Digitized by the Internet Archive in 2011 with funding from LYRASIS members and Sloan Foundation http://www.archive.org/details/economyinfeedingOOferr ovi- SrOERS AGElCtrLTOEAL ElPERDfflNT STATION, s . 43 CONNECTICUT Agricultural Experiment Station NE\V HAVEN, CONN. BULLETIN 215 DECEMBER, 1919 ECONOMY IN FEEDING THE FAMILY THE FOOD VALUE OF MILK By Edna L. Ferry CONTENTS Page Introduction 3 Constitution of Proteins 4 Tiie Proteins of Milk 7 The Vitamines of Milk 2i The Sugar of Milk 28 The Mineral Matters of Milk 28 The Cost and Economy of Milk 28 Summary 30 The Bulletins of this Station are mailed free to citizens of Connecticut who apply for them, and to others as far as the editions permit. CONNECTICUT AGRICULTURAL EXPERIMENT STATION OFFICERS AND STAFF December, 1919. BOARD OF CONTROL. His Excellency, Marcus H. Holcomb, ex-officio. President. James H. Webb, Vice President Hamden George A. Hopson, Secretary New Haven E. H. Jenkins, Director and Treasurer New Haven Joseph W. Alsop Avon Charles R. Treat Orange Elijah Rogers Southington William H. Hall South Willington Administration. Chemistry. Analytical Laboratory. Protein Research. Botany. Entomology. Forestry. Plant Breeding. Vegetable Growing. STAFF. E. H. Jenkins, Ph.D., Director and Treasurer. Miss V. E. Cole, Librarian and Stenographer. Miss L. M. Brautlecht, Bookkeeper and Stenographer. William Veitch, In charge of Buildings and Grounds. E. Monroe Bailey, Ph.D., Chemist in charge. R. E. Andrew, M.A. ^ C. E. Shepard, I Assistant Chemists. H. D. Edmond, B.S. j Frank Sheldon, Laboratory Assistant. V. L. Churchill, Sampling Agent. Miss Alxa H. Moss, Clerk. T. B. Osborne, Ph.D., D.Sc, Chemist in Charge. G. P. Clinton, Sc.D., Botanist. E. M. Stoddard,. B.S., Assistant Botanist. Miss Florence A. McCormick, Ph.D., Scientific Assistant. G. E. Graham, General Assistant. Mrs. W. W. Kelsey, Secretary. W. E. Britton, Ph.D., Entomologist; State Entomologist. B. H. Walden, B.Agr., Phillip Carman, Ph.D. M. P. Zappe, B.S., I. W. Davis, B.Sc, K. F. Chamberlain, Assistants. Miss Gladys M. Finley, Stenographer. Walter O. Filley, Forester, also State Forester and State Forest Fire Warden. A. E. Moss, M.F., Assistant State and Station Forester. H. W. HicoCK, M.F., Assistant. Miss E. L. Avery, Stenographer. Donald F. Jones, S.D., Plant Breeder. C. D. HuBBELL, Assistant. W. C. Pelton, B.S. THE FOOD VALUE OF MILK At the annual meeting of the Connecticut Dairymen's Asso- ciation in January, 1919, Miss Edna L. Ferry of this Station gave an address with the above title. "At the conclusion of Miss Ferry's address it was voted to ask the Experiment Station to prepare a bulletin on the food value of milk which could be distributed among consumers." In response to the request this bulletin has been prepared, which is largely a transcript of Miss Ferry's paper. Her untimely death has put on others the work of editing it which has consisted chiefly in slight changes in form and arrangement. Introduction. Milk is the only food that supplies all of the food elements which the new-born animal must have in order to live and grow. Among wandering Indian tribes the child whose mother fails to nurse it is doomed to die because no other milk can be had. In countries where milch animals are scarce, as in Japan and China, mothers from necessity, if not from choice, nurse their children for relatively long periods, sometimes for two and even three years. In countries where dairy cattle are abundant the cow is the foster mother of a large part of the infant population which for one reason or another does not have its mother's milk. The world has had no more pitiful tragedies in the present war than the starving to death — or to life-long inefficiency — of a large infant population. Hoover, who had the best chance to observe and who is given to sober statement without exaggeration, says : "One of the first acts of the Germans was to denude the people of Belgium to a very large extent and the north of France almost wholly of their cattle. In consequence it has been necessary to maintain a stream of condensed milk for the whole of the last four years. "The European races are absolutely dependent for the rearing of their young on these cattle. There is no cruelty to a population greater than to rob them of their dairy stock." The need of milk is not limited to the first year of life. When the child is able to enlarge its diet and take solid food, milk is 4 CONNECTICUT EXPERIMENT STATION BULLETIN 215. an indispensable adjunct. Of the 27 brands of "infant foods" in market, which were examined by this Station (Report 191 5, p. 324), 16 claim to contain milk and the directions for the use of 9 others prescribe mixture with milk. All through childhood and youth bread and milk and cereal and milk are recognized as "growing foods." Milk, too, is