August 7th, 2012

Survey Finds Significant Drop in Cholesterol Levels in Youths

New data from the National Health and Nutrition Examination Survey (NHANES), published in JAMA, show significant and perhaps surprising  improvements over the last 20 years in the lipid profile of youths aged 6-19 years. Among the key lipid parameters measured by the survey from 1988-1994 to 2007-2010:

  • Total cholesterol decreased from 165 mg/dL to 160 mg/dL (p<0.001)
  • Prevalence of elevated total cholesterol declined from 11.3% to 8.1% (p<0.002)
  • HDL increased from 50.5 mg/dL to 52.2 mg/dL (p<0.001)
  • Non-HDL decreased from 115 mg/dL to 107 mg/dL (p<0.001)

“Generally,” the authors report, “the sex-, age-, and race/ethnicity-specific trends for TC, HDL-C, and non– HDL-C were similar in direction to the overall trends and consistent with a favorable trend, although for each group, the magnitude was not the same and the trend was not always significant.”

The change over time in lipids in youths was paralleled by similar changes in adults, according to the investigators. They also note that the improvement in lipids occurred “despite an increase in obesity prevalence during the study period.”

The changes recorded in the survey are “clinically meaningful” and a “cause for optimism,” writes Sarah de Ferranti in an accompanying editorial. “But,” she asks, in the face of the increase in obesity, the decline in exercise, and other adverse trends, “why would childhood cholesterol improve?” She briefly considers several possible explanations for the improvement, including improved interventions and healthier lifestyles, but then finds “a more plausible explanation” to be “dietary shifts at a population level”:

Dietary intake of fat has declined over the past several decades and some studies suggest substitution of carbohydrates for dietary fat, particularly poor quality carbohydrates, might both promote obesity and explain some of the lipid changes reported [here].

Another less concerning cause may be the reduction in the use of trans fats over the study period, she writes.

One Response to “Survey Finds Significant Drop in Cholesterol Levels in Youths”

  1. Uffe Ravnskov, MD, PhD says:

    There is no evidence that the small changes of the blood lipids have anything to do with a smaller intake of saturated fat. As I have shown in a review (1) there is no evidence that total or LDL cholesterol is affected by the intake of saturated fat. This idea comes from old dietary experiments on healthy people, where the authors used vegetable oils saturated by hydrogenation instead of using natural saturated fat. Even if saturated fat is hypercholesterolemic the effect must be small. In a review of eight trials where the intake was reduced by 30-40 % the net reduction of cholesterol was only 0-4 %, and other studies have shown no effect at all. In experiments for instance, where carbohydrates were substituted with saturated fat, not even intakes between 20 % and 50 % of calories influenced total or LDL-cholesterol (1).

    1. Ravnskov U. Is saturated fat bad? In Modern Dietary fat intakes in disease promotion; Nutr Health 2010, part 2, p 109-119, available here: )