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Macrominerals are those for which the daily requirement is more than 100mg
Calcium
A widely distributed metal, chemical symbol Ca. Calcium is found in large quantities in the human body, 99% of it in the bones and teeth. It is absorbed from food through the walls of the intestines, and the process is helped by the presence of Vitamin D.
Deficiency
Calcium deficiency is rare, but can occur where there is a lack of Vitamin D, or a problem with absorbtion through the intestinal walls. It can lead to conditions such as rickets, in children, and the adult equivalent, osteomalacia. Rickets in childhood may encourage the development of osteoporosis in later life. A shortage of calcium will weaken bones, teeth, nails and hair, and may lead to the development of allergic reactions.
Overdose
Calcium is toxic in overdose quantities, and can cause kidney damage - surplus calcium is deposited in the form of calculi (stones) in the kidney or bladder, or as tartar on the teeth.The body has mechanisms for regulating absorption and disposing of any excess, excreting it in the faeces, urine and sweat. The way that the body uses calcium is a bit complicated: it competes with magnesium, and both minerals need to be present in the correct proportions for each to function as it should. If there are high calcium levels in the blood, magnesium can help to reduce them, while calcium can help deal with potassium deficiencies. Many minerals and trace elements are interdependent in this way.
Benefits
Apart from maintaining the health of bones, teeth, hair and nails, calcium is required for maintaining the fluid balance in the body, sending nerve impulses and enabling muscles to contract. It is involved in the coagulation of blood, the functioning of the heart and the secretion of breast milk in nursing mothers. Calcium is taken on a daily basis from the bones and teeth where it is stored, and constantly replenished. The levels of calcium in the blood are very carefully maintained, by two hormones, as small variations from the normal levels can cause cell damage and seizures.
Osteoporosis is a common problem, particularly for post-menopausal women, where calcium is withdrawn from the bones and not replaced. Therapeutic supplements of magnesium and calcium are used to treat this, as well as joint problems. To be assimilated into the bones, calcium requires the presence pf both magnesium and silicon, and osteoporosis has proved difficult to treat with mineral therapy. The emphasis now is on prevention rather than cure, encouraging teenage girls and young women to maintain adequate levels of calcium.
Sources
Calcium is found in milk, dairy products, hard tap water, pilchards and sardines, white bread and flour, leafy green vegetables and fortified cereals. It is estimated that the body normally only uses about 30% of the calcium present in the diet.
RDA (Recommended Daily Allowance)
The RDA for calcium varies between 500mg and 1000mg for healthy adults. Higher amounts are recommended for pregnant women (1200 mg) and for women over 45 (1500 mg), to help prevent osteoporosis.
Chlorine
Chlorine, chemical symbol Cl, is a trace element that is required for forming digestive acid in the stomach, and for the correct functioning of the body's carbon dioxide transport system. It is closely linked with sodium, and together these elements regulate the fluid balance, acid base balance and osmotic pressure in the blood. Although we need more than 100mg of chlorine a day, we usually get too much of it, in our salt intake.
Magnesium
Magnesium, chemical symbol Mg, is a metallic element which is stored in the body's cells, primarily in bones and muscles. Dietary megnesium is absorbed into the blood stream through the intestines, but only about 30 - 40% of the available element is taken up. The percentage increases if less magnesium is consumed. The amount of magnesium available is diminished according to the quantities of calcium, phosphorus, protein, saturated fat and fibre in the diet.
Deficiency
Magnesium is essential for the muscles to function correctly, and for proper communication between nerve cells. It is vital for cell division and for all reactions with phosphates. If cells become deficient in magnesium, the permeability of their walls changes, leading to the loss of both potassium and megnesium, these being replaced by sodium and calcium. In deficiency, muscles become weak, the person feels fatigued and may develop an irregular heartbeat. Deficiency of magnesium can lead to the development of kidney stones (due to excess calcium in the body). It also seems to be a factor in myocardial infarction, the heart attacks where a coronary artery becomes blocked: 100 years' ago, the average daily intake of magnesium was three to four times higher than today's RDA, and a study of 1000 post mortems carried out at that time showed that not one individual died from a heart infarction.
Deficiency in magnesium seems to lead to a decrease in the efficiency of the autoimmune system: the link has been established in rats, where a magnesium deficient diet led to impaired defence against both allergic reactions and cancers. Large scale human trials have not yet been carried out.
A shortage of magnesium can develop gradually, leading to a range of symptoms including anxiety, fatigue, muscle weakness, cramps, insomnia, restless legs and nausea. It may also be implicated in premenstrual tension. Kidney disease, diabetes and some hormonal disorders can increase the shortage of magnesium.
Benefits
Magnesium is essential for the proper functioning of the body in many ways: it is required for nerves, muscles, the immune system, cellular function, 90 different enzymes require magnesium in order to metabolise energy. Treatment with magnesium supplements reduces the incidence of heart attacks, repeat attacks following an initial heart attack, and cardiac arrhythmia. Supplements have also been used successfully to treat some patients with asthma and allergies, and some with ME (chronic fatigue syndrome)
Sources
Magnesium is found in green vegetables, wholemeal flour, milk, eggs, fish, pulses, shellfish, nuts (especially peanuts), meat and cereals.
