EXPERIMENT STATION BULLETINS. 163 



4. Fats — (lard, tallow, butter, oils, etc.). 



5. Ash — (mineral matter). 



6. Water. 



The fiijst three of these from the standpoint of fuel have nearly the same value,* 

 that is, when a given weight of each is burned in the body it furnishes nearly the 

 same amount of heat. Protein has a slightly higher value than have the other 

 two. The fourth one, — fats, however, is as much more valuable than the first three 

 for fuel as hard coal is more valuable than wood. It liberates more heat, and 

 the inhabitants of the Arctic countries unconsciously recognize this fact when 

 they relish so much fat and oil in their daily food. Fats are worth, for this pur- 

 pose, about twice as much as the carbohydrates. The mineral matter or ash and 

 the water in a food have no value as heat producers. Pound for pound then, as 

 a source of heat and energy, starch and sugar, are worth nearly ^s much as is 

 lean meat (protein). From this standpoint alone starchy foods are much more 

 economical than the concentrated protein foods, commercially the starchy foods 

 being much cheaper than the protein foods. 



There is also a physiological side to view. A food to be a perfect food must not 

 only yield energy but it must also repair waste tissue and it is always in the pres- 

 ence of the protein compounds that this phenomenon is accomplished. In the 

 average man at ordinary work there is wasted or used up about three and one- 

 half ounces of protein per dayf and this amount must be made up or supplied 

 in the food or the physiological processes of the body will not be normal. Inde- 

 pendent then of the fuel supply of the body must be this three and one-half ounces 

 of protein to replace waste tissue caused by the performance of the natural, normal, 

 physiological functions of the body. After this amount is supplied it is then a 

 matter of economy to secure the balance of the requisite fuel where it can be 

 obtained the cheapest, and naturally that place would be among the carbohydrates 

 and fats. The science of a balanced ration is to furnish the expensive protein 

 only so far as it is needed, and to make up the bulk or main fuel supply from the 

 much less expensive carbohydrates and fats. 



Not all of the food that enters the system is utilized in the body.l There is a cer- 

 tain amount that always escapes digestion and assimilation because of the con- 

 dition in which it exists. § The nutriment may exist in the food but it may be so 

 incased in the cellulose wall that the fluids of the body are unable to get to it. 

 Hence we say that one food is more completely digestible than another. This holds 

 true especially with regard to foods containing a considerable amount of fiber. 

 Entire wheat flour, for example, is less digestible than high grade patent flours, || 

 possibly because of the larger amount of fiber in the entire wheat, making it more 

 difficult it would seem for the fluids of the body to dissolve the nutriment. For 

 the same reason such foods as whole wheat bread really furnish less energy 

 to the bodj'^ than white bread, for greater effort is required of the system to digest 

 it, and as a consequence the body material used up in this effort must be much 

 greater than with white bread. In other words, the cost of digestion of white 

 bread must be less than with whole wheat bread and therefore the net energy 

 furnished by white flour would be greater, it would seem, than by whole wheat 

 flour.** 



There is however, another point of view — one not usually mentioned but surely 

 as logical and just as pertinent. It is well known how essential it is that the 

 food of cows, sheep and horses contain considerable fiber or roughage. Feeding 

 the heavier concentrates without roughage would be liable to cause impaction 

 of the intestines. While in man the intestine is much shorter, at the same time 

 some bulk is desirable for exactly the same reasons that we feed roughage to the 

 animals. The major part of the cellulose in wheat is in the bran,tt and that is 

 the part rejected in preparing our high grade patent flour. Whole wheat flour con- 

 tains some of the bran and hence more fiber than exists in patent flour from 



*Bul. 13. part 9, U. S. Dept. of Agr., pp. 1245-1249. 



fBunge, Chap V. 



Jit is a well established fact that foods vary in the degree of digestibility and furthermore that 

 various conditions, such as palatability, preparation of the food, etc., have considerable influence 

 on this factor. 



§This refers especially to vegetable foods. It is believed that meats, well prepared, and milk, 

 etc, are more or less completely digested. 



II See Bui. U. S. Dept. of Agr., Office of Expt. Sta. Studies on Bread and Bread-making by Snyder. 



**See Armsby-Principles of Animal Nutrition. 



•ft Wheat contains 1.8% fiber while bran from the same wheat contains 9.0% fiber. See Henry's 

 Feeds and Feeding. 



