Monday, May 21, 2012

Is "Good" Cholesterol All That Good?

When it comes to cholesterol in your blood, all cholesterol is not the same. Statistically, people whose blood level of HDL cholesterol - the “good” cholesterol - is in the upper-normal range have reduced risks of developing heart disease. (And conversely, people whose LDL “bad”cholesterol is high have an increased risk of heart disease.) So it only makes sense that you should try to raise your HDL (and lower your LDL), right? This logic is so ingrained in us and in the medical profession that doctors routinely encourage patients with low HDL to change their diet, get more exercise, and take niacin (which is supposed to help raise HDL.) Drug companies have been trying to develop HDL-raising drugs for years - without success, I might add.

But now a new study casts serious doubt on the “good” cholesterol hypothesis. In the study, researchers reviewed the medical records of subjects with gene variations that cause the subjects to have high HDL levels. They hypothesized that subjects with high HDL because of genetic variations would have a reduced risk of heart disease. To their surprise, a high HDL due to an especially “good” genetic makeup had no effect on risk of heart disease.

So what’s going on? No one is arguing against the evidence that a high HDL is associated with a reduced risk of heart disease in normal persons, because it clearly is. But maybe the high HDL is not directly causing the reduced risk. (Remember, an association does not prove cause/effect.) And if a high HDL isn’t directly protective, then raising LDL through drugs or other means would be unlikely to be beneficial.

Incidentally, the same may not be true for the risk associated with high LDL, the “bad” cholesterol. Gene variations that caused high LDL levels were associated with increased risk of heart disease, as expected.

I’m guessing that this latest paper will lead to more research and a better understanding of the role lipoproteins play in the risk of heart disease. We need to find out, now, what’s actually lowering the risk of heart disease when we observe a high HDL, if in fact it’s not HDL itself.

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