High-density lipoproteins, or HDLs, are the good guys — the “garbage trucks” of the bloodstream, as described by C. Noel Bairey Merz, M.D., director of the Preventive and Rehabilitative Cardiac Center at Cedars-Sinai Medical Center in Los Angeles. HDLs typically transport about 20 to 25 percent of the cholesterol in your blood, carrying it away from tissues to your liver, which disposes of it. The more HDL in your bloodstream, the more artery-clogging cholesterol is being removed.
Research finds that for every 1 percent increase in your HDL level, your risk of a heart attack drops 3 to 4 percent. By comparison, a 1 percent drop in your LDL level reduces your risk of a heart attack just 2 percent. HDL is so beneficial that a high level may offer enough protection to cancel out a heart disease risk factor like having diabetes or being overweight.
Having low HDL, on the other hand, often signifies other problems. For instance, many people with low HDL also have high levels of other dangerous blood fats, such as triglycerides and remnant lipoproteins (more on this later). That makes sense, since low HDL means fewer “garbage trucks” disposing of the “trashy” cholesterol. Low HDL can also be a sign of insulin resistance and metabolic syndrome, or Syndrome X.
An HDL level of less than 40 mg/dl is risky, 40-59 mg/dl is average, and 60 mg/dl is protective.
Smoking, being overweight, being sedentary, and consuming a high-carbohydrate diet (more than 60 percent of your calories) contribute to low HDL. So does a family history of low HDL. In fact, about half of HDL imbalances are due to genetics. Women are lucky in that they generally have a higher HDL level than men. But some doctors think women need these higher levels to remain healthy, and they suggest an HDL level even higher than 60 (the usual target) is most desirable for women.
Another up-and-coming indicator of your overall risk of heart disease is your non-HDL cholesterol count. You see, not all “bad” cholesterol is equally bad. While LDL has long been the focus of cholesterol reduction efforts, researchers have recently identified several other lipoproteins, including VLDL and IDL (intermediate-density lipoproteins) that also affect your cardiovascular health. To take these into account, they’ve come up with a new measurement and focus of treatment: non-HDL cholesterol. Your non-HDL cholesterol count is simply your total cholesterol minus HDL, or put another way, the sum of your LDL, VLDL, and IDL.
In late 2002 researchers published an article in Circulation, the journal of the American Heart Association, confirming that if you have heart disease, your non-HDL level can help predict your risk of a heart attack or angina (chest pain) and determine treatments. “LDL cholesterol, even though it is a ‘bad’ cholesterol, tells only part of the story,” said lead author Vera Bittner, M.D., MSPH, professor of medicine in the division of cardiovascular diseases at the University of Alabama at Birmingham. “We found that while LDL cholesterol is important, the non-HDL cholesterol is the more important predictor — at least in this group of people with heart disease.”
Many people won’t know their levels of VLDL and IDL, and that’s okay. Current recommendations call for obtaining at least a total cholesterol and HDL level to determine CHD risk. If these levels don’t raise any red flags, there’s no reason to investigate further (unless you have CHD or a strong family history of heart disease). But if the levels are elevated, you’ll probably need more detailed tests, possibly including VLDL and IDL counts.