Sign of breast cancer

In a study of more than 38,000 overweight women, those with low HDL ("good") cholesterol (under 46 mg/dL) had roughly twice the risk of breast cancer of those with high HDL (over 63 mg/dL).

Researchers believe that low HDL is often a sign of insulin resistance, also called the metabolic syndrome. (Other signs are elevated levels of blood pressure, blood sugar, and triglycerides.) It's not the low HDL, but high levels of insulin, androgens, or some other hormone that may raise the risk of cancer.

What to do: If you're overweight, lose those extra pounds. (Low HDL wasn't linked to an increased risk of breast cancer in normal-weight women.) Exercise can help you slim down and--if you do enough--may raise your HDL.

J. Nat. Cancer Inst. 96: 1152, 2004.