The average daily allowance of protein may be estimated in two ways. Both have disadvantages as well as good points.

One way of estimating the protein allowance is on the basis of the actual amount of protein needed in a day. The average adult probably needs daily about 2 or 3 ounces of protein. Or to state the matter in a more accurate way, the protein in the day's meals should furnish daily 2 to 2 1/2 calories for each pound of body weight. If animal proteins are generously represented, the lesser amount may be adequate. For economy not more than one-third of the total protein in the adult diet should be furnished by animal foods. Less than this may be used. One egg, one glass of milk, and an ounce of cheese or a small piece of meat, give a liberal amount of animal protein in a day. Less than this may be sufficient. If plant proteins predominate largely, the greater amount may be needed. About one-third of the daily protein should be taken from the cereal grains-wheat, corn, rye, oats, rice, barley. After the allowances for animal and cereal proteins have been made, the remainder of the protein may come from nuts, legumes, and fruits and vegetables. If wise combinations of animal and plant proteins are made, the amount needed will probably lie between the two extremes.

Another way of estimating the protein allowance is on the basis of the proportion of total calories which protein should furnish. The average adult should receive daily from protein 10 to 15 per cent of the total calories in his food. If plant proteins predominate, 15 per cent of the total calories should be furnished by protein. If the number of calories needed is great because of much exercise, only 10 per cent, or even less, of the total calories need be furnished by protein.

The tables of 100-calorie portions (Tables XVI-XXI) may be used in estimating the amount of protein food that is required to meet the needs of the body, since one column states the number of calories a given food supplies in the form of protein.