Pre-Teens & Teens: Essential Nutrition

By Kara Rienzo, R.D.N.

Adolescence, the period between childhood and adulthood, is an important period of growth. Physical changes affect the body’s nutritional needs, while lifestyle changes, such as involvement in school, activities, sports, and work, can affect eating habits and food selection. Nutrition choices during this time can affect the teenager’s current health, as well as their health in the future.

As children enter into the teenage years, they become more independent and may become aware of the ethical and environmental issues and abuses implicit in animal agriculture. Others may choose a plant-based lifestyle for health reasons, or they may formally commit themselves to maintaining the vegan lifestyle their parents raised them to follow. It is normal for non-vegetarian parents to be concerned with whether their teenager is meeting their nutritional needs during this important time of growth and development. Changes in dietary habits may also lead to conflict during mealtime, which can be stressful for everyone. Meeting with a Registered Dietitian Nutritionist (R.D.N.) can help to ease concerns and the R.D.N. can offer tips and suggestions to help make family mealtime simple and enjoyable for everyone.

Key Nutrients

Calories

Teenagers require additional calories as they are growing, but this can vary based on activity level. Teenagers who are more physically active and involved in sports need more calories to help them meet their energy needs for optimum athletic performance. Diet analysis by a Registered Dietitian can help to ensure the vegetarian or vegan teen athlete is getting everything he or she needs during this important time of growth and development.

Protein

Protein is important for growth and maintenance of muscle. Eating a wide variety of plant-based foods can help to ensure that vegetarian and vegan teenagers are consuming all the necessary amino acids and easily meeting their protein needs. It was previously believed that “protein complimenting” or intentionally combining specific foods was necessary, but as long as teenagers are eating an adequate amount of calories from different sources, it’s likely their protein intake will be sufficient as well. Protein recommendations for teenagers should amount to 10 percent of total calorie intake. Research has shown that vegans typically consume protein as 10-12 percent of their diet, whereas non-vegetarians consume 14-18 percent of calories from protein [1]. Good sources of protein include legumes, soy products, meat alternatives, nuts, and nut butters.

Iron

The mineral iron plays an important role in the body by helping to build red blood cells and aiding these cells in carrying oxygen to give the body energy [2]. Making sure to consume enough iron can ensure optimal performance in school and sports. Teenagers who do not get enough iron can suffer from anemia, which is low iron in the blood, and they can feel weak or tired. It is especially important that teen girls who have begun to menstruate get enough iron, as it can be lost with heavy menstrual periods. The Recommended Dietary Allowance (RDA) for boys and girls ages 9 to 13 years is 8mg/day [3]. For boys ages 14 to 18 years it is 11mg/day and for girls ages 14 to 18 years the RDA is slightly higher at 15mg/day [3].

Foods that are high in iron include legumes, whole grains, green leafy vegetables, nuts, nut butters, dried fruits, and iron-fortified cereals. Including a source of vitamin C (citrus fruits and juices, bell peppers, tomatoes, and melon) with iron rich foods can help increase iron absorption by the body.

If your doctor decides it is necessary to take an iron supplement, due to chronic anemia, make sure to take it every day and eat a diet rich in fiber and abundant in water, as iron supplements can cause constipation. If you are also taking a calcium supplement, be sure to take these two supplements at different times, as calcium can interfere with the absorption of iron by the body.

Calcium

Calcium, with vitamin D, is used to build bones during periods of rapid growth and development in childhood, adolescence, and early adulthood [2]. Bone health in adulthood depends on bone density acquired during this age window, so it is extremely important to ensure teenagers, especially girls, are consuming the RDA of 1300mg of calcium each day [4]. It is not uncommon for teenagers to fall short on their calcium needs, due to busy schedules or food preference. While bone density is largely affected by genetics, factors like diet and exercise can help to increase “peak bone mass” to better protect against osteoporosis and fractures from weakened bones later in life [5]. Lifestyle factors can also cause less calcium to be absorbed by the body. These include smoking cigarettes and drinking soda, caffeine, or alcohol [5]. Good sources of calcium include fortified non-dairy milks, calcium fortified juice, tofu, green leafy vegetables, broccoli, almonds and almond butter, sesame seeds and tahini, legumes, and figs.

