BLOG: Fish vs. flax

The number one-selling individual nutritional supplement is now omega-3. While it is beyond the scope of a blog to review the entire metabolic process of how omega-3s work in the body (join the Ocular Nutrition Society and listen to my lecture on it), let me just say it is effective and necessary for systemic and eye health.

Given the significance of this essential nutrient, we should take a brief look to see if it holds up to the “hype” and sort out the truth from the sales pitch. Yes, we hear how this or that product has omega-3 for eye health or some other health benefit. One of the more popular forms of vegetarian omega-3 is flaxseed (both in the grain form or the oil). But most health experts do not consider flaxseed oil a beneficial source of omega-3 fatty acids when compared to fish oil. I’ll explain why.

The health benefits associated with omega-3 consumption result from eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the biologically active forms. Fish oil is the direct source of EPA and DHA; flaxseed oil is not. The omega-3 content of flax oil is in a precursor form called alpha-linoleic acid (ALA). ALA is a shorter chain form of essential fatty acid and, for the positive health effects to be manifest, ALA must be converted in the body to EPA and DHA (both longer chain fatty acids). However, this conversion process is very inefficient in humans. Additionally, there are gender variations: women only convert about 5% of ALA to EPA, whereas men only convert about 1%, according to some studies.

The low conversion of ALA to the biologically active omega-3 fatty acids EPA and DHA is due to an enzyme deficiency. Over hundreds of thousands of years the human body has developed genes optimized for metabolizing direct sources of EPA and DHA (fish) not ALA (flax). ALA conversion is further diminished by factors such as a diet high in short chain omega-6 fatty acids, saturated fat, sugar, excessive cholesterol and alcohol, as well as deficiencies in vitamins and minerals. The combination of these factors with enzymatic deficiencies makes flax oil a poor source of EPA and DHA.

Unlike EPA and DHA, ALA is a source of calories and can be converted to fat stores. Research suggests excessive ALA consumption could increase the risk of developing prostate cancer, obviously in men. Clinical studies have clearly demonstrated that flaxseed oil supplementation does not provide the same health benefits as fish oil. This is not to say that shorter chain essential fatty acids are completely worthless because another “intermediate” acid, called stearidonic acid, does have some anti-inflammatory properties. This is why some people (mostly women) will achieve some positive effects for dry eye disease when ingesting flax seed oil.

One of my latest “favorite” commercials is for the new “Kellogg's Raisin Bran Omega-3 from Flaxseed cereal.” The ingredients list includes whole grain wheat, rice, sugar, raisins, wheat bran, brown sugar syrup, whole flaxseeds, glycerin and 2% or less of salt, malt flavor, soluble corn fiber and BHT for freshness. Notice that four of the first five ingredients are sugar (the package lists 17 grams of it), with a total of 44 grams of carbohydrates (mostly processed or “simple” carbs). Their big push (on the front of the box) says: “Omega-3 250 mg ALA from flaxseed.” Note that the ingredients list “whole” flaxseeds, which means that they will not break down in the body. The net omega-3 here is essentially zero. This is just one example of marketing hype.

Lastly, flaxseed oil is also the most “tenuous” of the seed oils and, therefore, will oxidize and go rancid very quickly. So, if you see it on the shelf (not in the refrigerated section) in the store, you might pass on it. And if you want to ingest whole flax seeds, it’s best to grind them and eat them right away. Otherwise, what goes in will just come out the same way.