The Co-op Food Stores of New Hampshire and Vermont

added 03/05/10

by Mary S. Choate, M.S., R.D.

High-speed changes in body composition, growth, and psychological and social development during the ages from approximately 13 to 19 years old transform a child into an adult. Eating well to support all these changes is easily forgotten in the rush. However, nutrition during this period is far too important to ignore, and with a little planning can result in an array of tasty, nourishing meals and snacks, fit for a teen’s active lifestyle and maturing body.

Adolescence brings unique nutritional needs

Teenagers grow rapidly in height, and weight. Body composition is changing, skeletal mass is increasing, and sexual organs are developing.

In girls, weight increases six to nine months before height gains occur. Estrogen and progesterone, the female sex hormones, promote the deposition of abdominal fat, the pelvis widens, hips broaden, and the skeleton grows thicker and taller. Lean muscle mass increases. Menstruation begins.

In boys, height and weight gains occur at the same time. Under the influence of testosterone, boys gain more muscle mass than fat and develop a heavier skeleton.

Before puberty, boys and girls have similar proportions and amounts of fat and lean muscle. During adolescence, boys double their muscle mass and girls gain more body fat. By the end of adolescence, the normal percentage of body fat is approximately 23% for adult females and about 12% for adult males. This of course, is an average. Athletic girls would gain more muscle and less fat than average. Sedentary boys would gain more fat and less muscle than average.

These significant and rapid changes have important implications for the nutritional needs of teenagers, particularly regarding calories, iron, calcium, and protein for increased bone mass, muscle growth, and blood volume.

Teen Nutrition: They Need More of Most Everything

Calorie Needs
Calorie needs differ widely based on growth rate and physical activity. The RDA for calories during adolescence ranges from 2200 to 3000 calories per day. This is based on teenagers of average weight and light activity levels, so should be adjusted upwards for larger or more active teens.

Protein Needs
Getting enough protein is not a problem for most teens. However, if calorie intake is decreased because of illness or chronic dieting, protein will be used for energy and will not be available as raw material for new tissue building and repair. The RDA for protein ranges from 44 grams per day for 15 to 18 year old girls to 59 grams per day for 15 to 18 year old boys.

Minerals: Calcium and Iron Are in Short Supply
During adolescence, the need for all minerals increases, but calcium and iron intakes are often marginal. A diet of soft drinks in place of milk with meals and snacks, and low calorie or unbalanced diets can easily leave out these important minerals.

Because of increased muscle, skeleton, and hormone development, calcium needs are greater during adolescence than at any other time. Adequate calcium intake during this important bone-building period decreases the risk of osteoporosis, the brittle bone disease, in later life. Teenaged boys are more likely than girls to have an adequate calcium intake. The dietary reference intake for calcium for both sexes, 9 to 18 years old, is 1300 milligrams per day. Good sources of calcium include dairy products, calcium-fortified soy products, kale, collards, broccoli, almonds, and calcium-fortified juices and breakfast cereals.

Growing bodies require an expanded blood supply, and red blood cells contain the highest concentration of iron of any tissue in the body. In girls, the onset of menstruation creates an additional need for iron, while teen athletes are at a higher risk of iron deficiency as a result of increased exercise and training. Overall, surveys find that iron deficiency is prevalent in teens of both genders. Unfortunately, a deficiency in iron during adolescence can impair growth, and immune function. The RDA for males ages 11 to 18 is 12 milligrams of iron per day. For females, ages 11 to 18, the RDA is 15 mg per day. Good sources of iron are meat, eggs, vegetables, grains, and fortified cereals.

Everything Grows Better with Vitamins
Vitamin needs during adolescence are even higher than the needs during childhood. Thiamin (B1), riboflavin (B2), and niacin (B3) are needed in increased amounts to release energy from the additional carbohydrates eaten by growing teens. Increasing muscle mass and an expanding blood supply demand vitamins B6, B12, and folate. Vitamin D helps build bone during growth spurts, while vitamins A, C, and E preserve the structure and function of newly formed cells.

