II. FOOD AND HEALTH.
From the point of view of the political economist, the idle man has no right to participate in the food-supply of the active worker. Whatever may be the correctness and force of the arguments which the economist may use by way of proving that the non-worker and non-producer has no right to participate in the ordinary nutritive supply of his fellows, the physiological standpoint assumes another and different aspect. The idle man grows hungry and thirsty with the regularity of the man who works. He demands food and drink as does his energetic companion; and the plea that idleness can need no food-support, may be met in a singularly happy and forcible fashion by a plain scientific consideration. In the first instance, the idle man might, by an appeal to science, show, that whilst he apparently spent life without exertion, his bodily functions really represented in their ordinary working an immense amount of labour. Sleeping or waking, that bodily pumping-engine the heart does not fail to discharge its work, in the circulation of the blood. The rise and fall of the chest in the sleeping man remind us that it is not death but his ‘twin-brother sleep,’ that we are observing. If we make a calculation respecting the work which the heart of a man, idle or active, performs in twenty-four hours, we may discover that it represents an amount of labour equal to one hundred and twenty foot-tons. That is to say, if we could gather all the force expended by the heart during its work of twenty-four hours into one huge lift, such force would be equal to that required to raise one hundred and twenty tons-weight one foot high. Similarly, the work of the muscles of breathing in twenty-four hours, represents a force equal to that required to lift twenty-one tons one foot high. These are only two examples out of many, which the ordinary work and labour of mere vegetative existence, without taking into consideration any work performed—in the popular sense of the term—involves.
We thus discover that, apart altogether from the every-day labour of life, in which brain and muscles engage, an immense amount of work is performed in the mere act of keeping ourselves alive. Nowhere in nature is work performed without proportionate waste, or wear and tear of the machine that works. This dictum holds quite as true of the human body as of the steam-engine. And as the engine or other machine requires to be supplied with the conditions necessary for the production of force, so the living body similarly demands a supply of material from which its energy (or the power of doing work) can be derived. As the engine obtains the necessary conditions from the fuel and water it consumes, so the living body derives its energy from the food upon which it subsists. Food in this light is therefore merely matter taken from the outside world, and from which our bodies derive the substances required for the repair of the waste which the continual work of life entails. In the young, food serves a double purpose—it supplies material for growth, and it also affords substance from which the supply of force is derived. In the adult, whilst no doubt, to a certain extent, the food supplies actual loss of substance, it is more especially devoted to the performance of work, and of maintaining that equilibrium or balance between work and repair, which, as we have seen, constitutes health.
Viewed in this light, the first important rule for food-taking is founded on the plain fact, that in the food we must find the substances necessary for the repair of our bodies, and for the production of the energy through which work is performed. Food-substances in this light fall into two well-marked classes—namely, into Nitrogenous and Non-nitrogenous substances. Another classification of foods divides them into organic and inorganic, the former being derived from animals and plants—that is, from living beings—while the latter are derived from the world of non-living matter. Thus, animal and plant substances represent organic foods; while water and minerals, both of which are absolutely essential for the support of the body, represent inorganic food materials. It would appear that from living matter alone, do we obtain the materials for generating force. The inorganic water and minerals, however, appear to be absolutely necessary for the chemical alterations and changes which are continually taking place within the body.
Adopting the classification of foods into the Nitrogenous and Non-nitrogenous groups, we discover examples of the first class in such substances as albumen, seen familiarly in white of egg and other substances; gluten, found in flour; gelatin, obtained from hoofs and horns; legumin, obtained from certain vegetables; casein, found in milk; and allied chemical substances. These substances possess a remarkable similarity or uniformity of composition. It would appear that in the process of digestion they are reduced to a nearly similar state, and on this account they can replace one another to a certain extent in the dietaries of mankind.
The nitrogenous foods have often been popularly termed ‘flesh-formers,’ and doubtless this name is well merited. For, as the result of experiment, it would seem that the chief duty performed by the nitrogenous parts of our food is that of building up and repairing the tissues of the body. They also produce heat, through being chemically changed in the blood, and thus aid in the production of force or energy. But it would also appear tolerably certain, that in a complex fashion the nitrogenous parts of our bodies assist or regulate in a very exact manner the oxidation or chemical combustion of the tissues.
It should be noted that nitrogenous foods are composed chemically of the four elements, carbon, hydrogen, oxygen, and nitrogen; the presence of the last element giving the characteristic name and chemical features to the group. Most of these foods in addition contain small proportions of sulphur and phosphorus.
