DEAR DOCTOR K:
For years my doctor has been telling me about the benefits of high levels of HDL cholesterol. Now I read that high HDL may not protect against heart disease after all. Is “good” cholesterol still good for you?
The HDL cholesterol story is a cautionary tale. It demonstrates once again that even the most persuasive theories about what should make us healthy need to be put to the test.
It has been solidly established that people who have high levels of LDL (bad) cholesterol have a higher risk of developing heart disease. Moreover, it has been solidly established that treatments that lower LDL cholesterol reduce the risk of developing heart disease.
It also has been solidly established that people with HDL levels above 60 milligrams per deciliter (mg/dL) tend to have a lower risk for heart disease. Since HDL cholesterol removes fat from the plaques in arteries, that observation made sense.
Not unreasonably, doctors and scientists assumed that boosting HDL with medication would lower cardiac risk even more. There are several drugs that have been around for 30 years — particularly gemfibrozil and niacin — that modestly raise levels of HDL. These drugs were tested in people with heart disease. They did lower the risk of new heart problems, but it wasn’t clear if they achieved that benefit by raising HDL cholesterol or through some other effect.
Then several different types of drugs were developed that could dramatically raise HDL levels. Most doctors, myself included, bet that such drugs would probably reduce the risk of heart disease. Why? Because all the evidence seemed to point in that direction.
Before such drugs were approved by the Food and Drug Administration, however, the agency required that studies involving large numbers of people be conducted to prove the value of the drugs. To make a long and painful story short, over the past five years these drugs have proved very disappointing. Not only have they not convincingly lowered the risk of heart trouble — in some cases, they have increased the risk.
In addition, a recent Harvard study pooled health information on more than 116,000 people genetically predisposed to produce higher-than-normal amounts of HDL. Surprisingly, this group did not show the predicted lower risk of heart attack.
How can this study be squared with previous studies that have convincingly showed that people with high levels of HDL have a lower risk of heart disease? The most likely conclusion is that it is not the high HDL levels, but rather something else about people who have high HDL levels that protects them from heart disease.
Many lifestyle changes raise HDL cholesterol and indisputably reduce your risk of heart disease: regular exercise, healthy weight, avoiding trans fats, quitting smoking and moderate use of alcohol. These lifestyle changes may not work through their effects on your HDL level, but they surely and powerfully do work.