<<Disclaimer: Verify this information before applying it to your situation.>>

Hi A.G.Franklyn,
In a post to the celiac list,   Wed, 8 Jul 1998 09:17:00 -0500, you said:

>>>>
In a posting someone stated that magnesium and calcium compete for
absorption. Actually, you should always take them together because your
body needs the magnesium to absorb the calcium. You also need vitamin D
to absorb calcium. That's why there are so many combimation products on
the market that contain a combination of all three, ie. (calcium,
magnesium & vitamin D). They do not compete with one another.
<<<<

While one could argue a semantic issue here, and I think my choice of the
term "compete" was not a good choice, your post got me questioning my
position.

I originally encountered the notion that calcium could block magnesium
absorption in a post from Dr. Loren Cordain of the University of Colorado,
August 14, 1997. With his permission, I submitted the following post to the
celiac list, Sept. 7, 1997:

>>>>
On another list, Loren Cordain, Ph. D. pointed out that:

"Ironically, high calcium
diets may have a deleterious effect upon bone mineralization because of
their hypomagnesic effect.   Mg deficiency is a known cause of
hypocalcemia (5).   The resultant hypocalcemia stems from PTH
unresponsiveness (6), since the effects of PTH are magnesium dependent(7)."

I will now point out that celiac disease is often associated with
parathyroid abnormalities.

In a later statement from the same post, Dr. Cordain said:

 "A recent review article (9) showed
that post-menopausal women given magnesium supplements over a 2 yr
period had a significant increase in their bone mineral density, whereas
meta-analyses of calcium supplementation and bone mineral density have been
equivocal."

                                REFERENCES

1.      Varo P.  Mineral element balance and coronary heart disease. Int J
Vit Nutr Res 1974;44:267-73.
2.      Evans GH et al.  Association of magnesium deficiency with blood
pressure lowering effects of calcium.  Journal of Hypertension
1990;8:327-337.
3.      Luft FC et al.  Effect of high calcium diet on magnesium,
catecholamine, and blood pressure of stroke-prone spontanneously
hypertensive rats. Proc Soc  Exp Biol Med 1988;187:474-81.
4.      Sellig MS et al.  Magnesium interrelationnships in ischemic
heart disease: a review. Am J Clin Nutr 1974;27:59-79.
5.      Rude et al.  Functional hypoparathyroidism and parathyroid
hormone end organ resistance in human magnesium deficiency. Clin
Endocrinol 1976;5:209-224.
6.      Rude et al.  Parathyroid hormone secretion in magnesium
deficiency. J Clin Endocrinol Metab 1978;47:800-06.
7.      Estep H, et al.  Hypocalcemia due to hypomagnesemia and
reversible parathyroid hormone unresponsiveness. J Clin Endocrinol
1969;29:842-48.
8.      Ryzen E, et al.  Low intracellular magnesium in patients with
acute pancreatitis and hypo calcemia. West J Med 1990;152:145-48.
9.      Sojka JE et al.  Magnesium supplementation and osteoporosis.
Nutr Rev 1995;53:71-4.
<<<<

Since that post, Cordain and others have continued to look at magnesium.

Here is an excerpt from a post by Dr. Cordain, June 11, 1998, on the
Paleodiet list:

>  High
>dietary calcium can can cause magnesium deficiencies, even when normal
>levels of magnesium are ingested (10).   Because supplemental magnesium
>appears to prevent bone fractures and can result in increased bone
>density (11), it is possible that the high consumption of dairy
>products, at the expense of magnesium rich fruits and vegetables may
>unexpectantly result in a reduced bone mineral density.
>
>10.     Evans GH, Weaver CM et al.  Association of magnesium
>deficiency with the blood-lowering effects of calcium. J >Hypertension
>1990;8:327-337.
> 11.     Sojka JE, Weaver CM.  Magnesium supplementation and
>osteoporosis. Nutr Rev 1995;53:71-74.

I cannot assert certain knowledge. I can only tell you what I believe, and
why I believe it.

I hope that is helpful.
best wishes,
Ron Hoggan