In fact, the opposite is true—if you choose fatty foods low in saturated and trans fats, a study from the American Heart Association shows. Researchers had participants eat a low-fat diet, a moderate-fat diet, or a moderate-fat diet that included an avocado a day. After five weeks, all three groups had lower cholesterol levels. But the avocado eaters’ levels dropped almost twice as much as the others’, thanks in part to the fruit’s heart-healthy monounsaturated fats, says lead researcher Penny Kris-Etherton, Ph.D. The study participants ate a whole avocado per day, but one-fifth of an avocado daily is enough to get the benefits, Kris-Etherton says. Try it on toast with salt and lemon juice, pureed into smoothies, or spread over sandwiches instead of mayo.