RDA (Recommended Daily Allowance)
The RDA for magnesium is around 300mg, and 450mg for pregnant women and nursing mothers.
Phosphorus
Phosphorus, chemical symbol P, is a non-metallic element, occurring naturally in the form of phosphate salts.
Deficiency
Lack of phosphorus leads to weight loss, weakness, loss of bone density (it is required to make calcium phosphate, one of the main components of bone tissue), loss of appetite and stiff joints. Anaemia and problems of the respiratory system and central nervous system are all associated with phosphorus deficiency.
Overdose
Too much phosphorus in the diet prevents the proper absorption of calcium, zinc, iron and magnesium.
Benefits
Phosphorus is needed by the enzymes that metabolise fat, protein and glucose. It is essential for the processes by which the body produces and stores energy, and it helps in the formation of nucleic acids for cell division.
Sources
There is phosphorus in practically all foods, but particularly high protein ones, such as meat, dairy, pulses and milk, as well as leafy green vegetables and most fruits.
RDA (Recommended Daily Allowance)
The RDA is about 800mg for healthy adults, 1200mg for pregnant women and nursing mothers.
Potassium
Potassium, chemical symbol K, a metallic element needed by all plants and animals. It is closely related to sodium, in that it often works with it, but to opposite effect. Potassium and sodium together control the electrical potential of the nervous system, allowing nerve signals to be transmitted and muscles to contract regularly.
Deficiency
Potassium deficiency can lead to muscle weakness, fatigue, fluid retention, loss of appetite, thirst, low blood pressure, constipation and problems with the kidneys and nervous system. It affects the functioning of the heart, and its sensitivity to some drugs, including digitalis. Potassium and magnesium deficiency both cause similar effects and tend to occur together. Potassium requires the presence of magnesium before it can be used by the body's cells. Potassium is one of the most frequently prescribed mineral supplements (another is iron). This is because levels are depleted by the use of diuretic tablets, which many people take.
Overdose
Generally speaking, the body excretes any excess potassium in the urine, but sometimes high potassium levels in the blood are caused by severe fluid loss - perhaps due to prolonged attacks of vomiting or diarrhoea. Kidney failure can also lead to an excess of potassium in the body. Symptoms of overdose include drowsiness, disorientation, weakness and cardiac arrhythmia, leading potentially to cardiac arrest. High potassium intake may also make anticoagulant drugs less effective.
Benefits
Potassium is required as mentioned above for the correct working of the nervous system, the muscles and the heart. It maintains the body's osmotic balance, and is required by several enzyme processes, including the metabolism of protein. The right balance of potassium is required to prevent cardiac arrhythmia.
Sources
Potassium is found in most foods, particularly fresh fruits and vegetables (potatoes are a very rich source), meat, milk, wholemeal flour, coffee, tea and cereals. Coffee is one of our primary sources, as it contains about 45mg per cup.
RDA (Recommended Daily Allowance)
There is no RDA per se. Most people consume between 2 and 4 grams a day.
Sodium
Metallic element, chemical symbol Na, of which human beings need about 3 grams a day. Although it is essential for all animals, in excess it is dangerous - and most of us consume between 5g and 15g in our daily diet - up to 5 times more than the recommended amount. Sodium is absorbed from the stomach and small intestine, and is then filtered from the bloodstream by the kidneys. More than 90% of sodium intake is eliminated from the body in the urine.
Deficiency
As you might expect, sodium deficiency is very rare - but it can occur, either when sodium recycling is impaired by kidney problems, or when heavy sweating is caused by hot conditions or hard work. Symptoms include low blood pressure, dizziness, muscle weakness, respiratory problems, mild fever, weight loss and a general feeling of unwellness.
Overdose
Too much sodium can raise the blood pressure, and make high blood pressure worse in people who already suffer from it. This can lead to heart and kidney problems. It can also cause migraines and lead to a condition called hypernatraemia, which is characterised by fluid retention and mental confusion, and may lead to seizures and even coma. As mentioned above, most of us consume too much salt: on average only 12% of our sodium intake is supplied by the mineral occurring naturally in foodstuffs; about 50% is supplied by processed food; and some 40% added at the table. We owe it to our children to bring them up with a low salt habit - it becomes harder to adapt to less salt as we become older. Try to reduce your sodium by using herbs and spices for seasoning, and salt substitutes such as Lo-Salt or Pan-Salt, where some of the sodium chloride is replaced with potassium chloride.
Benefits
Sodium ions are the main ions in the fluid contained in the cells of the body. Their interaction with potassium ions is essential for survival and for the normal functioning of nerves and muscles. Sodium regulates the water balance in the body and maintains the acid-alkali balance. It is involved in the manufacture of adrenaline and amino acids.
Sulphur
Non-metallic element, chemical symbol S.
Deficiency
Deficiency is extremely rare, and would occur only if the diet contained too little protein.
Benefits
Sulphur is necessary to form some amino acids and the proteins that make skin, nails, tendons, cartilage and hair.
Sources
It is found in both animal and vegetable proteins - meat, dairy, pulses and nuts.
RDA (Recommended Daily Allowance)
There isn't an official RDA.