the most commonly prescribed food for adults in severe illness and a resource in time of sudden exhaustion. It is hardly too much to say that public health, content and civilization follow the cow. The work of Dr. Osborne at this Station has largely con- tributed to the discovery of the reasons for this unique value of milk which are leading to a greater appreciation and more rational use of it. This work has been in a way incidental to a general study of the character and function of proteins and of the laws of nutrition. The investigations on the chemistry of the proteins have been carried on for many years by Dr. Osborne and in the nutrition studies which followed he has had the valuable cooperation of Dr. Lafayette B. Mendel of Yale University. Constitution of Proteins. The foundation of our new knowledge regarding milk was laid by finding out and setting forth the composition and struc- ture of a large number of different proteins, which are the flesh- growing materials of the body and an indispensable part of all the vital body fluids. This work showed for the first time their great variety and the fact that a nearly identical percentage composition of their elements (nitrogen, carbon, oxygen, hydro- gen, and sometimes sulphur and phosphorus) went along with wide differences in structure and in physical and chemical properties ; and that in the same food material, whether animal or vegetable, two or more proteins of quite different quality were usually found together. Dr. Osborne's work, with that of others, showed that a protein was no such simple thing as salt or sugar, but was made up of about eighteen different complexes, knots of nitrogen-containing groups called amino-acids, each of them a complicated structure in itself. CONSTITUTION OF PROTEINS. The following table gives the names of these amino-acids, the approximate percentage of each in several of the common proteins and shows the striking differences in their amount. Comparative composition of proteins. AMINO-ACIDS Glycocoll Alanine Valine Leucine Proline Phenylalanine .... Aspartic acid Glutaminic acid . . Serine Tyrosine Cystine Histidine Arginine Lysine Tryptophane, about Ammonia ZEIN (maize) per cent. o.oo 13-39 1.88 19-55 9.04 6.55 1.71 26.17 1.02 3-55 ? 0.82 1-55 0.00 0.00 3-64 GLIADIN (wheat) per cent. 0.00 2.00 3-34 6.62 13.22 2.35 0.58 43.66 0.13 1.50 0.45 1.49 3.16 ? 1. 00 5-22 casein (milk) per cent. 0.00 1.50 7.20 9-35 6.70 3-20 1-39 15-55 0.50 4-50 ? 2.50 3.81 7.61 1.50 1.61 lactal- BUMIN (milk) per cent. 0.00 2.50 0.90 19.40 4.00 2.40 1. 00 10.10 ? 2.20 ? 1-53 3.01 8.10 + 1.32 EDESTIN (hemp.- seed) per cent. 3-80 3.60 6.20 14.50 4.10 3-09 4-SO 18.74 0.33 2.13 1. 00 2.19 14.17 i-6s 88.87 \.72 66.92 56.46 82.2? In view of these great differences of structure and composi- tion of proteins, the question arose : have they nevertheless about the same food value as has been assumed, or have they not ? If they have not, the principles on which our whole art of cattle feeding is founded has lost a large part of its foundation. Clearly, the only w^ay to settle the question was to study the feeding effect of each protein by itself on both growth, maintenance and production. Before the work here was begun, all experimenters who en- deavored to feed animals on diets composed of pure nutrients failed. Both mature and young animals promptly declined in weight on such diets. To-day we have such an understanding of the influence of food on growth that merely by changing a single constituent of the diet we can stop the growth of a young animal at any stage of development, maintain it for many months in perfect health, but without growth, and later cause it to grow 6 CONNECTICUT EXPERIMENT STATION BULLETIN 21 5. again at a normal rate to full maturity and reproduce. It is due to the use of milk in the earlier attempts in feeding animals experimentally that we owe our success in developing methods of feeding which have opened up entirely new fields for investigation. Our first attempts to make an animal grow on a mixture of pure protein, fat, carbohydrate and inorganic salts were no more successful than those of our predecessors, but we soon found that animals which failed to thrive on our artificial diets could be restored promptly to excellent condition by giving them a mixture of dried milk, starch and lard, and that control animals fed on a similar diet from weaning grew normally to full maturity and reproduced. Although the artificial diets were almost exactly like the milk diets, in respect to the kind and proportion of the then known nutrients, the milk diet was entirely adequate as a food, whereas the artificial diet was wholly inadequate. Wherein this profound difference lay was a mystery. By a process of elimination we were forced to the conclusion that the