Brief Guide to Mineral Supplements

Like any advanced life form, the human body is a highly complex mechanism. From our food - our fuel - we draw on an intricate chemistry of carbohydrates, fats and proteins for energy, plus vitamins (organic nutrients) and minerals (inorganic nutrients) to keep the system running in good order. There are more than twenty of these minerals, each playing a role in bone structure, body fluids, the operation of the nerve system, and the functioning of enzymes (biochemical catalysts that, for instance, help to release energy from food). The ones we need in relatively large quantities (sometimes called bulk minerals) are: calcium, chloride, magnesium, phosphorus, potassium, sodium and sulphur. There are others that we need in smaller quantities (called trace minerals), but which are equally important; these include: boron, chromium, cobalt, copper, fluoride, iodine, iron, manganese, molybdenum, selenium and zinc.

Minerals have been ascribed a large range of functions in the human body. It is well known, for instance, that calcium is important for the development and strength of bones and teeth; iron is essential for the development of red blood cells (which carry oxygen around the body); sodium (as found in salt) is involved in muscle contraction and nerve transmission. There are many other such connections:

• Calcium (in addition to its importance to bones and teeth) plays an essential role in blood clotting, nerve transmission and muscle contraction.
• Chromium appears to play a part in maintaining blood glucose levels.
• Copper helps the body take up iron.
• Iron (in addition to its role in red blood cells) bolsters the immune system.
• Iodine plays a key role in creating thyroid hormones.
• Magnesium is involved in the work of enzymes, and in muscle function and the formation of bones and teeth.
• Phosphorus is important for bones and teeth, and is associated with the creation and delivery of energy.
• Selenium helps to regulate the thyroid gland and serves as an antioxidant combating the free radicals associated with ageing; selenium deficiency has been linked to cardiovascular disease and cancer.
• Zinc is essential to the functioning of the immune system, the reproductive system, and the body's ability to repair tissue and wounds.

From our food. The following minerals, for example, are contained in the foods listed beside them:

• Calcium: milk, yoghurt, cheese, leafy green vegetables, fish, orange juice, bread, nuts
• Chromium: broccoli, orange juice, grape juice, liver, red wine, potatoes, garlic, basil
• Copper: green vegetables, cereals, beef, poultry, seafood, nuts, seeds, cocoa
• Iron: beef, poultry, pork, liver, fish, shrimps, beans, spinach, raisins
• Magnesium: dark green leafy vegetables, fish, nuts, cereals, soybeans, cocoa
• Manganese: nuts, peas, beans, tea, cereals
• Phosphorus: milk, yoghurt, cheese, peas, beans, beef, poultry, eggs, cereals
• Potassium: dried fruits, bananas, berries, milk, meat, peas, beans, cereals
• Selenium: seafood, brazil nuts, walnuts, beef, poultry, pasta, rice
• Zinc: beef, chicken, pork, oysters, yoghurt, beans, almonds

Mineral supplements are, basically, pills (or liquids) that contain specific minerals, designed to supplement the minerals that you normally ingest through food. They are not food substitutes. In the commercial field of mineral supplements, it is often suggested that, if minerals are good for you in certain ways, then it must be better to have more of them.

Under normal circumstances, not really. Virtually all medical authorities say that you can get enough minerals from the food that you eat - provided that you have a healthy, varied and balanced diet. That includes the recommended five daily servings of fresh fruit and vegetables. A healthy body is naturally able to adjust its absorption of minerals to meet its requirement: if it receives more than it needs in food, it simply expels it. In the case of iron, the body usually absorbs only about 6 per cent of the iron delivered by food. Really, the only people who need to take mineral supplements are those who suffer from specific medical conditions, for instance digestive problems that make them unable to absorb the minerals in food. Anyone suffering from anaemia relating to iron-deficiency will probably be prescribed iron supplements; and for similar reasons, so too may women who suffer from heavy periods. Calcium supplements may be prescribed for post-menopausal women in danger of contracting osteoporosis (severe loss of calcium in the bones). Women in early pregnancy may be encouraged to take calcium and iron supplements. Other people who might need to take mineral supplements include:

• those who simply cannot be bothered to eat a healthy and balanced diet;
• those who are unable (or unwilling) to eat more than 1200 calories a day (the recommended daily average intake - or Guideline Daily Amount (GDA) - is 2000 calories for women and 2500 calories for men);
• vegetarians following a severely restricted diet (such as a macrobiotic or fruitarian diet);
• smokers and big consumers of alcohol, because tobacco and alcohol interfere with the body's ability to absorb minerals.

The growing trade in vitamin and mineral supplements has given rise to a number of medical studies to assess their value. Many of these have concluded that supplements are unnecessary. A number of national medical authorities have published Recommended Daily Allowances (RDA) - or Recommended Daily Intakes (RDI) - for minerals, expressed in milligrams (mg) and micrograms (mcg). The lists all vary slightly, and vary with specifications for age and gender, but typical values include:

Calcium 1200 mg
Chromium 100 mcg
Copper 900 mcg
Iodine 150 mcg
Iron 18 mg
Magnesium 400 mg
Manganese 2 mg
Molybdenum 45 mcg
Phosphorus 1000 mg
Selenium 55 mcg
Zinc 15 mg

The RDAs generally coincide with the minerals that are naturally available through a healthy and balanced diet - and represent the levels needed to avoid mineral deficiency. There are equivalent RDAs for vitamins.

The Expert Group on Vitamins and Minerals, reporting for the Foods Standards Agency in 2003, concluded that vitamin and mineral supplements can be dangerous if taken in excess, and it published Safe Upper Levels (SULs) for mineral intake. For instance the SUL for zinc was put at 25 mg, above which there might be a danger to health - for instance, damage the immune system. In the USA the equivalent is the Upper Level (UL), the 'maximum level of daily nutrient intake that is likely to pose no risk of adverse effects'. Here again, various dangers of exceeding such Upper Levels have been cited, such as: an excess of selenium (which has been given a UL of 400 mcg) may lead to hair loss and brittle nails; an excess of manganese (UL 11 mg) may result in muscle and nerve disorders; an excess of calcium (UL 2500 mg) and iron (UL 45 mg) could cause gastrointestinal problems. The general advice is that, if you really want to take vitamin and mineral supplements, without a medical need to do so, find a product that delivers no more than the Recommended Daily Allowance.

http://dietary-supplements.info.nih.gov (US National Institute of Health, office of Dietary Supplements)
www.eatwell.gov.uk/healthydiet (Food Standards Agency)
www.nutrition.org.uk (British Nutrition Foundation)

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