Chemical elements that enable the body to perform essential functions

Minerals are chemical elements that are necessary to maintain health. The body does not manufacture minerals and therefore it must obtain them from dietary sources (see Good sources of vitamins and minerals).

Your doctor may prescribe mineral supplements if you have a medical condition that interferes with the ability of your body to absorb minerals (see Malabsorption) or if you need extra amounts of certain minerals, as may happen in pregnancy. Most people should not need mineral supplements because a balanced diet usually provides sufficient amounts. You should not take mineral supplements unless you need them because excessive doses of some minerals can be toxic.

What are the types?

Many minerals are necessary to maintain good health. The most important minerals prescribed to treat deficiencies include iron, calcium, magnesium, zinc, fluoride, iodine, and phosphorus.


This mineral is a vital component of haemoglobin, the oxygen-carrying pigment in blood. A correctly balanced diet usually provides sufficient supplies of iron but deficiency sometimes occurs in women with heavy menstrual periods (see Menorrhagia), pregnant women, and women who have recently given birth. Vegans, and people who have persistent blood loss due to conditions such as a peptic ulcer, may also be deficient in iron.

Iron is usually taken orally as a liquid or tablets and can be purchased over the counter. Side effects of taking iron supplements may include darker stools, constipation or diarrhoea, nausea, and abdominal pain. In certain cases when the body cannot absorb sufficient iron from the digestive tract, for example following extensive bowel surgery, injections of iron may be needed. Although these injections are given deep into muscle, staining of the skin at the injection site may result.


This is essential for formation and maintenance of bones and teeth, as well as for muscle contraction and transmission of nerve impulses. Dairy products usually provide sufficient calcium.

An increased dietary intake is recommended for women who are pregnant or breast-feeding because both fetal bone formation and maternal milk production require large amounts of calcium. Elderly people may need supplements because the body absorbs calcium less efficiently with age. Calcium supplements may also be prescribed to prevent bone disorders such as osteoporosis and to increase blood levels of calcium in people who have hypoparathyroidism or kidney failure. In addition, calcium may be given by intravenous injection to treat cardiac arrest. Severe calcium deficiency leads to cramps and muscle spasms and may be treated with calcium injections. Side effects of calcium include constipation and nausea.


This mineral is needed for healthy teeth and bones, muscle action, and transmission of nerve impulses. Magnesium supplements may be prescribed for certain conditions that can interfere with the absorption of magnesium from food, including alcohol dependence, repeated vomiting, or long-term diarrhoea. Excessive doses of magnesium may cause nausea, vomiting, diarrhoea, and dizziness.


This mineral is used for growth and to help wounds to heal. Deficiency is rare; it usually occurs only in malnourished elderly people, and may also occur in people with severe burns or other traumatic injury because zinc is used up rapidly in the healing process. In these cases, zinc supplements are sometimes prescribed. Zinc is usually taken orally but may also be given as a topical treatment for skin disorders, such as nappy rash. Taking overly large doses of oral zinc may cause side effects such as fever, nausea, vomiting, headaches, and abdominal pain.


The mineral fluoride helps to prevent tooth decay and makes bones stronger. Water is very often the main dietary source because fluoride occurs naturally in some water supplies or is added to the drinking water in many areas. Fluoride is also an ingredient in most toothpastes. Your dentist may recommend fluoride supplements in the form of drops or tablets if the water in your area is not fluoridated or if you are susceptible to dental caries. If you take excessive fluoride, you may develop fluorosis, in which the teeth become discoloured (see Discoloured teeth).


This mineral is essential for the formation of thyroid hormones, which control the rate at which the body uses energy and which are vital for normal growth in childhood. Supplements are rarely needed because sufficient iodine is usually present in the diet. Important sources of iodine include seafood, bread, and dairy products. Radioactive iodine may be given to people with a goitre or hyperthyroidism in order to shrink the thyroid gland. Excessive amounts of iodine can suppress the activity of the thyroid gland, leading to hypothyroidism.


The mineral phosphorus is an essential part of the diet. It is present in many foods, including cereals, dairy products, eggs, and meat. Much of the phosphorus contained in the body is combined with calcium to form the structure of the bones and teeth. Hypophosphataemia, in which the body contains an abnormally low level of phosphorus, may occur in some forms of kidney disease, hyperparathyroidism, and malabsorption.

Deficiencies of this mineral can be treated with phosphate supplements. In addition, hypercalcaemia, in which blood levels of calcium are abnormally high, may be treated using phosphates. Diarrhoea is a potential side effect of phosphate supplements.


Iron swallowed in relatively small amounts can cause potentially fatal poisoning in children. Keep your medicines in a safe place and seek urgent medical help if you suspect that a child has taken any tablets.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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