water- soluble portion of the milk contained something which was essential for life, and later that the fat component contained something which was indispensable for long-continued growth. This discovery that milk contains two hitherto unsuspected substances, now known as the water-soluble and fat-soluble vitamines, which will be referred to later, made it possible for us to become pioneers in the study of various problems relating to growth and maintenance. The field of study thus opened has been entered by numerous investigators here and abroad with results of far-reaching importance. The experiments here to be described were made with albino rats because these small animals are omnivorous and can be fed with such quantities of the experimental rations as we are able to prepare in the laboratory in a state of purity. To insure perfect accuracy it is necessary that these rations shall consist of ingredients which are chemically pure and to prepare such rations in quantity is very laborious and costly. The results of^ these experiments can be accepted as giving evidence of the true food value of milk because they are in harmony with our experience in feeding not only ourselves but also farm animals. The question may be asked — Are the results of experiments in CONSTITUTION OF PROTEINS. 7 feeding rats, or other of the lower animals, applicable to human beings ? While the foods suited to different species of animals may differ widely in their appearance and physical properties, the digestible nutrients contained in them are very much alike in their chemical characters, so that by the processes of digestion quite similar products result from apparently very different kinds of food. Such differences as exist are rather in proportion than in kind. Furthermore, the tissues of the different types of animals are chemically even more alike than their foods and, consequently, their nutritive requirements are in principle much more nearly the same than those unfamiliar with the chemistry of nutrition would suppose. The conditions in feeding farm animals are necessarily so complex that it is generally impossible to recognize the influence of any individual constituent of the ration. In our experiments with rats, on the contrary, the conditions have been so simplified that definite conclusions can be drawn regarding the role of each factor involved. Thus, if two series of animals are fed on mix- tures of protein, fat, carbohydrate and inorganic salts, which are identical except for the kind of protein used, and one series grows normally whereas the other fails to grow at all, it is obvious that the protein alone was the determining element in the food. By means of large numbers of such experiments extending over a period of several years, we have fixed the nutritive values of many proteins, several fats, the various inorganic salts and also have studied a number of combinations of natural food products both of animal and vegetable origin which are extensively used in the daily rations of man or domestic animals. The Proteins of Milk. Previous to 1912 a discussion of the nutritive value of any food stuff would have been confined to a consideration of the total quantities of protein, fat, carbohydrate and salts which it contained and its value as a source of energy. As a result of work which has been done at this Station, and later in other laboratories, the field for discussion has become much broader, for it has been demonstrated that the quality of the protein present in any food is of even more importance than the quantity, 8 CONNECTICUT EXPERIMENT STATION BULLETIN 215. and a realization of the essential role which the so-called vita- mines play in normal nutrition has raised many more problems. Milk contains several different proteins, but there are only two which occur in notable quantity, and these are casein, the protein found in cheese, and lactalbumin, the principal protein of whey. These two proteins differ not only in their chemical structure, but also in their nutritive value. Both suffice to pro- mote the normal growth of young rats, but lactalbumin is some- what more efficient for growth than is casein, for in comparable periods of time a given quantity of lactalbumin will enable an animal to gain about 33 per cent, more in weight than the same amount of casein. This is instructive from a practical standpoint for it demon- strates that the whey, obtained as a side product from the manu- facture of cheese, contains one of the most valuable food proteins known and should not be wasted. Casein, which forms about 80 per cent, of the milk proteins, is more easily digested than any other protein known and behaves in the digestive tract very much like a predigested protein. This property makes it especially desirable as a food for infants or persons