An interesting advance in our knowledge of the part played by nitrogenous foods in the work of the body was made, when an idea of Liebig was overthrown by later experimentation. Liebig supposed that the nitrogenous foods required first to be actually converted into tissue—that is, into bodily substance—before their energy or work-producing power could be liberated. In this view, muscular force, through which we move, was believed to be dependent on the changes, destructive or otherwise, which take place in the muscles. The substance called urea, chiefly given off as a waste product by the kidneys and chemically representing nitrogenous waste, was in Liebig’s view regarded as representing the results of muscular force which had been exerted. But two scientists, Fick and Wislicenus of Zurich, proved, by a laborious series of personal experiments in mountain ascents, that a non-nitrogenous diet will maintain the body for a short time during the performance of severe work, no great increase in the amount of urea given off being noticed. The work in question was proved to have been performed on the carbon and hydrogen of the food consumed. These experiments have led to the now accepted view, that a muscle, instead of losing substance during work and thus wasting, in reality consumes nitrogen, and grows. The exhaustion of the muscle is dependent not so much on chemical waste, as on the accumulation within it of the waste products of other foods. The muscle, in other words, is merely the agent whereby so much energy, derived from the food, is converted into actual and applied force. Did muscle really waste, as Liebig supposed, the heart’s substance would be entirely consumed by its work of one week!
Such being the functions and nature of nitrogenous foods, we may now glance at the non-nitrogenous division. Four groups of foods are included in this latter class—namely (1) Starches and sugars, or ‘amyloids’ as they are often termed; (2) fats and oils; (3) minerals; (4) water. The starches and sugars include not merely starch and sugar, as ordinarily known, but various gums, and certain acids, such as lactic and acetic acids. Starch, as in bread, is a most important food. These foods appear to go directly to maintain animal heat, and to give energy, or the power of doing work, to the animal frame. The heat-producing powers of starches and sugars are certainly inferior to those of the fats and oils. But starches and sugars can be converted into fat within the system; and hence persons who suffer from a tendency to obesity are warned to exclude these foods from their dietaries. Starches and sugars likewise appear to assist in some measure the digestion of nitrogenous foods. That fats and oils are heat-producing foods is a fact taught us by the common experience of mankind that northern nations consume the greatest proportion of fat. The heat-producing powers of fat have been set down at two and a half times as great as those of starch and sugar; and there is no doubt that, in addition to assisting in the conversion of food into body substances, the fatty parts of our food also assist in the work of removing waste matters from the body. Fat, in addition, being chemically burned in the blood, gives rise to the force which we exert in ordinary muscular work.
The mineral parts of our food play an important part in the maintenance of the frame. We thus require iron for the blood, phosphorus for the brain and nerves, and lime for the bones; whilst a variety of other minerals is likewise found in the blood and other fluids of the frame. The uses of the mineral constituents of our body are still a matter of speculation. Small as may be the quantity of certain minerals required for the support of the body, serious health-derangement may result when we are deprived of these substances. Thus, scurvy appears to be a disease associated with the want of the mineral potash in the blood; and the cure of this disease is therefore accomplished when we supply to the blood those mineral elements which have previously been deficient. Common salt, or chloride of sodium, as it is chemically termed, although not entering into the composition of the body, appears to form an important part of all the secretions; and there can be little doubt that this mineral aids the formation and chemical integrity of the gastric juice of the stomach.
Water forms the last item in the list of non-nitrogenous foods. Of all foods, perhaps, water is the most important, seeing that it is a substance which, in the absence of all other nourishment, can sustain life for a period numbering many days. Thus, whilst a man dies in from six to seven days when deprived of solid food and water, life may be prolonged to as many as sixty days on water alone. The high importance of water as a food is abundantly proved, when we discover that it constitutes about two-thirds of the weight of the body; that it enters into the composition of the brain to the extent of eighty per cent.; that the blood consists of nearly eighty per cent. of water; and that even bone contains ten per cent. of this fluid. Entering thus into the composition of every fluid and tissue of the body, and being perpetually given off from lungs, skin, and kidneys in the ordinary work of life, there is little wonder that water assumes the first place amongst foods. Regarding the uses of water as a food, we see that it dissolves and conveys other foods throughout the system; that it assists in removing waste products; and that it also takes a share in regulating the temperature of the body through its evaporation on the skin.
Having thus considered the chemistry of foods, we may now pass to discuss the natural rules which science describes for the health-regulation of life in the matter of diet. A primary rule for food-taking is that which shows that, for the due support of the body, we require a combination of nitrogenous and non-nitrogenous foods. This fact is proved by the consideration that milk, ‘nature’s own food,’ on which the human being grows rapidly in early life, is a compound of both classes of foods. So also, in an egg, from which is formed an animal body, we find a combination of the two classes. Death results if we attempt to feed on either class alone; and as the body consists of both classes of substances, the justification for the combination of foods is complete. Man can obtain the required combination of nitrogenous and non-nitrogenous foods from animals alone, from vegetables alone, or from animals and vegetables combined. The water, of course, which is an absolutely essential feature of all dietaries, is regarded as an additional item. In regulating the dietary of mankind, it is found that the food of nations is determined largely, or completely, by their situation on the earth’s surface. Thus, the northern nations are largely animal feeders; whilst the southern peoples of the world are to a great extent vegetarians. Individual experience and taste produce amongst the units of a nation special proclivities in the way of diet. But we can readily see that mankind, with that elasticity of constitution and power to avail themselves of their surroundings, can adapt themselves to their environments, and become animal feeders, vegetable feeders, or subsist on a mixed dietary at will. This is the true solution of the vegetarian controversy. It is climate and race which determine the food of a nation. It is individual intelligence, liking, and constitution which determine variations and departures from the dietaries of the race.
