1) Their energy requirement per unit of weight is higher than that of adults.
2) Their food should contain a higher proportion of body-building materials (protein and mineral elements) and of vitamins than that of adults.
3) Their diet should be selected with special care to include only foods which are readily digestible.
Energy Requirements Qualitatively, the nutritional factors necessary for the child are the same as those required to nourish an adult, namely, energy of fuel, protein, mineral salts and vitamins, plus suitable amounts of water and fiber.
Quantitatively, however, their requirements differ. This is due to the fact that:
1) The basal metabolism, the amount of energy used in internal processes of the body, is considerably higher in youth than in adult life.
2) The child is usually much more active than the adult, and uses a great deal of energy in work and play.
3) Lastly, the child must have extra energy to grow on or to store in the new tissues that are being built.
Need for Tissue-Building Material Protein is required for building muscle tissues, as well as for the growth of the various organs; whereas the average adult does not need more than 10 percent of his calories in the form of proteins, about 15 percent of the calories as protein will probably be safer allowance for growing children, who are storing protein.
Moreover, probably about two-thirds of the protein in the diet of children should be from the foods of animal origin (chiefly milk and eggs), which furnish complete proteins and those more efficient for growth than vegetable proteins. Hence, if a child is fed a quart of milk daily, he will be fairly certain to receive a safe surplus of protein in the best available form.
The alimentary tract of infants is not equipped to digest starches and fats, and only gradually develops the ability to handle these food materials so that only small amounts of very thoroughly cooked starchy foods can be given during the first year, while fats must be restricted in amount even in the second year.
Raw vegetables and most raw fruits have to be introduced with caution as the digestive tract becomes stringer and the teeth are well-developed.
Infants and young children seem to have less immunity to the presence of bacteria in the intestinal tract and the mucous membrane lining their alimentary tract is also more sensitive to irritating substances than in later life. Foods which are difficult to masticate, such as vegetable, nuts, etc., should be given to young children only in finely minced or ground form.
Lastly, it should be fairly obvious that it is essential to limit the foods used in the diet of children to such foods as are easily digestive or readily handled by the digestive tract of the child at the special age for which one is planning.