When I accepted the invitation of the Royal Society of Arts to deliver the Cantor Lectures -- an invitation by which I was greatly honoured -- it was my intention to speak on the more general aspects of nutrition in relation to public health. But during the time that has elapsed since then I have seen, heard and read much both in the lay Press and elsewhere which leads me to believe that the significance of the term, 'nutrition', is not always fully understood. It has seemed to me desirable, therefore, to attempt an explanation of it, for if its meaning be clearly comprehended, its importance to the national health will become self-evident. This explanation must of necessity deal with fundamentals, familiar possibly to many of you. But there may be others of my audience, or who may read these lectures in their published form, whose understanding of nutrition is less complete: to these I especially address myself.
It is not possible to comprehend the relationship of food to nutrition, and of both to health and disease without some understanding of the structure of the body, of the functions of food, of the processes involved in the function of nutrition, and of the pathological changes brought about in the organs and tissues of the body by derangements of nutrition consequent on faulty food.
The human body, like the bodies of all plants and animals, excepting those of a very lowly order, is made up of countless millions of cells. Each cell is composed of a microscopic mass of protoplasm enclosed in a delicate membrane and having a differentiated part -- the nucleus. Every cell is a perfect physico-chemical laboratory, doing specialized work and needing special materials, both for this work and for the maintenance of its structure and functions. The protoplasm, or essential substance of living cells, is the physical basis of organic life. Upon it depend all the vital functions: nutrition, secretion, growth, reproduction, irritability and motility. It is subject to change or differentiation of the most varied sort: forming epithelium, bone, muscle, nerves, glands, organs of special sense, etc. It is a viscid, colloidal material made up of water (hydrogen and oxygen), carbon, nitrogen, and a number of other elements in complex and unstable combinations. The nitrogenous substances, known as proteins, enter largely into its structure, as do a number of inorganic salts. In addition to these, the cells contain another indispensable component: a phosphorized fat called lecithin. This substance facilitates the absorption of nutriment by the cell, the discharge of such specific products as it may contribute to the processes of the body as a whole, and the elimination of the end-products of its chemical activities.
The nucleus is the directing centre of the functional activity of the cell. It consists of a network of filaments whose meshes are filled with a special kind of protein containing phosphorus (nucleo-protein). Along the course of these filaments there are granules formed of an iron-containing protein (chromatin). Upon the integrity of the nucleus and the normal structure of its proteins depend all the vital processes. Presently we shall see how important the specific proteins of the nucleus are, how important are the mineral elements -- phosphorus and iron -- entering into their composition, how important is the optimum supply to the cells of all elements and complexes needed for cellular activity. For the root of the whole matter of food and nutrition is the nourishment of the cell, whether it be of bone, epithelium, muscle, gland, nerve or special sense. The inevitable consequence of its faulty nourishment is depreciation of its structure and functions -- the foundation upon which a vast edifice of disease is built.
Man is made up of what he eats. The constituents of his food are those of which his body is composed. His foodstuffs, derived from the vegetable and the animal kingdoms, consist, for the most part, of matter that is living, that was formerly living or that is derived from matter that was formerly living. Man cannot himself build up living tissue from materials which have in themselves no necessary connection with living protoplasm. This, plants do for him. Out of the earth and air, and under the influence of the sun, they transmute certain inorganic substances -- mineral salts, water and carbon dioxide -- into organic foodstuffs suited to his use and to the use of the animals whose produce or whose flesh he uses as food. He is, indeed, created out of the earth; and according as the earth provides, by way of plant and animal life, the materials needed by his body, so is that body well, ill or indifferently made and sustained.
Food may be defined as anything which when taken into the alimentary tract provides on digestion materials for the nourishment of the body; materials wherewith its cells fashion themselves each after its kind; materials to sustain their structure and to co-ordinate and control their functions; materials wherewith tissues of specialized functions elaborate their products; and materials to provide energy for cellular work.
The substances wherewith these purposes are effected are oxygen, water and the digestion products of proteins, fats, carbohydrates, inorganic elements and vitamins. Apart from oxygen and water, those at present known to be indispensable to the performance of the body's functions are thirty-six in number. Of these eighteen are amino-acids, derived from the proteins of the food. Eleven are inorganic elements: sodium, potassium, calcium, magnesium, phosphorus, iron, copper, sulphur, manganese, chlorine and iodine. One is glucose, derived chiefly from carbohydrates (though the body can in certain circumstances convert proteins and fats into glucose). One is linoleic acid, derived from fats. And five are vitamins: called respectively vitamins A, B, C, D and E.
