While the study of specific food materials is of abstract physiological value, especially those containing but a single nutrient like the sugars in our study of the carbohydrates, nevertheless the most practical interest lies in the influence of a mixed diet upon the basal metabolism. We have for consideration in this connection the results of 15 experiments in which the metabolism was studied after a mixed diet. Of these, 13 were calorimeter experiments and 2 were respiration experiments. The composition of the diet used in these 15 experiments is given in table 235. Additional evidence as to the influence of a mixed diet upon the metabolism is also given in an abstract of four calorimeter experiments, previously published, which followed several days of fasting.

Table 235. - Percentage Composition Of Mixed Diets Used In Experiments

1Computed.

2Diet on this day also included sugar, for which the composition is, carbohydrate, 100 p. ct. and fuel value, 3.960 cals. per gram.

3For composition of black bread used in diet of this day, see table 50, page 124. Sugar in the diet is not included in the composition here given.

Calorimeter Experiments

In our earlier investigations with the respiration calorimeter in Middletown practically all of the experiments following a 2-days' fasting experiment were with mixed diet. These have already been considered in a previous section of this report, in which the metabolism during fast and after food as measured in 24-hour periods was discussed.1 It is desirable, however, to group them in abstract here with other calorimeter experiments with mixed diet not yet discussed. In two of the mixed-diet experiments, but two food materials were used, one of the experiments being with crackers and milk and the other with cereal and milk. In 8 experiments excessive amounts of food were taken, either as breakfast or supper. In all but one of the calorimeter experiments the measurements were made with the Middletown respiration calorimeter. The experiment with H. L. H. was made with the bed calorimeter in Boston. In the first four experiments discussed the determinations were made in 24-hour periods. The basal values in all cases were determined on some other than the experimental day.

1See pp. 52 to 72.

A. H. M., February 2-3, 1906

For the experiment with 70 grams soda crackers, 50 grams graham wafers, and 1,030 grams whole milk, a basal value was used which was obtained in November 1905. (See table 22, page 70). The fuel value of the diet was 1,250 calories, of which 15 per cent came from protein, 39 per cent from fat, and 46 per cent from carbohydrates. The ingestion of this food in three portions during the day resulted in an increment of 149 grams in carbon-dioxide production, 80 grams in oxygen consumption, and 239 calories in heat production. The doubtful expediency of employing a basal value so far removed from the values obtained in the food experiment has already been discussed in our previous consideration of these results and need not be further emphasized. The main point to be noted here is the fact that the crackers-and-milk diet resulted in an increment of approximately 14 per cent in the heat production.

D. W., January 12-14, 1906

The subject took 166 grams of a dry cereal and 450 grams of whole milk each day in three portions. (See table 13, page 62). This diet had a fuel value of 943 calories, of which 14 per cent came from protein, 20 per cent from fat, and 66 per cent from carbohydrates. The basal value used was determined in a fasting experiment of two days preceding the food experiment. On the first food day there was only a slight increment over the basal average value, the metabolism being essentially the same as that on the last day of the fast. On the second day with food there was a considerable increment in the metabolism, which amounted for the heat production to 184 calories. Here again we must call attention to the previous discussion as to the errors involved in the used of a base-line of this character. It is clear, however, that the ingestion of the food arrested the fall in the metabolism incidental to fasting and finally produced a rise.

H. R. D., December 7-8, 1905

The diet consisted of 125 grams orange juice, 1,427 grams milk, 181 grams of a dry cereal, 128 grams eggs, and 149 grams apples. This amount of food was taken in three portions at the ordinary meal times. (See table 11, page 61). The basal value used for comparison was determined in a 2-day fast immediately preceding the food day. The fuel value of the diet was 2,086 calories, of which 16 per cent came from protein, 35 per cent from fat, and 49 per cent from carbohydrates. The ingestion of this amount of food resulted in a positive increase in metabolism, as shown by the total increment in the heat production of 189 calories, or approximately a 10 per cent increase.

N. M. P., December 11-12, 1905

The food intake in this experiment (see table 12, page 61) was much larger than in that with H. R. D., the diet consisting of 260 grams orange juice, 97 grams dry cereal, 914 grams milk, 233 grams bread, 13 grams butter, 634 grams cocoa, 179 grams eggs, 362 grams beans, 184 grams bananas, and 222 grams crackers, a total amount of 3,098 grams, with a fuel value of 4,486 calories. Of this energy, 14 per cent came from protein, 30 per cent from fat, and 56 per cent from carbohydrates. As in the preceding experiment, the food was taken in three portions at the usual meal times. The increase in heat production as a result of taking this food was 379 calories, or approximately 17 per cent. The nitrogen excretion also increased considerably.