Why I don't like flax oil as a source of Omega-3

I know right off that some people will read this post and disagree heartily with what I am about to write. I love discussion - especially when it can be well supported by research - so if you have comments, please leave them!

I get asked a lot of questions about the best supplemental sources of Omega-3 fatty acids. Omega-3 fatty acids are essential fatty aids or EFAs. As the word essential implies, this group of fats are a requirement for normal health and cellular function. The body cannot make these fats itself, so it must – as with essential vitamins and minerals – obtain them from an outside source such as a food or a dietary supplement. Technically speaking, there are only two EFAs: the Omega-6 fatty acid Linoleic Acid (LA) and the Omega-3 fatty acid Alpha Linolenic Acid (ALA). From these, the body can derive the other four essential fatty acids: Gamma Linolenic Acid (GLA), Eicosapentaenoic Acid (EPA), Docosahexaenoic Acid (DHA), and Arachadonic Acid (AA). These four can also be ingested pre-formed.

Flax seed oil is an outstanding source of the Omega-3 fatty acids ALA. Other good sources are canola, pumpkin, walnut oils. The issue at hand is that most people are supplementing these things (versus using the food - like eating walnuts or pumpkin seeds) to obtain a specific health benefit. Virtually all the good research associated with health associated claims is directly related to EPA and DHA from fish oils. There is not substantial evidence that ALA alone from sources such as flax or canola has any of these effects, despite the fact that the body can create EPA and DHA from ALA.

Why? This may be because the ability to convert ALA to EPA and DHA can be impaired by a variety of factors including a diet high in the Omega-6 fatty acid Linoleic Acid (LA), trans-fats, and saturated fats, alcohol intake; deficiencies (even sub-clinical) of niacin (B3), vitamin B6, vitamin C, zinc or magnesium; diabetes and insulin resistance. Scientific studies report the human conversion of ALA to EPA and DHA to be between 0.2 (1) and 15 percent (2). That is incredibly inefficient. This blog recently discussed the new paper from the Journal of the American College of Cardiology that recommended 500mg per day of Omega 3 (specifically from EPA and DHA) for the prevention of heart disease (Omega 3 Updates, 27 Aug 2009). Assuming that you were doing a great job of converting your ALA, you would need to take over 3,300 mg (3.3 grams) of flax oil to get the equivalent of one 500mg fish oil capsule. If you are at the low end...well, you do the math.

Furthermore, ALA converts almost entirely to EPA (3) and minimally to DHA (which gives the greatest benefits for the brain). Therefore, for health benefits attributed to EPA and/or DHA, foods or products containing these preformed fatty acids should be the preferred source.

And I don't want to completely knock flax. The seeds are a great source of ALA, fiber, and lignan - which may have some of its own health benefits. Flax seeds or meal an excellent addition to muffins, pancakes, or other foods where they can nicely boost nutritional content. But if you want the health benefits of EPA and DHA, eat fatty fish or take fish oil.


References:
1) Pawlosky RJ, Hibbeln JR, Novotny JA, et al. Physiological compartmental analysis of alpha-linolenic acid metabolism in adult humans. J Lipid Res. 2001; 42: 1257–1265.
2) Emken EA, Adlof RO, Gulley RM. Dietary linoleic acid influences desaturation and acylation of deuterium-labeled linoleic and linolenic acids in young adult males. Biochim Biophys Acta. 1994; 1213: 277–288.
3) Mantzioris E, Cleland LG, Gibson RA, et al. Biochemical effects of a diet containing foods enriched with n-3 fatty acids. Am J Clin Nutr 2000;72:42-48.