Researchers have found that a diet rich in fish, seafood, and grains — also called polyunsaturated fats — is better at preventing heart disease than a diet containing olive oil, nuts, and avocados — called monounsaturated fats. Although both types of fats are healthy, people should probably include more of the first than the second in their diet to keep a healthy heart, the scientists say. Too much cholesterol has long been linked to increasing risks of developing heart disease, but it has been less clear how the various dietary fats — saturated, monounsaturated and polyunsaturated — make people susceptible to the disease. Lawrence L. Rudel and colleagues developed a method to determine the effects of the three types of dietary fats on acyl-coenzyme A, a key molecule involved in the metabolism of fatty acids. The scientists found that mice fed diets high in saturated and monounsaturated fat showed an increase in acyl-coenzyme A compared to mice fed a diet enriched in polyunsaturated fat. These results suggest that polyunsaturated fat is a more suitable replacement than monounsaturated fat for dietary saturated fat, the scientists concluded.