To prevent cardiovascular disease, adults are told to get their cholesterol under control, but children (and their parents) may have also taken the message to heart. The average total cholesterol level for U.S. youths dropped nine points in less than two decades (from 164 mg/dL to 155 mg/dL), according to research published in JAMA.

Based on data from a nationally representative group of 26,047 youths ages 6 to 19, the report found that levels of “bad” cholesterol — low-density lipoprotein (LDL) — fell, while levels of the “good” type — high-density lipoprotein (HDL) cholesterol — rose, results described by the researchers as favorable and potentially good for young people’s future cardiovascular health.

The human body needs cholesterol to build cells, but the liver generally produces all that’s needed, and excess cholesterol (generally from foods) can cause problems. It can build up on the interior walls of blood vessels, causing them to narrow and possibly blocking blood flow to the heart.

To assess young people’s cholesterol levels, measurements were recorded periodically from 1999 to 2016 for total cholesterol, HDL, LDL, non-HDL cholesterol, triglycerides (a type of fat), and apolipoprotein B (a protein component of LDL). For about half of the youths, all cholesterol levels were considered to be in the normal range. Still, about 15 percent of young children (ages 6 to 11) and 25 percent of adolescents (ages 11 to 19) had at least one level rated as unhealthy. Getting exercise, staying slim, eating healthily, and not smoking can help keep cholesterol under control. For children 10 and older, cholesterol medicine may be prescribed if changes in diet and exercise do not help.