Fish oil is produced by the tissues of oily fish, such as mackerel, herring, salmon and cod. Flaxseed oil, also known as linseed oil, is derived from the dried seeds of the flax plant. Both oils are rich sources of omega-3 fatty acids, which are a type of unsaturated fat linked to various health benefits. The human body cannot synthesize omega-3 from other non omega-3 sources and it must be obtained from the diet.
ALA vs. EPA and DHA
The main difference between flaxseed oil and fish oil is the type of omega-3 they contain. Flaxseed oil contains α-linolenic acid, ALA, while fish oil contains eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA. The human body can convert ALA into EPA and DHA, but conversion is inefficient. According to the DHA-EPA Omega-3 Institute, in men, conversion of ALA into EPA is reported to be between 8 and 0.3 percent while conversion into DHA is reported to be between 4 and 0 percent. Women of reproductive age have higher efficiencies.
Benefits of the Different Omega-3
Most of the benefits associated with omega-3 arise from the EPA and DHA, not ALA. In the body, EPA is used to create hormone-like substances that have anti-inflammatory properties and can alleviate the symptoms of arthritis and gout and help prevent cardiovascular diseases, as reviewed by A. Manerba and colleagues in "Future Cardiology." DHA is an important component of the brain and retina. On the other hand, the benefits obtained from ALA supplementation are believed to arise through the conversion of ALA in EPA and DHA.
Fish Oil Advantages
With respect to the constituent omega-3, fish is definitely superior to flaxseed oil. A 1g capsule of fish oil provides the recommended daily intake of EPA and DHA. These two omega-3s cannot be found in any plant product. The beneficial effects of fish oil have been widely documented and many doctors recommend fish oil supplementation.
Flaxseed Advantages
The one major advantage of flaxseed oil over fish oil is that it is free from contaminants. Certain fish from which fish oil is made can accumulate contaminants such as mercury, arsenic and DDT. Swordfish is known to accumulate the highest amounts of contaminants, followed by albacore tuna. Because of this, pregnant women are advised to avoid eating these fish and the general population is advised to eat no more than two servings of fatty fish per week. However, it must be pointed out that testing has shown many fish oil supplements do not contain these contaminants.
Another advantage of flaxseed oil is that ALA can be converted into other omega-3s, not just EPA and DHA.
Considerations
Ideally, people should consume both flaxseed oil and fish oil to reap the benefits of both. Even if the diet is rich in EPA and DHA, the body still needs an adequate intake of ALA. For vegetarians and vegans, algal supplements of EPA and DHA are available.
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