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NEW YORK (Reuters Health) - High levels of high-density lipoprotein cholesterol - a.k.a. "good cholesterol" -- may be linked to lower risks of cancer as well as heart attacks, new research suggests.
Dr. Richard Karas of the Molecular Cardiology Research Institute at Tufts University in Boston and his colleagues had previously found that people with low levels of low-density lipoprotein (LDL, a.k.a. "bad" cholesterol) were actually at higher risk of cancer.
While that finding raised concerns that treating people to lower their cholesterol could be upping their cancer risk, Karas told Reuters Health, that doesn't seem to be the case.
In the current study, the researchers used the same body of research-dozens of "gold standard" clinical trials of cholesterol-lowering drugs called statins-to investigate whether there might be a relationship between their high-density lipoprotein (HDL) levels and cancer risk. (Karas and one of his co-authors have received consulting fees or grants from two statin manufacturers.)
Their analysis, of 24 studies in all, included about 76,000 people assigned to take statins and nearly 70,000 people who were given placebo. They followed subjects for an average of about five years.
The risk of developing any type of cancer during follow-up decreased as a person's baseline HDL cholesterol levels rose, Karas and his colleagues found. Doctors recommend that HDL levels be above 40 milligrams per deciliter (mg/dL) for men and above 50 mg/dL for women.
For example, for people with HDL levels of 30 mg/dL, there would be about 15 cases per 10,000 people per year; among people with HDL levels of 50 mg/dL, there would be just 10 cancers for every 10,000 people. Each 10 mg/dL increase in HDL levels reduced cancer risk by 36 percent.
"Really, the higher the better," Karas said. People can increase their HDL levels by exercising, eating well, maintaining a healthy weight, drinking moderately, and not smoking, he added. Taking statins will modestly increase HDL levels.
"Our most effective HDL-raising drug that's currently available is niacin," he added, noting that just 10 percent of people who could benefit from the drug are taking it.
Niacin is a B-vitamin, but given in mega-doses; the findings should in no way be seen as recommending that people start taking the drug to cut cancer risk, Karas warned. But, he added, the findings do suggest the idea is worth investigating.
It's unclear why HDL cholesterol would reduce cancer risk, but it may be due to its antioxidant effects, according to Karas. HDL cholesterol may also help the immune system in its task of searching for and destroying abnormal and potentially cancerous cells, he added.
Whether HDL directly affects cancer risk or not is unclear. Low HDL cholesterol could also simply be a marker for chronic conditions that increase disease risk, such as inflammation, Dr. Jennifer G. Robinson of the University of Iowa in Iowa City notes in an editorial accompanying the study.
But, she added, the healthy habits that help people maintain high levels of good cholesterol also "have a significant impact on the prevention of most of the chronic diseases associated with aging."
The things that people can do to up HDL cholesterol levels-exercising, quitting smoking, eating right, keeping their weight under control-are good for us no matter what, Robinson wrote.
SOURCE: Journal of the American College of Cardiology, June 22, 2010.