536 U. S. BUREAU OP FISHERIES 



Under ordinary conditions of preparation whale oil is not very 

 satisfactory for food. It is difTicult to obtain accurate figures con- 

 cerning the use of whale oil, but probably the larger portion is hydro- 

 fenated. It is reported that in Europe considerable quantities of 

 ydrogenated whale fat are used in the manufacture of margarines. 



ENERGY VALUE 



As is well known, the energy value of fats is greater than that of 

 any other substance included in the human dietary. Protein and 

 carbohydrates, such as stai'ches and sugars, produce approximately 

 4 calories per gram when burned in the body. Fats, on the other 

 hand, supply about 9 calories per gram when oxidized under the same 

 conditions. Accordingly, fats have an energy value roughly 23^ 

 times that of protein and carbohydrates. 



Fats that have been separated from extraneous substances, such 

 as water, tissues, and cellular material, have an energy value of about 

 4,080 calories per pound. On the other hand, products like butter 

 and margarines contain water, casein, and salt, and therefore possess 

 a lower energy value. Since the legal standard for butter and oleo- 

 margarine requires that they contain 80 per cent fat, we might 

 assume that the energy value of butter and margarines is something 

 like 3,300 calories per pound. Considered from a dietary standpoint, 

 the energy value of fish fats would be approximately 4,080 calories 

 per pound, which is the same as that for vegetable fats, and roughly 

 one-fourth greater than that of butter and m^jgarine. 



A further conception of the dietary value of some fat-rich fish and 

 fish products may be obtained by comparing these with som.e common* 

 articles of the diet. It is generally considered that such foods as 

 veal, whole milk, baked beans, and sirloin steak are very hearty and 

 are well suited to the needs of those engaged in strenuous labor. On 

 the other hand, one commonly thinks of mackerel and snioked her- 

 ring as valuable only for the Friday dinner; of canned sardin-es as a 

 constituent of the picnic lunch, to be eaten when one is carefully 

 avoiding strenuous labor; and of shad roe as a delicacy consumed 

 for palatability rather than for energy value. As a matter of fact, 

 we find ^ that smoked herring supplies 755 calories per pound as 

 compared with 745 calories per pound of breast of veal; mackerel 

 supplies 370 calories per pound as compared wath 310 calories for 

 whole milk; canned sardines furnish 950 calories per pound as com- 

 pared with 975 calorics per pound supplied by sirloin steak; and shad 

 roe furnishes 600 calories per pound, as compared with 555 calories 

 per pound of baked beans. 



Obviously, a portion of the energy value of these foods is derived 

 from their protein content, but the above comparisons have been 

 included with the hope of correcting the misconception concerning 

 the inferiority as a source of enej-gy of canned sardines, mackerel, 

 shad roe, and smoked' herring to such food materials as veal, milk, 

 sirloin steak, and baked beans. 



^Alwater, W. 0.: Principles of nutrition and nutritive value of food. United States Department of 

 Agriculture Farmers' Bulletin No. 142, 1902, 48 pp., 1 chart. Washington. (See pp. IG and 17.) 



