A plant-based diet is critical in maintaining the proper nutrient balance. Human beings evolved on a diet with a ratio of omega-6 to omega-3 essential fatty acids (EFA) of approximately 1. In Western diets the ratio is closer to 20-1. Excessive omega-6 polyunsaturated fatty acids and such a high omega-6/omega-3 ratio promote diseases including cardiovascular disease, cancer, and inflammatory and autoimmune diseases. Increased levels of omega-3 and a low omega-6/omega-3 ratio exert suppressive effects, protecting against heart disease, certain forms of cancer, and providing relief in conditions including asthma and autoimmune disorders.
Because meat, soy, grains, nuts, and oils contain an abundance of omega-6 fatty acids, a diet which emphasizes these foods is not in the best interest of health. A diet which emphasizes fruits, vegetables (especially leafy green varieties, which are rich in omega-3), beans and some seeds is best.
Choose flaxseeds and chia seeds over nuts. The former are high in omega-3 and low in omega-6. Also, choose beans and other legumes over soybeans and soy-based products (1/2 cup of tofu has 5,466 mg omega-6 and just 733 mg omega-3). Finally, when choosing overt fat sources (foods which derive most of their calories from fat), opt for olives and avocados over oils (soybean, olive, canola). Yes, olives and avocados are high in omega-6. One avocado has 2,200 mg omega-6 and only 150 mg of omega-3. But the omega-3/omega-6 ratio in flaxseed (2,350 to 600) will offset the disproportionate amount of omega-6 present in avocado. Therefore, for each avocado you consume (perhaps one a day), add 1 tbsp of flaxseed. Some may wish to add a DHA supplement (with or without EPA) to top off omega-3 consumption. This is particularly relevant for diets relying heavily on grains, oils, nuts, and other sources of the omega-6 fatty acid linoleic acid (LA), as large quantities of this EFA inhibit the production of DHA.
A judicious plant-based approach will ensure that your consumption of essential fatty acids is close to the 1:1 ratio on which our ancestors evolved.