504 



IT. S. BUREAU OF FISHERIES 



This example, showing the amount of energy or heat units in 

 starch, is not the whole story. It happens that many foods, and 

 particularly fish, contain larger amounts of the so-called protein and 

 fat tj^pes of food material than they do of the carbohydrate type 

 (starches or sugars), which is so characteristic of vegetable food- 

 stuffs. Fats or oils have the highest food value and are commonly 

 recognized to be the most concentrated form of energy. They sup- 

 ply the quicldy-burned fuels for the body, while the proteins play a 

 particularly iiuportant role in replacing losses from wear and tear in 

 the body cells themselves. 



Table 1. — Analyses of the ash of fish flesh 



Fish 



Lime 

 (CaO) 



Phos- 

 phorus 

 (PjOs) 



Magne- 

 sium 

 (MgO) 



Potas- 

 sium 

 (K3O) 



Sodium 



(NajO) 



Sulphur 



(SO3) 



C hloriae 



(CI) 



Anchovies (salted) 



Eel .-. 



Haddock (salted) _ 

 Pike 



Salmon (fresh) 



Per cent 

 4.22 

 45.83 

 3.39 

 7.38 

 8.60 



Per cent 

 18. 11 

 43.18 

 13.70 

 38.16 

 20.32 



Per cent 

 1.88 



1.90 

 3.81 

 9.49 



Per cent 



2.17 



.18 



13.84 



23.92 



24.40 



Per cent 

 38.80 

 9.48 

 36.51 

 20.45 

 13.66 



Per cent 

 0.93 



.31 

 2.50 



Per cent 



33.25 



.17 



38.11 



4.74 



21.44 



Both the proteins or nitrogenous constituents of foods and the 

 carbohydrate or starchy constituents of foods have the same fuel 

 value; namely, 1,860 calories per pound. On the other hand, the fats 

 or oils have a fuel value of 4,220 calories per pound. The proteins 

 do not give up all their energy in the body as fats and carbohydrates 

 do. The reason for this is simple ; namely, the fats and carbohydrates 

 in the body (as well as when burned outside) are completely consumed 

 to form carbon dioxide and water, while the proteins are only partially 

 consumed and are excreted in the form of creatinin, urea, ammonia, 

 and so on. 



In addition to the proteins, fats, and carbohydrates (which con- 

 stitute by far the greater proportion of our foods) there is another 

 highly important food essential, namely, the inorganic matter more 

 commonly given in food-value tables as ash. All living matter con- 

 tains inorganic or ash constituents, and in the case of bones and 

 teeth the percentage of these is high. Because our body can neither 

 be built nor function without these inorganic substances, our foods 

 must contain them. Deficiencies in the diet of calcium (lime) or 

 iotline, for instance, give rise to serious ailments and physical defor- 

 mities. Fortunately, fish and shellfish are characterized by contain- 

 ing an unusually wide range of the necessary mineral elements. 

 Goiter is extremely rare among the Japanese, and this may probably 

 be attributed to their extensive use of both animal and vegetable 

 sea foods. Table 1 shows the percentage of various types of mineral 

 matter in several species of fish. 



GENERAL COMPOSITION OF FISH AND SHELLFISH 

 FRESH FISH 



The pioneer work on the composition of American fish was done 

 by Prof. W. O. Atwater (1888) for the United States Bureau of 

 Fisheries during the period 1880-1887. This is a classical piece of 



