Fish oils have been a topic of avid interest since 1980, when scientists first linked the paucity of heart disease among Greenland Eskimos to their diet, which is rich in marine oils. Subsequent research has demonstrated that omega-3 fatty acids from fish oils, specifically eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA, confer protection against atherosclerosis, or hardening of the arteries. The American Heart Association now recommends that you eat at least two fish meals every week to obtain sufficient amounts of omega-3 fatty acids. However, contamination of many fish species has raised questions about the safety of regularly consuming fish or their oils.
Contaminants
According to Elson Haas, M.D., author of "Staying Healthy with Nutrition," it is nearly impossible to purchase a contaminant-free fish. The indiscriminate dumping of industrial wastes into the planet's waters has tainted them with lead, mercury, cadmium, polychlorinated biphenyls, flame retardants and other toxic chemicals. These toxins are assimilated by microscopic marine organisms and are increasingly concentrated as they move through the food chain. Ultimately, creatures such as swordfish, sharks, tuna and humans experience the greatest exposure.
Effects of Toxins
The toxins found in fish and their oils have been linked to a variety of disorders, including learning disabilities, developmental delay and attention-deficit disorder in children, and neurologic and psychiatric illness, skin disease and even cancer in individuals of all ages. Ironically, a 2003 review in "Archives of Pathology and Laboratory Medicine" reveals that ongoing consumption of mercury-laden fish reverses any perceived cardiovascular benefits and actually increases your risk for heart disease.
Removing Toxins from Fish Oil
Commercial producers of fish oils are aware of the potential for contamination in their products. Some manufacturers go to great lengths to use fish from deeper, colder and presumably cleaner waters or to only extract oils from non-predator fish, which provides oils with lower levels of toxins. However, since ocean-water contamination is ubiquitous, most manufacturers now subject their oils to processes that dramatically reduce the levels of unwanted material in the finished products. Molecular distillation and "oil refining" are the most commonly employed purification techniques.
Molecular Distillation
Distillation of raw fish oils requires converting their omega-3 fatty acids to molecules that are easily separated from the bulk product without changing the underlying chemical nature of EPA and DHA. Because the distillation process selectively extracts molecules of specific weights, meticulous quality control is possible. Molecular distillation produces the purest fish oils, but it is an expensive process.
Oil Refining
During oil refining, naturally acidic fish oils are neutralized and sequentially bleached and deodorized with absorbents and steam. This provides a product of uniform color and minimal odor with acceptable levels of contaminants. Oil refining is cheaper than molecular distillation, but the final product is not as pure, and some oxidation of the oils can occur during heating. Many fish oil manufacturers use a combination of distillation and refining to obtain a marketable product.
Fish Oil Safety
A March 23, 2009, article in "The New York Times" reported that ConsumerLab.com, an organization that conducts independent tests of various supplements, examined 41 fish oil products and found that none of them were contaminated with PCBs or mercury. However, some of these products contained less EPA and DHA than their labels claimed. The authors of the 2003 "Archives of Pathology and Laboratory Medicine" article similarly demonstrated there was no detectable mercury in five commercial fish oil products used in their study. Therefore, most fish oil products appear to be safe, but those bearing "USP Verified" or "USP Certified" labels have undergone testing to ensure they meet minimal safety standards.
Considerations
Although fish oil has been associated with a number of health benefits, the weight of scientific evidence only supports a small number of uses. EPA and DHA have been shown to reduce triglyceride and cholesterol levels, help prevent coronary heart disease, or CHD, and reduce mortality in people who already have CHD. According to the Agency for Healthcare Research and Quality, the evidence for benefit in other conditions, such as rheumatoid arthritis, kidney disease, inflammatory bowel disease or diabetes is currently insufficient to merit regular supplementation with fish oil for these disorders. Even though fish oils are generally safe, you should understand that their benefits may not be as far-reaching as is commonly advertised.
References
- "American Journal of Clinical Nutrition"; The composition of the Eskimo food in north western Greenland; Bang H, et al.; 1980
- "Staying Healthy with Nutrition"; Elson M. Haas, M.D.; 2006
- "Archives of Pathology and Laboratory Medicine"; Measurement of Mercury Levels in Concentrated Over-the-Counter Fish Oil Preparations: Is Fish Oil Healthier Than Fish?
- "The New York Times"; Really? The Claim: Fish Oil Supplements Can Contain Mercury; Anahad O'Connor; March 23, 2009
- Agency for Healthcare Research and Quality: Effects of Omega-3 Fatty Acids on Lipids
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