Calcium is the most abundant mineral in the human body. It is essential for a host of physiological functions and for the normal growth and development of the skeletal system. One of the most misrepresented issues in human nutrition is the issue of calcium, and some of these issues have already been discussed. In chapter 1 the negative impact of high protein, particularly animal-protein diets, on calcium absorption and storage was discussed, and in chapter 4 the availability of calcium from dairy products was also investigated. It was shown that most diets in affluent societies are directly responsible for calcium loss from bone, and that distinct correlations exist between the consumption of dairy products and the incidence of
osteoporosis. High-protein diets cause calcium loss in the urine, and animal proteins pose a greater risk than plant proteins.18,19,20,21,22 The reason for this is that sulphate (a product of protein metabolism) excretion is linked to calcium excretion.
High sodium diets also cause calcium loss via the urine as do diets rich in chloride.23 Calcium homeostasis is best achieved by a balanced relationship between macro- and micro-nutrients. Dietary excesses of anions seem to inhibit absorption of calcium, and dietary excesses of cations seem to cause calcium loss. Affluent diets and diets rich in animal products are usually high in sodium and can thus account for substantial calcium loss in the urine. In contrast, whole-food programmes will provide a superb relationship between the macro and micro nutrients, and will curtail the loss of urinary calcium. Some investigators have found that phytic acid (found in grains and legumes), may impact negatively on calcium absorption, but this issue has not yet been satisfactorily resolved as other investigators did not find similar results.23 Grains, legumes, nuts, some seeds and dark green vegetables, are excellent sources of calcium, and if care is taken to regularly include these calcium-rich foods