Fish oils and supplements contain omega-3 fatty acids that your body cannot make. Mayo Clinic states that the two most important fatty acids in fish oil—eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—improve cardiovascular function, reduce triglycerides and decrease the risk of strokes. To get an adequate dietary intake of DHA and EPA from non-animal sources, vegetarians need to consume omega-3 fatty acids from plants rich in alpha-linolenic acid (ALA). Your body then converts the ALA to DHA and EPA.
Flaxseed oil provides the highest alpha-linolenic acid content from a plant source. The Linus Pauling Institute states that it contains 7.3 grams of ALA per 1 tablespoons serving. You can purchase flaxseed oil from natural foods stores and larger groceries. Because it is extremely perishable, keep it refrigerated. The University of Michigan cautions that heating flaxseed oil causes oxidation. Its nutty taste and aroma make it a good replacement for olive oil in salad dressings or butter on fresh bread.
Walnut oil, at 1.4 grams, and canola oil, at 1.3 grams, provide enough ALA per 1 tablespoon serving to meet the 1.1 grams Adequate Intake for adult females, cited by to the University of Michigan. Both oils fall short of the daily Adequate Intake of 1.6 grams for adult males. A serving of soybean oil, at 0.9 grams, has the next highest oil amount of ALA. Mustard oil follows with 0.8 grams.
Nuts contain less ALA than oils; however, they provide dietary options for vegetarians to boost omega-3 intake. Tufts University ranks English walnuts as the best nut source of ALA, with a content of 2.6 grams per 1 ounce. serving. Black walnuts contain 0.6 grams per serving, according to the Linus Pauling Institute. Tufts University states that pecans only have 0.3 grams per serving.
Ground flaxseeds lead Tuft University's list of seed sources for omega-3 content, at 1.6 grams per 1 tablespoon serving. Other sources—poppy, pumpkin and sesame seeds—have trace amounts of omega-3 fatty acid: 0.1 grams per serving.
Tofu and fortified soy milk provide additional alternative sources of omega-3 fatty acids for vegetarians. Purdue University states that an 8 ounce serving of soy milk contains 0.37 grams of ALA. Linus Pauling Institute's chart of omega-3 plant sources shows that a half-cup of tofu has 0.7 grams.