ruminant fat is unique (was animal fats and EFA's)

[Guest guest]

Hey, ,

Me:

>Right, but those fat deposits are there to serve *them* - not just to

>accumulate for future human consumption.

P:

Well, of course, but in the strictest sense, everything's out for itself --

and whatever it is we're eating probably doesn't want to be eaten.

***Well there was a point to my statement of the obvious :0 And it's that

wild game probably actually USE their fat stores at least occasionally, thus

depleting them, whereas feedlot steer do not. With feedlot steer you're

pretty much guaranteed " x " amount of fat. But with wild game there's no

guarantee that each and every one that is killed and eaten will have all the

stores of fat that's part and parcel of feedlot steer. Which is why I still

question somewhat claims of how fatty some primitive diets are/were. Also,

as I mentioned earlier, leanness (as compared to feedlot steer) would confer

some adaptive advantage to wild ruminants who must literally run for their

lives, sometimes often, when confronted by predators. Although larger game,

such as musk oxen often 'circle their wagons' with their butts backed up to

each other and stave off attacks with their horns. Some may also range over

very large areas and so get a heck of a lot more exercise than their feedlot

brethren.

>>>To be sure, but historically, lean times for food animals were lean times

for people.

***Which would further point to the fact that a high fat diet, if that's

what was indeed consumed, was not a constant.

Me:

I've ready various sources of data on various

>critters and whenever their *diet* lipid profile changes, so too does their

>*body's* lipid profile. Or so it I thought. Why do humans even bother to

>take fish oil capsules, for example, if it has no effect on our FA profile?

P:

Part of your confusion may come from the distinction between ruminants and

most other animals. The bacteria in ruminants' digestive tracts are pretty

good at saturating the fat that comes their way, so that overall levels of

saturated and monounsaturated fat are relatively constant in ruminants

regardless of diet. In ruminants, it's chiefly the PUFA fraction which

varies according to diet. In non-ruminants, the story is completely

different, and the entire lipid profile varies with diet.

***Bingo! That is indeed the source of my confusion. I've been focusing on

*ruminants* in particular, since I'm interested in getting an idea of the

lipid profile of the dog's historical diet (as well as humans'), and

ruminants are the primary prey of grey wolves, and thus pre-domestication

dogs. I found some interesting info that confirms this last night. I realize

that you may already know this, but I thought I'd provide this explanation

and cite for others like me who might not have been aware of this

previously. The following quote is from " The Fats of Life " by Caroline Pond

(who studied Zoology at Oxford University, Ph.D. in insect flight, lectured

on physiology, has taught biology and veterinary anatomy at U. Penn, and has

been studying and teaching about adipose tissue for many years):

" Most animals do not synthesise enzymes that can digest cellulose, the major

structural carbohydrate of higher plants. Many micro-organisms and fungi can

produce such enzymes (thus many fungi can 'rot' wood) and most herbivorous

mammals harbour such organisms in some part of their gut to assist in the

digestion of tough plant material. Collaboration between micro-organisms and

mammals in the digestion of plants is most sophisticated in ruminants, which

have four stomach-like chambers in the gut. Rumination enables mammals to

digest foliage from which other herbivores can derive little nourishment and

is the main reason for the success of deer, antelope, buffalo, cattle,

sheep, goats and their relatives. As well as breaking down complex

carbohydrates, the micro-organisms also make major changes to the plant

lipids, with important consequences for the lipid metabolism of their hosts.

The first and by far the largest stomach is the rumen, which contains

millions of micro-organisms. They break down cellulose into glucose and

immediately convert much of it into short-chain soluble fatty acids such as

4-carbon butyric acid, and it is in this form that the products of cellulose

digestion reach the intestine and are absorbed. Such fatty acids pass

through the cells lining the intestine and thence into the blood, in which

they are carried quite easily because they are much more soluble in water

than the long-chain fatty acids.

Short-chain fatty acids are not incorporated into storage triacylglycerols

[triglycerides] but are quickly oxidised to release energy, in much the same

way as glucose is in simple-stomached (i.e. non-ruminant) animals. They may

also reach the mammary gland, where they are esterfied and secreted in the

milk, including that of cows, and thence to butter, from which butyric acid

was first isolated (the name 'butyric' means 'butter'). Fresh butter, in

which all the fatty acids are esterfied, is odourless but after boiling or

prolonged storage in air, it develops a strong, pungent smell, caused by the

release of short-chain fatty acids, among them butyric acid.

Phospholipids in the membranes of cells in grass and leaves contain mostly

unsaturated fatty acids, as do the triacylglycerols of many seeds. A

herbivorous diet thus includes plenty of polyunsaturates, but

micro-organisms in the rumen desaturate and otherwise modify many of them.

So most of the long-chain fatty acids actually absorbed by the gut are

saturated. Ruminant adipose tissue thus contains a much higher proportion of

triacylgycerols with saturated fatty acids. Most of the lipids in the blood,

from which foetal calves, lambs or fawns obtain the supplies they need for

growth, are also of this composition.

In simple-stomached animals such as pigs, rats, horses and ourselves,

digestion does not normally destroy the internal structure of the fatty

acids themselves: they are absorbed intact, in all the variety described in

the previous chapter. Consequently, the composition of the fatty acids in

adipose tissue and milk corresponds approximately to that of the diet. But

in ruminants, neither the abundance nor the composition of fatty acids in

membranes, adipose tissue or milk lipids corresponds to those of the diet,

and cannot readily be altered by changing the lipid content of the food. "

Pond, C.M. The Fats of Life. 2000. Cambridge University Press.

>>>>Bruce Fife, for example, attributes rising skin cancer rates to

increased PUFA consumption -- as the dermal and subdermal layers of fat

become more and more unsaturated, they're more and more vulnerable to UV

light from the sun.

***I told my mother that the other day - that PUFAs would make her skin more

susceptible to oxidation from the sun's heat/light. It just seems to make

sense. It reminds me of the regional variances in the lipid profile of

plants - the closer to the equator you get, the more saturated plant lipids

become. The further away you get (from the intense light and heat of

equatorial regions) the more UNsaturated plant lipids become. So it makes

sense that the heat/light of the sun would have the same (or similar) effect

on animal tissue depending on it's PUFA content.

>>>>There's no question we're hobbled by seriously lacking data. Perhaps if

the WAPF lab gets off the ground it can start compiling a truly

comprehensive and accurate database. (Perhaps some of these questions are

addressed in Enig's book, too; I haven't read it yet.)

***I have the book. She's got many lipid composition charts of various

foods, BUT, they're all from the USDA (

P.S. there's a very interesting discussion in the Pond book about the

differences in lipid profiles of human and cow's milk and how the lipid

profile of cow's milk may 'harm' human babies. I don't have time to post

that info now, but will in a later email. Perhaps *you* already know this,

but I thought I'd post it for anyone interested. There's also a fascinating

description of lipid distribution from inward out (SF to PUFA in response to

temp), in ruminant fat which I'll also post, when I get time

Suze Fisher

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