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A systematic review of the literature: Dietary omega‐3 fatty acids and tissue changes
Author(s) -
Whelan Jay,
Jones Laura
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1028-b
Subject(s) - polyunsaturated fatty acid , docosahexaenoic acid , fish oil , food science , arachidonic acid , eicosapentaenoic acid , canola , chemistry , triglyceride , fatty acid , biochemistry , fish <actinopterygii> , cholesterol , biology , enzyme , fishery
The recent FDA guideline approving qualified health claims for the long chain n‐3 PUFAs EPA and DHA (found in fish oils) did not include α‐linolenic acid (ALA), a rich component of flaxseed, canola and soybean oils. Although ALA is the biochemical precursor for EPA and DHA, there is some confusion as to whether the metabolic effects of dietary ALA act via its conversion to EPA/DHA. To address this question, we conducted a systematic review of >100 clinical trials to ascertain whether ALA, when supplemented to a typical Western diet, modifies the EPA and DHA content of tissue phospholipids (PL) (plasma and erythrocytes), and how these effects compare with the consumption of EPA/DHA (typically in the form of fish oil). This systematic review of the literature revealed that increasing the amounts of ALA (by as much as 35g/d) or EPA (3.2g/d) does not modify tissue DHA levels; only the consumption of DHA changes tissue DHA non‐linearly, with the largest changes occurring at doses <1g/d. Adding ALA to the diet increases the typically low tissue levels of EPA only ~2 fold, while EPA supplementation maximally changes plasma PL EPA levels 6 fold, with a maximum effect achieved ~1.6g/d. Both EPA and DHA equivalently depresses arachidonic acid levels by <25% even at the highest intakes. In summary, ALA can not be used as a surrogate for EPA/DHA. When supplemented at levels above typical consumption, ALA is poorly converted to EPA and DHA. In order to maximize tissue levels of EPA and DHA, both have to be supplemented because EPA is poorly converted to DHA and DHA is poorly retroconverted to EPA. (Supported by the TAES and NC1167)