Vitamins and minerals are collectively known as micronutrients, which means that they are required in tiny amounts by the body. Around 15 vitamins and 15 minerals are known to be essential for human health, growth and wellbeing. There is also a group of substances known as phytonutrients that is found in plants. Phytonutrients are thought to play an important role in ensuring long-term health and preventing disease.
Vitamins and minerals play a number of very important roles in the body. Without sufficient vitamin C, for example, the health of the gums, skin and teeth would deteriorate; and if a pregnant woman were deficient in folic acid, foetal development could be impaired. Fruit and vegetables are particularly rich in vitamins and minerals. They are also an excellent source of phytonutrients and antioxidants – active compounds believed to have a beneficial effect on health. These substances are thought to help protect the body from damage by free radicals – un-stable molecules that attack cells. The chart of vitamins, minerals and trace elements (minerals required in tiny amounts) found on the post:provides information on their food sources, roles, recommended daily allowances and symptoms of deficiency.
The group of micronutrients referred to as vitamins are organic substances that are essential for the health of the body. Vitamins have a diverse range of functions: they help to convert fat and carbohydrates into energy; they regulate the metabolism (the chemical process by which the body’s energy is stored and released); they keep the skin, teeth, bones, brain and nervous system healthy; they help to make DNA, which contains the genetic information of the cells and controls heredity; and they aid the absorption of essential minerals in the body.
Vitamins are a relatively new discovery in the science of nutrition, having been identified since 1896. Because the body is unable to make most vitamins, they form a vital part of the human diet. Vitamins fall into two groups – those that are soluble in fat (A, D, E and K) and those that are soluble in water (all the B vitamins – including folic acid, pantothenic acid, biotin and niacin – and vitamin C). Excess amounts of fat-soluble vitamins are stored in fat and excess amounts of water-soluble vitamins are passed out of the body in urine. Because fat-soluble vitamins do not pass out of the body, they can build up. Some vitamins are toxic in large quantities and this is why an excessive intake of some fat-soluble vitamins may, in rare instances, be hazardous to health. Water-soluble vitamins need to be included regularly in the diet because, with the exception of vitamin B12, they cannot be stored by the body.
The vitamin system is a delicate balancing act, for although each vitamin has several specific roles, all vitamins interact with each other and work as a team; if just one is deficient, the efficiency of the others can be affected.
Minerals are chemical elements that are needed by the body for healthy functioning; they are divided into macrominerals and microminerals or trace elements. Macro-minerals, such as calcium, magnesium, sodium and potassium, are required in comparatively large quantities, whereas trace elements, such as iron and zinc, are needed in much smaller amounts. Some minerals, such as chromium, selenium and iodine, are required in tiny amounts.
Minerals move along the food chain from the soil to the human diet. People receive their supply of minerals either from plants (plants extract minerals from the soil, which means that the quality of the soil has a bearing on the mineral content of food) or indirectly from animal products.
Minerals occur in minute quantities in the human body, and yet they are essential for a huge range of body processes – they help to build teeth, bones and connective tissue; they balance the chemicals in the blood and regulate the acid-base balance in bodily fluids; they influence the secretion of glands; they enable muscle contraction; and they are important in transmitting messages through the nervous system.
Various nutrients affect the body’s ability to absorb minerals: vitamin D, for example, is essential for the effective absorption of calcium, and vitamin C helps the body to absorb iron, particularly the iron found in plant foods. The body can maintain its own mineral balance over short periods of time, but if it does not receive an adequate intake from the diet, it will draw from mineral stores that are laid down in the muscles, the liver and even the bones.
If the dietary intake of minerals is too high, the excess is usually excreted, preventing any damage to the body. Although some nutritionists believe that the average Western diet is a poor source of minerals, and that supplements are necessary, other experts fear that the overuse of supplements can create an imbalance, because a large amount of one mineral may interfere with the absorption of another.
‘Phyto’ is Greek for plant, and the word ‘phytonutrients’ (or phytochemicals) is fairly new in the language of nutrition. It is an umbrella term for the protective compounds that are found in fruit, vegetables, herbs and other whole foods. Phytonutrients are active compounds that appear to have a profound effect on the maintenance of health and the prevention of degenerative diseases such as heart disease and cancer. Research into how phytonutrients work and their role in the body is accumulating, but it has long been known that people who eat a diet rich in fruit and vegetables have a lower incidence of cancer.
More than 100 phytonutrients have been identified, but it is estimated that there are several thousand. They include carotenoids, flavonoids, phyto-oestrogens, indoles and organosulphur compounds.
The yellow and orange pigments that occur in some fruits and vegetables are referred to as carotenoids. These protective phyto-nutrients are believed to help reduce the risk of heart disease and some forms of cancer. They include betacarotene (found in orange and yellow fruit and vegetables such as carrots and apricots, as well as broccoli and leafy greens); lycopene (found in tomatoes and red grapefruit); lutein (found in spinach) and zeanxanthin (found in corn, spinach, cabbage, broccoli and peas).
The characteristic colours, aromas and tastes of fruit and vegetables, such as berries, grapes, citrus fruits and onions, are provided by flavonoids. These colourful pigments are thought to bring several health benefits, including increased protection against heart disease and damage by free radicals -unstable molecules that can damage the body. They also help the liver to dispose of toxic materials and they may help to inhibit the formation of tumours.
Soya beans and other pulses contain compounds known as phyto-oestrogens. The consumption of soya is associated with a lower risk of oestrogenpromoted cancers, such as breast cancer, and may help to reduce the risk of heart disease.
Vegetables from the ‘cruciferous’ family (so-named because of their cross-shaped leaf stems) contain phytonutrients called indoles. These substances, found in broccoli, Brussels sprouts, cabbage, kale, cauliflower, cress and turnips, for example, have a protective effect, and may help to reduce the risk of cancer of the breast and colon.
The pungent phytonutrients found in the allium vegetables (including garlic, onions a and leeks) are known as organosulphur compounds. These substances are believed to have several beneficial effects on the body: these include lowering blood cholesterol; blocking the production of inflammatory agents; strengthening the immune system and helping the liver to detoxify potentially harmful substances. Organosulphur compounds are believed to help block damage from free radicals, thereby increasing the body’s resistance to cancer.
ANTIOXIDANTS AND FREE RADICALS
Antioxidants are protective nutrients found mainly in fresh fruit and vegetables; it is widely believed that they help to maintain long-term good health and protect the body from some of the effects of ageing and disease. They are compounds that prevent or delay the oxidation of sensitive molecules that occur in the body and in foods. The principal antioxidants are the vitamins C and E, and betacarotene. The last is turned into vitamin A by the body. Other antioxidants obtained from food include flavonoids and the minerals selenium, zinc, iron, manganese and copper (zinc, iron, manganese and copper are needed for the synthesis of the antioxidant enzyme superoxide dismutase).
Experts believe that antioxidants may help to protect the body’s cells from the damaging effects of free radicals. Free radicals are unstable molecules that are a byproduct of bodily reactions involving oxygen. For example, the breakdown of nutrients and the generation oi energy involves the production of free radicals. Free radicals can also be produced by external factors, such as pollution, cigarette smoke, fried and burnt food and sunlight.
Many scientists believe that free radicals play a part in the development of degenera-tive conditions such as heart disease, cataracts and certain cancers, as well as signs of ageing, such as wrinkles. Many people take antioxidant supplements in an attempt to prevent cell damage and protect themselves against illness and ageing, but it is important to include these nutrients in a varied diet.