No single foodstuff contains all these essentials. A properly constituted diet is such a combination of foodstuffs as does provide them all in proper quantity and proportion one to another. Their proportion, or balance, is a matter of great importance. We may, indeed, conceive of a properly constituted diet as a system of mutually adapted parts working together; absence or inadequacy of one part deranging the whole system. It may be said of the essential constituents of food, as Marcus Aurelius has said of other things: 'Meditate often upon the connection of these things and upon the mutual relation that they have one unto another. For all are, after a sort, folded and involved one within another and by these means all agree well together.'
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 play in 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 inadequately 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 the 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. Man's dependence on the earth is beautifully expressed by Robert Bridges when he says:
From Universal Mind the first-born atoms draw
their function, whose rich chemistry the plants transmute
to make organic life, whereon animals feed
to fashion sight and sense and give service to man,
who sprung from them is conscient in his last degree
of ministry unto God, the Universal Mind,
whither an effect returneth whence it first began.
(From The Testament of Beauty, by Robert Bridges Press, Oxford.)
Nutrition is the act or process -- it is, in fact, the series of co-ordinated processes -- whereby the nourishment of the body is effected. It consists in the taking-in and assimilation through chemical changes (metabolism) of materials with which the tissues of the body are built up and their waste repaired, by which the processes of the body are regulated, from which energy is liberated for the work the body has to do, and heat generated for the maintenance of its temperature. Nutrition is thus a fundamental function of the body. By the activity proper to it the structural integrity and functional efficiency of every cell is maintained. This, indeed, is its primary purpose; for if the mechanism of the body be perfect, and continue in perfection, it may be trusted to produce the energy needed for its work provided it be constantly supplied with suitable fuel. It is the mechanism that matters; the fuel (or Calories) is merely a question of the energy the body expends in the maintenance of vital processes -- respiration, circulation, secretion, etc. -- and in external (muscular) work.
The processes involved in the function of nutrition are mastication, deglutition, digestion, absorption, circulation, assimilation and excretion; the last including perspiration, exhalation, urinary excretion and defaecation There are thus three stages in nutrition: the first, effected in and by the alimentary tract; the second, in or by the cells composing the body; and, the third by the organs of excretory function -- skin, lungs, kidneys and bowel. It is of the utmost importance to realize that not only is the activity proper to the function of nutrition dependent on the efficient performance of all these acts, but their efficient performance is dependent on the adequate nourishment and functional efficiency of the organs and tissues performing them.
At this point, and to maintain the sequence of our story, reference might be made to the implications of these acts: mastication, digestion, absorption, assimilation, and so on. But it may be enough to remind you that they include the ordered operation of involuntary muscular action, the production of various digestive and other juices, the elaboration of ferments, or enzymes, and of catalytic agents needed for the speeding-up of chemical processes, the production of blood-forming substances, the interchange of body fluids, the transport of nutrients to the remotest recesses of the body, the removal of end-products of chemical action and of waste products from the body, and many other vital processes, all of which are influenced favourably or unfavourably by the constitution of the food. The alimentary tract and the organs (including the teeth) associated with it are of particular importance in this connection. They form a highly specialized mechanism designed for the nourishment of the body. The efficiency of the function of nutrition depends primarly on the functional efficiency of this mechanism and this, in its turn, on the constitution of the food.
Let me here draw your attention to some of the tasks which this mechanism has to perform. It splits up, by digestion, the foodstuffs in such a way that the essential nutrients are readily absorbed and made available to the cells in forms best suited to their use. Thus, the many and differing kinds of proteins, present in the plant and animal tissues we use as food, are all decomposed into fragments: the amino-acids to which previous reference has been made. From these fragments, on their absorption, the body builds up the proteins suited to it and to its different parts; for each part its special kind. Mark then, how important it is that the ingested proteins are of kinds that will furnish all the fragments needed. Similarly, the many kinds of carbohydrates -- starches, sugars, cellulose -- in food are all converted into glucose which is the chief fuel needed for the production of energy, muscular work and the maintenance of the temperature of the body. Likewise, the many kinds of fats, each containing different fatty acids, are converted by digestive processes into soluble soaps which pass readily through the intestinal wall and in their passage are re-converted into the fats needed by the body. The mineral ingredients of food are not only made avallable for use by the body but the intestinal canal itself regulates to a considerable extent their absorption and excretion. Each part of this mechanism has its own contribution to make to the furtherance of the function of nutrition. Thus, the stomach, in normal conditions, not only produces the acid and enzymes needed for gastric digestion but, by its normal contractions, it sustains the appetite for food. It produces, too, a substance which, by its combination with a material or materials of unknown nature contained in certain foodstuffs, gives rise to a product having the specific property of ensuring the normal formation of the red cells of the blood. Absence of one or other of the component parts of this product -- that produced in the stomach or that provided in certain foodstuffs -- leads to the occurrence of pernicious anaemia. This product is stored in the liver for use as required by the bone-marrow -- the birthplace of the red blood cells -- hence the use of liver extract for the cure of this disease. The stomach produces yet another substance which is necessary for the normal nutrition of the central nervous system. Thus early in the process of digestion is the welfare of these two most important tissues -- blood and nerve -- taken care of, and by the stomach.
