So does it matter if I get my omega 3 fatty acids from flax seed or from fish oil?  What is the difference anyway?  Well although the oils in flax seeds and fish oil are both omega 3 fatty acids, they are different kinds of omega 3.  The oil in flax seed is alpha-linolenic acid (ALA).  This oil needs to be converted in the body to Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Humans easily convert EPA into DHA in the body. Fish oil on the other hand contains both EPA and DHA and don’t need to be converted.

 EPA is the oil responsible for shifting your body from a pro-inflammatory state to an anti-inflammatory state.  DHA on the other hand is a primary component of cell membranes in the brain, retina and testis, with almost 60% of your brain made up of this oil. So both EPA and DHA are considered essential since our bodies can’t make them without consuming either ALA or EPA/DHA.  Since Fish oil contains the EPA and DHA in its active form it does not need to be converted in the body before it can have an anti-inflammatory effect in the body, unlike flaxseed oil which has to be converted first.

 The conversion from ALA to EPA however is not an efficient one.    The amount converted from ALA to EPA +DHA was estimated to be at best only about 12%.  In addition there is a significant amount of variability among different individuals with some being more efficient at converting ALA than others.  Some patients studied showing no conversion at all. For more information on these studies you can read the work of the DHA-EPA Omega 3 Institute at


To further complicate things, if your diet is high in omega 6 fatty acids (corn oil, sunflower oil etc) your body’s enzymes which breakdown ALA to EPA will cause the omega 6 oils to compete with ALA for this limited resource, further reducing the effectiveness of the ALA consumed.

Benefits of Flax seed Oil

Flax seed oil has the advantage of being free from mercury and other heavy metal contaminants often found in the fatty fish used for their EPA/DHA content.  Ideally organic flax seeds would be best to ensure they are not contaminated with pesticides.

Flax seeds also add additional nutritional value beyond their omega 3 content. They are a good source of dietary fiber and protein.  They contain both soluble and insoluble fiber.   The oil is also rich in vitamin E, β-carotenes and mineral (Herchi et al, 2012).  They also can be used in baking to replace eggs due to their mucilaginous nature.

Watch out for rancid oils!

Both flaxseed oil and fish oils are considered unstable and can oxidize easily causing them to go rancid.  Rancid oils have been linked to a number of health problems and can destroy the blood vessel lining mentioned by Dr. Esselstyn on yesterday’s Kojo Namdi Show.

Tips for preventing your oils from going rancid

1.       REFRIGERATE:  Always store your fish oil and flaxseed oil supplements in the refrigerator.

2.       GLASS BOTTLES: Choose supplements in glass bottles with tight lids to prevent oxygen from getting to them.

3.       LIGHT PROOF BOTTLES: Choose only supplements packaged in dark bottles which keep the light out.

4.       GRIND YOUR FLAXSEED: If you choose to use whole flaxseeds, be sure to grind them just before consuming them.   Whole flaxseeds are not easily absorbed and can cause serious damage to your intestines.  Waiting to grind them just before you consume them protects the oils from going rancid. The whole seeds should also be refrigerated to prevent them from going rancid.

5.       DISCARD “FISHY” SMELLING SUPPLEMENTS:  If your fish oil supplement tastes “fishy” throw it away.  It is already rancid. Periodically you should break a capsule to see if it smells or tastes fishy.

6.       ANTIOXIDANTS: Take an anti-oxidant supplement with your omega 3 supplements to help minimize the damage if your oil is slightly rancid.  One component of rancid oil is a chemical called anisidine.  This chemical is tasteless and odorless.  Anti-oxidants may help to minimize the damage to your body if it has started to turn rancid and you haven’t yet noticed a change in the smell.

7.       FRESH SUPPLY: Try to use the supplement you bought within about a month.  Although it may seem like a cost saving idea to buy a 3 month or more supply, you may end up throwing it away before you get a chance to use it.


If you are concerned about how your Fish Oil supplement rates in purity you can check IFOS at

.  This website posts consumer reports from some of the major supplement manufacturers.  Not all manufactures have their products analyzed by IFOS and just because a manufacturers results are posted doesn’t mean the product was properly stored by the local vitamin shop.  But at least it is a starting point.

Attard, M. (2010) What is the difference between fish oil and flaxseed oil?

Herchi,W., Arraez-Roman,D., Boukhchina,S., Kallel,H., Segura-Carretero,A., and Fernandez-Gutierrez,A.,(2012)  A review of the methods used in the determination of flaxseed components. Afri Journ of Biotech.  11(4): 724-731 retrieved from 

on January 19, 2012

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