BOSTON -- Need another reason to exercise? Scientists have discovered it makes cholesterol less dangerous.
A new study found that even modest exercise changes the size and density of cholesterol-carrying proteins so they do less damage. And the benefits occur even if people's total amount of cholesterol and their weight stay the same.
Staying active has many health benefits, but improving cholesterol is not usually considered one of them. People who exercise often lose weight, and while that can improve their cholesterol levels, exercise by itself was thought to have little or no effect.
Workouts fail to lower LDL, the dangerous form of cholesterol, and only rigorous exercise can nudge up HDL, the good form that protects against heart attacks.
But the study, by Dr. William E. Kraus of Duke University, found a new way that exercise can affect cholesterol -- by altering the number and size of the particles that carry cholesterol through the bloodstream.
His work, published in Thursday's issue of the New England Journal of Medicine, is the latest chapter in an evolving view of cholesterol's effects. A generation ago, doctors worried only about the total amount of cholesterol. Later, the importance of the main subtypes, especially HDL, became apparent. Now experts are turning their attention to the physical structure of cholesterol in the bloodstream.
Cholesterol is an essential fat, or lipid. It circulates through the body by attaching to protein particles. Cholesterol appears more likely to clog the arteries when it is carried by small, dense protein particles than when it is moved by relatively large, fluffy ones.
The latest study finds that people who exercise develop these bigger particles, even if their total amount of cholesterol stays the same.
The study, conducted at Duke and East Carolina University, involved 111 sedentary, overweight men and women. They were randomly assigned to three exercise groups: the equivalent of walking 12 miles a week, jogging 12 miles a week or jogging 20 miles a week. All were instructed to eat enough to keep their weight constant.
They found that the cholesterol effects of walking and jogging 12 miles were the same, while jogging 20 miles resulted in more pronounced changes.
Measuring protein particle size is sometimes done in large medical centers, but it is not part of standard physicals.
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