The Benefits & Side Effects of Omega-3 -6 and -9 Fish Oils

Salmon Fillet
Cooked salmon covered with spices in a dish with limes, rosemary, (Image: zeleno/iStock/Getty Images)

The benefits of including fish in your diet outweigh the potential side effects, according to the Harvard School of Public Health. The omega-3, omega-6 and omega-9 fatty acids in fish oil keep cells and nerves working and lower your risk for developing cardiovascular disease. Omega-3 and omega-6 must come from fish or fish oil supplements, but omega-9 is not an essential part of your diet because it's synthesized by your body.

Omega-3s in Fish Oil

The omega-3 fatty acids you’ll get from fish oil -- eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA -- are healthy polyunsaturated fats. In addition to their role in the structure and function of cells throughout your body, the omega-3s reduce your risk of cardiovascular disease through multiple actions. They fight inflammation, lower blood pressure, keep blood vessels healthy, and reduce levels of cholesterol and triglycerides. They may also help prevent rheumatoid arthritis and cancer, according to the Harvard School of Public Health.

Getting Your Omega-6s

Like omega-3s, omega-6 fatty acids are polyunsaturated fats that reduce your levels of cholesterol. The omega-6 -- linoleic acid -- may also lower your risk for developing type 2 diabetes, according to research cited in the "Journal of the Academy of Nutrition and Dietetics" in January 2014. Vegetable oils, seeds and nuts are much better sources of the omega-6s, but they’re also found in fish oil. For example, 1 tablespoon of corn oil has 7 grams of omega-6, while wild salmon has only 0.4 grams.

Omega-9 Fatty Acids

Omega-9, or oleic acid, is better known as the primary fatty acid in olive oil, but you’ll also get it from the oils in fish. Salmon and trout have roughly the same amount of omega-9 as omega-3, according to Purdue University. Omega-9 is a monounsaturated fat that reduces your bad cholesterol while increasing the amount of good cholesterol in your bloodstream. Oleic acid is also an essential component of the protective covering on nerves called the myelin sheath.

Mercury Contamination

The American Heart Association recommends eating fish twice weekly, but children and women who are pregnant or nursing should not eat fish that contains high levels of mercury. This means avoiding shark, swordfish, king mackerel and tilefish, according to the U.S. Food and Drug Administration. You should also limit canned albacore tuna to no more than 6 ounces weekly. Canned light tuna, salmon, pollock, catfish and shrimp are all considered low in mercury.

Supplement Concerns

Fish oil supplements are a good option if you don’t consume enough fish, but you should only take a dose recommended by your doctor. Large doses may interfere with blood clotting and lower your immune system’s effectiveness. Minor side effects, such as gas, heartburn and diarrhea, may be avoided by taking supplements with your meals. Because of the potential for interactions, consult your healthcare provider before taking supplements, especially if you have diabetes or depression, or take prescription medications.

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