Comparing Omega 3’s from Fish and Flax Seed Oil

Omega-3 fatty acids falls into two major categories:

- Plant derived (flax seed, yielding alpha linolenic acid or ALA) or;
- Marine derived (Fish oil, yielding both EPA and DHA);

Often people are confused which type of omega 3 would best suit their need. Following are important factory to help decipher which may be best for you:

Comparing General conversion of ALA

Since the human conversion of ALA to EPA and DHA is somewhat slow, only about 15% of ALA converts to EPA and 5% DHA (Cunnane 1995, Nutrition Advisory Panel, 1995). Therefore, it poses the question: To what degree does a person need DHA and EPA?

Individual Health and Lifestyle

Several factors inhibit conversion of ALA to it’s long-chain Metabolites (EPA and DHA)


The majority or research conducted with Omega 3 fatty acids has been done with fish oil, and has focused on the beneficial effects of EPA or DHA. On a gram-for-gram basis, fish oils are the optimal means of enhancing EPA and DHA in the body.

Fish oils are a concentrated, direct, source of EPA and DHA that can be used to target specific health concerns related to n-3 fatty acid deficiencies.
Chapter IV
Seal Oil
Flaxseed Oil - Alpha-Linolenic Acid (ALA) to convert to EPA, DPA and DHA

ALA is not equivalent in its biological effcts to teh long-chain n-3 fatyy acids found in marine oils. EPA and DHA are more rapidly incorporated into plasma and membrane lipids abd produce more rapid effcts than does ALA. Relatively large reserves of LA in body fats, as are in vegans or in the diet of omnivores in Western societies, would tend to slow down the formation of long-chain n-3 fatty acids from ALA. Therefore, the role of ALA in human nutrition becomes important in terms of long-term dietary intake. One advantage of the consumption of ALA over n-3 fatty acids from fish is that the problem of insufficient vitamin E intake does not exist with high intake of ALA from plant sources.

There is competition among the enzymes involved in the elongation and desaturation of LA and ALA. A ratio of LA to ALA of 4:1 or less has been shown to be optimal for the elonagtaion of 11g of ALA to 1g of EPA. This is important for vegetarians because their diets are typically rich in LA and poor in ALA. Because EPA is biologically more active than ALA and high in amounts of LA decrease the conversion of ALA to EPA, the optimal intake of LA relative to ALA is crucial for normal metabolism.

American Journal Clinical Nutrition 1999
Artemis P. Simopoulos


Conversion of ALA to EPA and DHA

The parent fatty acid ALA (18:3n-3), found in vegetable oils, such as flaxseed or rapeseed oil, is used by the human organism partly as a source of energy, partly as a precursor of the metabolites, but the degree of conversion appears to be unreliable and restricted. More specifically, most studies in humans have shown that, whereas a certain, though limited, conversion of high doses of ALA to EPA occurs, conversion to DHA is severely restricted. The use of ALA labeled with radioisotopes suggested that, with a background diet high in saturated fat, conversion to long-chain metabolites is 6% for EPA and 3.8% for DHA. With a diet rich in Omega 6 PUFA, conversion is reduced by 40% to 50%. It is thus reasonable to observe an Omega 6/Omega3 PUFA ratio not exceeding 4-6:1.

Restricted conversion to DHA may be critical; since evidence has been increasing that this long-chain metabolite has an autonomous function, e.g., in spermatozoa, the brain and retina, where it is the most prominent fatty acid. In nenates, deficieny is associated with visual impairment, abnormalities in the elctroretinogram and delayed cognitive development. In adults, the potential role of DHA in neurological function still needs to be investigated in depth.
Conversion of ALA and DHA., I.H. Gerster, Internat J Vit Nutr Res 68 (1998) 159-173

To convert LNA to EPA to series prostaglandins, the diet should provide optimum amounts amounts of the conversion co-factors: vitamin B3, B6, C and the minerals: Magnesium and Zinc.
Fats that Heal, Fats that Kill, Udo Erasmus, p.282

Some ALA can be inverted into our bodies to teh longer chain Omega 3's EPA and DHA. ALthough the scientific literature is mixed on this issue, humans may be unable to convert enough ALA to EPA and DHA to achieve optimal levels of these long-chain Omega 3's.
The Omega Connection, Dr. Andrew Stoll, p.215
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