HDL, or high density lipoprotein, has been referred to as the “good” cholesterol. Now we hear that certain HDLs might actually be bad for you and increase your risk of heart disease:

A small protein may be to blame. HDL with a small proinflammatory protein called apolipoprotein C-III (apoC-III) on its surface may nearly double the risk of heart disease in healthy men and women, according to Frank Sacks, professor of cardiovascular disease prevention at the Harvard School of Public Health and senior author on a paper in the April Journal of the American Heart Association. Conversely, Sacks’s study found, HDL without apoC-III may be especially heart-protective. A number of studies have shown that LDL (low-density lipoprotein)—the “bad cholesterol”—with apoC-III on its surface is particularly harmful, leading to higher incidence of plaque buildup in artery walls. Yet, Sacks says, this is the first large-scale prospective study with healthy subjects to show that apoC-III on HDL may have similar effects.

The scientists examined blood samples taken from 572 women in the Nurses’ Health Study and from 699 men in the Health Professionals Follow-Up Study, two of the largest long-term investigations of factors that affect women’s and men’s health. Over 10 to 14 years of follow-up, they documented 634 cases of coronary heart disease, which they matched with control subjects for age, smoking status and the date blood was drawn. After adjusting for those and other lifestyle-based cardiovascular risk factors, they found a nearly twofold increase in risk for HDL with apoC-III. The men and women whose levels of HDL with apoC-III were in the top 20 percent had a 60 percent higher risk of developing heart disease than those in the bottom 20 percent.

More here.