Q. I understand that “bad fats” can clog my arteries, but what do “good fats” do for you that’s good?

A. Alice H. Lichtenstein, DSc, director of the Cardiovascular Nutrition Laboratory at the Human Nutrition Research Center on Aging and executive editor of Tufts Health & Nutrition Letter, answers: “A diet rich in saturated fats can increase blood cholesterol levels, especially the more harmful LDL cholesterol. High LDL cholesterol levels can lead to the buildup of plaque in the arteries, increasing risk for heart attack and stroke. For that reason, saturated fats (along with trans fats, which have largely been removed from the U.S. food supply) are referred to as ‘bad fats.’

“Simply decreasing intake of saturated fats, however, is not the key to heart health. Research shows replacing fatty meats, butter, and bacon, with pasta, sugar-free cookies, and pancakes with maple syrup will not improve cholesterol or any other markers of cardiovascular health. One must replace saturated fats with unsaturated fats. There is strong evidence that replacing saturated fats with polyunsaturated is associated with lower blood levels of total and LDL-cholesterol, as well as lower risk of heart attack and stroke. Replacing foods high in saturated fat with monounsaturated-rich veg oils such as canola and olive oils has also been found to be associated with lower risk of cardiovascular disease and stroke.

“Canola, olive, and peanut oils, avocados, and most nuts, as well as high-oleic safflower and sunflower oils are good sources of monounsaturated fats. Good sources polyunsaturated fats include non-tropical plant oils (like soybean, corn, safflower, sunflower, and walnut oils), as well fatty fish (such as salmon, mackerel, and sardines), walnuts, and flaxseeds.

“When preparing food at home, cook with non-tropical plant oils instead of butter, choose fish and shellfish over red meat, and dress your salad or veggies with oil-based dressings rather than cream- or cheese-based.”