This article is from the Children Allergies and Asthma FAQ, by Eileen Kupstas Soo firstname.lastname@example.org with numerous contributions by others.
That enough? No? The primary source of calcium for most Americans is
milk or milk derived. If you discover you are unable to consume milk
or milk products -- whether because of lactose intolerance or milk
allergy -- you should seriously consider calcium supplementation.
Unfortunately, you may discover (as many do) that these, too, cause
intestinal distress (read: pain). If so, experiment with different
types of calcium (calcium citrate was the least distressing of all the
ones I tried). If you discover none of them work well, you may want to
cut down your meat consumption; some studies suggest that too high
levels of dietary iron may be a more important factor in osteoporosis
than lack of dietary calcium (mechanism speculative -- this also
implies not supplementing iron unless you have an actual deficiency.
Talk to your doctor about all supplementation, of course). You may
also need to supplement vitamin D.
You may need/want to check with a dietician or nutritionist
about your or your child's diet. One suggestion is choose a
calcium supplement with a 2:1 ratio of calcium and magnesium.
S. Rogers, Tired or Toxic?, considers this ratio VERY IMPORTANT.
Other nutritionists have also backed this ratio.