Features and sources of vitamins and minerals
Vitamin D
Vitamin D is essential for the absorption of Calcium and Phosphorus by the body. Deficiency of Vitamin D causes rickets (characteristic bow legs) in the young and osteomalacia in those whose bones have stopped growing.
Sources: Many of us make enough Vitamin D through the action of sunlight
on our skin. However there are certain vulnerable groups who may have insufficient
exposure to sunlight, e.g. someone who is bed bound or ill or who wears
a complete UV block all year round. These people need to ensure they get
enough Vitamin D in their diet from fortified milk, oily fish, eggs, fortified
breakfast cereal and margarine.
Calcium
Calcium is a mineral which helps to build and maintain a strong skeleton . We tend to think of our bones as a dead and fixed part of our bodies but, in fact, they are in a state of continuous change. New bone is constantly being formed and old bone lost. As a result our bones need constant nourishment and Calcium.
Sources: The best sources of Calcium are milk, cheese and yogurt. Low fat versions of these foods contain a similar amount of Calcium except cottage cheese and fromage frais. Other foods which contain Calcium include green vegetables, bread, nuts and beans. However these foods also contain other substances which bind to the Calcium and make it more difficult to absorb.
Vitamin C
Vitamin C has many different functions. It helps to build tough connective tissues such as those found in the blood vessels walls of the circulatory system. It also works as an antioxidant, protecting tissues against attack and damage by free radicals.
Deficiency: Lack of Vitamin C increases the exposure of the mouth and gums to infection and slows down the rate at which wounds and fractures heal. The presence of Vitamin C in the diet promotes the absorption of iron from foods other than meat. This is very important for vegetarians who are avoiding this single and best source of iron in the diet.
Sources: Vitamin C occurs mainly in foods of plant origin. Citrus fruits (oranges and grapefruit) and their juices, potatoes and green vegetables supply us with most of our Vitamin C requirement.
Iron
Iron is particularly important in young people because of the increases in lean body mass, blood volume and haemoglobin which occur in both sexes and to replace menstrual losses in girls.
Deficiency: Some young women in particular can become deficient in iron, especially if they lose a lot of blood in heavy periods. Symptoms of iron deficiency anaemia include tiredness, loss of appetite, irritability, paleness and a general feeling of being run down.
Sources: Meat, fish, chicken, wholemeal bread and breakfast cereals, eggs, green vegetables and dried fruit are the main sources of iron. Meat contains haem iron whereas most other iron containing foods, such as green vegetables contain non haem iron. The presence of Vitamin C in the diet can promote the absorption of non haem iron.
Vitamin A
Vitamin A is essential for maintenance of good skin and also for normal growth and development. Deficiency will slow down growth and may lead to disorders of the skin and cause disturbances of vision such as night blindness, which makes it difficult to see in a dim light.
Sources of Vitamin A include whole milk and fortified milk, butter, margarine, eggs, carrots, dark green leafy vegetables and liver. Low fat dairy products have very little Vitamin A because this fat soluble vitamin is removed along with the fat.
Vitamin E
Vitamin E deficiency leading to disease in adults is unknown. However vitamin E has antioxidant properties and it is thought to have a major protective role against tissue damage caused by pollutants and harmful chemicals. Many studies are investigating the suggestion that it may inhibit certain cancers.
Sources: Most plant tissues contain some Vitamin E and vegetable oils especially wheatgerm oil are good sources. Other sources include wholegrain breakfast cereals and breads, eggs and dark green leafy vegetables.
Vitamin B12
Vitamin B12 plays a part in the complex process of cell division in the body. It is especially important in conjunction with folic acid and iron, for the formation of red blood cells. It is also involved in the formation of the protective sheath of myelin which surrounds each nerve fibre.
Deficiency of Vitamin B12 (cobalamin or cobalt): Vegans, who abstain completely from foods of animal origin, including dairy produce, may suffer from a deficiency which can interfere with red blood cell formation and the production of the myelin tube or sheath which surrounds each nerve fibre. Some people who are unable to absorb Vitamin B12 from the foods they eat suffer from a serious disease known as pernicious anaemia, in which extreme anaemia is accompanied by degeneration of the nerve tracts in the spinal cord. It is caused by the absence of an intrinsic factor from the gut, which is essential for the absorption of Vitamin B12. It is not a deficiency disease because, if the intrinsic factor is absent, it will occur even when there is sufficient Vitamin B12 in the diet.