Beyond the stomach, in the duodenum, there are glands that not only secrete digestive juices but some that produce protective substances lest the acid contents of the stomach should, after they leave it, erode the mucous membrane of the bowel. The continued production of these alkaline and other protective substances is an important factor in the prevention of duodenal ulcer; and the continued functional efficiency of the glandular cells producing them is dependent on the quality of the food. There is no stage in the whole process of digestion, absorption and passage of the gastro-intestinal contents along their appointed way which is not regulated and controlled by some substance or substances derived from food. Even the time-table of events, which normally proceeds with clockwork regularity, is under such control. It cannot be too insistently stated that disturbance of these processes, disturbance of this time-table, and alterations in form or consistency of the faecal residues are signs that something is going wrong or has gone wrong with the function of nutrition.
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 organs and parts of the body, 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, overcrowding and lack of exercise; insufficient rest and want of sleep; overwork 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 determination of the constitution of the food is the first essential in the assessment of the efficiency or lack of efficiency of the function of nutrition; the correction of food-faults is the first essential in the restoration of this function to normal.
Disorder of the function of nutrition, brought about by faulty food, causes the body to react in a variety of ways, depending on the nature of the food-faults that give rise to it, the part or parts of the body effected by it, and the intervention or the non-intervention of toxic or microbic agents of disease. These reactions, involving as they do disturbance in structure or in functions of various parts of the body, manifest themselves as subnormal states of health or as actual disease in great variety of form.
It will be realized from these considerations how far-reaching are the aspects of nutrition. They include the chemistry of food, the chemical changes (metabolism) whereby the function of nutrition is effected, the activity of the various organs and tissues in response to food conditions, the structural and functional changes induced in organs and tissues by faulty food, and the conditions of the body that result from faulty nutrition. Nutrition touches upon, indeed embraces in its compass, many subdivisions of biology -- bio-chemistry, bio-physics, morphology, physiology, pathology and medicine. Knowledge of it helps to bridge the gulf between physiology and pathology -- a gulf in need of bridging -- it is, indeed, an essential foundation of rational medicine.
Nutrition is commonly spoken of as a condition of body -- excellent, normal or subnormal, as the case may be -- when, in truth it is a function of the body on which condition of body -- i.e. health -- depends. For a proper comprehension of nutrition and of the processes involved in it this distinction has to be borne in mind. Such terms as under-nutrition and malnutrition are nowadays in common use, often without a clear conception of their meaning. Sometimes they are used to signify a condition of body which under-nourished would more fittingly describe; sometimes to signify under-feeding. 'Malnutrition', we are reminded by Fowler in his Modern English Usage, 'is a term to be avoided as often as under-feeding will do the work', for malnutrition is not merely underfeeding but disorder of the processes of nutrition brought about, as a rule, by the habitual use of food of improper quality.
Nutrition is, also, commonly defined as 'food', 'nourishment', 'that which nourishes'. But, as we have just seen, it is something much more than this. Food is the instrument, nutrition is the act of using it. To employ the term 'nutrition' as an alternative one for 'food' is to miss its true meaning, to fail in comprehending not only that in which nutrition consists, but all that is meant by its derangements.
Health is variously defined as 'soundness of body', 'state of bodily or mental well-being', 'freedom from disease, disorder, pain or weakness'. It is, in fact, a variable condition of body as in good, bad, poor or ill health. At its best it is 'that state of being in which all the parts and organs are sound and in proper condition; that condition of the body and its various parts and functions which conduces to efficient and prolonged life. It implies, moreover, the ability to produce and rear offspring fitted to live and efficiently to perform the ordinary functions of their species'. (Century Dictionary.) This optimum state of being can be attained when -- but only when -- the animal organism is adequately nourished. Further, it is possible to produce at will in animals under experimental conditions every grade of health -- good, bad or indifferent -- by alterations in the composition of their diets. Specific diseases of many kinds can be produced by feeding them on diets having specific food-faults or prevented by the correction of these faults. 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. This, too, is the experience of stockbreeders. Is man an exception to a rule so universally applicable to the higher animals? It seems most unlikely that he can be, although it is to be recognized that his requirements for adequate nutrition, and the effects upon him of deficiencies of various food-essentials, are not necessarily the same as in animals. Indeed, these effects are known to differ in different species of animals. Nevertheless, the principles of nutrition are fundamentally the same in man and in animals. It may, therefore, be taken as a law of life, infringement of which will surely bring its own penalties, that the greatest single factor in the acquisition and maintenance of good health is perfectly constituted food. It is this thesis that I have to sustain in these lectures.
