On Wed, 23 Sep 1998, Ilya wrote:

> Todd Moody wrote:
> > Purslane is loaded with alpha-linoleic acid, and many other dark
> > leafy greens have substantial amounts of it.  From ALA we are
> > capable of making EPA and DHA.  Walnuts also have a significant
> > amount of ALA, although they are not available everywhere.

> I think you are confusing two different fatty acids: linoleic and
> alpha-linolenic (notice the N in the name), both essencial for health.

No, I know the difference.  Alpha-linoleic acid is another name
for linolenic acid, which is not the same as linoleic acid.  ALA
is an w-3 fat; LA is an w-6 fat.  Purslane is a good source of
ALA.  Walnuts are a fair source.  It is from plants such as
purslane and other greens that w-3 fats enter our food supply.

> From alpha-linolenic you can indeed make EPA and DHA, though some
> people have difficulty doing this and need direct supplementation
> (or food) with EPA and DHA.

Yes, this is due to problems with the delta-6 desaturase enzyme,
and I understand that this affects diabetics and the elderly.

> Walnut oil is only 5% ALA (dried walnuts
> are 56% fat by weight, not sure what this means for fresh walnuts).

According to the Eades, it's 7%; in other sources I've read 10%,
so who knows.

> Thus to get just 5gms of ALA from them you would have to eat about
> half a pound of walnuts. Then only part of this will get converted
> to EPA and DHA. Salmon fat is about 30% total EPA+DHA, animal brains
> also have much higher concentrations (than walnuts) of these. Even
> a small portion would provide large amounts of EPA and DHA.

I agree.  My point was only that it is possible to avoid a w-3
deficiency on a vegetarian diet, not that this is the best way to
get those fats.  According to Eaton, the fat of wild game animals
(not just the brains) has about 4% EPA+DHA, while the fat of
domestic cattle has none.

Clinically, it's not yet clear what the best form of w-3 fat is.
Theoretically, it ought to be EPA, but there is at least one
study that suggests that ALA has benefits that go beyond what one
would expect from its conversion to EPA, suggesting that there is
another pathway to be discovered.  It's probably best to get some
of both.

Todd Moody
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