Fish and flaxseed oils both provide omega-3 fatty acids, which are known to reduce inflammation. Omega-3s are important for brain memory and performance as well as behavioral function, according to the University of Maryland Medical Center. Omega-3s also may lower risk of cancer, heart disease, diabetes and arthritis. However, not all sources of omega-3s are created equal.
Identification
Flaxseed oil contains the essential fatty acid called alpha-linolenic acid, or ALA. The body must convert ALA into eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for use. EPA and DHA are found naturally in fish oil.
Significance
Flaxseed oil has 50 to 60 percent omega-3 fatty acids in the form of ALA. That's more omega-3s than in fish oil. However, the body isn't very efficient at converting ALA into DHA and EPA. That means the ALA from flaxseed may not have the same benefit as EPA and DHA from fish oil. The University of Maryland Medical Center reports that studies on whether flaxseed is as useful as fish oil for conditions such as arthritis and heart disease produce mixed results. Fish oil also is believed to protect against prostate cancer, while ALA may actually increase risk. Also, some people cannot convert ALA; sometimes, people with diabetes or schizophrenia lack the ability to do so.
Sources
Flaxseed oil is derived from the seeds of the flax plant. EPA and DHA are found in cold-water fish, including salmon, halibut, mackerel, sardines, herring and tuna.
Function
Some flaxseed tablets do not contain any flaxseed oil. Flaxseeds--but not flax oil--contain chemicals called lignans, which may play a role in preventing some forms of cancer, according to the University of Maryland Medical Center. Flaxseeds also contain fiber. Lignans and fiber are not present in flaxseed oil but are in many flaxseed tablet formulations, and some flaxseed products ramp up lignan content. Lignans have estrogen-like activity in the body, however, and the University of Maryland Medical Center notes that there is uncertainty about whether lignans are helpful or harmful in breast cancer.
Considerations
The dosage for fish oil supplements should be based on EPA and DHA amounts rather than the total amount of fish oil. A common omega-3 fatty acid content in fish oil capsules is 180 mg of EPA and 120 mg of DHA.
Dosage in flaxseed tablets varies widely, depending on whether the product offers omega-3s, lignans or both. When used as substitute for the omega-3s in fish oil, a 7.2 g dose of flaxseed oil is needed to equal 1 g of fish oil.
Warning
The University of Maryland Medical Center advises that some fish has potentially harmful contaminants, including heavy metals such as mercury, polychlorinated biphenyls (PCBs) or dioxins. Purchase fish oil from reputable sources that test ensure mercury and pesticide residues are not present in their products. The center recommends that those taking flaxseed supplements also seek reputable companies that certify their products do not contain heavy metals such as lead and mercury.
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