By James J. DiNicolantonio, PharmD
Current dietary guidelines recommend lowering saturated fat intake as well as exchanging saturated fat for omega-6 polyunsaturated fat. However, these recommendations are not evidence-based, as pointed out in my recent editorial entitled, "The Cardiometabolic Consequences of Replacing Saturated Fats with Carbohydrates or Omega-6 Polyunsaturated Fats: Do the Dietary Guidelines Have it Wrong?" published in BMJ’s Open Heart.
Like omega-3 fatty acids, omega-6 fatty acids are essential for healthy brain function and normal growth and development. But unlike omega-3 fatty acid, which helps reduce inflammation, too much omega-6 fatty acid tends to promote inflammation. Making sure you get just enough—but not too much—omega 6, especially in relation to omega-3, is key. Omega 6 fatty acids are found in vegetable oils, such as corn and safflower oil, as well as a few plant-based oils, such as evening primrose oil.
These dietary guidelines are based on old data from the 50s and 70s which associated an increased intake of saturated fat with heart disease. But the data could never prove that eating foods high in saturated fat caused heart disease, nor could these data prove that lowering the intake of such foods, or replacing saturated fat with omega-6 fat would lead to improved outcomes or extend life.
While it was thought that replacing saturated fat with omega-6 fats would lower cholesterol, and thus lower the risk of heart disease (a flawed theory to begin with), increased intake of omega-6 may increase the susceptibility of LDL (low-density lipoprotein — the "bad" cholesterol) to oxidation. LDL per se is not harmful, but oxidized LDL is, and this is one possible mechanism why a recent meta-analysis of trials has shown an increased risk of death due to coronary heart disease and death due to cardiovascular disease when saturated fat is replaced with omega-6 polyunsaturated fat (mainly from corn and safflower oil).
Thus, evidence from clinical trials indicates that the American Heart Association’s 2009 scientific statement recommending that all Americans ingest at least 5 to 10% of their energy from omega-6 fats may be causing more harm than good. Additionally, the low-fat craze has caused us to switch from low-fat to “high refined carbohydrate and sugar." Data from a very large, national study called the National Health and Nutritional Examination Survey (NHANES) show that sugar and refined carbohydrate increased substantially during the obesity and diabetes epidemic in America, whereas saturated fat did not increase.
Thus, it is highly likely that the overconsumption of sugar/refined carbohydrates (and not saturated fat) is the direct cause of diabetes and obesity around the world. There is no proof that foods high in saturated fat are harmful.
Published: March 19, 2014
James J. DiNicolantonio, PharmD, is a cardiovascular research scientist with the Mid America Heart Institute at Saint Luke’s Hospital, Kansas City and Wegmans Pharmacy, Ithaca, NY.