Adolescence (ages 13 to 17 years) and its extension into late adolescence/young adulthood (ages 18 to 21 years) are crucial times for good nutrition, because they are important years for growth and optimal development. Approximately half of adult bone mass is obtained by age 18, with boys gaining more bone mass and size compared with girls. By early adulthood, individuals have also become sexually mature—which means that while men have gained more lean mass, women have accumulated more fat mass, which is important for reproductive health.

Yet adolescents tend to eat more fast food, processed food, and sugar-sweetened beverages than do other age groups, and they eat fewer vegetables, fruits, whole grains, and milk than recommended. Their energy-rich, nutrient-poor diets lead many adolescents to have insufficient intake of several nutrients, including calcium, iron, and fiber. Teens and young adults also love to consume snacks, which while not inherently nutritionally detrimental, these snacks often contain unhealthy fats and added sugars—-dietary constituents that the Dietary Guidelines for Americans suggest limiting.

Nutrient requirements for adolescents aged 14 to 18 years are often extrapolated from adult DRIs but may be adjusted to reflect the lower average body weight of the younger age group. Most Recommended Dietary Allowances (RDAs) and Adequate Intakes (AIs) increase at 19 years of age to match recommended intake levels for adults up to age 50 or older. However, the recommendations for phosphorus, calcium, and iron—-nutrients important for growth and development—are higher for 14- to 18-year-olds. The recommendations are sex-specific, too, to account for the unique physiological changes and needs of boys and girls.

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