The American Heart Association (AHA) had issued a Presidential Advisory on dietary fats and cardiovascular disease (CVD) that offers conclusions and recommendations to help reduce saturated fat and replace it with polyunsaturated and monounsaturated fat to lower cholesterol in the context of a healthy diet. Among the conclusions and recommendations:
- Randomized clinical trials showed that polyunsaturated fat from vegetable oils replacing saturated fats from dairy and meat lowers CVD.
- A dietary strategy of reducing intake of total dietary fat, including saturated fat, and replacing the fats mainly with unspecified carbohydrates does not prevent CHD.
- Prospective observational studies in many populations showed that lower intake of saturated fat coupled with higher intake of polyunsaturated and monounsaturated fat is associated with lower rates of CVD and all-cause mortality.
- Saturated fat increases LDL cholesterol, a major cause of atherosclerosis and CVD, and replacing it with polyunsaturated or monounsaturated fat decreases LDL cholesterol.
- Replacing saturated with polyunsaturated or monounsaturated fat lowers blood triglyceride levels, an independent biomarker of risk for CVD.
- Replacing saturated with polyunsaturated fat prevents and regresses atherosclerosis in nonhuman primates.
- Overall, evidence supports the conclusion that polyunsaturated fat from vegetable oils (mainly n-6, linoleic acid) reduces CVD somewhat more than monounsaturated fat (mainly oleic acid) when replacing saturated fat.
Sacks FM, Lichtenstein AH, Wu JHY, et al. Dietary fats and cardiovascular disease: A presidential advisory from the American Heart Association. [Published online ahead of print June 15, 2017]. Circulation. doi:10.1161/CIR.0000000000000510.
This AHA advisory nicely reviews the evidence on the relationship between dietary fat and coronary heart disease. It also clarifies some of the previous confusion, noting that seemingly contradictory evidence in some studies that show that decreasing saturated fat in the diet does not decrease heart disease came from studies where the saturated fat calories were replaced with calories from simple carbohydrates, primarily sugars. When saturated fat is replaced with mono- and polyunsaturated fats, there is an improvement in LDL cholesterol, triglycerides, and the development of heart disease. Main sources of saturated fat are dairy fat (butter), fat from red meats, palm oil, palm kernel oil, and coconut oil. Polyunsaturated fats are contained in canola oil, corn oil, soybean oil, peanut oil, safflower oil, sunflower oil, and walnuts. Monounsaturated fats include olive oil, avocados, and tree nuts such as almonds, cashews, hazelnuts, pistachios, and pecans. The advisory states that a “reduction in total dietary fat or a goal for total fat intake is not recommended.” Rather, a movement from saturated to unsaturated fats is recommended in the context of an otherwise healthful dietary pattern such as the DASH or Mediterranean diet. —Neil Skolnik, MD