minerals

minerals Minerals are specifically inorganic compounds occuring naturally in the Earth's crust or lithosphere. They consist of a metal element in the form of a salt or oxide and are often crystalline in nature and usually highly insoluble, the more soluble salts having been washed from the land into the rivers and seas. Consider, for example, three calcium minerals; the fluoride, the phosphate, and the carbonate. The first, calcium fluoride or fluorspar, exists as beautiful crystals, often seen in caves, and is highly insoluble. However, in regions where it is found sufficient fluoride enters the drinking water to prevent dental caries, making fluoridation unnecessary. The second, calcium phosphate is modestly soluble, and may originate from the decayed teeth, bones, and sea shells of living creatures accumulated over aeons of time. It, together with calcium carbonate, or the chalk of limestone deposits, is what makes water ‘hard’ and furs up the kettle. Thus through the drinking water, even in those who do not consume dairy products (the major dietary source), the intake of calcium can be assured. Only in special circumstances is supplementation of calcium intake required, as in pregnancy. However, there is recent evidence that for the avoidance of osteoporosis in later life it is important for school-age girls to increase their calcium intake above the usual norm.

All the essential elements that are needed by the body in inorganic form have minerals as their source of origin, although many will be derived through the intermediacy of plant or animal material in the diet. For example, our small but essential need for manganese is satisfied through leafy vegetables, such as spinach. Where the mineral intake is inadequate we seem to know, adding that extra sprinkle of salt on our meals. Trace elements such as copper, molybdenum, and iodine, and even the somewhat larger requirement for iron, may be satisfied through the drinking water, but this has a geographic dependency, requiring that the water passes over appropriate minerals before entering the domestic supply. The thyroid gland needs iodine to make the hormone thyroxine. If the iodide content of the blood is too low the gland in the neck swells to produce a goitre. In the county of Derbyshire in England the local rocks are such that the iodide content of the drinking water is very low indeed, so that goitre was common in the region, where it was known as Derbyshire Neck. Goitre has now disappeared, as most table salt is iodized, either because sodium iodide is added to the sodium chloride in the preparation of table salt, or more generally because salt deposits containing traces of sodium iodide are used without attempting to remove the iodide.

A more likely source of minerals other than drinking water is provided by the food we eat, in which plants and animals have already accumulated what is necessary. Thus a healthy diet is one which contains all our needs, and we have presumably evolved so that all our mineral requirements are met in this way. Strict vegetarians and vegans are probably more aware of these requirements as, for example, it is difficult on a purely vegetable diet to maintain an adequate intake of vitamin B₁₂, with its essential cobolt mineral component. In this instance supplementation of the diet with cobalt salts does not help, as man cannot make the vitamin: it has to be supplied in the diet.

Our intake of iron is essential for maintaining red blood cell formation. Women have a higher requirement than men because of the monthly blood loss through menstruation. Many animal foods, such as liver, are a rich souce of iron, although iron supplementation in the aged and those who are slightly anaemic can be achieved with the mineral itself, in the form of iron sulphate tablets. Until the 1950s, and into the 1960s, iron tonics were popular over-the-counter products bought in chemists shops. One called ‘Dr Parrish's Chemical Food’ was particularly popular. The way it was made is of interest. Pure iron wire was weighed out and the calculated amount of phosphoric acid added, just sufficient to dissolve the wire. The resulting fluid was then mixed with syrup, and red colouring added to produce the tonic. In the eyes of the public it clearly contained real iron and would certainly give them strength. It was as if some believed that the wire was reconstituted in the body, adding some sort of steely structure to the human frame.

Today, in the developed world, it is difficult to be mineral deficient while eating a normal, balanced diet. However, in Victorian times it was common among the wealthier classes to visit health-giving spas in order to ‘take the waters’, which meant drinking quanties of water directly welling up out of the earth. The spas were often associated with hot water springs where the visitors would immerse themselves in pools. Some spas are of great antiquity, such as those started by the Romans all over Europe. The waters were often sulphurous and smelt rather badly of rotten eggs. The benefits of visiting spas probably owed more to a placebo effect than for any other reason. Even today many no longer drink tap water; bottled mineral water is the fashion. The labels on the bottles give long lists of the mineral contents. One well known brand of mineral water used to include on its label the amount of ‘radioactivite’. Often hot spring waters come from great depths and are in contact with radioactive minerals, which impart traces to the water. In recent times the amount of ‘radioactivite’, which was in any event miniscule, has disappeared from the label. The reason that mineral water is popular today is less because of its mineral content but rather to avoid contaminants in tap water. The contaminants are usually the result of the use of agrochemicals, fertilizers, and sprays used to increase crop yields, which then get washed into rivers and reservoirs and hence into drinking water. The most common culprit is inorganic nitrate. Those who feel they are mineral deficient can avail themselves of numerous products in health shops, where tablets containing all the needed minerals in the correct ratios can be found.

Alan W. Cuthbert

See also composition of the body; metals in the body; salt.