This month a presidential advisory from the American Heart Association states that "Well-conducted scientific research overwhelmingly supports limiting saturated fat in the diet to prevent diseases of the heart and blood vessels" (Circulation, June 13, 2017;135(24)). The report, written by some of the most respected researchers in the field, recommends that people should substitute unsaturated vegetable oils for saturated fats to help prevent cardiovascular disease (CVD). Saturated fats are found primarily in meats, dairy products and eggs as well as in coconut oil, palm oil and palm kernel oil. Sources of polyunsaturated fats include corn, soybeans, nuts and peanuts, while monounsaturated fat sources include olive oil, safflower oil and avocados. The AHA report stresses that this shift should be made as part of an overall healthful high-plant dietary pattern such as a Mediterranean diet or the DASH diet.
The AHA team's review of studies from the past 50 years shows that:
• Replacing saturated fats in dairy and meat with polyunsaturated fat from vegetable oils lowers CVD and reduces risk for heart attacks by 30 percent.
• Saturated fat increases LDL cholesterol, while replacing saturated fats with polyunsaturated or monounsaturated fats decreases LDL cholesterol.
• Replacing saturated with polyunsaturated or monounsaturated fat lowers blood triglyceride levels, an independent marker of risk for CVD.
• Reducing intake of all fats and replacing the fats with refined carbohydrates does not lower CVD.
Saturated Fat May Not Be the Culprit There is some disagreement among the scientific community about why eating large amounts of foods that are high in saturated fats is associated with CVD and other diseases, and no one has proven that saturated fats cause disease. The dietary patterns recommended by the AHA (Mediterranean or DASH diets) are very high in anti-inflammatory foods from plants, while meats and other animal sources of saturated fats are pro-inflammatory, which could account for their reduction in CVD. Some scientists think that red meat and processed meats may be associated with ill health because of other factors such as Neu5Gc or TMAO.
Many studies have shown that you do not prevent heart attacks just by reducing saturated fat intake (Annals of Internal Medicine, March 17, 2014). To help prevent heart attacks, diabetes and premature death, you need to replace the saturated fats in meats and dairy products with polyunsaturated fats found in plants. There is no health advantage to replacing saturated fats with sugar and other refined carbohydrates found in bakery products, most dry breakfast cereals, pasta, sugared drinks and sugar-added foods (Am J Clin Nutr, June 7, 2017).
Coconut, palm and palm kernel oils are among the richest sources of saturated fats, but no one has shown that they are associated with increased risk for heart attacks. We do have data to show that coconut oil raises LDL cholesterol more than olive oil or safflower oil do.
The Food Industry Often Misuses Data The meat and dairy industries try to use the confusion about saturated fats and dietary cholesterol to assure the public that their products are not linked to health problems. I believe that scientists, doctors, nutritionists and fitness authorities should stop talking about components of foods such as types of fats or carbohydrates. There would be less confusion if they talked instead about which specific types of foods are healthful and which should be limited or avoided. A healthful diet is loaded with fruits, vegetables, whole grains, beans, nuts and other seeds, and restricts meat from mammals, processed meats, sugar-added foods, sugared drinks including fruit juices, other refined carbohydrates and fried foods.
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