The Experimental Method in Research on Nutrition
As you are probably aware, it is customary in the investigation of nutritional problems in the laboratory to use the experimental method and to feed animals -- rats, as a rule -- on synthetic diets composed of purified food-materials, but lacking this or that essential according to the nature of the inquiry in hand. The results of such experiments, though of great value in the ascertainment of the function of a given essential of food, and in the precise determination of the bio-chemical and pathological changes resulting from its want, are open to the objections that the observations made in rats are not necessarily applicable to human beings, that synthetic diets such as are used in these experiments are never eaten by human beings, that human diets are rarely or never wholly lacking in any single food-essential, that their deficiencies are usually multiple, and, that the diets of mankind are often unbalanced in other regards, such, for instance, as in their high content of carbohydrates relative to other food-essentials. The validity of these objections cannot be gainsaid; nevertheless, it may be remarked in passing that the frequency with which results observed in rats are applicable to man is remarkable -- a fact which will be the better appreciated from the examples I am about to place before you. Further, without such experiments on animals the vast amount of knowledge revealed by them within recent years would, for the most part, be hidden from us, and we would still be in ignorance of the kind of consequences to expect in man from his continued use of food of faulty constitution. We would, moreover, be in ignorance of what a properly constituted diet is.
But when in such investigations, diets composed of food-materials in common use by man or diets in actual use by human beings are used in the feeding of our animals, most of these objections do not arise, and the results observed have a more direct application to man, provided the faulty combinations of the food-materials entering into the diets are such as uninstructed man himself commonly employs. It has seemed to me necessary, therefore, to use in my experimental work diets composed of the actual materials that human beings eat; and it is with such diets that most of my work has been done.
Before giving examples of the effects of such faulty diets on the animal organism, let me draw your attention to the relation of the national diets of India to the physical efficiency of the races using them.
Food and Physical Efficiency
Nowhere in the world is the profound effect of food on physical efficiency more strikingly exemplified than in India. As you know, India has some 350 million inhabitants, made up of many races presenting great diversity in their characteristics, manner of life, customs, religion, food and food-habits. The tribes of the Indian Frontier, and of Himalayan regions, the Peoples of the Plains -- Sikhs, Rajputs, Mahrattas, Bengalis, Ooriyas, Madrassis, Kanarese and many others -- exhibit, in general, the greatest diversity of physique. And as each race is wedded to its own manner of living, to its own national diet, comparison between them is easy.
The level of physical efficiency of Indian races is, above all else, a matter of food. No other single factor -- race, climate, endemic disease, etc. -- has so profound an influence on their physique, and on their capacity to sustain arduous labour and prolonged muscular exertion. 'As we pass from the North-West region of the Punjab down the Gangetic Plain to the coast of Bengal, there is a gradual fall in the stature, bodyweight, stamina and efficiency of the people. In accordance with this decline in manly characteristics it is of the utmost significance that there is an accompanying gradual fall in the nutritive value of the dietaries.' So wrote McCay, as a result of his investigations, a quarter of a century ago. My own observations have served to confirm his conclusions, though I find other causes in addition to protein-insufficiency -- to which he attached chief importance -- for the decline he refers to. This decline extends also to the peoples of the south and west of India, being especially apparent in certain parts of the Madras Presidency. This is not to say that in these parts there are not many people of good physique nor that in the north of India there are not many whose physique is poor. But speaking of the generality of the people, it is true that the physique of northern races of India is strikingly superior to that of the southern, eastern, and western races (Fig. 1). This difference depends almost entirely on the gradually diminishing value of the food, from the north to the east, south and west of India, with respect to the amount and quality of its proteins, the quality of the cereal grains forming the staple article of the diet, the quality and quantity of the fats, the mineral and vitamin contents, and the balance of the food as a whole. In addition to these questions of quality there is the further one of quantity. In regard to the latter little need be said; for it is obvious that if a man is not getting enough to eat he cannot be physically efficient. Unfortunately, the numbers in India who do not get enough to eat may be counted by the hundred thousand.
Figure 1. Note fine physique of races (Mahratta, Sikh, Pathan) whose diets are well constituted and poor physique of those (Bengali, Madrassi) whose diets are ill-constituted. Note similar effect on rats fed on those diets. From left to right, the rats represent Sikh, Pathan, Mahratta, Goorkha, Kanarese, Bengali, Madrassi.
