About one in five U.S. kids and teens ages 6 to 19 has abnormal cholesterol levels, according to the National Center for Health Statistics (NCHS 2015). And among the 16-to-19 age group, the number rises to more than one in four.

“[This] is concerning because high cholesterol levels are a major factor contributing to heart disease and stroke,” says Mary Lou Gavin, MD, a pediatrician specializing in weight management and senior medical editor at KidsHealth.org. “Research shows that cardiovascular disease has its roots in childhood.”

Cholesterol is a lipid, or fat. The body uses cholesterol to help digest fatty foods and form cell membranes and hormones (progestagens, glucocorticoids, mineralocorticoids, androgens, and estrogens). The liver produces about 1,000 mg of cholesterol daily, which is enough for healthy functioning. Fruit, vegetables, and grains don’t have any cholesterol. Dietary cholesterol comes from:

• dairy products (e.g., milk, cheese, and ice cream),
• egg yolks,
• meat,
• poultry, and
• seafood.

To travel through the bloodstream, cholesterol has to combine with proteins. The combination of cholesterol and proteins is called lipoproteins. Low-density lipoproteins (LDL), or “bad cholesterol,” are the primary cholesterol carriers. Too much LDL in the bloodstream can build up inside blood vessels. The buildup forms plaque—a hard substance that can cause blood vessels to become stiffer, narrower, and blocked. Plaque makes it easier for blood clots to form. A blood clot can cause a heart attack or stroke.

High-density lipoproteins (HDL), or “good cholesterol,” on the other hand, carry cholesterol away from the arteries and back to the liver, where it’s processed and sent out of the body. HDLs might even help remove cholesterol from areas of plaque. High levels of LDL increase heart disease and stroke risks. High levels of HDL can help protect the circulatory system. Here’s a mnemonic to remember good versus bad cholesterol: LDL starts with “l” for “lousy”; HDL starts with “h” for “healthy.”

Total cholesterol, based primarily on levels of LDL and HDL cholesterol, is a measure of the total amount of cholesterol in the blood. The combination of high levels of LDL and low levels of HDL indicates an increased risk of heart attack and stroke.

According to the U.S. Centers for Disease Control and Prevention (CDC 2015), desirable cholesterol levels for adults are:

• LDL = less than 100 mg/dl
• HDL = 60 mg/dl or higher
• Total cholesterol = less than 200 mg/dl

According to Gavin, desirable levels for kids and teens are:

• LDL = less than 110 mg/dl
• HDL = 40 mg/dl or higher
• Total cholesterol = less than 170 mg/dl

Factors that can contribute to high cholesterol levels include:

• eating foods high in fats, especially saturated and trans fats;
• having a parent with high cholesterol;
• being obese, related to diet and exercise; and
• having diabetes.

The study by the NCHS shows that teens ages 16 to 19 were most likely to have high total cholesterol, high LDL, or low HDL (26.9% for ages 16 to 19 versus 21.0% for ages 6 to 19 overall). This is why your students should know about:

• the need for screening to learn their cholesterol levels and
• how a healthy diet and daily exercise can help improve cholesterol levels.

Classroom activity
Ask your students to write an essay addressing the following question: The American Academy of Pediatrics recommends (AAP 2011) that all children be screened for high cholesterol at least once between ages 9 and 11 years and between ages 17 and 21 years. Why? Resources cited below are appropriate for their research.

Michael E. Bratsis (mbratsis@kidshealth.org) is senior editor for Kids Health in the Classroom (kidshealth.org/classroom). Send comments, questions or suggestions to mbratsis@kidshealth.org.

On the web
Article, video, quiz for students: http://teenshealth.org/en/teens/cholesterol.html, http://bit.ly/lipo-science-vid, http://bit.ly/cholesterol-quiz

References
American Academy of Pediatrics (AAP). 2011. Physicians recommend all children, ages 9–11, be screened for cholesterol. http://bit.ly/2cgI1mQ
Centers for Disease Control and Prevention (CDC). 2015. Cholesterol fact sheet. http://bit.ly/1pz0zxh
National Center for Health Statistics (NCHS). 2015. Abnormal cholesterol among children and adolescents in the United States, 2011–2014 http://bit.ly/cholesterol-kids

Editor’s Note

This article was originally published in the November 2016 issue of The Science Teacher journal from the National Science Teachers Association (NSTA).

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