If drinking water percolates through areas containing dolomite, limestone or chalk, the calcium and magnesium within the rocks can increase the mineral content of the water considerably. Water with a high calcium and magnesium content is described as hard water, while that with a lower content of calcium and magnesium is described as soft water. Evidence suggests that the calcium and magnesium in hard water are protective of disease, particularly cardiovascular disease. This does not relate to some pharmacological action of either calcium or magnesium but likely reflects the fact that most of the populations in Western nations are deficient in these two minerals, particularly magnesium. Minerals are required in specific ranges, and these ranges not only ensure adequate supply of the minerals but also ensure that one mineral does not cause depletion of other minerals. Certain minerals compete for absorption and high intakes of one combined with marginal intake of another can therefore lead to mineral deficiencies.
Another problem with the Western diet is that it does not supply adequate zinc. Studies consistently show that the zinc status of Westerners is generally poor. As both calcium and magnesium can inhibit zinc absorption, those living in hard water areas who enjoy high intakes of calcium and magnesium may be at risk of zinc insufficiencies if their zinc intakes are marginal. In this respect, researchers1 have investigated the mineral status of healthy children living in regions of Canada. Some children lived in Halifax where the water supply is very soft containing 33 parts per million of calcium and magnesium, and some lived in Guelph where the water supply is very hard containing 330 parts per million of calcium and magnesium. The researchers found that the children in the soft water area had significantly higher hair zinc levels that those children living in the hard water region. The authors concluded that the high calcium intakes of the children in Guelph may be a contributory factor in their poor zinc status.
Interestingly the children living in Halifax were significantly heavier and taller than those living in Guelph. As zinc is required for correct growth, and deficiency is known to cause stunted growth in children, it may be that the poorer zinc status of the children from Guelph was a cause or contributory factor in their lesser statures. The authors noted that 31 % of the children living in Guelph had zinc mineral levels below 70 μg which is indicative of a serious zinc deficiency. Only 6 % of the children from Halifax had similar deficient status. In another study of UK school children, only 3.7 % of the children had hair zinc levels below the 70 μg threshold. Of course, while it is easy to suggest that the high intakes of calcium or magnesium are to blame for these deficiencies, it should be noted that such a poor zinc status can only be obtained with a low zinc intake. These children are not zinc deficiency because of excessive calcium and magnesium, but the calcium and magnesium may contribute further to deficiency in already zinc deficient children.
Dr Robert Barrington’s Nutritional Recommendation: Mineral imbalances can cause deficiencies in certain minerals because minerals compete for absorption. In particular marginal intakes of zinc can be problematic if intakes of calcium or magnesium are too high. Ensuring optimal intakes of all minerals, in balanced amounts in necessary to supply the body with adequate nutrition. This is why single mineral supplementation with isolated nutrients is not recommended without oversight from an experienced nutritionist.
RdB