In general the races of northern India are wheat-eaters, though they make use also of certain other whole cereal grains. Now the biological value of the proteins of whole wheat is relatively high; and the wheat is eaten whole, after being freshly ground into a coarse flour (atta) and made into cakes called chapattis. It thus preserves all the nutrients with which Nature has endowed it, particularly its proteins, its vitamins and its mineral salts. The second most important ingredient of their diet is milk, and the products of milk (clarified butter or ghee, curds, buttermilk); the third is dhal (pulse); the fourth, vegetables and fruit. Some eat meat sparingly, if at all; others, such as the Pathans, use it in considerable quantity. Their food thus contains -- when they can get the food they want, which they do not always do -- all elements and complexes needed for normal nutrition (with the possible exception of iodine in some Himalayan regions) and abundance of those things that matter from the point of view of the structural and functional efficiency of the body. In conformity with the constitution of their dietaries they are the finest races of India, so far as physique is concerned, and amongst the finest races of mankind. Familiar as I am with the chapatti-fed races of northern India, I have little patience with those who would have us believe that 'white flour' is as good an article of diet as 'whole wheat flour'. White flour, when used as the staple article of diet, places its users on the same level as the rice-eaters of the south and east of India. They are faced with the same problem; they start to build up their dietaries with a staple of relatively low nutritive value. If their health and physical fitness are not to suffer, they must spend more money on supplementary articles of diet in order to make good the deficiencies of white flour than if they had begun to build on the surer foundation of whole wheat flour (Fig 2). So it is with rice, which is the staple article of diet of about ninety millions of India's inhabitants. The rice -- a relatively poor cereal at best -- is subjected to a number of processes before use by the consumer; all of which reduce -- some to a dangerous degree -- its already sparse supply of certain essential nutrients. It is parboiled, milled or polished; often all three. It is washed in many changes of water and, finally, it is boiled. It is thus deprived of much of its proteins and mineral salts and of almost all its vitamins. Add to this that the average Bengali or Madrassi uses relatively little milk or milk-products, that by religion he is often a non-meat-eater, that his consumption of protein, whether of vegetable or of animal origin, is, in general, very low, that fresh vegetable and fruit enter into his dietary but sparingly, and we have not far to seek for the poor physique that, in general, characterizes him. In short, it may be said that according as the quality of the diet diminishes with respect to proteins, fats, minerals and vitamins, so do physical efficiency and health; a rule which applies with equal force to the European as to the Indian.
Figure 2. White flour versus while wheat flour, showing individual weight curves of young rats fed on white flour or whole wheat flour alone or in combination with butter or yeast or both.
The arrows indicate day of death (usually from pneumonia). Note high mortality in rats fed on white flour diets: 30 per cent as compared with 4 per cent in those fed on whole wheat flour diets.
Relative Values of National Diets of India
This truth will probably be best appreciated by a reference to an experiment carried out in my laboratory some years ago, with the object of determining the relative values of certain national diets of India: Albino rats were employed in this test. The cycle of development in the rat takes place about thirty times as quickly as in man, so that the experiment about to be described, which lasted 140 days, would correspond to the observation of human beings, under the same experimental conditions, for a period of nearly twelve years. Seven groups of twenty young rats, of the same age, sex-distribution and bodyweight, were confined in large, roomy cages under precisely similar conditions of life. To one group the diet as prepared and cooked by the Sikhs, was given; to another that of the Pathans; to a third that of the Mahrattas; and so on through Goorkhas, Bengalis, and Kanarese to Madrassis. The results on the eightieth day of the experiment are shown in Fig. 1; from which it will be seen that the various diets ranged themselves in the following descending order of nutritive value: Sikh, Pathan, Maharatta, Goorkha, Kanarese, Bengali and Madrassi. At the end of 140 days the animals in each group were weighed and an average taken of their aggregate weight. The rat which conformed most closely to the average for its particular group was photographed side by side with the average rats from other groups. The photograph shown in Fig. 1 is the result. From it we see that it conforms to the results of observations made in man himself. In brief, the best diet -- that of the Sikhs -- contains in abundance every element and complex needed for normal nutrition, the worst diet -- that of the Madrassi -- has many faults: it is excessively rich in carbohydrates, and deficient in suitable protein, mineral salts and vitamins. Presently we shall see that this difference in the nutritive value of these diets is reflected in the diseases from which the people of the north and south of India suffer.
