Minerals are inorganic chemicals (unlike vitamins that are organic) and have three major functions in the body. They:
The main minerals are iron, calcium, magnesium, potassium, sodium and phosphorus, and are described below.
The body also requires a number of trace elements which are also essential, but are required in such small quantities a deficiency would be unlikely, so they are not described here.
Most of the iron inside a human being forms the red pigment haemoglobin in blood. Iron is also stored as myoglobin in the muscles. Myoglobin has a similar function to haemoglobin except within the muscles, in that it stores oxygen. Iron is stored in the liver - hence animal liver is a very rich source of iron. However, women who are pregnant should avoid eating liver as it can lead to a Vitamin A overdose.
A deficiency of iron causes anaemia, which is diagnosed by a blood test. Anaemia is usually treated in the short term by a prescription of iron tablets or by a blood transfusion in the most severe cases. The elderly are more at risk of becoming anaemic, as:
Other groups at risk of anaemia include menstruating and pregnant women and children.
The best dietary sources of iron are red meat, which contains iron in an easily absorbable form. Vegetarian sources of iron include beans, nuts, dried apricots, wholegrains and fortified breakfast cereals, but these sources of iron are not as readily available to the body. Their absorption can be enhanced by the concurrent consumption of food or drink containing Vitamin C, eg a glass of pure orange juice.
Calcium makes up about 17% of our total bodyweight, and 99% of it is stored in our bones and teeth. The other 1% is used in muscle contraction (including the beating of the heart), blood clotting and the correct function of nerve cells. Calcium requires vitamin D in order to be absorbed, otherwise it will pass through the body.
A calcium deficiency will cause growth related problems such as rickets and stunted growth.
The richest sources of calcium are dairy products, including milk, cheese and yoghurts; other sources include soya, fortified flour and fish where you eat the bones, such as kippers and anchovies or canned fish (where the bones are softer). Some dark green vegatables also contain useful amounts of calcium.
Phosphorus is the second most abundant mineral in the body, after calcium. It is used in the process that liberates energy from food. It is also a constituent of many organic materials in the body including fats, proteins, carbohydrates and nucleic acids. Some of the vitamin B group are necessary to ensure the correct functioning of phosphorus. Phosphorus also helps in the building of bone and teeth.
Phosphorus is found in many foods and a deficiency is unlikely. The richest source of phosphorus is yeast extract. Other sources include meat, fish, dairy products, peanuts and oats.
Magnesium is a constituent of the green colouration, chlorophyll, in leaves and plants. Consequently, rich supplies of magnesium are found in green vegetables. Magnesium is also found in soya beans, nuts, fish, potatoes and pulses.
Like phosphorus, magnesium helps in the process of liberating energy from food. It also ensures the correct function of the parathyroid gland. The parathyroid gland produces a hormone called parathormone that balances calcium and phosphorus levels to ensure correct bone development.
Sodium is found in the body as common salt (sodium chloride) and is contained in all bodily fluids. Its main function is to maintain the balance of fluids in the body, but it is also used in the functioning of muscles and nerves. On a normal diet, people are likely to eat more sodium than is necessary, which can lead to increased blood pressure and the increased risk of a stroke in susceptible individuals. This is because salt is usually added to processed foods including gravy, ready meals and tinned vegetables. Current recommendations are to reduce the amount of salt in our diet by cutting down on processed food and not adding salt at the table.
The only exceptions in which you are likely to need more salt are in situations where you would sweat a lot more than normal, eg a marathon runner running in a hot climate.
Potassium works in conjunction with sodium in bodily fluids and may lower blood pressure. You are likely to get all the potassium you need from your diet, but rich sources of potassium include bananas and other fruit, sea food, pulses, nuts, seeds and poultry.
Symptoms of potassium deficiency include muscle weakness, tiredness and confusion, but potassium deficiency is only likely to be experienced by athletes or those who have experienced excessive fluid loss through illness (eg diarrhoea, emesis or sweating). Excessive potassium is toxic and can cause a heart attack.