Answer to Question 1
Fish, not fish oil supplements, is the preferred source of omega-3 fatty acids for most healthy people. Evidence is mixed for people with heart diseaseseveral studies show improvements in blood lipids and prevention of further heart disease, whereas others reveal no benefits or even increased metabolic risks from supplements. For people with specific forms of heart disease, however, the American Medical Association recommends 1,000 milligrams (1 gram) or more a day of EPA and DHA. Supplements can help such people to meet this goal, but in large doses they may bring risks, such as increased bleeding, delayed wound healing, and immune suppression. The benefits and risks from EPA and DHA illustrate an important concept in nutrition: too much of a nutrient is often as harmful as too little.
Answer to Question 2
Low-density lipoproteins (LDL) are lipoproteins that transport lipids from the liver to other tissues such as muscle and fat; they contain a large proportion of cholesterol. High-density lipoproteins (HDL) pick up cholesterol from body cells and carry it away to the liver for disposal. Both LDL and HDL carry cholesterol, but high blood LDL concentrations warn of an increased risk of heart attack, whereas low HDL concentrations are associated with a greater risk. Thus, some people refer to LDL as bad cholesterol and HDL as good cholesterolyet they carry the same kind of cholesterol. The key difference to health between LDL and HDL lies in the proportions of lipids they contain and the tasks they perform, not in the type of cholesterol they carry. When LDL cholesterol is too high, it contributes to lipid buildup in tissues, particularly in the linings of the arteries, that can trigger inflammation and lead to heart disease; HDL cholesterol opposes these effects, and when HDL in the blood drops below the recommended level, heart disease risks rise in response.