Both flaxseed and fish oil contain essential omega-3 fatty acids; however, fish oil contains two fatty acids: docosahexaenoic acid, or DHA, and eicosapentaenoic acid, or EPA. Flaxseed oil capsules contain alpha-linolenic acid, or ALA. "Essential" means that these fatty acids must come from your diet; your body can't make them. The benefits of DHA and EPA have been better established than those of flaxseed oil. Your body can break down ALA into DHA and EPA, but it does so inefficiently.
Conversion
It's not yet clear whether ALA has equal benefits of its own compared to fish oils or if its benefits come primarily from the breakdown into DHA and EPA, Frank Sacks, M.D. of Harvard School of Public Health reports. Studies published by British researchers from the Institute of Human Nutrition in the October 2002 issue of the "British Journal of Nutrition" found that in healthy young men, 8 percent of ALA converted to EPA and 0 to 4 percent to DHA. In women, 21 percent of ALA converted to EPA and 9 percent to DHA. The higher amount in women may relate to women's higher estrogen concentrations.
Uses
Fish oils also appear to reduce the risk of heart disease by lowering cholesterol and triglyceride levels. Fish oil may also lower blood pressure, with DHA possibly having more benefit than EPA, the Mayo Clinic states. Fish oil may also reduce the risk of abnormal heart rhythms. The evidence for ALA reducing cholesterol levels and heart disease is not as strong as it is for fish oil, according to the Linus Pauling Institute. Fish oil may also reduce inflammation in chronic disorders such as rheumatoid arthritis. While fish oils appear to decrease the risk of age-related macular degeneration, ALA may increase the risk, the University of Maryland Medical Center cautions, although more studies are needed.
Contaminants
Fish oil comes from large ocean fish such as swordfish, tilefish, salmon and tuna. Fish can contain contaminants such as mercury and polychlorinated biphenyls, or PCBs, which can increase the risks of developing cancer in humans. Flaxseed oil, which comes from plants, doesn't pose the same risk. Laboratory tests in the United States have not shown contamination of supplements to be a problem, the Linus Pauling Institute states, but the theoretical risk remains.
Vegetarian Use
Flaxseed oil has advantages over fish oil for vegetarians. Strict vegetarians may not eat any animal products, including oil obtained from fish. Flaxseed oil provides a viable alternative to consuming animal products for vegans and other strict vegetarians.
References
- University of Maryland Medical Center; Omega-3 Fatty Acid; Steven Ehrlich, N.D.; June 2009
- Linus Pauling Institute; Essential Fatty Acids; Jane Higdon; December 2005
- Mayo Clinic; Omega-3 Fatty Acids, Fish Oil, Alpha-Linolenic Acid; April 2011
- Harvard School of Public Health; Ask the Expert: Omega-3 Fatty Acids; Frank Sacks, M.D.
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