CHICAGO (AP) — Taking fish oil or vitamin D? Big studies give long-awaited answers on who does and does not benefit from these popular nutrients. Fish oil taken by healthy people, at a dose found in many supplements, showed no clear ability to lower heart or cancer risks. Same for vitamin D. But higher amounts of a purified, prescription fish oil slashed heart problems and heart-related deaths among people with high triglycerides, a type of fat in the blood, and other risks for heart disease. Doctors cheered the results and said they could suggest a new treatment option for hundreds of thousands of patients like these.