Nutrition experts, including the American Dietetic Association, now agree that with careful planning, vegetarian diets can be healthy for teen-agers. At a minimum, any healthy diet must include a variety of foods that supply enough calories and nutrients for normal body growth and function. Fortunately, almost all of the essential nutrients — carbohydrates, protein, fats, vitamins, minerals, and fiber — can be found in both animal and plant foods.

Typical types of vegetarian diets include vegan, lacto-vegetarian, and lacto-ovo-vegetarian, depending on whether you prefer to avoid all or only some animal products.

• A strict vegan diet has vegetables, fruits, grains, legumes (beans and peas), seeds, and nuts, but no animal products of any type (no meat, no eggs, no dairy products).
• A lacto-vegetarian diet is identical to a vegan diet, except it also includes dairy foods.
• A lacto-ovo-vegetarian diet is identical to a vegan diet, except it includes dairy foods and eggs.

Some people consider themselves vegetarian, but are technically semi-vegetarians because they also eat fish and chicken.

If you are interested in following a vegetarian diet, be aware of several health concerns involving:

• Calories — Fruits, vegetables, and grains are relatively high in bulk (fiber) and low in calories and fat compared with meat, eggs, and dairy products. Make sure that you get enough calories, including at least 20 percent from fat.
• Protein — Protein supplies amino acids, which are needed for the growth, repair and maintenance of body tissues. You can get all the necessary amino acids by eating a variety of grains, legumes, seeds, nuts, and vegetables. One of the best sources is soy; soy protein is considered to be nutritionally equivalent to the protein found in meat.
• Iron — Foods high in iron include dried beans, tofu, green leafy vegetables, whole grains, iron-fortified cereals and breads. Absorption of iron is improved by eating foods high in vitamin C along with iron-rich foods.
• Calcium — Dairy products are high in calcium. Non-dairy sources of calcium include calcium-fortified orange juice, green leafy vegetables, tofu, calcium-enriched soymilk, and sardines.
• Vitamin B12 — This important vitamin is found only in animal foods, including eggs and dairy products. Vegans can look for foods fortified with vitamin B12 (cobalamin or cyanocobalamin), such as soymilk or cereal. You should probably also take a multivitamin that includes vitamin B12.
• Vitamin D — Vitamin D is added to milk and most soy beverages. The body also makes vitamin D when the sun shines on your skin.
• Zinc — The body needs this mineral to fight infections and keep the skin healthy. Good vegetarian sources include whole-grain cereals, nuts, and legumes.

Any vegetarian diet can be healthy for people of any age, if meals and snacks are carefully planned. Discuss your dietary plans with your doctor or a registered dietician who can make sure that your plan has all the necessary daily nutrients.