with weak digestions. For centuries people have been accustomed to use foods of animal origin with bread and other cereal products which form so large a proportion of the average dietary. Bread and milk, eggs on toast, meat sandwiches and the use of milk on breakfast cereals are just a few illustrations of this custom. If any one who was enjoying a meal of any of these mixtures were asked why he chose the combination of the animal with the vegetable product instead of eating either one alone, he would probably say that "it tasted good." or "it satisfied his appetite better that way," or something else equally indefinite. It is only recently, while engaged in investigating the nutritive value of wheat flour, that we discovered how well the proteins of milk, eggs and meat supplement the deficiencies of the wheat proteins. We now have a truly scientific reason for this universal dietary practice. If an animal is fed on wheat flour as the sole source of protein in an otherwise adequate ration, it will grow very slowly, if at all, even when relatively large amounts of the proteins are eaten. If, however, one-third of the wheat protein is replaced by an THE PROTEINS OF MILK. equivalent quantity of protein in the form of milk, eggs, or meat, the animal will grow at a practically normal rate. o O O O O O O o O o CO <£> ^ cu o CO ID "* N H r-i pH iH rH To illustrate this as well as the results of our other experi- ments with various diets of known composition, in a condensed form, we have employed charts giving the curves of body lb CONNECTICUT EXPERIMENT STATION BULLETIN 215. weight during the time of feeding. In reading these charts the squares running horizontally represent time of feeding expressed in days, running vertically the weight of the animal in grams (i gram equals about Vao of an ounce). The heavy black lines show the rate at which the animal gained weight; the more nearly vertical these lines the more rapid the growth. Chart I gives a graphic representation of the curves of growth of a number of rats which have been fed in these ways, and Figure i gives the photographs of two of these animals. Figure i • Rat ^2']'] was fed on a diet in which gliadin from wheat flour furnished the protein. On this food he gained only 10 grams in ten weeks. Rat 5314 was fed on a mixture of wheat flo^ir and milk. On this food he gained 160 grams in nine weeks. This illustrates the importance of combining milk with the cereals instead of feeding the cereals alone. All of the animals shown in this chart were of the same size and age, and were growing vigorously when put on the experi- mental diets. The differences in size at the end of each experi- ment are due solely to the protein of the diet. In this series of experiments the percentage of protein and nutritive ratio of the mixtures were practically identical, the foods differing only in THE PROTEINS OF MILK. I I the kind of protein. The animals in the group labelled "flour" received all of their protein from wheat flour, those in the groups labelled "flour + milk," "flour + egg," and "flour -|- meat" received a diet whose concentration of protein was the same as that of the "flour" group, but one^third of the protein was furnished by milk, egg, or meat respectively, the remaining two- thirds being furnished by flour. It is obvious that relatively small quantities of these animal proteins greatly improved the value of the food for growth. The value of these animal products lies in the fact that they are chemically so constituted as to , supplement the chemical deficiencies of the flour proteins. To those who are unfamiliar with the chemistry of proteins this may seem mysterious and confusing, hence a few words of explanation are necessary. By digestion the proteins are broken up into the amino-acids already mentioned on page 5, which are then used in con- structing the new proteins of the tissues of the growing animal. Unless the food protein furnishes a sufficient amount of each of these amino-acids which are needed to make the tissues required for normal growth the animal grows correspondingly slower than it would if more of the needed amino-acid were available. Wheat flour contains two proteins, one of which, called gliadin, yields only a very small amount of the amino-acid called lysine. The effect of a limited supply of lysine on growth is illustrated by rats 5277 and 5265, whose curves of body weight are shown in Chart i. These were fed on a diet in which all of the protein was furnished by gliadin. They have been maintained in good health, but have gained only about 10 grams. The rats on the "flour" diets grew somewhat more than those on the gliadin food because flour contains another protein which yields more lysine than does gliadin and hence supplements to some extent this deficiency of the gliadin. However, the amount of lysine thus supplied was too little to promote normal growth. In this connection it is interesting to note how perfectly a young animal can be maintained in health, but without growing even for a very long time when its diet is adequate in respect to everything except the chemical constitution of its food protein. Such animals can be thus kept as infants for indefinite periods. 