Flaxseed oil capsules are a vegetarian source of omega-3 fatty acids. Unlike animal sources of this nutrient, however, flaxseed oil contains a type omega-3 fatty acid called alpha-linolenic acid. Your body must first convert ALA into eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DPA. These two omega-3 fatty acids are naturally found in fish oil. Although it is not known if flaxseed oil is as beneficial as fish oil, you can still get a healthy dose of omega-3s by supplementing your diet with flaxseed oil capsules. Flaxseed oil is a source of polyunsaturated fatty acids such as alpha-linoleic acid. The alpha-linoleic acid and related chemicals in flaxseed oil seem to decrease inflammation. That is why flaxseed oil is thought to be useful for rheumatoid arthritis and other inflammatory (swelling) diseases. Flaxseed oil, also known as flax oil or linseed oil, is made from flaxseeds that have been ground and pressed to release their natural oil.