Low total cholesterol may be a sign of cancer rather than a cause, as some researchers have suggested, and men who have low cholesterol actually have a lower risk of developing high-risk prostate cancer, two teams reported on Tuesday.
Both studies, reported in the journal Cancer Epidemiology, Biomarkers & Prevention, shed new light on the role of cholesterol and cancer.
For years, researchers had noticed that people who have lower total cholesterol — a combination of both low-density lipoprotein or LDL, the "bad" kind, and high-density lipoprotein or HDL, the "good" kind — appeared more likely to have certain types of cancers than other people.
That was worrisome because having low cholesterol, and particularly low levels of "bad" LDL cholesterol, has been shown to protect against heart attacks and strokes.
"Our study affirms that lower total cholesterol may be caused by undiagnosed cancer," Dr. Demetrius Albanes, a senior investigator at the National Cancer Institute, part of the National Institutes of Health, said in a statement.
"In terms of a public health message, we found that higher levels of 'good' cholesterol seem to be protective for all cancers," he said.
The 18-year study of nearly 30,000 Finnish male smokers is the largest and longest of its kind. During that period, 7,545 men developed cancer.
The men with lower total cholesterol levels — below 230 milligrams/deciliter — had an 18 percent higher risk of cancer overall — just as in earlier studies.
But, when they excluded cancers that occurred in the first nine years of the study, this risk disappears.
"This finding supports the idea that the lower serum total cholesterol level we detected as a possible cancer risk factor may actually have been the result of undiagnosed cancers," Albanes told reporters in a telephone briefing.
They also found men who had higher levels of HDL or "good" cholesterol (above 40 milligrams/deciliter) had a 14 percent lower risk of cancer even after excluding nine years of early cases.
MORE STUDIES NEEDED
Albanes said the notion that high levels of HDL may protect against cancer is new and needs to be confirmed in other studies, particularly among women.
"The results should help dispel any lingering concerns anyone might have that having low cholesterol could cause cancer," Eric Jacobs of the American Cancer Society told reporters.
A companion study of more than 5,000 U.S. men by Elizabeth Platz of Johns Hopkins University in Baltimore and colleagues found a link between low cholesterol and a lower risk of high-grade prostate cancer among 5,586 men over 55.
They found that if men had total cholesterol of less than 200 milligrams/deciliter, they had a nearly 60 percent lower risk of developing high grade prostate cancer, the riskiest kind.
It is not clear whether taking cholesterol-lowering statin drugs might help men with prostate cancer. That would need to be studied, Platz said.