RELATION OF FOOD TO HEALTH The quantity of food required to maintain the body in vigor varies with the climate and season, clothing, occupation, work and exercise, the state of individual health, age, sex, and body weight. Modern conditions of food preparation frequently stimulate the appetite so that one consumes food far in excess of the body's requirements. When coupled with insufficient exercise the results are bad. When prolonged it may lead to such diatheses as obesity and gout, and even though these conditions may not be produced, the temporary effects, the congestion of the digestive tract, the intestinal stasis, all exert a reflex action upon the central nervous system with the pro duction of headache, mental fatigue and lassitude. Conversely the lack of sufficient food is also deleterious. In the complete absence of food life can rarely be sustained over ten days. An insufficient diet has another important effect. Individuals who are poorly nourished have their resistive forces lowered to such an extent that they fall a ready prey to invasions by micro organisms and the probabilities of a fatal termination are also much greater. This is illustrated by the severe epidemics which have so frequently been associated with famine.
Associated with the question of an insufficient diet is the question of an unbalanced diet, by which we mean one in which the proper proportion of protein, carbohydrate and fat are not represented. Economically the parallelism of poverty and want in connection with these is sometimes very close, though we also see an unbalanced diet resulting from a perversion of appetite or inability, from other circumstances, to secure the necessary materials. Thus an anemia may be due to lack of
meat, an excess of carbohydrates and fats may produce acne and eczema or an excessive concentration may produce con stipation. In addition diseases such as pellagra and beriberi appear to owe their origin to an unbalanced dietary. We shall discuss these briefly later.
Substances consumed as food may exert directly a toxic or injurious action on the body in various ways. Thus ignorant people may undertake to use naturally poisonous substances as food and suffer severely as a consequence, employing for ex ample, toadstools, certain poisonous fish or plants containing toxic alkaloids. Through accidents in preparation or for commercial reasons, extraneous poisonous substances may be present in toxic amounts, such as the heavy metals, arsenic or formaldehyde. Or the food stuffs, while normally wholesome and harmless, may through some natural change become toxic, as for example the development of solanin in potatoes and of ergot in rye. Some will consume excessive quantities of alcoholic beverages, such as beer, wines or whisky, etc. Or lastly some individuals have iodiosyncrasies toward certain foodstuffs. The manifestations of these idiosyncrasies very much resemble an anaphylactic reaction. Among the food stuffs for which these reactions have been noted, are straw berries, certain sea foods, eggs, oatmeal and tomatoes.
There are three deficiency diseases whose common character warrants their receiving especial attention, namely scurvy, beri beri and pellagra.