Brenna JT, Salem N Jr, Sinclair AJ, Cunnane SC; International Society for the Study of Fatty Acids and Lipids, ISSFAL. (2009) Prostaglandins Leukot Essent Fatty Acids. Feb-Mar;80(2-3) 85-91.
File Download: Download the ISSFAL Statement on Omega-3 (documenting the inefficiency of ALA to DHA conversion) (192.53 KB)
Blood levels of polyunsaturated fatty acids (PUFA) are considered biomarkers of status. Alpha-linolenic acid, ALA, the plant omega-3, is the dietary precursor for the long-chain omega-3 PUFA eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA).
Studies in normal healthy adults consuming western diets, which are rich in linoleic acid (LA), show that supplemental ALA raises EPA and DPA status in the blood and in breast milk. However, ALA or EPA dietary supplements have little effect on blood or breast milk DHA levels, whereas consumption of preformed DHA is effective in raising blood DHA levels.
Addition of ALA to the diets of formula-fed infants does raise DHA, but no level of ALA tested raises DHA to levels achievable with preformed DHA at intakes similar to typical human milk DHA supply.
The DHA status of infants and adults consuming preformed DHA in their diets is, on average, greater than that of people who do not consume DHA. With no other changes in diet, improvement of blood DHA status can be achieved with dietary supplements of preformed DHA, but not with supplementation of ALA, EPA, or other precursors.
Evidence reviewed here shows that humans cannot effectively convert ALA (an omega-3 from plant sources) into DHA (a longer-chain omega-3 found in fish and seafood).
This is an extremely important finding, because the health benefits associated with consuming 'omega-3' fatty acids relate only to EPA and DHA - not to ALA.
This paper represents the official position of ISSFAL (the International Society for the Study of Fatty Acids and Lipids) - an independent organisation that includes most of the world's leading scientists in this area.