Sources: Vitamin B12 is found in a small amount in all animal tissues but it is absent from foods of vegetable origin. It is only required in minutes amounts and vegetarians usually obtain sufficient amounts from eggs and milk. However, vegans who abstain completely from foods of animal origin (including dairy foods) may suffer from a deficiency. Sources of Vitamin B12 include meat, meat products and offal, milk, cheese, fish eggs, Bovril.
Vitamin K
Vitamin K is essential for the normal clotting of blood. Without Vitamin K the liver is unable to make prothrombin which is the precursor of the blood clotting enzyme thrombin.
Sources: Vitamin K is present in most foods but green leafy vegetables are the richest source. Bacteria in the bowel are also able to make Vitamin K in additional to that in our food. In most cases the amount made available in this way is sufficient to meet our needs
Folic Acid
Folic Acid is involved in the production of nucleic acids and in the formation of red blood cells. A deficiency causes megaloblastic anaemia. Folic acid deficiency during pregnancy is likely to lead to a premature baby or low birthweight. If a woman's diet is deficient in folic acid before conception or during the early stages of pregnancy there is an increased risk that the baby will be born with neural tube defects such as spina bifida.
Sources: Folic acid is found in small amounts in a wide variety of foods, such as fortified breakfast cereals, bread, fruit and green vegetables, potatoes, offal and marmite.
Vitamin B6
Vitamin B6 is involved in protein metabolism, red blood cell formation and in maintaining a healthy nervous system. Since protein needs go up during pregnancy for foetal development, Vitamin B6 is a critical nutrient during this time.
Deficiency is very rare in man, but there is a lot of interest in the role of Vitamin B6 in the alleviation of pre-menstrual tension and mood swings. Unfortunately the results of these studies are inconclusive as yet.
Sources: The main sources of Vitamin B6 include meat, milk, potatoes and other vegetables.
Thiamin, Riboflavin, Niacin
Thiamin, Riboflavin, Niacin and Pantothenic acid are part of the B group of vitamins which each have distinctive roles, yet tend to function as a team. They act as co-factors in different enzyme systems in the body. These vitamins are needed for the steady release of energy from the carbohydrate and fat in food.
Deficiency of Thiamine: The deficiency disease, beriberi, is almost unknown in this country, but still occurs in Far Eastern countries, where the standard of living is very low. In these countries the main staple food is polished rice, from which the thiamine rich seedcoat has been removed.
Sources: Good sources of these B vitamins include meat and meat products, milk and milk products, bread and fortified breakfast cereals, potatoes and vegetables.
Magnesium
Magnesium is necessary for muscle tone and relaxation and is an important mineral in bone formation.
Deficiency: Magnesium deficiency can cause high blood pressure and, in extreme cases, heart attacks.
Sources: Good sources of magnesium include wholegrain cereal and bread, nuts and tea.
Sodium, Potassium and Chlorine
Sodium, Potassium and Chlorine are involved in the transmission of nerve impulses and muscle contraction, including the beating of the heart.
Deficiency of Potassium: A low potassium intake can cause high blood pressure or your heart to beat erratically, a condition known as arrhythmia.
Deficiency of Sodium Chloride: A deficiency of sodium chloride can cause muscle cramps and upset the water balance of the body.
Sources: Food sources include table and cooking salt, bread, cereal products, meat, fruit and vegetables.
Zinc
Zinc is a constituent of many enzymes and as such is essential to the body. Prolonged shortage of zinc can lead to retarded physical and mental development in young people.
Sources: The main sources of zinc include meat and meat products, milk and milk products, bread and cereal products.
Selenium
Selenium is an essential trace element and is an important barrier against oxidative tissue damage. Deficiency of selenium has been associated with abnormal muscular function.
Good sources of Selenium include fish, offal, meat, cheese, eggs, milk and cereal.