For decades nutritionists have debated the merits of polyunsaturated and saturated fat. Polyunsaturated fats are liquid at room temperature whereas saturated fats are solid. Saturated fats are found primarily in animal products and are thought to raise risk of heart disease in part by raising blood cholesterol levels. In contrast, polyunsaturated fats are thought to lower blood cholesterol levels and consequently, to lower risk of heart disease.
There is however, also debate about the effects of the two types of polyunsaturated fat, namely omega-6 and omega-3 fats.
Omega-6 fat predominates in oils such corn, sesame and soybean oils. The major omega-6 fatty acid, linoleic acid, is an essential fatty acid, meaning that it is needed for growth and survival.
Omega-3 fats are provided by fish oil and are found in smaller amounts in walnut, canola and soy oil. One type of omega-3 fatty acid, alpha-linolenic acid, is also an essential fatty acid. Soybean oil is one of the few sources of both essential fatty acids.
Despite their ability to lower blood cholesterol levels, concerns have been raised that too much omega-6 fat may be unhealthy because these fats, according to some evidence, increase inflammation. An increased inflammatory state has been linked with a host of modern maladies including heart disease, arthritis and cancer. Critics of omega-6 fat recommend avoiding foods that are high in omega-6 fat.
However, evidence for the pro-inflammatory effects of omega-6 fats has waned in recent years. Findings from a new study from the National Institute of Health and Medical Research in France provide important insight into the debates about these different types of fats. For this study, the dietary intakes of omega-3 and omega-6 polyunsaturated fat were assessed in 843 adults beginning in 1994-1996. Over the next twelve years, dietary intake was assessed at least 6 different times. As might have been predicted, intake of omega-3 fat was associated with a decrease in inflammation, as measured by a decrease in CRP, a protein thought to be a good indicator of overall inflammation. However, intake of omega-6 fat was also associated with a decrease in inflammation.
The authors concluded that “our results … show that omega–6 polyunsaturated fat intake in general and linoleic acid intake in particular displays the same beneficial pattern as omega-3 polyunsaturated fat intake.” These findings are consistent with the views of the American Heart Association regarding omega-6 fats in the diet.
Julia C, Touvier M, Meunier N, et al. Intakes of PUFAs were inversely associated with plasma C-reactive protein 12 years later in a middle-aged population with vitamin E as an effect modifier. J Nutr 2013.