12 CONNECTICUT EXPERIMENT STATION BULLETIN 215. Chart II shows how Httle growth was made during nine months on a diet in which ghadin from wheat flour furnished all the protein. At the end of these nine months the rat was given a similar diet containing enough dried milk to replace the gliadin, Figure 2 Figure 2 shows the contrast between feeding a good or a bad protein to a young rat. The two tipper rats are five months old and have been fed on diets exactly alike except the one at the top had casein from milk on which it grew normally, and the one in the middle had gliadin from wheat flour on which it could not grow at all, so that when it was five months old it weighed exactly the same as the rat at the bottom which was only one month old. and in two weeks on that food it gained as much in body weight as it had during the preceding nine months. It continued to grow normally on the milk diet to full adult size; a striking illustration of the value of milk proteins for growth. If, instead THE PROTEINS OF MILK. 13 f t i \ - , f \ \ \ \ \ / \- /'"' > \\ \ \ \ '-D \ x^ ^ \\ -'-' Ji \\ - \, 2 V \ \ , \ \ \ f \ \ s \ > \ \ ""^ ■\ s "-- — 4 / - L ~ V- ( \ E \ u ^ ^+- ' 'o , D- \ ■*- \ 5 /'a \ r ! ^ ^ -^ — s M-l >! _jj- j_; XJ CTt a ^3 s n f 1 QJ Oi ^ 13 X •*-' e CJ (U B N (L) nl Ul ,C bo rl js Tl iH u u a s 00 0) m ♦0 rt s »^ rt -<^ s -Q .S c cS o -o M-( d 3 rt •+-1 &P s tn 1* 3 C r: n -t-i ,r^ tn 9 « (J dJ ^ 1— 1 1 — 1 ^ & U5 6 b < ■4-> 1) iH ^ 0^ Si 3 n ■-5 ?^ q=l bo 'O ^ r^ -*-» >> s OJ Ui /^ H ^ a "*-* rl (U to 1- oj & 'O ^ c ' ' T— 1 JS ■OD S c bO MH V H—l Q -a ^ g c ^ -^ O v l-H ♦o OJ ^ 1 — 1 .3 •0 ^ H 60 rt tn C^j C < c . XI be H T-l rt 3 bO C 3 a a '3 bo >. 4J J! >> 3 "-W M-l c >y 'c3 Si Li IV ' ' ^ •+-1 a ;«' -o 03 b ^ rG OJ ' ' HH .5i tH ^ a! \ J / ^ I / -f^ -^ ^ V y / / / i 4' ,0 j / / / / 1 / x\ / 1 Rec 3very 3 Mi7k v\th Na *• Butt tura/ P ;r-fat rotein / s^ 20 Days 1 Da^ ys Chart VI. Chart VI shows that butter fat contains something essential for normal growth. These curves show that after feeding a diet of purified food- - stuffs, the fat being lard, the animals after growing normally for several weeks suddenly began to lose weight. When a part of the lard was replaced by butter fat (shown by the beaded line), they immediately recovered. These animals would have died in a few days if this change had not been made. 2 2 CONNECTICUT EXPERIMENT STATION BULLETIN 21 5. dies. Such animals frequently suffer from sore eyes and in many cases develop large ulcers on the eyeball. A small amount of butter fat added to the diet causes an immediate recovery of health, gain in weight and prompt restoration of the eyes to their normal condition. This marvellous effect is due to the presence in the butter fat of something of, as yet, unknown nature, which for the time being is called the fat-soluble vitamine. The presence or absence of this substance in any foodstuff can be detected only by feeding young animals. Chart VI shows the weight curves of rats which declined on a diet in which lard was the sole fat component and then rapidly recovered when part of the lard was replaced by butter fat. Recently it has been reported from some parts of Europe that many children have been afflicted with a disease called xeroph- thalmia, which is characterized by the development of ulcers on the eyeball. Figure 5 shows a photograph of a child thus affected. This condition is strikingly like that exhibited by rats fed on rations deficient in the butter-fat vitamine, and is probably due to the same cause, for these xerophthalmic children who had been fed almost entirely on skim milk and cereals were promptly cured by whole milk or cod liver oil. It is still unproved that this butter fat vitamine is essential for adults. We have maintained mature rats for many months in good condition on diets containing no known source of this substance, and as yet they have shown no signs of malnutrition. For the normal growth and development of the young, however, it is absolutely essential.