Rates of obesity and diabetes in American youth are still too high, but there’s a silver lining in the data: kids’ cholesterol levels are down. The proportion of children with high cholesterol dropped by 28% over the last two decades, according to a new Centers for Disease Control and Prevention (CDC) study, and their average overall cholesterol levels also fell slightly.
The scientists can’t say for certain what caused the decreases, but they think lifestyle and environmental changes — like declines in teen smoking and reductions in trans fats in processed and fast foods — had something to do with it. “We know that dietary intake of saturated fat and trans fats and exposure to secondhand smoke are related to blood cholesterol, so changes aimed at limiting these may have contributed to the changes that we observed,” study author Dr. Brian Kit, a pediatrician and epidemiologist at the CDC, told HealthDay.
For their study, published in the Journal of the American Medical Association (JAMA), the CDC researchers looked at 16,000 children and teens aged 6 to 19 who participated in the U.S. National Health and Nutrition Examination Surveys during three periods: 1988-94, 1999-2002 and 2007-10.
In the most recent study period, 8.1% of kids and teens had high total cholesterol, down from 11.3% in 1988-94. Further, overall cholesterol levels dropped, from 165 mg/dL to 160 mg/dL over the same time period. The researchers also found that kids’ levels of artery-clogging triglycerides and “bad” cholesterol, or LDL, dropped, while levels of “good” cholesterol, or HDL, went up. Overall, the proportion of youngsters with either low HDL or high LDL cholesterol or triglycerides fell from 27.2% in the 1988-94 to 22% in 2007-10.
(MORE: New Advice: Kids Should Be Screened for High Cholesterol)
High total cholesterol levels are a major risk factor for heart disease, and researchers think the risk may begin as early as childhood. Late last year, a government-appointed panel recommended cholesterol screening for all children aged 9-11 in order to identify at-risk kids and get them to make diet and lifestyle changes early on. The advice was controversial, however, because of concerns that widespread screening would lead to increased prescription of powerful statin drugs. Experts say the medications should be used only in the most serious cases — in fewer than 1% of kids — and not in children under 10.
While the new CDC data offer hope that cholesterol trends have taken a turn for the better, the good news is somewhat shadowed by the fact that 1 in 10 U.S. kids still has high cholesterol levels that may lead to a higher risk of heart disease later on. And 17% of American kids are still obese.
“We may have a small effect in the right direction from lower cholesterol, but I’m worried it will be overwhelmed by the earlier onset of obesity in younger and younger children,” Dr. Sarah de Ferranti, director of preventive cardiology at Boston Children’s Hospital, who wrote an editorial accompanying the new study in JAMA, told the Associated Press. “I’m still pretty worried about how many kids are going to wind up patients of adult cardiologists.”
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In addition, public-health efforts to take trans fats out of foods may have resulted in some collateral damage. In 2006, the federal government started requiring all processed food manufacturers to list the amount of trans fat in their products, and a larger push to take trans fats out of food entirely led to their removal from many processed foods. Going one step further in 2008, New York City passed a ban on using artificial trans fats in restaurants — a measure that ended up affecting many national chain restaurant menus more widely, and led to a an 86% increase in healthier food choices at fast-food restaurants in New York.
The downside? The Los Angeles Times reported:
In reducing saturated fat and removing trans fats, many manufacturers have pumped up the sugar and carbohydrate content. That may help explain why obesity among children and adults continued to grow through much of the study period, even as cholesterol readings improved.
Further research is needed to identify what environmental changes will yield the best results for the health of America’s youth, but De Ferranti rattles off a few that could work: “Examples of other interventions that could have positive population-level effects on health include taxation of carbonated beverages, improved access to water in schools and in the workplace, and environmental changes to promote daily physical activity,” she wrote in her editorial.
“Improvements in child and adolescent lipid values over the past two decades are significant and may portend improved cardiovascular disease outcomes for the future, but much work should be done to better understand the changes and to build upon them,” De Ferranti concluded.
MORE: NYC’s Trans Fat Ban Worked: Fast-Food Diners Are Eating Healthier