Hi Alan,

> > The effect is a longer retaining in the stomach, and
> > enhanced digestion (since enzymes have more time to act).
> > [...]
> Not quite...it contains protein and is thus clumped in the stomach
> due to the action of hydrochloric acid. The "digestion" of milk thus
> takes much too long with little or no nutritional rewards.

Since milk coagulates in calves' stomachs, your preceding sentence
implies that it is an error of nature??

> >  - Are you sure digestion of casein by other enzymes (e.g. trypsin)
> > does not release *any* calcium?
>
> Yes. Rennin (or chymosin as it is also known) breaks down casein to
> paracasein, which then recombines with the calcium to form calcium
> paracaseinate (which separates out). In other words, the same procedure
> as is used to make cheese is also used by the body (of babies) to get
> at the calcium.

I have no time to examine the question in depth, but I explored a few
abstracts, which say that

 -From the digestion of casein micelles by pepsin and trypsin, casein
phosphopeptides (CPP) are recovered [1]. The CPP are bonded with
calcium.
 -"A moderate and exchangeable binding to Ca2+ of the CPP molecule well
substantiates the high absorbability of calcium from milk and dairy
products." [2]
 -"CPP injected into a ligated loop of rat small intestine enhanced
absorption of calcium from the loop and augmented the deposition of
calcium in the femur." [3]
 -Aged ovariectomized rats fed a diet in which the only source of
calcium is Ca-bonded CPP do not lose bone mass [4].

So, if the Ca-CPP bond is really the bond you were talking about, we
see that in fact this bond plays in _favor_ of milk.


> >  - Anyway, even if you think that rennin is necessary to use the
> > calcium from milk, calcium should be more available in other forms of
> > dairy (e.g. cheese).
> >
> Yes and no. Cheese is a two-edged sword. On the one hand it makes
> the calcium available and on the other, it contains much less
> phosphorus than the original milk. In other words, the ratios are
> upset and the consumption of cheese thus has to rob the body of
> phosphorus.

Okay, here are a few numbers

          Ca         P      Ca/P
      (mg/100 g) (mg/100 g)
Blue      528      387      1.4
Brie      184      188      1.0
Camembert 388      347      1.1
Cheddar   721      512      1.4
Colby     685      457      1.5
Gruyere  1011      605      1.7

These are only examples, but you see that all ratios Ca/P are
favorable (larger than 1).

> > 25% of a high amount can't be considered as "poor" (like if you earn
> > $1,000,000 each month and pay 75% taxes, yon can't say you are "poor"!).
> >
> Don't dwell on the quoted 25% unless you know who paid for such
> research results.

The 25% figure was from one study, but there are others which indicate
absorption rates between 20% and 40% (there is a lot of individual
variability). Some of these studies have been published in the most
prominent medical journals.

> Dwell on the fact that the U.S.A., with the highest
> per capita milk consumption, also has the highest per capita incidence
> of osteoporosis.

As Tom said, a correlation is not a causal relation. For example, one
could say that in the US, the percentage of post-menopausal women
taking hormone-replacement therapy is among the highest, and yet
taking hormones is known to be effective (up to a certain point)
against bone loss. The purpose of the above is not to say that all
women should take hormones, but to illustrate the logical leap in your
argument.

Again, let me repeat that I am not pro-dairy. Milk indeed has some
inconvenients, but I don't think it is such a bad source of calcium as
you say.

--Jean-Louis Tu <[log in to unmask]>


REFS:

1. Ono T, et al. Casein phosphopeptides from casein micelles by
successive digestion with pepsin and trypsin. Biosci Biotechnol
Biochem. 1998 Jan;62(1):16-21.

2. Sato R et al. Characterization of phosphopeptide derived from
bovine beta-casein: an inhibitor to intra-intestinal precipitation of
calcium phosphate. Biochim Biophys Acta 1991 Apr 29;1077(3):413-5

3.  Sato R, et al. Casein phosphopeptide (CPP) enhances calcium
absorption from the ligated segment of rat small intestine. J Nutr Sci
Vitaminol (Tokyo). 1986 Feb;32(1):67-76.

4. Tsuchita H Dietary casein phosphopeptides prevent bone loss in aged
ovariectomized rats. J Nutr 1996 Jan;126(1):86-93