An Omega-3 Substitute

Omega-3 fatty acids are essential nutrients, meaning they are necessary for health but the body cannot make them on its own and must get them from food. While there is no other nutrient that can serve as a substitute for omega-3s, you don't have to get omega-3s from fish oil, as there are plant-based substitutes that also supply dietary omega-3s. However, omega-3 supplements containing alpha-linoleic acid (ALA), such as flaxseed oil, may not provide the same health benefits as supplements containing the types of omega-3 fatty acids found in fish and other marine sources -- eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA.

DHA From Algae

Omega-3 supplements containing algae are a good source of DHA -- one of the essential long-chain, omega-3 fatty acids commonly supplied by fish. Algae is actually the reason why many fish are high in DHA, as DHA-rich algae is the food source from which fish get their omega-3 content. Algae supplements are an ideal omega-3 alternative for vegetarians and people concerned about mercury levels in fish oil supplements. According to the University of Maryland Medical Center, research shows that omega-3 fatty acids like DHA are important for reducing inflammation and supporting cognitive functions, and reducing your risk of developing heart disease.

ALA From Flaxseed Oil

Plant and seed oils -- flaxseed oil, in particular -- also provide vegetarian omega-3 fatty acids. However, flaxseed oil supplements contain only AHA, a "short-chain" omega-3 that the body must convert to a "long-chain" omega-3 like EHA or DHA, in order to make use of it. According to a 2009 U.S. News & World Report article, it is unknown whether the body is able to effectively convert ALA to a long-chain form. Accordingly, omega-3 supplements containing ALA may not produce the same health benefits of omega-3 supplements with DHA and/or EHA, which include fish oil and algae. For example, according to MedlinePlus, unlike fish oil, flaxseed oil doesn't seem to lower elevated levels of blood triglycerides related to heart disease and diabetes.

Food Sources

In addition to supplements, foods also contain omega-3 fatty acids, although it is hard to find DHA or EHA outside of fish sources unless you enjoy eating algae or krill. Fish that provide good sources of DHA and EHA include cold-water fish such as salmon, halibut, herring, mackerel, sardines and tuna. In addition to flaxseed oil, ALA is found in canola oil, soybeans and soybean oil, pumpkin seeds and oil, and walnuts. Many foods, including milk, eggs, yogurt and even orange juice are now fortified with omega-3 fatty acids; however, to make sure you're buying a worthwhile product, Katherine Tallmadge of the American Dietetic Association recommends checking the label to make sure the product contains sufficient quantities -- at least several hundred milligrams -- of DHA or EHA, rather than ALA. If you are a vegetarian, also check the sources of the omega-3s in fortified foods, as they may come from fish.

Considerations

The American Heart Association recommends getting 250 to 500 mg of long-chain omega-3s daily -- the equivalent of eating two servings of fish per week. If you do not eat fish or take fish oil supplements, algae-derived DHA supplements are the best way to get health-beneficial omega-3s into your diet. Keep in mind that a healthy diet also includes omega-6 fatty acids in addition to omega-3s. According to the University of Maryland Medical Center, for general health, the ratio should be in the range of 2:1 to 4:1, omega-6 to omega-3. Omega-6 fatty acids are available in supplemental oils containing linoleic acid and gamma-linolenic acid, although the average diet already provides plenty of omega-6 fatty acids, according to UMMC, so supplements are not usually necessary.