Zinc

Zinc is an important mineral to consume during adolescence, as it promotes growth and sexual maturation [2]. The daily recommendation of zinc for vegetarian and vegan children is twice as much compared with their non-vegetarian counterparts. Vegetarian and vegan boys and girls ages 9 to 13 years need 16 mg/day of zinc, where boys ages 14 to 18 years need 22 mg/day and girls ages 14 to 18 years need 18 mg/day [3]. The reason for the higher recommendation is that vegetarian diets are relatively low in zinc and zinc from plant foods is less absorbed when compared with zinc from animal sourced foods [6].

Foods high in zinc include legumes, nuts, wheat germ, whole grains, and fortified cereals. A way to increase absorption of zinc from foods is through different food preparation techniques. Sprouting grains, beans, and seeds can help to increase the bioavailability, or the degree to which food can be absorbed and used by the body, of zinc [6]. Zinc is also in most multivitamins and can help to meet daily nutrient needs.

Vitamin D

As previously mentioned, vitamin D is necessary for bone building by helping the body absorb calcium. If a teenager is not getting enough vitamin D, it can affect the body’s ability to maintain strong bones and teeth, which can lead to an increased risk of osteoporosis and fractures from weakened bones later in life [5]. Exposing the skin to sunlight normally produces vitamin D, which can then be used by the body, but many factors come into play, including the use of sunscreen, skin pigmentation, and location in which a teenager is living [7]. Teenagers who are dark-skinned, live in regions with little sun, or who have no dietary source of vitamin D are recommended to take supplements [7]. The RDA of vitamin D for teenagers is 600 IU/daily [4].

Foods high in vitamin D include fortified non-dairy milks and fortified cereals. Vitamin D3, or cholecalciferol, is derived from animals and can be found in fortified foods or supplements. Vitamin D2, or ergocalciferol, is derived from plants and is the ideal source of vitamin D for vegetarians or vegans.

Vitamin B₁₂

Vitamin B₁₂ is necessary for healthy blood and nerve function [2]. Vegan teenagers should consume foods fortified with vitamin B₁₂ since it is only found naturally in foods that come from animals. However there are plenty of foods that are fortified with vitamin B_12, including fortified plant-based milks, some meat alternatives, vitamin B₁₂ fortified nutritional yeast, and some fortified ready-to-eat cereals. It is recommended that vegan teenagers consume 2 to 3 servings per day of foods fortified with vitamin B₁₂ or take a vitamin B₁₂ supplement either in a multivitamin or as an individual supplement in the dose of 25 mcg/day [8]. Consuming vitamin B₁₂ in small, frequent doses helps the body absorb it more efficiently.

Vegan Teenagers

* based on a 2000 calorie diet

(Adapted from [9])

Meal Ideas for Teens

Resources

1. Mangels, R., Messina, V., Messina, M. (2011). The dietitian’s guide to vegetarian diets: Issues and applications, 3rd ed. Sudbury, MA: Jones and Bartlett Learning.
2. Byrd-Bredbenner, C., Moe, G., Beshgetoor, D., Berning, J. (2009). Wardlaw’s perspectives in nutrition, 8^th ed. New York: McGraw-Hill.
3. Food and Nutrition Board, Institute of Medicine. Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, D.C.: National Academies Press, 2001.
4. Food and Nutrition Board, Institute of Medicine. (1997). Dietary reference intakes for calcium, phosphorus, magnesium, vitamin D, and fluoride. Washington, D.C.: National Academies Press.
5. Matkovic, V., Fontana, D., Tominac, C., Goel, P., Chestnut III, C.H. (1990) Factors that influence peak bone mass formation: a study of calcium balance and inheritance of bone mass in adolescent females. The American Journal of Clinical Nutrition (52); 878-888.
6. Hunt, J. R. (September 2003). Bioavailability of iron, zinc, and other trace minerals from vegetarian diets. The American Journal of Clinical Nutrition (78:3); 6335-6395.
7. Wagner, C.L., Greer, F.R. (2008); American Academy of Pediatrics Section on Breastfeeding; American Academy of Pediatrics Committee on Nutrition. Prevention of rickets and vitamin D deficiency in infants, children, and adolescents. Pediatrics, (122); 1142-1152.
8. Food and Nutrition Board, Institute of Medicine (1998). Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B₁₂, pantothenic acid, biotin, and choline. Washington, DC: National Academy Press.
9. Loma Linda University (2008). The Vegetarian Food Pyramid. Retrieved from http://www. vegetariannutrition.org/food-pyramid.pdf