended and manured kitchen-garden was richer in vitamin C than that grown in an ill-tended and in-adequately manured one.
Examples of this kind might be multiplied, but these suffice to indicate ways in which agricultural practice is linked with the quality of food, with nutrition and with health. If, indeed, man is to derive all the benefits that the soil is so ready to yield to him, he must employ his intelligence and his knowledge in rendering it fit to yield them to him.
Impoverishment of the soil leads to a whole train of evils : pasture of poor quality; poor quality of the stock raised upon it; poor quality of foodstuffs they provide for man; poor quality of the vegetable foods that he cultivates for himself; and, faulty nutrition with resultant disease in both man and beast. Out of the earth are we and the plants and animals that feed us created, and to the earth we must return the things whereof we and they are made if it is to yield again foods of a quality suited to our needs.
The alimentary tract is very prone to suffer both structurally and functionally in consequence of faulty food and to become the prey of pathogenic agents of disease or the harbourer of parasites. Further, states of ill-health of this tract often provide conditions precedent to the development of diseases of faulty nutrition. In such circumstances essential constituents of food may not be absorbed in sufficient quantity for the needs of the body or for those of certain communities of cells, and disease due to their deficiency may arise.
Many years ago (1918), when the newer knowledge of nutrition was in its infancy, I obtained some dozens of healthy monkeys from the jungles of Madras. Some I fed on faulty and ill-balanced food deficient in vitamins and mineral elements, others on perfectly constituted food. The latter remained in good health; the former developed gastro-intestinal ailments, ranging from gastritis and ulcer to colitis and dysentery, while one amongst them had a commencing cancer of the stomach.
The passage of years has not dimmed the recollection of this crucial experiment nor detracted from the far-reaching importance of the results yielded by it. Indeed, there is, perhaps, no more significant fact in regard to the function of nutrition than that this highly specialized alimentary mechanism on which the nourishment of the body depends is itself amongst the most susceptible of the structures of the body to faulty nutrition.
Nutrition is affected adversely by a number of factors: imperfect oxygenation of the blood and tissues, as from faulty breathing, lack of fresh air, bad ventilation, over-crowding and lack of exercise; insufficient rest and want of sleep; over-work and fatigue; worry and emotional excitement; lack of sunshine; insufficient calories for the work the body has to do; excessive consumption of alcohol; indigestible food; gastro-intestinal disorder; and, many conditions of ill-health. But by far the most important factor is food of improper constitution.
The interaction of faulty food, faulty nutrition and microbic or toxic agents leads to the spontaneous appearance of many others or to their controlled appearance at the will of the experimenter. I know of nothing so potent in maintaining good health in laboratory animals as perfectly constituted food; I know of nothing so potent in producing ill-health as improperly constituted food.