By Asma B Omer
VITAMINS
Until the beginning of the 20th century, it was thought that the only components of the diet essential for health, growth and reproduction were pure proteins, fats, carbohydrate and some inorganic elements such as Calcium, Phosphorus and Magnesium.
This view changed when it was found that additional materials also occur in the diet - the vitamins. Although only needed in minute amounts, vitamins are essential to health. They are divided into two groups (a) fat-soluble and (b) water-soluble. The first group includes vitamins A, D, E and K. The second group encompasses the B-complexes and vitamin C.
The absence of a vitamin from the diet or its presence in insufficient quantities can lead to both general and specific deficiency symptoms. Classic deficiency diseases such as rickets, scurvy and beriberi, no longer exist in modern societies, but subclinical deficiency, which can only be detected via a blood test, are not uncommon and could be responsible for a number of today's degenerative diseases. Conversely, the excessive intake of vitamins, either from large doses of vitamin supplements or very unusual diets cannot be ruled out. The excessive intake of the water-soluble vitamins, albeit not desirable, has little effect as they are rapidly excreted in the urine.
In contrast, a high intake of fat-soluble vitamins can be dangerous, as the body cannot get rid off them in the same way as the B-vitamins. Instead, they accumulate in the body (mainly in the liver and spleen).
Because of the risk of vitamin toxicity, especially that of A, D, E and K, it is advisable to read the label and take these supplements as indicated. Seeking advice from appropriate sources is important, especially for those under medical supervision and/or taking prescribed medication. This might help to avoid some of the adverse effects of duplication and prolonged usage.
THE ANTIOXIDANTS
Beta-carotene (a raw form of vitamin A), vitamin C and vitamin E are among the many compounds in food that have antioxidant properties. These antioxidants help to counter the damaging effects of reactive oxygen species, called free radicals. Free radicals are generally produced by the body's normal metabolic processes, but are scavenged and disposed of in a controlled manner by the body's sophisticated defence system. If they are left to accumulate, they can damage key cellular molecules such as DNA and cell membranes. Cells with damaged DNA may be more prone to developing cancer.
Free radicals can also readily oxidise polyunsaturated fatty acids, leading to rancidity. In cell membranes, the oxidation of polyunsaturated fatty acids can also damage the body's cells. Oxidation of LDL cholesterol may play a part in the formation of plaques, which gradually build up in the walls of the blood vessels. This leads to the thickening and narrowing of the arteries and eventually raised blood pressure and heart disease.
Those who consume appreciable quantities of orange and yellow fruits and dark green or orange vegetables seem to be less prone to some forms of cancer. B-carotene may play a role in the body's natural defence mechanism against cancer by helping to destroy free radicals and regenerating vitamin E. Similarly, vitamin C may work directly by destroying free radicals or indirectly by helping to reactivate the most powerful natural antioxidant - vitamin E. Alpha-tocopherol, the most potent antioxidant vitamin, can help prevent the oxidation of LDL cholesterol and the formation of free radicals, and in turn contribute to the prevention of coronary heart disease. Other groups of antioxidants are continually being discovered, including the flavinoids such as those found in red wine, green tea extract, broccoli and tomato. Clearly, all of these antioxidants have a role to play. They work like armour in a very sophisticated and complicated manner, with one antioxidant complementing the role of another. This again illustrates the importance of having a varied and balanced diet, as no single food (with the exception of human milk) will provide all the materials required for optimum health.
VITAMINS
Until the beginning of the 20th century, it was thought that the only components of the diet essential for health, growth and reproduction were pure proteins, fats, carbohydrate and some inorganic elements such as Calcium, Phosphorus and Magnesium.
This view changed when it was found that additional materials also occur in the diet - the vitamins. Although only needed in minute amounts, vitamins are essential to health. They are divided into two groups (a) fat-soluble and (b) water-soluble. The first group includes vitamins A, D, E and K. The second group encompasses the B-complexes and vitamin C.
The absence of a vitamin from the diet or its presence in insufficient quantities can lead to both general and specific deficiency symptoms. Classic deficiency diseases such as rickets, scurvy and beriberi, no longer exist in modern societies, but subclinical deficiency, which can only be detected via a blood test, are not uncommon and could be responsible for a number of today's degenerative diseases. Conversely, the excessive intake of vitamins, either from large doses of vitamin supplements or very unusual diets cannot be ruled out. The excessive intake of the water-soluble vitamins, albeit not desirable, has little effect as they are rapidly excreted in the urine.
In contrast, a high intake of fat-soluble vitamins can be dangerous, as the body cannot get rid off them in the same way as the B-vitamins. Instead, they accumulate in the body (mainly in the liver and spleen).
Because of the risk of vitamin toxicity, especially that of A, D, E and K, it is advisable to read the label and take these supplements as indicated. Seeking advice from appropriate sources is important, especially for those under medical supervision and/or taking prescribed medication. This might help to avoid some of the adverse effects of duplication and prolonged usage.
THE ANTIOXIDANTS
Beta-carotene (a raw form of vitamin A), vitamin C and vitamin E are among the many compounds in food that have antioxidant properties. These antioxidants help to counter the damaging effects of reactive oxygen species, called free radicals. Free radicals are generally produced by the body's normal metabolic processes, but are scavenged and disposed of in a controlled manner by the body's sophisticated defence system. If they are left to accumulate, they can damage key cellular molecules such as DNA and cell membranes. Cells with damaged DNA may be more prone to developing cancer.
Free radicals can also readily oxidise polyunsaturated fatty acids, leading to rancidity. In cell membranes, the oxidation of polyunsaturated fatty acids can also damage the body's cells. Oxidation of LDL cholesterol may play a part in the formation of plaques, which gradually build up in the walls of the blood vessels. This leads to the thickening and narrowing of the arteries and eventually raised blood pressure and heart disease.
Those who consume appreciable quantities of orange and yellow fruits and dark green or orange vegetables seem to be less prone to some forms of cancer. B-carotene may play a role in the body's natural defence mechanism against cancer by helping to destroy free radicals and regenerating vitamin E. Similarly, vitamin C may work directly by destroying free radicals or indirectly by helping to reactivate the most powerful natural antioxidant - vitamin E. Alpha-tocopherol, the most potent antioxidant vitamin, can help prevent the oxidation of LDL cholesterol and the formation of free radicals, and in turn contribute to the prevention of coronary heart disease. Other groups of antioxidants are continually being discovered, including the flavinoids such as those found in red wine, green tea extract, broccoli and tomato. Clearly, all of these antioxidants have a role to play. They work like armour in a very sophisticated and complicated manner, with one antioxidant complementing the role of another. This again illustrates the importance of having a varied and balanced diet, as no single food (with the exception of human milk) will provide all the materials required for optimum health.