The B vitamins occur in whole grains, enriched cereals, animal protein, green vegetables, legumes, seeds, and nuts. The only reliable source of Vitamin B12 are animal products or supplements. Liver, yeast, leafy vegetables, legumes, and orange juice are especially rich sources of folate. Processors add vitamin D to fluid milk (but not to other dairy products), and summertime sun exposure stimulates production of the vitamin in our skin. Fat-soluble Vitamin A exists in whole milk and fortified low fat milk and is found in liver, fish liver oil, and eggs. Carrots and dark leafy green vegetables are rich in beta-carotene, which the body can convert to vitamin A as needed. Vitamin C is abundant in green and red peppers, dark green leafy vegetables, broccoli, tomatoes, potatoes, strawberries, and citrus. Vegetable oils and margarine, wheat germ, green leafy vegetables, and nuts are good sources of vitamin E.

The Problems:

Just when their bodies need it most, teenagers’ lifestyles become too busy to think about eating right. Needing extra sleep to rest their active and growing bodies, they stay in bed until the last possible moment and miss breakfast. After school there are sports practices and drama rehearsals. Late night snacking and eating out become the norm.

• Irregular meals, dieting, and meal skipping may lead to nutrient deficiencies. This problem is worse in girls, who tend to skip more meals and diet more often than boys. Excessive dieting that leads to anorexia and/or bulimia requires intervention by parents and healthcare professionals as soon as it is identified.

• Snacking on low nutrient foods such as high fat chips, cookies, and candy may replace nutritious foods and lead to excessive fat and calorie intakes and vitamin and mineral shortages.

• A regular habit of eating fast foods can lead to nutrition imbalances. Choosing poorly results in a high saturated fat, high sodium and excess calorie intake that may result in obesity and chronic diseases such as diabetes and heart disease in later years.

Can a teenager’s poor diet be saved? You bet. Like so many of life’s challenges, the problem often contains its own solution. In this case, making healthful foods and snacks easily available and educating teens on what is happening to their bodies can help them choose appropriate snacks and meals to meet their goals. Choosing the right body fuel supports athletic training objectives, healthy hair, teeth, and skin, maximal height, strong muscles, and overall well being.

The Solutions:

• Keep the kitchen stocked with foods that are easy to prepare. Whole grains breads and crackers, low fat deli meats, nut butters, baby carrots, prepared vegetable and fruit salads, whole fruit, yogurt, sliced cheese, lowfat milk, and calcium-fortified juice can help a teen make a healthy meal or snack in minutes. (See “Cooking for Teens” on page x)

• Pack take-along snacks for after-school activities. Try cut up veggies and a sealed container of low fat dip, low fat popcorn, whole grain pretzels or crackers and cheese, fresh fruit, yogurt, milk, fortified soy milk, bite sized fortified breakfast cereal, fruit juice, or pudding.

• Choose wisely at fast food restaurants. A regular hamburger or grilled chicken sandwich (without the special fatty sauce) and small fries saves calories and fat over a supersized double cheeseburger and fries. Low fat milk, instead of soda, goes a long way towards meeting a teen’s calcium requirement. A salad meets one of the three vegetable servings recommended as the daily minimum.

• Leftover pizza for breakfast or cereal and milk for supper are unusual, but nutritionally sound, choices for teen meals, especially when the pizza has extra veggies and the cereal is fortified with vitamins and minerals.

• Vegetarian or other diets should be discussed with a knowledgeable nutritionist to ensure they will meet the needs of growing adolescents. Vegetarian diets, when planned correctly, can easily meet nutrition requirements. (Pick up a copy of the “Vegetarian Nutrition for Teens” handout on the pamphlet wall near the service desk of both stores.)

• A daily multivitamin can help to fill in the gaps for teens too busy to eat right every day. A separate calcium supplement is needed for those who cannot consume at least three to four servings of dairy or calcium-fortified equivalents each day.

Adolescence is a time when adequate nutrition has a long lasting impact on future health. Adequate nourishment at this stage lays the foundation for strong healthy bones, muscles, heart, arteries, and immune system. As teens move through adolescence, parents can provide behind-the-scenes support: fill the house with quick, tasty, and nutritious foods to fuel their journey, and they will eat it.