Achieving optimal n3 fatty acid status: the vegarian's challenge…or not

January 1, 2014 Human Health and Nutrition Data 0 Comments

Achieving optimal n3 fatty acid status: the vegarian's challenge…or not

Year: 2014
Authors: Harris, W.S.
Publication Name: Am J Clin Nutr
Publication Details: Volume 100 (suppl); Pages 449S to 452S


The long chain n 3 (omega 3) fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), although originally synthesized by microorganisms in the oceans, are primarily obtained from the consumption of fish. Vegetarians, by definition, do not eat fish and thus consume virtually no EPA and DHA. Because conversion of the plant derived n 3 fatty acid alpha linolenic acid (ALA) to EPA and DHA is very low, n 3 tissue concentrations in vegetarians are lower than in omnivores. This review asks 2 questions: what is the evidence that increased n 3 concentrations reduce the risk of cardiovascular disease in vegetarians, and, if it does, how can vegetarians increase their blood and tissue concentrations of these animal derived fatty acids? At present, both cardiovascular risk markers and cardiovascular events appear to be significantly reduced in vegetarians compared with those in omnivores. If so, and in the absence of data to show that risk in vegetarians could be even lower with higher n 3 concentrations, then the second question becomes moot. However, the absence of evidence is not evidence of absence; therefore, at our present state of knowledge, increasing n 3 concentrations is not an unreasonable goal for vegetarians. This can be accomplished by a variety of approaches, including increased intakes of ALA, consumption of stearidonic acid enriched soybean oil (if and when it comes to the market), and the use of supplements containing EPA, DHA, or both derived from non animal sources (microalgae, biotech yeast, and, in the future, biotech plant oils). (Authors abstract)
In 2004, the Omega 3 Index was proposed as a new marker of risk of death from heart disease.  The EPA plus DHA content (expressed as a percentage of total fatty acids) of red blood cell (RBC) membranes has been validated as a biomarker of tissue n 3 fatty acid status and reflects longer term n 3 fatty acid status much as glycated hemoglobin does for glucose. n 3 fatty acid intakes and blood concentrations are lower in vegetarians than in meat eaters. In a recent study, the mean Omega 3 Index was 3.7 per cent in 167 individuals who had been vegans for an average of 12 y. A larger series including omnivores, vegetarians, and vegans was studied. Plasma proportions (percentage of total fatty acids) of EPA and DHA were reduced in a stepwise manner by eating pattern, but ALA proportions did not change. If increases in the Omega 3 Index in a vegetarian diet did in fact afford additional health benefits, then how might this be accomplished without eating fish or fish oils? The most obvious approach would be to consume more ALA (and less linoleic acid). It is the amount of ALA that is consumed, not the ratio of ALA to linoleic acid that determines the amount of EPA that is produced.
Vegetarian and vegan dietary patterns are associated with reduced risk of cardiovascular disease, and at present, few data are available to confirm that this risk may be reduced even more by the provision of marine n 3 fatty acids. This would be an important question for future researchers to examine. Achieving a cardioprotective
Omega 3 Index (ie, 8 per cent of RBC fatty acids as EPA plus DHA) is challenging for individuals who will not eat oily fish, the primary dietary source of these fatty acids. Some nonanimal sources of n 3 fatty acids are appearing in the marketplace, but they are expensive (10 times the cost of equipotent fish oils) and not widely available. Increasing demand for such products will undoubtedly increase supply and reduce costs as more individuals begin to appreciate the health benefits of both n 3 fatty acids and a vegetarian diet.  (Editors comments)

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