The relations between food and work naturally present themselves as topics of the highest importance. In determining the standard of health, it is clear that from our food alone, we can obtain the energy or power of work required for the discharge of the duties of life. An interesting point therefore arises regarding the differences which are entailed by varying conditions and amounts of labour. Dr Letheby tells us that an adult man in idleness requires, to obtain from his food for the support of his body, 2.67 ounces of nitrogenous matter and 19.16 ounces of non-nitrogenous matter per day. If the individual is to participate in ordinary labour, the amount of nitrogenous matter obtained from his food must be increased to 4.56 ounces, while the non-nitrogenous must be represented by 29.24 ounces. In the case, lastly, of active labour the amount of food required must be increased to 5.81 ounces of nitrogenous, and 34.97 ounces of non-nitrogenous matter.
Dalton gives the following as the quantity of food, per day, required for the healthy man, taking free exercise in the open air: meat, sixteen ounces; bread, nineteen ounces; fat or butter, three and a half ounces; water, fifty-two fluid ounces. It ought to be borne in mind that these amounts of food represent the diet for a whole day compressed, so to speak, into a convenient and readily understood form. Another calculation, setting down the daily amount of food required by an adult, at nitrogenous matter three hundred grains, and carbon at four thousand grains, shows that these amounts would be obtained from eighteen ounces of bread; one ounce of butter; four ounces of milk; two ounces of bacon; eight ounces of potatoes; six ounces of cabbage; three and a half ounces of cheese; one ounce of sugar; three-quarters of an ounce of salt; and water (alone, and in beverages) sixty-six and a quarter ounces—a total of no less than six pounds fourteen and a quarter ounces. Summing up the question of the amounts of food required by a healthy adult daily, and excluding water in all forms as a matter of separate calculation, it may be said that four and a half ounces of pure nitrogenous matter would be required in addition to three ounces of fatty food, fourteen ounces of starch or sugar, and one ounce of mineral matter. An ordinary adult consuming in twenty-four hours, food items equal to those contained in one pound of meat and two pounds of bread, may be regarded as consuming food of sufficient amount for ordinary work. When the work is increased, the diet must naturally be increased likewise. We find that persons in active employment require about a fifth part more nitrogenous food, and about twice the quantity of fat consumed by those engaged in light work; the sugars and starches remaining the same.
An interesting practical calculation has been made regarding the amounts of different foods required to perform a given and fixed piece of work. Taking the work performed by the German observers already named, as a standard, namely, that of raising a man’s weight (one hundred and forty pounds) ten thousand feet high, it has been found that the amounts and cost of various foods required for the performance of this work is as follows: Bread, 2.345 pounds, cost 3½d.; oatmeal, 1.281 pounds, cost 3½d.; potatoes, 5.068 pounds, cost 5¼d.; beef-fat, 0.555 pounds, cost 5¼d.; cheese, 1.156 pounds, cost 11½d.; butter, 0.693 pounds, cost 1s. 0½d.; lean beef, 3.532 pounds, cost 3s. 6½d.; pale ale, nine bottles, cost 4s. 6d.
The proportion of the different food-elements in an ordinary dietary has been set down as follows: nitrogenous matter one, fats six, starches and sugars three; and these proportions appear to be represented with singular exactness in the ordinary dietaries which experience has recommended to mankind. Excess of food in the matter of nitrogenous elements tends to induce diseases of an inflammatory and gouty nature, and likewise leads to fatty degeneration of the tissues. When, on the other hand, there exists lack of nitrogenous substances, the individual experiences weakness, want of muscular power, and general prostration. The healthy mean is that in which the proportions of nitrogenous and non-nitrogenous food are maintained as above indicated.
In the construction of dietaries, a few practical hints remain for notice. Thus, as regards sex, the dietaries of women are usually, in the case of the working-classes, estimated at one-tenth less than those of the opposite sex. Age has an important influence in determining the amount and quality of food. The growing body consumes more food, relatively to work and weight, than the adult, inasmuch as it requires material for new tissue. An infant under eight or nine months should receive no starch whatever in its dietary, because it is unable to digest that substance. Health is naturally a condition in which the question of foods assumes a high importance, and various dietaries, as is well known, are adapted for the cure of disease. The relation of food to work has already been alluded to, and statistics detailed; but it may be added that the brain-worker requires his food in a more readily digestible form, and also in smaller bulk and in more concentrated shape, than the muscle-worker or ordinary labourer. What has been said concerning foods will tend to show how wide is the field which the subject of nutrition occupies. It may only here be added, that the education of the individual in health laws and in the science of foods and food-taking, forms the only sure basis for the intelligent regulation of that all-important work—the nourishment and due support of the frame in relation to the work we perform and to every circumstance of life.