From: russ@wpg.com (Russell Lawrence)
Subject: Re: Milk and calcium (here we go again)
Organization: WP Group
Date: Sun, 24 Jan 1993 05:57:48 GMT

From article <1993Jan23.174154.349@pixel.kodak.com>, by young@clpd.kodak.com (Rich Young):
> Protein does not, in and of itself, "leach calcium from the bones."
> High protein intake tends to increase calcium excretion in the urine.
> This excreted calcium is taken from the blood.   The body requires 
> a fairly delicate balance of calcium which is transported by the 
> blood.  If the blood level of the mineral is too low, the body will 
> draw upon its reserve stores, the bones, and seek to raise the blood 
> levels.  When all is well, both removal and deposition of calcium 
> are ongoing processes.  It is only when removal outpaces deposition 
> that there is a potential problem; and if blood calcium is high in 
> the first place, perhaps due to increased consumption, then one 
> might reasonably expect a similar rise in urinary calcium, regardless 
> of diet...

[see the abstract below]

> It is not clear that excessive consumption of vegetable protein
> would not cause increased urinary excretion, but this is difficult
> to test, since excessive consumption of protein from vegetable
> sources is much less likely due to the decreased nutrient density
> of most plant sources.  

[see the abstract below]

> There is, however, at least one study which 
> implicates cereal grains in bone loss, and another which mentions 
> soy protein.  

Post them.

> My own opinion is that excessive protein consumption,
> regardless of source, will increase urinary excretion of calcium.

[see below]

> ...
> It is not at all clear that anything except the fat content of
> dairy products is 'harmful" to adults and children older than
> one year.  Skim milk is an excellent source of calcium, and the
> bugaboo regarding protein is a red herring, since it is total
> protein consumption which is the key factor in urinary calcium
> excretion...

What's the basis of your opinion?  The evidence below supports 
a different conclusion.

====================================================================
Breslau NA  Brinkley L  Hill KD  Pak CY  
Relationship of animal protein-rich diet to kidney stone formation
  and calcium metabolism.
J Clin Endocrinol Metab 1988 Jan;66(1):140-6

We wished to determine whether different types of dietary protein
  might have different effects on calcium metabolism and on the
  propensity for renal stone formation. Fifteen young normal subjects
  were studied during three 12-day dietary periods during which their
  diet contained vegetable protein, vegetable and egg protein, or
  animal protein. While these three diets were constant with respect to
  Na, K, Ca, P, Mg, and quantity of protein, they had progressively
  higher sulfur contents. As the fixed acid content of the diets
  increased, urinary calcium excretion increased from 103 +/- 15 ( +/-
  SEM) mg/day (2.6 +/- 0.4 mmol/day) on the vegetarian diet to 150 +/-
  13 mg/day (3.7 +/- 0.3 mmol/day) on the animal protein diet (P less
  than 0.02). Despite the increased urinary calcium excretion, there
  was a modest reduction of urinary cAMP excretion and serum PTH and
  1,25-dihydroxyvitamin D levels consistent with acid-induced bone
  dissolution. There was no change in fractional intestinal 47Ca
  absorption. The inability to compensate for the animal protein-
  induced calciuric response may be a risk factor for the development
  of osteoporosis. The animal protein-rich diet was associated with the
  highest excretion of undissociated uric acid due to the reduction in
  urinary pH. Moreover, citrate excretion was reduced because of the
  acid load. However, oxalate excretion was lower than during the
  vegetarian diet [26 +/- 1 mg/day (290 +/- 10 mumol/day) vs. 39 +/- 2
  mg/day (430 +/- 20 mumol/day); P less than 0.02]. Urinary
  crystallization studies revealed that the animal protein diet, when
  its electrolyte composition and quantity of protein were kept the
  same as for the vegetarian diet, conferred an increased risk for uric
  acid stones, but, because of opposing factors, not for calcium
  oxalate or calcium phosphate stones.

Institutional address: 
     Center in Mineral Metabolism and Clinical Research
     Department of Internal Medicine
     Dallas
     Texas.
====================================================================

-- 
Russell Lawrence, WP Group, New Orleans (504) 443-5000
russ@wpg.com   uunet!wpg!russ