In the March American Journal of Clinical Nutrition, 67: 438-444, 1998, there
is a study entitled "Dietary Protein Intake and Urinary Excretion of Calcium:
A Cross-Sectional Study in a Healthy Japanese Population."

They found that animal protein increases calcium excretion--but are the
numbers significant?  Quote from page 441 of the study:

"From the multiple regression equations contained, it was estimated that an
increase in urinary calcium excretion was 1-2 mg with a 1 gram increase in
protein catabolized to energy."

And did the Paleodiet, probably high in animal protein, cause osteoporosis?

Question: how much of protein is catabolized to energy?  The calcium loss was
only significant after adjustments for other variables in the elderly Japanese
(50-79 yo subjects.)  Their muscle mass is probably lower than younger people,
who would use more protein to maintain lean mass.

More importantly, even if you are eating 50 grams more protein than your body
needs, is the loss of 50 to 100 mg of calcium significant?  The same can be
lost from habitual coffee consumption.

Populations that have eaten five pounds of meat or more per day when settling
the West did not show any evidence of osteoporosis.  It is this kind of data
that makes me question whether this study of elderly Japanese should really
have us that concerned.

Robert Crayhon
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