Cholesterol: Up with the Good … But How?
July 12, 2011
Once upon a time, cholesterol seemed easy: High cholesterol was bad, and you did everything you could – exercise, lose weight, eat a low-fat diet – to lower it.
Even then, of course, doctors knew that one kind of cholesterol, HDL or high-density lipoprotein, is actually good for cardiovascular health and should be kept high. But most of the lifestyle measures that lower LDL, or bad cholesterol, also tend to raise HDL as well.
With the introduction of cholesterol-lowering medications in the late 1980s, the story became more complex. The best of these medications tend to be very effective at lowering LDL but not so effective at increasing HDL. As a result, scientists have been studying new drugs and new combinations that might be even more effective than existing ones by raising the “good” while lowering the “bad.”
Results from a large government study released recently IN May added yet another twist to the cholesterol story, leaving patients, doctors and researchers to wonder exactly what is good and what is bad when it comes to cardiovascular health.
The study looked at the combination of niacin (Niaspan), a B vitamin known to boost HDL, plus simvastatin (Zocor), a statin effective at lowering LDL cholesterol. After 32 months, the subjects taking the niacin/statin combination did indeed show the expected increase in HDL, but they were no less likely than those in the placebo group to suffer a heart attack or other cardiac event. And those in the niacin/statin group had a slightly higher risk of having a stroke.
The number of strokes was very low in both groups (1.6 percent versus 0.7 percent) so the increased risk in the niacin group may have been due solely to chance. The surprise, though, was the lack of a clear benefit from raising HDL.
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Observational studies have for decades shown that persons with higher levels of HDL (45 mg/dL or higher) live longer and are less likely to have a heart attack than persons with lower levels of HDL. One study (American Journal of Cardiology, February 2011) found that men with the highest HDL cholesterol in their 60s were most likely to live to age 85 and longer.
Most of these studies show associations rather than cause and effect. Major ways of increasing HDL are weight loss, exercise, moderate alcohol consumption and not smoking. The men who lived to age 85 were also more likely than other subjects to be of normal weight and to have these heart-healthy habits.
One important function of HDL is reverse cholesterol transport: It removes excess LDL from the arteries and transports it to the liver. Studies have found reverse cholesterol transport to be an important factor in protecting against heart disease.
Women tend to have higher HDL levels than men, and exercise is known to be very effective in boosting blood levels. Mediterranean-type diets, with their focus on omega-3 fatty acids, monounsaturated fats (such as olive oil) and nuts, have been recommended for cardiovascular health in part because of their effect on HDL cholesterol.
As for cholesterol medications, statins are generally recognized as the most effective at lowering LDL and total cholesterol. A reduction of 25 to 55 percent in LDL can be expected, but the increase in HDL is only 5 to 15 percent.
Torcetrapib, a cholesteryl ester transfer protein (CETP) inhibitor, was developed specifically to increase HDL, but it was pulled from the market after a large study revealed an increased risk of heart attacks and deaths among subjects taking the drug.
One recent study published in the New England Journal of Medicine (January 13, 2011) suggested that the level of HDL in the blood may not be as important as how well that HDL is performing its function of reverse cholesterol transport. According to some theories, HDL might be converted in some cases to an inactive, ineffective form by inflammation or other factors.
The whole story of cholesterol – HDL and LDL – is far more complex than originally thought. Heart experts have not backed off from their view that treating high LDL is not enough. Some persons using statins to get their LDL to acceptable levels still have heart attacks, and roughly half of these patients have unacceptably low levels of HDL.
It’s not a question of whether HDL is “good” but rather how HDL is to be raised and how well these high-density lipoproteins do their work of moving and removing excess LDL. As a result of the recent studies, the big losers are the drug companies who are spending considerable money looking for the ideal medication. The winners are those who get their HDL up the old fashioned way, through regular aerobic exercise, weight control, a heart-healthy diet and good habits.