It seems “good” cholesterol is just OK. After a large body of research found that people with low HDL levels were more likely to suffer heart attacks, researchers began to look into ways of boosting HDL cholesterol levels, hoping it would clear out the LDL cholesterol that clogs arteries and causes heart problems. But a large study shows that this isn't the case. The federally funded study of 3,400 U.S. adults at high risk of heart attacks and strokes was called off 18 months early because HDL-boosting drugs clearly failed to lower the risk. Possibly worse, patients who took the HDL-boosting drug showed a higher rate of strokes when blood flow to the brain is obstructed, though it's unclear whether the increase was a fluke or related to the drug. “This sends us a bit back to the drawing board,” said Susan B. Shurin, acting director of the National Heart, Lung and Blood Institute.