Here is some useful information on calcium and magnesium.
Arguably we are removing magnesium sources (whole foods dark greens etc whole grain seeds and nuts) and increasing calcium with high levels of dairy.
"Even though dietary surveys suggest that many Americans do not consume recommended amounts of magnesium, symptoms of magnesium deficiency are rarely seen in the US. However, there is concern about the prevalence of sub-optimal magnesium stores in the body. For many people, dietary intake may not be high enough to promote an optimal magnesium status, which may be protective against disorders such as cardiovascular disease and immune dysfunction [7-8]. "
Magnesium
Office of Dietary Supplements • National Institutes of Health
Table of Contents
Magnesium: What is it?
What foods provide magnesium?
What are the Dietary Reference Intakes for magnesium?
When can magnesium deficiency occur?
Who may need extra magnesium?
What is the best way to get extra magnesium?
What are some current issues and controversies about magnesium?
What is the health risk of too much magnesium?
Selecting a healthful diet
References
Reviewers
http://ods.od.nih.gov/factsheets/magnesium.asp
This is useful on magnesium and calcium and put in very straightforward terms
http://www.drlam.com/a3r_brief_in_do...umandAging.cfm
And these are calcium recommendations for the military
1000mg/day
In the Dr Lam article at the bottom looks at advantages of a lower calcium intake.
There are reasons why calcium is less available to plants in the natural un farmed environment (although it is more of the earth's crust than magnesium). Magnesium may be better retained in the soil and so more widely available. Plants do their best to balance their needs and appear to have more calcium than magnesium. Whole from a quick check wild grains and nuts are high in magnesium. Wild marine products appear about balanced.
Factors Affecting soil Ca Availability
Calcium is found in many of the primary or secondary minerals in the soil. In this state it is relatively insoluble. Calcium is not considered a leachable nutrient. However, over hundreds of years, it will move deeper into the soil. Because of this, and the fact that many soils are derived from limestone bedrock, many soils have higher levels of Ca, and a higher pH in the subsoil.
* Soil pH: Acid soils have less Ca, and high pH soils normally have more. As the soil pH increases above pH 7.2, due to additional soil Ca, the additional "free" Ca is not adsorbed onto the soil. Much of the free Ca forms nearly insoluble compounds with other elements such as phosphorus (P), thus making P less available.
* Soil CEC: Lower CEC soils hold less Ca, and high CEC soils hold more.
* Cation competition: Abnormally high levels, or application rates of other cations, in the presence of low to moderate soil Ca levels tends to reduce the uptake of Ca.
* Alkaline sodic soil (high sodium content): Excess sodium (Na) in the soil competes with Ca, and other cations to reduce their availability to crops.
* Sub-soil or parent material: Soils derived from limestone, marl, or other high Ca minerals will tend to have high Ca levels, while those derived from shale or sandstone will tend to have lower levels.