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People with high levels of high-density lipoprotein (HDL)—known as good cholesterol—not only have a two- to three-fold lower risk of heart disease, new research shows they also appear significantly less likely to develop cancer, according to a study published in the June 22, 2010, issue of the Journal of the American College of Cardiology.
The study—the first comprehensive analysis of the relationship between HDL-C and cancer risk among statin trials—reveals a 36 percent lower rate of cancer for every 10 mg/dl higher level of HDL-C, which is independent of other potential risk factors including baseline LDL (bad) cholesterol, age, body mass index, diabetes, sex and smoking status.
“There is a strong and important relationship between the level of good cholesterol that people have in their blood and their risk of getting cancer. This supports another potentially important role for HDL in the body,” said Richard Karas, M.D., Ph.D., executive director, Molecular Cardiology Research Institute,
The mechanisms by which HDL-C is protective against cancer have yet to be teased out, according to Dr. Karas, noting the current study does not imply a causal relationship. There are several plausible explanations for the beneficial effects of HDL-C that need further investigation, and include its:
· Antioxidant properties: Oxidants or oxidizing agents contribute to cancer risk by attacking DNA—the genes inside our cells—thereby converting healthy cells to cancerous cells. HDL may work by soaking up harmful oxidants and reducing cell damage.
· Role in immune surveillance: As HDL travels through the body, some experts suspect it may alter the immune system so that the body is better equipped to find and target developing cancers.
· Anti-inflammatory properties: A persistent proinflammatory state can sustain cancer cell growth and survival and has also been found to contribute to other chronic diseases; HDL may serve as a mediating factor, reducing inflammation.
Dr. Karas says patients should talk with their doctor about personal risk factors for both heart disease and cancer, adding that this study reinforces the importance of getting a full cholesterol screening panel that includes total cholesterol, LDL-C, HDL-C and triglycerides.
“Patients need to be informed and understand what each cholesterol number means for their overall health and risk of disease,” he said.
The best way to boost HDL levels is by adopting a healthy lifestyle—exercising regularly, eating a healthy diet, consuming alcohol only in moderation and not smoking cigarettes. For individuals who are considered at high risk for heart disease, there are medications available to help increase levels of HDL-C.
Whether HDL-C itself or its association with other health-promoting behaviors is driving the potential role it has in reducing one’s risk of cancer is challenging, as discussed in the accompanying JACC editorial.
“This study suggests that HDL might be an important marker for all lifestyle risk factors we know contribute to both heart disease and cancers—smoking, obesity and inflammation, for example,” said Jennifer Robinson, M.D., MPH, professor of Epidemiology and Medicine at the University of Iowa College of Public Health, and author of the editorial. “Since low HDL appears to be a marker for chronic disease risk, this is just another reason why we need to emphasize improved lifestyle among these patients.”
In a secondary analysis of other potential risk factors, authors confirmed their earlier report that LDL-C levels are inversely associated with the development of cancer. Data also showed a significant and direct association between both age and body mass index and the rate of incident cancer, such that every 5-year increment in age was associated with a 33 percent relatively higher cancer rate and every 1-kg/m2 increment in BMI was associated with a 21 percent relatively higher cancer rate.
A total of 24 randomized controlled trials of lipid-altering interventions were identified and baseline HDL-C levels and incident cancers were analyzed across treatment and control arms. Taken together, these large-scale trials enrolled 145,743 patients; the median duration of follow up was 5 years and there were 8,185 incidents of cancer reported.
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