If you’ve checked out FishOilBlog.com before, you know that a flood of research published in recent years confirms the heart/health benefits of omega-3s (and you may have also picked up on the fact that the modern Western diet is severely deficient in omega-3s and high in omega-6s!).
Both fish oil and flaxseed oil contain omega-3, but only fish oils contain EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These long-chain omega-3s play an extremely important role in the normal function of the heart, brain, eyes, nervous system, kidney and liver. (DHA is also a key constituent of cell membranes, especially in the brain and eyes.) Flaxseed oil, on the other hand, contains ALA, a short-chain omega-3. In order to derive any health benefits from flaxseed oil, the human body must first go through an extra step converting the ALA to EPA/DHA.
Unfortunately, the standard American diet makes it especially hard for the body to convert the ALA in flaxseed oil to the EPA/DHA it needs. According to quite a few studies (like this one, this one and this one), the body will convert only a very miniscule amount of the ALA found in flaxseed oil into DHA and EPA with some people unable to convert ALA to DHA at all. One of the studies found a conversion rate from ALA to DHA as low as 0.2%! As another study states, thousands of investigations have proven the benefits of fish oil, but only a relative few have been done on the benefits of flaxseed oil.
Another serious issue to consider in the great fish oil vs. flax debate is that, while flaxseed oil consists of about 54% ALA (which can at least be converted to EPA), the remaining 46% is made up of the pro-inflammatory omega-6 called LA (linoleic acid), which Americans already over-consume. LA also competes with omega-3s like EPA/DHA when it comes to incorporation into cell membranes, where omega-3s exert most of their benefits.
While it does seem that flaxseed oil has some positive effects, the omega-3s in fish oil enjoy much stronger, more abundant evidence of health benefits and are already in the format your body needs to start putting them to good use right away. This should put the fish oil vs. flaxseed oil debate to rest!