Many people, including doctors, tout flaxseed oil as a substitute for fish oil. Some studies, however, indicate that flaxseed oil may not be as reliable as fish oil as a source for those important omega-3 fatty acids.
Flaxseed is universally accepted as the best vegetarian source of anti-inflammatory omega-3 fatty acids, and research has shown that the flaxseed’s unique nutritional profile can help regulate hormones, improve skin health and even protect against heart disease. Flaxseeds are particularly rich in a short-chain omega-3 fatty acid calledALA(alpha linolenic acid). But calling flax a “substitute” may be a stretch.
The reason: Flaxseed oil provides short-chainALA, some of which the body converts into the long-chain omega-3 fatty acids EPA and DHA, like those in fish oil.
Some new tests show that the body’s ability to perform this conversion may vary from person to person. The rate of conversion may be particularly inefficient in some individuals, especially for DHA (docosahexaenoic acid), which is essential for brain development in infants and brain protection during aging.
For example, taking high daily doses of flaxseed oil (3,000 mg alpha linolenic acid) caused no increase of omega-3 DHA in the blood of subjects, finds a new Emory University study. Flaxseed oil did, however, result in a synthesis of some EPA (eicosapentaenoic acid), the other important omega-3 fatty acid in fish oil.
Similarly, researchers at the National Institutes of Health find that feeding rats alpha linolenic acid, as found in flaxseed oil, did not increase DHA in brain cells.
And British researchers found that flaxseed oil is a “limited source” of long-chain omega-3 fatty acids, especially in men, who are less apt than women to convert flaxseed oil to EPA or DHA.
Bottom Line: If you want to be sure you get the benefits of both short- and long-chain omega-3s, your best bet is to incorporate both flaxseeds or flaxseed oil AND fatty fish and/or fish oil supplements into your daily routine.
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 Harper CR et al. Flaxseed oil increases the plasma concentrations of cardioprotective (n-3) fatty acids in humans. J Nutr. 2006 Jan; 136(1): 83-7.
 Demar JC Jr. et al. Alpha-Linolenic acid does not contribute appreciably to docosahexaenoic acid within brain phospholipids of adult rats fed a diet enriched in docosahexaenoic acid. J Neurochem. 2005 (4): 1063-76.