* Just what these vitamines are has not been discovered yet, but at least three types exist, namely the fat-soluble or "A" vitamine; the water-soluble, "B," and the antiscorbutic, "C" vitamine. Milk contains some of the antiscorbutic vitamine * It is worth noting that Dr. H. C. Wells, who had charge of the dis- tribution of food in Rumania for the American Red Cross, tells us he made successful application of our observation that cod liver oil contains much of the fat-soluble vitamine. A cargo of cod liver oil at Archangel having been offered to him he im- mediately ordered it sent to Rumania hoping by its use to save the eye- sight of thousands of children whose eyes were in the same condition as those of rats fed on a diet deficient in the fat-soluble vitamine. By giving this cod liver oil to these children a large majority were saved from permanent blindness, even after their eyeballs had become entirely opaque. THE VITAMINES OF MILK. 23 which prevents scurvy, though less than do some of the vegetable and fruit juices, notably orange juice. This vitamine is sensitive to heat, hence children fed on pasteurized or boiled milk are more susceptible to infantile scurvy than are those fed on unheated milk, unless the scurvy-preventing vitamine is given them in some fruit or vegetable juice in which it is abundant. The relation of the fat-soluble vitamine to nutrition, and its presence in butter fat have already been discussed at considerable Figure 5 This child was fed on skim milk, and as a result an ulcer developed on one eyeball. This was because it did not get any of the so-called fat- soluble vitamine which is present in the butter fat. Plenty of cream, butter, or cod liver oil will cure this child's eye. Young rats develop this same disease when fed on diets free from the fat-soIuMe vitamine and are promptly cured by adding a little butter to their diet. (Photograph from Bloch, C. E., Ugeskrift for Laeger, Mar. 8, 1917, 79, 309, 349.) length. It is only necessary to add that this vitamine is quite resistant to heat, for we have passed live steam through melted butter fat for two and one-half hours without destroying its potency. The third type of vitamine, known as the water-soluble vita- mine, is also present in milk. Without an adequate supply of 24 CONNECTICUT EXPERIMENT STATION BULLETIN 215. this food accessory in the diet, life cannot be maintained. An animal which is fed on a ration containing no known source of this vitamine dies within a short time. If, however, when ap- parently dying, a very little of this food accessory is given, it recovers with surprising rapidity. This may be given in the form of milk, yeast, commercial wheat embryo, or any other natural foodstuffs. Days Chart VII. Chart VII illustrates the typical recovery (in Period 4) of a rat which had declined on a diet lacking the so-called water-soluble vitamine (Periods 2 and 3), when the animal was given milk which contains this vitamine. This rat would have been dead in a few days if the milk had not been given. Chart VII shows the rapid decline in weight typical of feed- ing a food deficient in the water-soluble vitamine. It also shows the effect of feeding an abundance of dried milk as a source of this vitamine. That the water-soluble vitamine is something apart from and independent of the fat or protein of the milk is shown by the results of our experiments. For many years we used the product obtained by evaporating to dryness milk freed from fat and protein as a source of the water-soluble vitamine in the diets fed to our experimental animals. THE VITAMINES OF MILK. 25 Chart VIII , shows that this product which we have called "protein-free milk" is just as efficient as a source of water- soluble vitamine as is the whole milk. Contrary to what appears to be generally believed, the water-soluble vitamine is resistant to heat. "Protein-free milk" prepared by evaporating at a temperature not far below that of boiling water is just as efficient 260 24-0 220 /-^ 1 /-^ "^ / \ r vW ^^ r n- \X V Bod> weight / .^^ 180 160 140 120 iOO 80 E . / 1 / \ ^ / ^/ /v, 0^ ' \3\ / ^r J , 4 Food eaten / /■ / '""" .,-—■■ / "^ / / \ -.^ / 1 20 40 60 80 100 120 140 160 180 200 220 240 I Days Chart VIII. Chart VIII Is a further illustration of the necessity of an abundance of the water-soluble vitamine in the food, if the animal is to live. In Period 1 the animal grew normally on an ordinary mixed diet. In Period 2, on a diet adequate, except for the lack of this vitamine, it declined rapidly and would soon have died if some source of this vitamine such as protein- free milk (milk freed from fat and protein) had not been fed (Period 3). The protein-free milk contains not only the salts and the lactose of the milk but also the water-soluble vitamine. On the casein diet the weekly food intake (shown by the dotted line at the bottom) declined steadily from nearly 80 grams to a little over 20 grams, but rose immediately to about 80 grams when the protein-free milk (water-soluble vitamine) was given. 