Researchers have long known that people with lower total cholesterol—which combines low-density lipoprotein, or “bad” cholesterol, and high-density lipoprotein, “good” cholesterol—seemed more prone to certain types of cancer, a concerning trend since low cholesterol (especially the “bad” kind) is protective against heart attacks and strokes. Now, researchers are reporting low total cholesterol could be a sign of cancer. “Our study affirms that lower total cholesterol may be caused by undiagnosed cancer,” said Dr. Demetrius Albanes, a senior investigator at the U.S. National Cancer Institute, Reuters reports. “In terms of a public health message, we found that higher levels of ‘good’ cholesterol seem to be protective for all cancers.” In the study, the largest and longest of its kind, almost 30,000 Finnish male smokers were followed over 18 years. During that time, 7,545 developed cancer; the men with lower total cholesterol levels (below 230 milligrams/deciliter) had an 18 per cent higher risk of cancer, as has been shown in other studies. But when they excluded cancer that developed in the first nine years of study, the risk disappeared. “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 said. Another study of more than 5,000 U.S. men found a link between low cholesterol and a lower risk of high-grade prostate cancer among 5,586 men over 55.