Since few of our foods consist of a single foodstuff, and we are not likely to make even a single meal on pure fat, or pure protein, or pure carbohydrate alone, we are sure to get some building material in any diet, but we must see to it that we are getting amounts which furnish the best possible conditions for growth and repair.

As we have already seen, nitrogen in the form of protein is necessary to the life of every cell in the body. From protein, too, muscle is built, though we cannot build good muscle merely by feeding protein; a diet moderate in its amount of protein, but with plenty of fuel for healthy exercise is best for muscle building. Under all ordinary conditions, if ten to fifteen Calories in every hundred (10 to 15 per cent of the total Calories) are from protein, the need for this kind of building material will be met. Thus a family requiring 10,000 Calories per day should have from 1000 to 1500 of these as protein Calories. The following table gives the protein Calories in the 100-Calorie portions of some common food materials.

Table Showing Distribution Of Calories In 100-Calorie Portions Of Common Food Materials

Food Material

Weight

Distribution of Calories

Protein

Fat

Carbo-hydrate

Ounces

Almonds, shelled ......................

0.5

13

77

10

Apples, fresh..............................

7.5

2

6

92

Bacon..........................................

0.5

6

94

-

Bananas.......................................

5.5

5

6

89

Beans, dried................................

1.0

26

5

69

Beef, lean round .........................

2.5

54

46

-

Bread........................................ ........

1.4

14

4

82

Butter.......................................

0.5

1

99

-

Cabbage....................................

13.3

21

7

72

Carrots.......................................

10.1

10

5

85

Cheese, American .......................

0.8

27

73

-

Cod, salt (boneless) ....................

3.1

98

2

-

Cornmeal..................................

1.0

10

5

85

Eggs, whole................................

2.7

36

64

-

Flour, white.................................

1.0

12

3

85

Lamb chops.................................

1.3

23

77

-

Lentils........

1.0

29

4

67

Marcaroni...................................

1.0

15

2

83

Milk, whole......

5.1

19

52

29

Milk, skimmed.....

9.6

37

7

56

Oats, rolled......

0.9

17

16

67

Peanuts, shelled........................

0.6

19

63

18

Peas, canned............................

6.4

26

3

71

Peas, dried......

1.0

27

3

70

Salmon, canned.....

2.4

54

46

-

Veal.........

3.2

70

30

-

Walnuts, shelled.........................

0.5

10

82

8

Notice that some foods, like bread, have about the right proportion of protein calories; others, like beef, beans, and peas are very high in protein calories. By combining some foods high in protein with others containing little or none, we can get the right proportion. Thus, 100 Calories of beef combined with 400 each of bread and butter will give 900 Calories of which 114, or 12.7 per cent, are from protein.

Protein Calories

Total Calories

Beef.............

54

100

Bread.................................................................

56

400

Butter...............................................................

4

400

Totals .........

114

900

(114 900 = 0.127 or 12.7%)

It is interesting to work out other combinations which give these good proportions.