There have been some good posts on calcium and osteoporosis ("little
bone" in the past few weeks.  Here's some additional information which
you may find surprising.  My sources are Wardlaw & Insel's _Perspectives
in Nutrition_ 2nd edition, pages 437-447, and Garrison & Somer's _The
Nutrition Desk Reference_ 2nd edition, pages 58-60 and the Selected
Topics chapter on minerals.  Enjoy:

 - Calcium absorption may be reduced by physical and emotional stress,
 and may result in unexplained dumping of calcium into the intestinal
 tract.  A loss of as much as 900mg may occur each day during times of
 worry and tension.  Fecal excretion can be twice the dietary intake.

 - Excessive protein intake results in urinary overexcretion of calcium.
 Further, high dietary protein may also increase bone resorption,
 predisposing an individual to osteoporosis.  This may be a problem
 especially in the United States, where the typical American consumes
 two to three times the necessary daily requirement of protein.

 - Calcium interacts with other minerals, one being phosphorus.  The
 dietary phosphorus:calcium ration should be 1:1.  The _average_
 American diet contains two parts phosphorus for every one part calcium.
 At this ratio, excess calcium is removed from bone tissue and blood
 levels are depressed, resluting in increased calcium excretion and bone
 demineralization.  These conditions are promoted by high-phosphorus
 foods such as soda pop, diet pop, processed foods (cheese spreads,
 meats and convenience foods), peanuts, eggs, meat, and organ meats, as
 well as by a low intake of calcium-rich foods.

 - Regular tea drinking blocks calcium absorption due to the tannins in
 tea.

 - Steroid use causes bone loss by blocking osteoblast (cells that make
 bone) activity.

 - Cottage cheese is not a good source of calcium, since most of the
 calcium in it is lost during its production.

 - Calcium carbonate (dolomite, Tums, etc.) is a natural antacid.  Since
 calcium cannot be absorbed without a high acid environment in the
 stomach, the use of calcium carbonate actually inhibits calcium
 absorption.  Calcium citrate, itself an acid, is much better,
 especially for elderly people, since the average 60 year old has only
 15% of the stomach acidity of the average 30 year old.  However, taking
 calcium in any form with meals can help its absorption, since stomach
 acid secretion is stimulated when you eat food.

 - _The American Journal of Clinical Nutrition_ (54:193S, 1991) reports
 that dietary calcium may reduce the risk of colon cancer, by binding
 irritants and preventing the spread of malignant cells.