Freedom of Well-Fed Animals from Disease
So impressed was I by the adequacy of the northern Indian's diet that during the later years of my experimental work I used it as the diet of my stock rats. These numbered about 1,000. Their food consisted of chapattis lightly smeared with fresh butter, sprouted Bengal gram (pulse), raw, fresh vegetables (cabbage and carrots) ad libitum, milk, the hard crusts of bread (to keep their teeth in order), a small ration of meat with bone once a week, and water. They were kept in stock for about two years -- a period approximately equal to the first fifty years in the life of a human being -- the young being taken as required for experimental purposes, and the remainder used for breeding. During the five years prior to my leaving India there was in this stock no case of illness, no death from natural causes, no maternal mortality, no infantile mortality. It is true that the hygienic conditions under which they lived were ideal, that they were comfortably bedded in clean straw, that they enjoyed dally exposures to the sun practically the whole year round, and that the care bestowed upon them was great; but the same care was bestowed during these years on several thousand deficiently-fed rats, which developed a wide variety of ailments (vide infra) while the well-fed animals enjoyed a remarkable freedom from disease. It is clear, therefore, that it was to their food that this freedom was due. If man himself did not provide in his own person the proof that a diet composed of whole cereal grains, or a mixture of cereal grains, milk, milk-products, pulses and vegetables, with meat occasionally, sufficed for optimum physical efficiency, this experience in rats would do so. It is not, therefore, unreasonable to conclude that if by minute attention to three things -- cleanliness, comfort and food -- it is possible to exclude disease from a colony of cloistered rats, it is possible greatly to reduce its incidence by the same means in human beings and to produce a race whose physique is as nearly perfect as nature intended it to be.
Supposing now we cut out the milk component of this diet or reduce it to a minimum, we find that disease soon begins to make its appearance, especially if at the same time we limit the consumption of fresh vegetable foods. I have repeatedly made these restrictions with the result that respiratory diseases, gastro-intestinal diseases and maladies consequent on degenerative changes in mucous membranes and other structures of the body become frequent. It is apparent, therefore, that the diet of the Sikhs is only health-promoting so long as it is consumed in its entirety. Indeed, we know that those of this race who, for whatever reason, do not consume adequate quantities of milk, milk products and fresh vegetables, do not long retain the fine physique for which the Sikhs are famous. These food-materials are for them and in their own parlance, takatwar khurak (foods that give strength); nowadays we speak of them as 'the protective foods', since they make good the deficiencies of muscle meat, refined cereals, etc., which enter so largely into the diets of western peoples.
Before leaving this experience, let me emphasize two things: the first, that all things needful for adequate nourishment of the body and for physical efficiency are present in whole cereal grains, milk, milk-products, legumes, root and leafy vegetables and fruits, with egg or meat occasionally. What is eaten besides these is more a matter of taste than of necessity. And the second: that the diet must be complete in every essential. It is not to be expected that by substituting, for instance, wholemeal bread for white bread, health will benefit greatly unless the substitution completely restores the balance of an ill-balanced diet, nor that by adding bottled vitamins or mineral elements to a faulty diet its faults will be remedied, unless they be confined to vitamins or mineral elements. The correction of food faults lies first in their computation and thereafter in the construction of a diet so balanced and complete as to satisfy all physiological needs. Fortunately, the layman need not concern himself with such computations, though in institutions they may be necessary. It suffices for him to know that in whole cereal grains, milk, milk products, eggs and fresh vegetables he has foods that, when used in adequate quantities, will maintain the structural integrity and functional efficiency of his body.
Consider now another experiment, also in rats (Fig. 3). Two identical groups, twenty in each, from the above-mentioned stock were used in it. They were housed in colonies: both in large cages of the same dimensions. One group was fed on a diet similar to that used by the Sikhs; the other on a diet such as is commonly used by the poorer classes in England. The latter diet consisted of white bread, margarine, over-sweetened tea with a little milk (of which the rats consumed large quantities) boiled cabbage and boiled potato, tinned meat and tinned jam of the cheaper sorts. It has many faults, of which vitamin and mineral deficiencies are the chief. The first thing one noticed, as this experiment progressed, was that the members of the former, and well-fed, group lived happily together. They increased in weight and flourished. The other group did not increase in weight; their growth was stunted; they were badly proportioned; their coats were staring and lacking in gloss; they were nervous and apt to bite the attendants; they lived unhappily together and by the sixtieth day of the experiment they began to kill and eat the weaker ones amongst them. When they had disposed of three in this way I was compelled to segregate the remainder. The experiment was continued for 187 days, or for a period which would correspond to about sixteen years in man. During this period three animals in the former group died -- one (a pregnant animal) from an abdominal injury, one from an undiscovered cause, and one from pneumonia. In the latter group six died of pneumonia and three were killed by their fellows. The survivors in both groups were killed and subjected to post-mortem examination. The outstanding differences in the incidence of disease in the two groups were these: disease of the lungs was much commoner in the group fed on the poorer class Britisher's diet; gastro-intestinal disease (gastritis, gastric congestion, outgrowths of epithelium in the stomach, and intestinal stasis) was frequent in this group, while that receiving the Sikh diet was free from it. Indeed, the animals fed on the poorer class Britisher's diet fared little or no better than those, in another experiment, that were fed on a diet in common use in Madras, and the maladies from which they suffered were much the same. The results of this experiment indicated clearly that a diet, such as is commonly used by the poorer classes in England, gives rise in rats to two chief classes of ailment -- pulmonary and gastrointestinal -- while a more perfectly constituted diet, such as is commonly used by northern Indian races, affords a considerable measure of protection against both. It is not unreasonable, therefore, to expect that, other things being equal, similar results will arise in man from the use of these diets. We do, in fact, find that these two classes of ailment are amongst the most frequent of the maladies afflicting the poorer class Britisher (Fig. 5) as well as the poorer class Madrassi.
