cow's milk vs. human milk (was ruminant fat is unique)

[Guest guest]

>>>>>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.

>>>>I'd be quite interested, and I'm sure others on this list would be

too. I'm aware of the fact that babies tend to do better on goat's milk,

but I assumed that was due to differences in goat milk's protein content,

not the fat content. I'm slightly skeptical, too, since many healthy

cultures consumed tons of cow dairy, but OTOH I don't know how early

children were started on cow dairy, and they certainly nursed a lot longer

than most kids nowadays.

Hi ,

Just looking at my wording, and I think " harm " might be to strong of a word.

But, judge for yourself.

" Many non-ruminant animals, including rabbits, guinea-pigs and ourselves,

harbour micro-organisms in the large intestine which digest complex

carbohydrates to short-chain fatty acids in the same way as those of the

rumen do. Guinea-pigs can synthesise long-chain fatty acids and hence

triacylglycerols from such precursors. But in humans most short-chain fatty

acids are quickly oxidized as fuel in the liver, or, particularly in the

case of butyric acid, by the cells of the large intestine itself, and they

make no contribution to storage lipids. The production of small quantities

of short chain fatty acids in the bowel means that non-ruminants such as

ourselves have the biochemical equipment to deal with them. These capacities

were simply expanded when humans took to eating ruminant milk and milk

products which, as pointed out in Chapter 3, is a recently acquired and

highly unusual habit. Being small molecules, short-chain fatty acids

evaporate readily, and contribute to the smell of the gases that emerge from

the gut.

The milk of all monkeys and apes, including women, contains a lower

proportion of lipids in total (and substantially more lactose), than that of

almost all other mammals. Although lipids are more abundant in the milk of

cows, ewes and other ruminants, a smaller fraction are polyunsaturated fatty

acids and far more are short-chain or medium-chain, than is the case in

primates milk. As explained in Chapter 3, some of the polyunsaturates

contain trans double bonds that may not be suitable for primates. Lambs,

calves, kids and fawns have efficient means of obtaining enough

polyunsaturated fatty acids from their mothers, both during gestation and

while suckling, and of getting them to the growing nervous system and eye

where they are most needed. But human infants are not so adapted, and have

proportionately larger brains, so problems can arise when they are fed

cow's, goats' or ewes' milk.

Regular doses of cod liver and other fish oils help to restore the balance

of saturated, monounsaturated and polyunsaturated fatty acids, but the mix

still may not supply the growing nervous and immune systems (both major

users of specific kinds of polyunsaturated fatty acids) as well as that of

human milk. Biochemists have recently developed a means of 'protecting'

lipids from the micro-organisms in the rumen: globules of seed oils, or any

other lipid, are coated with strands of protein, which are bound together

with formaldehyde. Microbial enzymes cannot penetrate this wall of

cross-linked protein, so the particles and their precious contents pass

unscathed into the cow's fourth stomach. Here, strong acids and enzymes

secreted by the stomach lining digest away the protein, releasing the

lipids, which are then emulsified, hydrolysed and absorbed in the usual way.

Such technology has achieved modest success in increasing the proportion of

cis polyunsaturated fatty acids in the lipids of cows' milk, thereby

improving its nutritional value to humans.

Of the animal milks so far analysed, that of carnivores is closest in fatty

acid composition to women's milk. Dog and ferret milk has more fat (7.9% and

6.7% respectively) than human milk (3.6%) but the fatty acid compositions

are almost identical, with a high proportion of polyunsaturates, and almost

no fatty acids shorter than C14:0. Perhaps Romulus and Remus, the mythical

bastard twins who were suckled by a she-wolf and grew up to found the city

of Rome, have something to teach us about the ideal baby food. "

Pond, C.M. The Fats of Life. Cambridge University Press. 1998.

*Groan...* I can just see dairy dog farms cropping up, resulting in the

canine version of the holstein

So, do you think that too much reliance on cow's milk (as opposed to

mother's milk) in growing infants might hinder brain development? Thoughts

on any of this?

Suze Fisher

Web Design & Development

http://members.bellatlantic.net/~vze3shjg/

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