The omega-3 fats found in oily fish such as mackerel, herring, sardine and salmon appear to have broad-ranging benefits, particularly with regard to the health of the cardiovascular system and brain. Omega-3 fats in fish come in two principle forms: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). While these fats can be found abundantly in fish and fish-oil supplements, there are concerns about the sustainability of these sources (there are only so many fish in the sea). Also, for individuals who do not wish to or can’t eat fish, these sources are simply not an option.
These issues have led some, quite reasonably, to seek alternative sources for EPA and DHA. One potential option here is the fat alpha linolenic acid (ALA). Found in certain nuts, seeds and vegetables, ALA is what is known as a chemical ‘precursor’ of EPA and DHA. In theory at least, ALA consumed in the diet might be converted into EPA and DHA by the body. Previously, though, there has been the thought that conversion of ALA to EPA and DHA is slow and generally inadequate. This has led to the idea that upping ALA intake is unlikely to do much to bolster EPA and DHA levels in the body.
The idea that ALA might have value in raising EPA/DHA levels was tested again recently. In this study, individuals were given supplements of ALA (in the form of flaxseed oil), fish oil, and sunflower oil (control) for a 12-week period. What the researchers found was that fish oil supplementation increased the levels of both EPA and DHA significantly (as you’d expect). More interesting, though, was the finding that ALA supplementation led to a significant increase in EPA levels, though it did not raise DHA levels significantly. In this study, flaxseed oil was given at three dosages: 1.2, 2.4 and 3.6 grams per day. On the two higher dosages led to a significant increase in EPA levels. Yet, the lower of the two effective dosages represents quite a low dose of flaxseed oil (about ½ teaspoon a day).
The results of this study suggest that supplementing with ALA (e.g. as flaxseed oil) or increasing ALA intake from foods (e.g. walnuts) may be a viable way for individuals to boost EPA levels in the body. That still, however, means that some individuals might miss out of whatever benefits higher levels of DHA may have to offer. As it happens, vegetarian sources of DHA (say, derived from algae) are relatively readily available. Some of these supplements contain EPA, though usually at quite low dosages compared to their DHA content (see http://www.water4.net/ for an example). Taking such as supplement is probably a good idea for non-fish eaters looking to nourish themselves as best as possible. Adding flaxseed oil to such a supplement would be a good ploy too, I think, in that it will help to ensure good levels of EPA in the body too.
Barcelo-Coblijn G, et al. Flaxseed oil and fish-oil capsule consumption alters human red blood cell n”3 fatty acid composition: a multiple-dosing trial comparing 2 sources of n”3 fatty acid. Am J Clin Nutr, 2008; 88(3): 801-9.