Posted by Larry Hoover on August 26, 2007, at 11:44:21
In reply to Re: LHA vs EPA and DHA, posted by Jamal Spelling on August 26, 2007, at 4:22:46
> Thanks Meri and Larry.
>
> Just the other day I was having a disagreement with my sister, whose dietician told her that ALNA was the 'best' of the three, and that she needn't worry about EPA and DHA.Best for what? We cannot exclude physiological benefits of ALNA simply because it is a poor raw material for EPA or DHA. That said, it is not a substitute for pre-formed EPA and DHA.
> Well, now I am armed with an actual reseach paper to show her...
>
> JamalHere's a better one for that...
The most rigorous examination of the conversion of ALNA to DHA that I have ever reviewed is the following one. It was a long-term study of radio-labelled (carbon 13) ALNA, supplied as a minor component of diet over a period of time to 15 each of healthy men and women, and its fate. I'm going to quote from the full-text version (Results) of this study: "The average daily ALA intake equaled 1,129 mg or 4,056 µmol. Approximately 78.5 mg or 6.96% of dietary ALA was incorporated as ALA into plasma phospholipids. Of this ALA pool, 99.98% was converted to EPA, which corresponded to 6.95% (78.4 mg) of ALA intake. The remaining 0.18% of the ALA plasma phospholipid pool, which was equivalent to 0.013% (0.14 mg) of ALA in the diet, was converted directly to DHA in the liver, before it appeared in the plasma phospholipids as DHA. Only 1% of the EPA in plasma phospholipids, which was equivalent to 0.07% (0.80 mg) of ALA consumption, was converted to DPA. All DPA from the plasma phospholipid pool was converted to DHA. Thus, the total amount of ALA from the diet that was ultimately converted to DHA was 0.08% (0.94 mg)."
Summary: Averaged over 30 humans, ALNA conversion to EPA was less than 7%, and to DHA less than 0.1%. If you read the full-text, you'll find convincing arguments that earlier work had over-estimated ALNA conversion by factors of 2 to 4.
Full-text: http://www.jlr.org/cgi/content/full/46/7/1474
Abstract:
J Lipid Res. 2005 Jul;46(7):1474-83. Epub 2005 Apr 16.
Compartmental modeling to quantify alpha-linolenic acid conversion after longer term intake of multiple tracer boluses.
Goyens PL, Spilker ME, Zock PL, Katan MB, Mensink RP.
Department of Human Biology, Maastricht University, Maastricht, The Netherlands.To estimate in vivo alpha-linolenic acid (ALA; C18:3n-3) conversion, 29 healthy subjects consumed for 28 days a diet providing 7% of energy from linoleic acid (C18:2n-6) and 0.4% from ALA. On day 19, subjects received a single bolus of 30 mg of uniformly labeled [(13)C]ALA and for the next 8 days 10 mg twice daily. Fasting plasma phospholipid concentrations of (12)C- and (13)C-labeled ALA, eicosapentaenoic acid (EPA; C20:5n-3), docosapentaenoic acid (DPA; C22:5n-3), and docosahexaenoic acid (DHA; C22:6n-3) were determined on days 19, 21, 23, 26, 27, and 28. To estimate hepatic conversion of n-3 fatty acids, a tracer model was developed based on the averaged (13)C data of the participants. A similar tracee model was solved using the averaged (12)C values, the kinetic parameters derived from the tracer model, and mean ALA consumption. ALA incorporation into plasma phospholipids was estimated by solving both models simultaneously. It was found that nearly 7% of dietary ALA was incorporated into plasma phospholipids. From this pool, 99.8% was converted into EPA and 1% was converted into DPA and subsequently into DHA. The limited incorporation of dietary ALA into the hepatic phospholipid pool contributes to the low hepatic conversion of ALA into EPA. A low conversion of ALA-derived EPA into DPA might be an additional obstacle for DHA synthesis.
Best,
Lar
poster:Larry Hoover
thread:778268
URL: http://www.dr-bob.org/babble/alter/20070816/msgs/778819.html