Todd Moody wrote:
> 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.
Clearly you know the difference. Though this is the first time I have
seen linolenic acid referred to as alpha-linoleic. Are you sure this
is right? You might be thinking of gamma-linolenic, which, despite the
name is derived from linoleic acid. Everywhere before I have seen
references they were to linolenic and alpha-linolenic being the same
(gamma-linolenic being different).

> > 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.
This is just one of the steps. Linolenic is converted first to
stearidonic acid (18:4w3) then to eicosatetraenoic acid (20:4w3)
then to eicosapentaenoic acid (EPA 20:5w3) then to clupanodonic acid
(22:5w3) then to docosahexaenoic acid (DHA 22:6w3). Any one of these
steps could in theory be compromised.

> > 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.
I got my numbers from Udo Erasmus' book. Eades is a personal friend
of Sears and got much of his prostaglandin/essencial fat material
directly from him. Since 'Protein Power' came out he has reconsidered
his stance on flax oil and now recommends it to his patients.
Considering some statments that Sears has made I trust Udo a lot
more on essencial fats.

> 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.
Absolutely, I take quite a bit of flax oil (used to be huge amounts,
now very reasonable) as well as other oils.

> 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.
I specifically named brains because that's where much of those fats
are needed and used. Considering how easily they oxidize I would
not expect much of them used for plain old fat storage. Nowadays
there is this big scare about mad cow disease we don't eat brain
much, but this wouldn't be a problem for h/gs. (I remember fried
breaded brain being one of my favorite foods as a kid. Of course
frying it isn't very healthy, but what did I know).

> 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.
I never understood why it had to be an either or situation - it's
either ALA itself or EPA or something down stream. It seems the body
has uses for all of them, aside from needing one as a substrate for
another.

Ilya