26 CONNECTICUT EXPERIMENT STATION BULLETIN 215. as a source of vitamine as is an equivalent quantity of fresh, unheated milk. Even boiling for several hours does not destroy this vitamine. By what means this vitamine exerts its marvellously beneficial influence is still unknown. The rapid gains in weight following its use are always accompanied by a very great increase in the Figure 6. The lower picture shows a rat which had been fed for one month on a diet deficient in water-soluble vitamine. At this time the animal was so weak it was scarcely able to stand and would have died in a few hours if some source of this vitamine had not been furnished. After the picture was taken a small daily dose of yeast which is very rich in the water- soluble vitamine was given to the rat, the food remaining otherwise exactly as before. Twelve days later the upper picture was taken. The result is apparent. amount of food eaten, the weekly food intake frequently being doubled and sometimes even quadrupled when a small amount of vitamine-containing food is given to an animal declining on a food free from water-soluble vitamine. The vitamine may act simply as a stimulant to a jaded appetite, and the better growth may be THE VITAMINES OF MILK. 27 due solely to the increased food intake; or it may supply one or more essential factors needed to complete an inadequate diet, and the effect of adding the vitamine may be analogous to that obtained by adding a missing amino-acid, or a sufficient supply of some inorganic element which was present in too small an amount to permit of normal nutrition. When we know more about the chemical nature of the vitamines, we may be able to discover just what part they take in the processes of nutrition. Professor Hopkins of England reported some experiments in which he obtained very striking results by feeding daily small quantities of fresh milk to rats which were on a diet supposedly free from water-soluble vitamine. From his data the conclusion was drawn that milk is very rich in this type of food accessory. In some recent attempts to duplicate his results, we found it necessary to use much larger quantities of milk than he did in order to get comparable results. Undiluted milk contains all the vitamine necessary for the young animal, but in feeding babies it is the practice to dilute cow's milk with water and to reinforce the mixture with milk sugar. By this procedure the vitamine content of the original milk is so far reduced that the bottle-fed baby may get enough of this essential food factor only when it takes a liberal quantity of the food. Whenever appetite fails, the food intake and conse- quently the vitamine intafke are reduced. The effect of this is to further reduce the appetite because the amount of food eaten depends on the vitamine content of the diet. It is thus evident that under such circumstances the child goes from bad to worse and the endless troubles so familiar to mothers ensue.* In feeding young animals trouble is rarely encountered when * In this connection it is interesting that Dr. Amy L. Daniels and Dr. Albert H. Byfield have just published in the American Journal of Diseases of Children a report of their experience with additions of the water- soluble vitamine to the milk diets of bottle-fed babes. These experiments were founded on our discovery that milk contains less water-soluble vita- mine than had been previously supposed. In each case there was a marked increase in the rate of growth of the infant when the additional vitamine was given and a slowing of the rate when it was omitted. From these experiments it appears that the standard milk mixtures, used for feeding infants, furnish too little of the water-soluble vitamine even when con- sumed in normal amounts. 28 CONNECTICUT EXPERIMENT STATION BULLETIN 21 5. the food is right. On the other hand very sHght defects in the food lead to countless difficulties. The Sugar of Milk. At present we do not know whether or not milk sugar has any greater value for nutrition than have other carbohydrates. It has been thought that liberal quantities of milk sugar in the diet produce lactic acid in the intestine and thus transform the bac- terial flora from a type which produces putrefaction to one which checks this process. None of the other kinds of carbo- hydrates tested has this effect, but to what extent this change is advantageous to the body is as yet undecided. The Mineral Matters of Milk. Milk also holds a valuable place in the average dietary, on account of the composition of its mineral constituents. Cereal foods contain relatively little calcium, sodium or chlorine, hence animals are unable to grow on diets composed solely of cereals unless these inorganic deficiencies are supplemented. Milk, on the other hand, is rich in calcium, for it contains about three times as much as does the entire wheat grain, and about six times as much as does corn meal. The presence of an abundant supply of calcium in the food is essential, for