Many attempts have been made to arrive at the most satisfactory proportion of protein to fat to carbohydrate in the daily dietary .sx From a scientific point of view an estimate may be made from a consideration of the amounts of decomposition products in the urine and those eliminated from the lungs .sx The amount of carbon dioxide which is ejected daily from the lungs of the average man varies from 250 grams to 280 grams , but may be very much increased during periods of great muscular activity .sx On the contrary , the amount of urea in the urine remains fairly stationary and corresponds to about 15 grams to 18 grams of nitrogen .sx These products originate either from the decomposition of food or from the breakdown of tissues .sx If we take the case of the man doing a moderate amount of manual labour or muscular exercise then we find that he is losing combined carbon and nitrogen in the ratio of 16.6 to 1 .sx The food eaten should therefore be such as to make good this loss .sx Although proteins vary considerably in the way they have been synthesised , the ratio of carbon to nitrogen they contain remains remarkably constant , namely 3.5 to 1 .sx Taken alone , proteins would be grossly deficient in carbon , and consequently this must be made good by means of non-nitrogeneous substances such as fats and carbohydrates .sx Dr. Hutchinson considers that the standard amounts of the different foods required daily are :sx 100 grams of protein , 450 grams of carbohydrate and 75 grams of fat .sx Calculation shows that these would , if absorbed , furnish 2,950 Calories .sx Another diet due to Voit is :sx 120 grams of protein , 100 grams of fat and 333 grams of carbohydrate , which theoretically should produce 2,805 Calories .sx According to Halliburton and McDowall ( Handbook of Physiology , 1928 , page 428 ) 65 Calories will be dissipated in raising the water ( 2.6 kilograms ) in the food to the temperature of the body ; 96 Calories will be required to heat the air ( 16 kilograms ) entering the lungs ; 366 Calories , in evaporating 630 grams in the lungs and the remainder , 2,277 Calories are required to maintain the body temperature and also to be converted into internal and external mechanical work .sx According to Plimmer the diet of an adult should contain 3 ounces to 4 ounces of protein , 2 ounces to 3 ounces of fat , and 14 ounces to 18 ounces of carbohydrate .sx Although fat is a very powerful fuel-food some people are unable to digest it in the usual quantities , though it is extremely probable that in such people its digestion is often increased when the fat is accompanied by carbohydrates .sx We shall now consider the amounts of these three main classes of food that are present in the ordinary foodstuffs .sx Water constitutes a considerable proportion of nearly every article of food , and the essential .sx mineral matter is usually found in amounts up to about 1% .sx The composition of the different meats differ greatly in their proportions of protein and fat .sx On cooking , meat loses some of its water , with the result that it becomes a more concentrated food .sx Foods of vegetable origin take up large proportions of water , making it necessary to take relatively large quantities in order to obtain reasonable amounts of their nutritive material .sx In regard to its protein and carbohydrate contents , bread is a valuable food .sx It is , however , low in its fat content , as shown by the following analysis :sx protein , 6.5% ; fat , 1.0% ; carbohydrate , 51.2% ; cellulose , 0.3% ; mineral matter , 1.0%. Wholemeal bread contains less carbohydrates and about 1.5% of cellulose .sx The spreading of butter or margarine , each of which contains 80% to 85% of fat , on bread makes up for the deficit .sx Cheese contains roughly one-third of protein and one-third of fat , the remaining one-third being water .sx Though cheese is a concentrated food as regards both protein and fat , it has one disadvantage in that the fat is infiltrated throughout the protein .sx Unless the cheese is thoroughly converted into the liquid condition in the mouth , digestive difficulties may arise in the subsequent organs owing to the digestive juices being unable to penetrate the cheese lumps .sx Considered as a whole , eggs contain about 15% of protein and 10% of fat .sx Potatoes are rich in carbohydrates , the analysis being :sx protein , 2.2% , fat , 0.1 % , carbohydrates , 11.5%. Oatmeal is a particularly rich food .sx In the dry , uncooked form , it contains 14.6% of protein , 10.1 % of fat , 65.1% of carbohydrates and 2% to 3% of cellulose .sx Unfortunately the cellulose matter adheres tenaciously to the cell contents , and as the human digestive system is unable to deal with the cellulose coverings , there is a distinct tendency for the enveloped nutrients to be lost .sx Another disadvantage of oatmeal lies in the fact that it contains appreciable amounts of nitrogeneous bodies belonging to the class known as " purines , " of which uric acid is an important member .sx For this reason , oatmeal should be avoided by people having rheumatic tendencies .sx Oatmeal is now rendered more digestible by subjection to treatment with hot rollers , which brings about the disruption of the cellulose membranes .sx Cocoa and chocolate are useful energy-producers .sx They are rich in fat and carbohydrates and also contain some protein .sx As sources of vegetable protein , pulses , viz .sx , peas , beans , lentils , are valuable .sx Their chief drawback lies in their high content of cellulose matter .sx Peas , for example , contain 4.0% of protein , 0.5% of fat , 16% of carbohydrates and 0.5% of cellulose .sx Though cellulose is not digested by human beings , its presence in food in small proportions is not without advantage , for it tends to stimulate the intestines to action in expelling waste products .sx Some idea of the relative merits of various articles of food as energy producers may be obtained from the following table , which gives the number of ounces that must be taken to supply 100 Calories .sx In this table , almonds have been included as example of the nutritive value of nuts .sx Dried nuts provide a very concentrated form of food as they contain only from 4% to 5% of water .sx Fat comprises from 50% to 60% , protein from 15% to 20% , carbohydrates , 9% to 12% ; cellulose , 3% to 5% ; and mineral matter , 1% .sx The relatively high proportions of fat and cellulose , however , often render nuts difficult to digest .sx Advantage is taken of the high fat content of nuts in the manufacture of substitutes for butter , and sold either as nut-butter or after incorporation in margarine .sx In concluding this chapter , some reference will be made to the mineral requirements of the body .sx Though it is probable that they do not supply energy , they certainly play an all-important role in assisting in the absorption of food , in tissue and skeleton-building , in the proper functioning of the blood and other body fluids , and in maintaining various glands , e.g. , the thyroid , in a healthy condition .sx With the exception of common salt , mineral matter is not taken directly .sx It is received in the many food-stuffs and it is probable that the mineral content of a well-balanced diet is usually sufficient .sx The following figures , based on recent estimates , give some indication of the daily need of the chief inorganic substances :sx combined phosphoric acid , 3 to 4 grams ; combined sulphuric acid , 2 to 3 grams caustic potash , 2 to 3 grams ; caustic soda , 4 to 6 grams ; calcium oxide , 1 to 1.5 grams ; magnesia , 0.3 to 0.5 grams ; combined hydrochloric acid , 6 to 8 grams ; and iron , 0.006 to 0.012 grams .sx In addition , iodine should be mentioned , which is required in traces by the thyroid gland .sx It is not easy to say precisely the source from which this essential ingredient is derived in view of the very minute traces in which it sometimes occurs in food substances .sx The addition of small amounts of potassium iodide to certain table salt has undoubtedly proved beneficial to people having tendencies to goitre .sx One of the chief advantages of soup lies in its high mineral content , which incidentally plays a dual part .sx Besides supplying the body with valuable matter , it imparts to the soup an osmotic pressure of between 7 and 9 atmospheres , which is higher than the osmotic pressure of the body fluids , being about 6 atmospheres .sx Hence one of the chief effects of taking soup will be an attempt to raise the osmotic pressure of the bodyfluids .sx It is estimated that half-a-pint of soup will raise the osmotic pressure by one-half of an atmosphere .sx This increase in osmotic pressure is caused by an increased diffusion and absorption of dissolved substances from the intestinal tract .sx CHAPTER X .sx VITAMINS , HORMONES AND ANESTHETICS .sx EMPHASIS has been laid in the foregoing chapters on the body-building foods and the part played by carbohydrates and fats in supplying the requisite energy to keep the body in the state of health and activity .sx It has been found , however , that if the various articles of diet , proteins , fats , etc. , were all chemically pure , the growth , in the case of the young , and the standards of health would not be all that might reasonably be expected .sx Although the calorific values of fats obtained from different sources may be approximately the same , it happens that the nutritive values may differ very considerably .sx This is contrary to the principles already laid down .sx We have seen that fats and vegetable , animal and fish oils are compounds of glycerine and fatty acids , and can be resolved into their constituents by boiling with alkali , a process which the chemist calls " saponification .sx " If these oils and fats were chemically pure , then they should be entirely disrupted by such a treatment .sx As a rule , the natural oils and fats do not undergo complete decomposition in this manner .sx There is always a small proportion which does not yield to such drastic treatment .sx In assessing the value of these fats and oils the analytical chemist regarded this " unsaponifiable matter " as an impurity .sx Judged from the chemist's standard of purity this unsaponiliable matter was certainly not " fat " and it therefore was an impurity .sx Thanks to the pioneer work of Sir W. Gowland Hopkins , of Cambridge , dating from 1906 , it is now known that this " impurity " often contains just that substance and usually in the minutest amount , which enables the animal body to utilise the fat to its fullest advantage .sx Without it , the food may be of little or even no avail .sx Until 1912 , when Hopkins published his important experiments on the feeding of rats , it was believed that all fats possessed the same food or nutritional value .sx To-day , these small amounts of impurity are known to be of paramount importance , for it is in these " unsaponifiable fractions " that the fat-soluble vitamins are concentrated .sx Not all vitamins , however , are found in fats and oils .sx These accessory food-factors were first believed by Funk to belong to the class of nitrogenous bodies , known as amines , and were consequently given the generic name of " vitamines .sx " Although no vitamins have yet been isolated , sufficient is known of their probable constitution to state that , with the possible exception of vitamin B , they do not belong to the class of " amines .sx " The original name , " vitamines , " is yet another example of mistaken nomenclature .sx Instead of introducing a more suitable name , the original term has been retained , with the exception that the terminal e is deleted .sx It is a remarkable fact that , although these vitamins are essential to the life of animals , animals and human beings appear to be quite unable to manufacture them within their bodies .sx Their synthesis seems to be an exclusive property of life in the .sx vegetable kingdom .sx They are found in various parts of the animal body , e.g. , the liver of fish , but they originally must have been derived from some vegetable source .sx Vitamins , in the very small quantities that are actually required , must be taken in one's food .sx This condition is usually satisfied , especially if sufficient food is taken of vegetable origin and of which the vitaminic activity has not been destroyed in the process of cooking .sx Danger creeps in those foods that have undergone drastic chemical treatment , and this is especially true of margarine , for in preparing oils for margarine manufacture they have to be boiled and often subjected to hydrogenation .sx