On Thu, 14 Dec 2000, Amadeus Schmidt wrote:

> There must be some adjustment regulatives in the body that govern
> how much fatty acids are processed to longer and higher unsaturates.
> Probably the prostaglandin production too.

Well, I found at least some of the GJ Nelson material on dietary
AA.
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Lipids 32 (4): 415-420 (Apr 1997)

A human dietary arachidonic acid supplementation study conducted
in a metabolic research unit: rationale and design

Nelson GJ, Kelley DS, Emken EA, Phinney SD, Kyle D, Ferretti A

Western Human Nutrition Research Center, ARS, USDA, San Francisco,
California 94129, USA.

While there are many reports of studies that fed arachidonic acid
(AA) to animals, there are very few reports of AA feeding to
humans under controlled conditions. This 130-d study was
conceived as a controlled, symmetrical crossover design with
healthy, adult male volunteers.  The results of these studies
will be presented in the next five papers from this symposium.

------------------------------------------------
Lipids 32 (4): 421-425 (Apr 1997)

The effect of dietary arachidonic acid on platelet function,
platelet fatty acid composition, and blood coagulation in humans

Nelson GJ, Schmidt PC, Bartolini G, Kelley DS, Kyle D

Western Human Nutrition Research Center, ARS, USDA, San Francisco,
California 94129, USA.

The results from this study on blood clotting parameters and in
vitro platelet aggregation suggest that adding 1.5 g/d of dietary
AA for 50 d to a typical Western diet containing about 200 mg of
AA produces no observable physiological changes in blood
coagulation and thrombotic tendencies in healthy, adult males
compared to the unsupplemented diet. Thus, moderate intakes of
foods high in AA have few effects on blood coagulation, platelet
function, or platelet fatty acid composition.

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Lipids 32 (4): 427-433 (Apr 1997)

The effect of dietary arachidonic acid on plasma lipoprotein
distributions, apoproteins, blood lipid levels, and tissue
fatty acid composition in humans

Nelson GJ, Schmidt PC, Bartolini G, Kelley DS, Phinney SD, Kyle D,
Silbermann S, Schaefer EJ

Western Human Nutrition Research Center, ARS, USDA, SAn Francisco,
California 94129, USA.


A 50 day controlled trial with a high AA diet.  After consuming
the high-AA diet, the total red blood cell fatty acid composition
was significantly enriched in AA which mainly replaced linoleic
acid.  These results indicate that dietary AA is incorporated
into tissue lipids, but selectively into different tissues and
lipid classes.  Perhaps more importantly, the results demonstrate
that dietary AA does not alter blood lipids or lipoprotein levels
or have obvious adverse health effects at this level and duration
of feeding.  Dietary AA had no statistically significant effect
on the blood cholesterol levels, lipoprotein distribution, or
apoprotein levels.  Adipose tissue fatty acid composition was not
influenced by AA feeding.

--------------------------------------------------------------------
Lipids 32 (4): 449-456 (Apr 1997)

Effects of dietary arachidonic acid on human immune response

Kelley DS, Taylor PC, Nelson GJ, Schmidt PC, Mackey BE, Kyle D

USDA, ARS, Western Human Nutrition Research Center, Presidio of
San F Francisco, California 94129, USA.

However, the lack of any adverse effects (by AA) on Immune
Response indicates that supplementation with AA may be done
safely when needed for other health reasons.

-----------------------------------------

> I read that "DHA level is kept within tight limits".
> I consider this as the explanation why varying dietary inputs (of many
> items) are handled properly.
>
> But why then do we keep so much attention on the w-3/w-6 ratio and
> dietary influences from EPA and others?

There is some research that suggests that it is the absolute
amounts of EPA/DHA that matters, rather than the ratio.

> From a paleo nutrition viewpoint it would make sense that high AA input
> would be tolerated (if constant). But fatty acid compositions never found in
> nature cause trouble (like in domestic animal fat).
> Also in the prostaglandin terrain.

I don't think it has been shown that domestic animal fat causes
any health problem.  Instead, I think we have a tendency to
assume that this is happening, but that assumption is entirely
theory-driven.  But that is another matter.  The main thing is
that Sears' cautions about dietary AA are misplaced.

Todd Moody
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