Evolutionary Aspects of the Dietary Omega-6/Omega-3 Fatty Acid Ratio: Medical Implications

Abstract

Several sources of information suggest that humans evolved on a diet with an equal ratio of omega-6 (ω-6) to omega-3 (ω-3) fatty acids, whereas in today’s Western diet, this ratio is ~10:1 to 20–25:1. From an evolutionary perspective, Western diets are thus deficient in ω-3 fatty acids. This is problematic as while ω-3 and ω-6 fatty acids are important components of practically all cell membranes, they are not interconvertible in the human body. Moreover, a balanced ratio of ω-6 to ω-3 fatty acids is required for homeostasis and normal development. Excessive amounts of ω-6 polyunsaturated fatty acids (PUFAs) and a very high ω-6/ω-3 ratio, as is found in today’s Western diets, promote the pathogenesis of many diseases including cardiovascular disease, cancer, and inflammatory and autoimmune diseases. On the contrary, increased levels of ω-3 PUFA (a lower ω-6/ω-3 ratio) exert suppressive effects. We thus recommend that ω-3 and ω-6 fatty acids should be distinguished on food labels because they both are metabolically and functionally distinct and have opposing physiological effects. We further argue that a lower ratio of ω-6/ω-3 fatty acids is desirable as it is likely to reduce the risk of many of the chronic diseases of high prevalence in Western societies, as well as in the developing countries.