Physical Changes in Teenagers Affecting Dietary Needs

The Basics

• In order to grow taller and develop muscle mass, teens must have adequate calories, protein, fat and carbohydrates, according to Story and Stang. A teen girl needs 2,071 calories from ages 9 to 13 and 2,368 from ages 14 to 18. Teen boys need 2,279 calories from ages 9 to 13 and 3,152 from ages 14 to 18. Although both boys and girls need 34 grams of protein each day from ages 9 to 13, their needs increase as they get older. Girls need 46 grams a day from 14 to 18, and boys need 52. Carbohydrate needs remain the same at all ages -- 130 grams a day. For girls, fat needs increase 1 gram, from 10 to 11 grams a day, while boys' needs increase from 12 to 16 grams a day.

Calcium

• Some nutrients become more important for teens, either because they need more of them for growth and development or because they tend to have lower intakes. Story and Stang note that teens tend not to drink enough milk or eat dairy products to meet their needs for 1,300 milligrams of calcium a day. Inadequate calcium intake can lead to osteoporosis in middle age, as humans lay down most of their lifetime supply of bone mass in their teen years. The American Academy of Pediatrics' Bright Futures publication notes that 45 percent of the permanent adult skeleton is formed in adolescence.

Iron

• Teens̵7; rapid growth means an increased need for iron. Iron requirements nearly double for girls between ages 9 and 18, due to iron loss with menstruation. Between the ages of 9 and 13, teen girls need 8 milligrams of iron, but by age 14, they need 15 milligrams. Teen girls also tend not to take in enough iron, according to Story and Stang. Teen boys, however, also need iron to fuel increased muscle mass and because their blood volume expands as they grow. Boys need 11 milligrams of iron a day. Adolescents from low-income families are particularly at risk of getting inadequate nutrients such as iron, calcium and zinc, according to the AAP's publication.

Healthy Fats

• Although high-fat diets -- especially in combination with excess sugar -- can create problems with obesity, teens should not cut back on healthy fats, according to pediatrician William Sears. Brain development continues in adolescence, as the brain continues to make neurological connections and cover the nerves with myelin, a special waxy coating that makes the nerve pathways more efficient. Teen brains need Omega-3 fats and oleic acid to produce myelin, and Sears notes that while teens may eat saturated or hydrogenated fats, they tend to skimp on quality Oemga-3 fats found in sources such as salmon. Teens are also more likely to eat fries than foods high in oleic acid, another healthy fat found in found in olive oil, almonds, pecans, macadamias, peanuts and avocados.