The rate of physical growth during the toddler, preschool, and
childhood years slows substantially when compared to the growth
rate of an infant. A growth spurt that requires large increases
in caloric intake occurs at puberty. Nutrient needs vary accordingly
and substantially, as outlined in the dietary reference intakes
(DRIs) for various age ranges (Chapter 23, eTable 23.1). Calorie needs have the greatest variability.
The DRIs for energy for 1 to 2 years of age are based on age and
weight, while those after 3 years include allowances for gender, height,
and physical activity (Chapter 23, eTables 23.1 and 23.2). The general guidelines must
be adjusted to account for individual variation in body size, stage
of growth, physical activity, and state of health or illness.
Protein requirements are based on age and weight, with the requirement
decreasing with age relative to weight but the total requirement increases
with age. Additional factors, such as growth rate and state of health
or illness, impact upon protein needs. It is important to recognize that
recommended protein intakes assume high-quality protein providing
amino acids essential to humans, such as eggs, milk, meat, poultry,
and fish. If protein is primarily derived from lower-quality plant
protein sources, the total requirement is increased. North American childhood
diets generally contain more than adequate amounts of protein, but
certain groups, including vegetarians, children with severe food
allergies, those with limited access to foods, and children with
severe food selectivity, are at risk for inadequate protein intake.
Fat requirements decrease from infancy through early childhood.
Fat provides 40% to 50% of total calorie intake
for infants. Restriction of fat intake in children under 2 years
old is not advised because it may compromise growth.1 However,
fat intake should gradually be decreased to approximately 30% by
age 5 years and through adolescence. This decrease occurs as children
transition from breast milk or infant formulas during the first
year, whole milk during the second year, and then to lower fat milk
after age 2. Intake of fruits, vegetables, and whole grains products
should gradually decrease.
From age 5 years to early adolescence is a period of slow but
steady growth. Dietary intakes of iron, calcium, zinc, and vitamins
B6, A, D, and C are often less than recommended, but deficiencies
are unlikely because most children in the United States have access
to fortified foods. Ideally, apart from adequate intake of energy and
protein, children obtain their vitamins and minerals from a variety
of nutrient-dense foods, including whole grain cereals, fruits,
and vegetables. The nutritional requirements of adolescents increase
at the time of the pubertal growth spurt. The nutrient needs of
individual teenagers differ greatly, being associated more with
their growth rate than with chronological age.
Adolescents are at risk of deficiencies in two important minerals:
iron and calcium. Rapid growth leads to an increased requirement
for iron at ...