56 NEW HAMPSHIRE EXPERIMENT STATION [Bull. 242 



matter in these mixed meals and that if one knows the air-dry weight 

 of the mixed foods for one day, one week, or for any desired period 

 of time, one can multiply this by the factor 5 and have a close esti- 

 mate of the total energy intake. 



GENERAL DISCUSSION 



Innumerable analyses of the energy value of various foods have 

 already been made. The tables of Atwater and Bryant, i first pub- 

 lished in 1896, have been of incalculable service in computing the 

 total energy intake in the food eaten daily, and are today the basis of 

 most of the tables of energy values of foods printed in the best modern 

 textbooks on dietetics and nutrition. 2 Many of these early analyses 

 have dealt with cooked foods, but in the course of years the methods 

 of cooking have changed and many combinations of previously pre- 

 pared foods are now on the market. It is, therefore, difficult oftentimes 

 to calculate the caloric intake in the modem diet from the Atwater- 

 Bryant tables. The elaborate study of ready-to-serve foods carried 

 out by Gephart and LuskS in the Childs restaurants has helped con- 

 siderably, so far as the servings from this particular chain of restau- 

 rants are concerned. And yet our own data show that even in these 

 restaurants the methods of cooking and the preparation of the serv- 

 ings are not sufficiently standardized to enable one to compute with 

 accuracy the energy intake from the calories claimed to be in the 

 different portions served. The Battle Creek Sanitarium, emphasizing 

 the signifiance of vegetables, likewise prints on its menu cards the 

 calories in the food served. But the food at Childs restaurants and 

 at the Battle Creek Sanitarium is not necessarily representative of 

 the food served in other restaurants or in one's home. Hence we must 

 use the old Atwater-Bryant tables, which are in many ways inade- 

 quate for computing the energy content of the modern diet. 



One of the three factors determining the true energy value of a 

 food is the amount of energy in the food leaving the body undigested 

 in the excreta. With humans this loss of energy is small, and the 

 actual heat of combustion of human food can be accepted as indicative 

 of its true energy value. But with cattle a large proportion of the 

 food eaten leaves the alimentary tract undigested. Hence the heat of 

 combustion of cattle food cannot be considered indicative of its real 

 energy value, but the heat of combustion of the feces must also be 

 determined. The development of the oxy-calorimeter at the Nutri- 



(1) Atwater, W. O., and C. D. Woods, U. S. Dept. Agric, Office Expt. 

 Sta., Bulletin No. 28, 1896; revised editions published in 1902 and 1906 by 

 Atwater, W. O., and A. P. Bryant. 



(2) See, for example, Rose, M. S., Feeding the family, New York, 1925; 

 Laboratory handbook for dietetics, New York, 1929; The foundations of nu- 

 trition, New York, 1927. 



(3) Gephart, F. C, and G. Lusk, Analysis and cost of ready-to-serve 

 foods, Chicago, 1915. 