Food and Peptic Ulcer
Another example may be provided by peptic ulcer (gastric and duodenal). This malady is very common in the south of India, rare in the north. It is, in fact, fifty-eight times more common in the latter part of India; it is particularly so in Travancore. In order to determine whether or not it was related in its genesis to diet the following experiment was undertaken. Three groups of young rats, from the healthy stock above referred to, were fed as follows: one on the well-constituted diet as used by the Sikhs, but reinforced with additional milk; one on the carbohydrate-rich, protein-poor, vitamin-poor and mineral-poor diet in common use by the poorer class Madrassi; and the third on the diet -- largely made up of tapioca -- in common use by the poorer classes in Travancore, amongst whom peptic ulcer is so common. This diet has many faults, of which protein, mineral and vitamin deficiencies are the chief. The experiment was continued for close on 700 days, a period which would correspond to about fifty years in man. Many animals in the last two groups died during its course, from the usual respiratory and gastrointestinal diseases. The results revealed at post-mortem examination of all the animals were, as far as peptic ulcer was concerned, as follows: first group (Sikh diet), nil, second group (Madrassi diet), 11 per cent; third group (Travancore diet), 29 per cent incidence of peptic ulcer.
Here, again, we see that a disease common in certain parts of India (as it is in this country) can be produced in rats by feeding them on the faulty diets in common use by the people of these parts, while other animals, fed on a perfectly constituted diet in common use by human beings, amongst whom peptic ulcer is rare, remain free from it. Surely, if we are to place any reliance on animal experiments of this kind, we must regard faulty and ill-balanced food as a cause of gastric and duodenal ulcer in human beings? How it causes it, whether by direct or indirect action or want of action, or because of want of this or that essential of food or excess of this or that one, is a matter of little consequence -- though of much scientific interest. What is of consequence, not only to the people of India, but, I venture to affirm, to the people of this country, is that by the continued use of a perfectly constituted diet they are unlikely to develop gastric or duodenal ulcer.
Experimental Beri-Beri and 'Stone'
Examples of this kind, occurring in my own experience, might be multiplied to an extent that would occupy many hours in their narration. I must, therefore, limit their numbers. Two will suffice: As no doubt you all know there is a disease called beri-beri, which is prevalent in certain parts of the tropics, chiefly amongst rice-eaters. It is not prevalent amongst rice-eaters in other parts of India, nor is it so prevalent in its endemic homes as a comparatively recent broadcast by the B.B.C. may have led some of you to suppose: every other woman in the south of India does not suffer from beri-beri. About forty years ago Eijkman noticed that if fowls were fed on an exclusive diet of polished rice they developed a type of polyneuritis which had certain likenesses to beri-beri -- a malady in which polyneuritis is a prominent symptom. He found, moreover, that they did not develop this 'nutritional polyneuritis' -- as he rightly called it -- when they were fed on unpolished rice or on polished rice to which the rice-polishings were added. So he, and his colleague, Grijns, concluded that there was something -- vitamin B1 as it ultimately proved to be -- in the rice-polishings which prevented the nutritional polyneuritis in birds, a something that might possibly prevent beri-beri in man, as indeed it (vitamin B1) is now known to do. But to prevent is one thing, to cause, if the preventive be removed, is, or may be, another. It is nowadays an almost universal belief that on a diet of polished rice or on a diet devoid of vitamin B1 beri-beri develops after a few months. Theoretically, this is possible, in practice it is a rare occurrence. For no one, even in localities where beri-beri is endemic, ever does live on an exclusive diet of polished rice or on a diet devoid of vitamin B1; always the diet contains some of this factor, however little that may be. Further, only a relatively small proportion of persons subsisting on diets deficient in vitamin B1 do develop beri-beri, even in endemic areas of the disease. If one feeds pigeons on a diet almost devoid of this vitamin they develop polyneuritis, but polyneuritis is only one of the symptoms of human beri-beri; there are two others, equally important -- grave disorder of the heart and oedema. Now supposing one does, as I have often done, feed pigeons on diets similar to those in actual use by human sufferers from beri-beri, then we find that a disease having all the pathological characters of true beri-beri does develop in a proportion of the birds, just as it does in a proportion of human beings. But this diet is not devoid of vitamin B1, although it is low in it. It does not contain enough of it to prevent the disease, or enough of some other factor in addition to vitamin B1, to prevent the development of the complete syndrome, or, alternatively, to prevent the development or operation of the ultimate causal agents of the malady. Now if in such a diet one substitutes whole wheat flour for a part of the rice and at the same time we add to it fresh vegetables, such as tomatoes, then the disease does not arise, either in birds or in man. I have, myself, so prevented human beri-beri in a certain gaol in the East where it was wont to break out year after year; and many others, since the days of Takaki -- who first prevented it in the Japanese Navy as long ago as 1882 -- have by similar means prevented it. This is another example of the control that the use, in animal experiments, of human diets may exercise over results reached by the use of a single component of them, such as polished rice.
