01/12/08 If you think your levels of "good cholesterol" are good enough, a new study published in the December 2008 issue of The FASEB Journal suggests that you may want to think again. In the report, researchers from the University of Chicago challenge the conventional wisdom that simply having high levels of good cholesterol (HDL) and low levels of bad cholesterol (LDL) is necessary for good heath. Instead, they show that the good cholesterol has varying degrees of quality and that poor quality HDL is actually bad for you.

"For many years, HDL has been viewed as good cholesterol and has generated a false perception that the more HDL in the blood, the better," said Angelo Scanu, M.D., a pioneer in blood lipid chemistry from University of Chicago and first author of the study. "It is now apparent that subjects with high HDL are not necessarily protected from heart problems and should ask their doctor to find out whether their HDL is good or bad."

The researchers came to this conclusion after reviewing published research on this subject. In their review, they found that the HDL from people with chronic diseases such as rheumatoid arthritis, kidney disease, and diabetes is different from the HDL in healthy individuals, even when blood levels of HDL are comparable. They observed that normal, "good," HDL reduces inflammation, while the dysfunctional, "bad," HDL does not.

"This is yet one more line of research that explains why some people can have perfect cholesterol levels, but still develop cardiovascular disease," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "Just as the discovery of good and bad cholesterol rewrote the book on cholesterol management, the realization that some of the 'good cholesterol' is actually bad will do the same."

According to the U.S. Centers for Disease Control and Prevention, approximately 17 percent of all American adults have high total cholesterol, putting them at risk for heart disease. Cholesterol is a waxy, fat-like substance used by the body to maintain the proper function of cell membranes and is encapsulated within two types of proteins as it travels in the body—low density lipoproteins (LDL) and high density lipoproteins (HDL). High levels of LDL or total cholesterol are an indicator of increased risk for heart disease. High blood cholesterol elicits no physical symptoms, making medical screenings necessary for detection.