Not too long ago, when it came to blood cholesterol, most of us knew only our total number—say, 190 (under 200 is desirable) or 250 (over 240 is high). But then scientists told us it wasn’t so simple, that there are two basic kinds of cholesterol in our blood: LDL (low-density lipoprotein, the “bad” type), which promotes coronary artery disease, and HDL (high-density lipoprotein, the “good” type), which helps remove cholesterol from the system. And we need to have both types measured.
But matters are still more complicated. Why do some people with given levels of LDL and HDL develop heart disease while others with the same levels do not? Some researchers now believe that a key factor is the size and density of LDL particles, which range from very small, densely concentrated particles to large “fluffy” ones. Studies have linked smaller, dense LDL particles to a higher risk of heart disease compared to larger particles, which may be relatively benign. This is true even if your LDL level is in the desirable range. For instance, if your LDL is a healthy 110, but you have lots of small, dense LDL particles, it may be the equivalent of having a high LDL reading of 160 or more, in terms of the effect on coronary risk. Moreover, small, dense LDL tends to go along with a constellation of related problems that increase the risk of cardiovascular disease—low HDL, high triglycerides (fats in the blood), high blood sugar, high blood pressure, and obesity.
Small particles are dangerous because they are better able to get into artery walls where dangerous plaque forms, thus promoting atherosclerosis. They are also more easily oxidized, and oxidized LDL plays an important role in atherosclerosis. In addition, they are less easily cleared from the bloodstream.
Sizing up what to do
Like much else about blood cholesterol, LDL and HDL size and density are largely a matter of your genes. However, the same steps that help improve cholesterol levels in general—diet, exercise, and loss of excess body fat—also improve LDL and HDL size and density.
The key dietary change for improving LDL size is to cut down on refined carbohydrates—that is, sugary or starchy foods. It isn’t necessary to go on a very-low-carb diet—just moderate your carb intake and choose healthy, high-fiber carbs. That’s good advice for many reasons. Surprisingly, saturated fat tends to raise levels of large LDL particles, the less harmful kind, suggesting that saturated fat may not be as bad as was once thought (see page 1). Part of the heart benefit of moderate alcohol consumption may come from its ability to raise levels of both large LDL and large HDL. Statin drugs lower LDL level, but have a relatively small effect on LDL size. In contrast, high-dose niacin and some other cholesterol-lowering drugs can substantially improve LDL size.
So should you have your lipoprotein particle size measured? This remains controversial. There are several methods to measure particle size, and no general agreement about which is best or how the tests should be standardized. Moreover, it’s still not clear how much the results add to an evaluation of traditional risk factors, or whether improving particle size will actually prevent heart attacks and deaths. Studies are underway to assess this.
Final thoughts: If you’re at average coronary risk, you needn’t worry about the size of your cholesterol particles. It’s enough to know your LDL and HDL levels and do all you can to prevent heart disease. But if you are at increased risk for a heart attack—because of diabetes, obesity, or a family history of premature heart disease or stroke, for instance—you might discuss such testing with your doctor