We have seen that if rats be fed on the perfectly constituted diet of the Sikhs they remain in good health: they do not, for instance, develop stone in the urinary tract. But if one removes from this diet the milk and milk products and cuts down the fresh vegetable foods to a minimum, then many of them do develop this condition. They develop also a wide variety of other ailments, but it is with 'stone' that I am here concerned. If we replace the milk or butter they do not develop this condition. This is an observation of great importance to the wheat-eating races of northern India, amongst whom 'stone' is so common. For it is precisely these articles of diet -- milk, milk products and fresh vegetables -- which the poorer classes amongst them have to cut out when times are hard. There are, no doubt, other factors concerned in the causation of 'stone'; but the broad fact remains that a perfectly constituted diet rich in milk, milk products and fresh vegetable foods affords a high degree of protection against it.
Variety of Disease in Improperly Fed Animals
I have mentioned the freedom from disease enjoyed by well-fed and hygienically housed albino rats. During the last eighteen years of my experimental work in India I used many thousands of animals -- rats, pigeons, fowls, rabbits, guinea-pigs and monkeys -- feeding them on diets not synthetically prepared from purified foodstuffs but from foodstuffs in common use by the people of India; my purpose, as previously hinted, being to learn what relation the food used by the people had to the diseases from which they suffered. At the risk of being tedious I shall now enumerate the maladies I have encountered in these improperly-fed animals, leaving out of count such manifestations of ill health as weakness, lassitude, irritability and the like, which are commonly met with in malnourished animals. Here is the list. Skin diseases: loss of hair, gangrene of the feet and tail, dermatitis, ulcers, abscesses, oedema. Diseases of the eye: conjunctivitis, corneal ulceration, xerophthalmia, panophthalmitis, cataract. Diseases of the ear: otitis media, pus in the middle ear. Diseases of the nose: rhinitis, sinusitis. Diseases of the lungs and respiratory passages: adenoids, pneumonia, broncho-pneumonia, bronchiectasis, pleurisy, pyothorax, haemothorax. Diseases of the alimentary tract: dental disease, dilatation of the stomach, gastric ulcer, epithelial new growths in the stomach (two cases of cancer), duodenal ulcer, duodenitis, enteritis, colitis, stasis, intussusception and a condition of the lower bowel suggestive of a pre-cancerous state. Diseases of the urinary tract: pyonephrosis, hydronephrosis, pyelitis, renal calculus, nephritis, urethral calculus, dilated ureters, vesical calculus, cystitis, incrusted cystitis. Diseases of the reproductive system: endometritis, ovaritis, death of the foetus in utero, premature birth, uterine haemorrhage, testicular disease. Diseases of the blood: anaemia, a pernicious type of anaemia, Bartonella muris anaemia. Diseases of the lymph and other glands: cysts, abscesses, enlarged glands. Disease of the endocrine glands: goitre, lymph-adenoid goitre, adrenal hypertrophy, atrophy of the thymus, haemorrhagic pancreatitis (very occasionally). Diseases of the heart: cardiac atrophy, cardiac hypertrophy, myocarditis, pericarditis, hydropericardium. Diseases of the nervous system: polyneuritis, beri-beri, degenerative lesions. Diseases of bone: crooked spine, distorted vertebrae (no work was done on rickets -- a known 'deficiency disease'). General diseases: malnutritional oedema, scurvy, prescorbutic states.
All these conditions of body, these states of ill health, had a common causation: faulty nutrition, with or without infection. They are the clinical evidence -- the signs and symptoms -- of the structural and functional changes in organs or parts of the body that result directly or indirectly from faulty nutrition. It will be noted that local infections and maladies of a chronic and degenerative kind are conspicuous amongst them. These maladies are, in short, the symptoms of malnutrition as observed in animals fed on faulty diets -- some of them admittedly very faulty -- in use by human beings, or on food-materials in use by them. It is reasonable, then, to expect that maladies of a similar order are likely to result from malnutrition in human beings. In my next lecture I shall endeavour to make clear how it is that food of improper constitution leads to that disturbance of structure or function of organs or parts of the body which is 'disease'.