cow's milk vs. human milk

[Guest guest]

Hi ,

Me:

>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?

P:

I don't know, but I'm somewhat skeptical about their claim that human milk

is so low in fat. We know that women eating a SAD give milk that is low in

fat, but that women eating a healthy traditional diet give a much fattier

milk. Are there any figures on the fat content of such mothers' milks?

Me again:

Pond doesn't provide a lipid profile of human milk, although I'd imagine one

or more could be found in an Internet search. It would certainly be

important to know the diet of the person whose milk is profiled. I'd love to

see some mother's milk profiles of some of the folks WAP studied...

However, here's an interesting quote from the book that addresses the

lowish fat of human breast milk, mentioned in a previous quote:

In a chapter entitled " fat people " Pond writes:

" In higher primates, an adequate supply of the right kinds of long-chain

polyunsaturated fatty acids is essential to nourish the foetus's brain

during gestation, and, particularly in humans, it remains important into the

suckling period. Maternal obesity could help to ensure adequate supplies,

though rather inefficiently, since most adipose tissue tracylglycerols

contain saturated or monounsaturated fatty acids that are not suitable for

making neural phospholipids. There is certainly significant movement of

fatty acids from mother to foetus across the placenta: during the first half

of pregnancy the lipids go mainly to the brain and other neural tissues, but

in the final three months they accumulate in adipose tissue, with the result

that human babies are unusually fat at birth. It could be argued that

neonatal obesity is an incidental consequence of the evolution of mechanisms

for transferring larger quantities of lipids from mother to foetus. Lipids

cannot be easily used for energy production during gestation, so as the

nervous system's need for them wanes, they have to be deposited in the

adipose tissue.

A larger brain uses more energy so, as well as requiring more lipid early in

pregnancy for the raw materials of brain growth, more carbohydrate is needed

to sustain it in action. Its metabolism accounts for a substantial fraction

of the foetus's total heat output, but overheating is potentially dangerous

and must be avoided. Hair reduction, and minimising the amount of adipose

tissue in and on the abdomen would help the mother to dissipate heat

efficiently. The necessary lipid stores accumulate elsewhere in the adipose

tissue on the buttock and thighs.

This anomalous growth pattern may also explain why primate milk is

exceptionally low in lipids: brain development in primate infants is so

nearly complete shortly after birth that they don't need many more

precursors for phospholipids to complete the job. Since the other tissues

are growing quite slowly and the babies are carried by their mothers, they

don't need energy-dense milk as much as calves and fawns that grow fast and

have to run for their lives from birth onwards. These contrasts in the

timing of the use of lipids in development, and the amount of strenuous

activity that neonates perform also mean, of course, that feeding babies on

cows' milk provides them with lipid to spare and so they fatten, but feeding

calves on women's milk would leave them abnormally thin. Veal is very lean

because the calves are separated from their mother within a few days of

birth and raised on diluted or even synthetic milk. "

More from Pond on human breast milk:

" In brief, too many trans fatty acids may impair the maturation of important

non-regenerating organs like the nervous system and the eye, or the capacity

of tissues to respond effectively to injury or infection. Cow's milk (used

to make powdered baby milk) contains more trans fatty acids than women's

milk... "

" As might be expected in view of the unique chemical composition and

physical state of milk, lipid digestion in mammalian neonates has some

special features that disappear at weaning. The saliva of human infants, rat

pups and calves (and probably other mammals) contains a lipase that

hydrolyses triacyclglycerols, so digestion begins in the mouth. Since milk

is already a lipid-in-water emulsion, emulsification by stomach churning and

bile secretion is much less important to its digestion. The milk of humans,

gorillas (and possibly other primates) and carnivores also contains a

lipase, which supplements the action of lipases that the neonates produce

for themselves. It has been proposed that adding a lipase could make

artificial infant food more digestible for premature or sick babies. "

[note this is the second similarity she notes between carnivore and human

milk - the first being nearly identical lipid profile]

This is a very interesting book and I'd recommend it to anyone interested in

lipids and their evolutionary history, both in mammals and plants. It was

recommended to me by a cat person who's widely read in nutrition research

and actually has access to a lot of unpublished and prepublished work at her

job. Plus she reads fluently in 3 languages and since she's in Switzerland,

probably gets ahold of stuff that's not easily accessed here. Anyway, she

was the first person to recommend Enig's book to me at a time when I was

quoting too heavily from Udo's book. I'm glad she recommended it because I

have found the Pond book fascinating, especially since she gives an

historical/evolutionary context to just about everything.

Suze Fisher

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