BioEd Online

Teacher Background

Food provides energy to the body for growth, maintenance and activity. It also supplies building blocks for bones, muscles and other tissues of the body. Making the right food choices can promote and maintain good health throughout life.

Most teenagers do not eat enough foods that promote bone and muscle health. To develop and maintain strong bones, their diets should include plenty of calcium-rich foods, like low-fat dairy foods and green leafy vegetables. Vitamin D, which is made in the skin when it is exposed to mild doses of sunlight, helps the body to absorb calcium. Vitamins A and C also are necessary for proper bone development.

Bone is remodeled throughout life. Old bone is removed and new bone is formed. During childhood and teenage years, new bone is added faster than old bone is removed. As a result, bones become larger and denser. Bone formation occurs faster than bone removal until about age 30. After this age, breakdown of bone begins to occur at a faster rate than bone formation. Bone loss accelerates with age and can be particularly rapid in women in the years around menopause. This can lead to osteoporosis, or “porous bone,” a condition in which bones are not rebuilt as quickly as they are broken down. These weakened bones are more likely to fracture. Teenagers can help prevent osteoporosis later in life by including enough calcium in their diets and by exercising.

Protein, found in meats, fish, dairy products and beans, is used by the body to build muscles and the scaffolding within bones. In addition, protein can serve as an energy source for growth and movement. Energy also comes from carbohydrates (breads, pasta, vegetables and sugars), fats and oils.

The “Nutrition Facts” label on packaged foods can be used to make better food choices. This label lists the amounts of nutrients present in grams or as a percentage of the recommended Daily Value. A food product that claims to be a “good source of calcium” must contain at least 100 milligrams (mg) of calcium per serving. This is about one tenth of the total amount of calcium needed by a person each day.

Objectives and Standards

Concepts

• Good eating habits help maintain bone and muscle strength.

• Some foods, such as complex carbohydrates, are good energy sources.

• Other foods provide building materials for bones and muscles.

Science, Health and Math Skills

• Gathering information

• Comparing

• Charting

• Drawing conclusions

• Inferring

Materials and Setup

Materials per Group of Students (see Setup below)

• Several "Nutrition Facts" labels from a variety food packages

Materials per Student

• Copy of the student page

Setup

1. Have students bring in nutrition labels from food packages.

2. Put a mixture of labels from different kinds of foods in plastic bags and place them in a central location.

3. Have students work in groups of 3–4.

Safety

Please follow all school district and school laboratory safety procedures. It always is a good idea to have students wash hands before and after any lab activity.

Procedure and Extensions

1. Have each student make a list of everything he or she ate during the past 24 hours (including snacks).

2. Distribute the “Healthy Choices” page. Point out the basic food groups shown on the page and have students identify the food group category in which each item on their lists belongs. Some items may fall into more than one food category. Encourage students to discuss these foods within their groups to decide where they belong. For example, a large portion of lasagna might count as one serving from the bread/pasta group, one serving from the dairy group (cheese) and one serving from the meat group (ground beef or sausage).

3. Have each student make a chart and list all of the food groups in separate columns. Students then should record in the appropriate column what they ate over the past 24 hours and the number of servings eaten for each item listed. Have students compare their totals to the recommended numbers of servings.

4. Ask, How many of you had the recommended amounts of fruits, vegetables and dairy products? Did anyone exceed the recommendations for fats and sweets? How about breads and pastas? Distribute the “Calcium for You” page, which focuses on calcium—a nutrient important for strong bones. Have students refer to their “Healthy Choices” sheets and identify any foods that they ate that are sources of calcium. Next, have them calculate the number of milligrams of calcium that they included in their diet over the past 24 hours.

5. Ask students, Is there room for improvement in your eating habits? Have the Materials Manager from each group collect a bag of nutrition labels from the materials table. Have each group observe their food labels and rank the foods from best to worst in terms of the nutrients needed for bones and muscles (calcium, protein, Vitamins D, C, and A). Then have groups share their lists with the rest of the class.

6. Conclude by asking students to suggest simple changes they could make to improve their diets. Record their ideas. You may want to discuss the word “diet” with students. Even though it is frequently used to describe an eating program to promote weight-loss, “diet” also can mean the usual things that a person eats.

Extension

Have students consult the Internet for additional information on diet and nutrition. “The Nutrition Source” from Harvard’s School of Public Health
(www.hsph.harvard.edu/nutritionsource), U.S. Food and Drug Admin­istration (www.fda.gov), National Institutes of Health (www.nih.gov), and the US Department of Agriculture (www.nal.usda.gov/fnic/foodcomp) are good places to start.

Handouts and Downloads

Download color images from The Science of Muscles and Bones Teacher's Guide.