it not only contributes to the maintenance of the proper neutrality of the body fluids, but is needed to form strong and well-developed skeletons. A liberal consumption of milk by growing children is, therefore, desirable as a "factor of safety" against deficiencies in the mineral nutrients of the other constituents of the dietary. The Cost and Economy of Milk. Now let us consider the cost of this exceptionally valuable food as compared with other common foods and see how much truth there is in the statement that its cost makes its free use prohibitive to all but a few. It is difficult to put an exact value on a complicated product like milk, but a fair estimate of its relative value compared with other food products can be reached by calculating the cost of the several types of food elements in milk and other staple products. Milk suffar has the same food value as cane sugar. We can COST AND ECONOMY OF MILK ' 29 buy a pound of the latter for 11 cents, so we may assign this vakie to the sugar in milk. Milk fat has a higher value than have ordinary food fats as shown by the higher price of butter, but let us assume that in milk, fat is worth no more than lard, say about 35 cents a pound. One hundred pounds of average milk contain about 12.5 pounds of solids of which five pounds is sugar, worth 55 cents at 11 cents a pound, and four pounds of fat worth $1.40 at 35 cents a pound, or $1.95 for the fat and sugar. One hundred pounds of milk contain 46^ quarts, which at 16 cents a quart is $7.45. Subtracting $1.95 from $7.45 leaves $5.50 for the 3.3 pounds of dry protein in the one hundred pounds of milk, or $1.67 per pound. Now, how much does dry protein cost in meat or eggs? One hundred pounds of lean round of beef contain 7.3 pounds of fat worth $2.55. Subtracting this from $50, which one hundred pounds of this cut of beef now costs at retail, leaves $47.45 for 19.5 pounds of dry protein, or $2.43 a pound; 76 cents a pound more than milk protein. The difference is even greater for eggs, for by the same method of calculating, in storage eggs at 55 cents a dozen protein costs $2.64 a pound, or 97 cents a pound more than milk protein. According to this method of calculation only when the lean round of beef sells for 35 cents a pound and eggs sell for 35 cents a dozen are they as cheap sources of protein as is milk at 16 cents a quart. Thirty-five cents spent for milk at the present price buys nearly as much protein, about two and one- half times as much fat and more than twice as much energy as is contained in a pound of lean Hamburg steak. In buying milk, moreover, one is procuring protein of exceptional value because it enhances the nutritive value of our cereal foods. In addition one is obtaining a liberal supply of vitamines, whose value cannot be estimated in dollars and cents, for as yet we have no adequate knowledge regarding their relative abundance in different foods. Since milk is so vitally essential as a food for growing chil- dren and is such a valuable supplement to a diet composed largely of cereals, vegetables, meat, sugar and fats, the production of milk should be stimulated so that there may be an abundance of milk and milk products of the highest possible grade at prices which shall put them within the reach of all. 30 connecticut experiment station bulletin 215. Summary. Milk is absolutely essential for the life of infants and very young children. It is a most desirable adjunct to the diet of older, rapidly growing children. It is the main dietary reliance in cases of disordered digestion or extreme illness. Milk contains an abundance of protein, fat, carbohydrate and mineral nutrients, and its proteins are not only of superior value when used alone, but they are especially adapted to supplement the protein deficiencies of the cereals which form so large a part of the daily ration of mankind. Its mineral nutrients also supplement the deficiencies of the cereals, meat, sugar and fats in these important elements. Moreover it contains the three vitamines without which life cannot be maintained. The scurvy-preventing vitamine is destroyed by heat and there- fore if infants are fed on pasteurized or sterilized milk the use of orange juice or some vegetable extract is necessary to avoid the possibility of scurvy. Whole milk contains enough water-soluble vitamine to meet an infant's requirements, but if "the top of the bottle" diluted with water is fed, the supply of this essential vitamine may be insufficient unless it is supplemented from some other source. Milk is the only food known which is capable of serving as the sole constituent of an adequate ration. Milk is a cheaper form of food at i6 cents a quart than either beef at 35 cents a pound or eggs at 35 cents a dozen. 3n University of Connecticut Libraries 39153029230176