Vitamin k Health Dictionary

A term applied to a group of substances which exist in minute quantities in natural foods, and which are necessary to normal nutrition, especially in connection with growth and development. Some – A, D, E and K – are fat-soluble and can be stored in the body. The remainder – C, B12 and other members of the B complex – are water-soluble and are quickly excreted. Most vitamins have now been synthesised. When they are absent from the food, defective growth takes place in young animals and children, and in adults various diseases arise; whilst short of the production of actual disease, persistent deprivation of one or other vitamin is apt to lead to a state of lowered general health. Certain de?ciencies in DIET have long been known to be the cause of SCURVY, BERIBERI, and RICKETS. A diet containing foods such as milk, eggs, butter, cheese, fat, ?sh, wholemeal bread, fresh vegetables and fruit should contain su?cient vitamins. Details of the various vitamins are given in APPENDIX 5: VITAMINS.... vitamin

A fat-soluble vitamin essential for normal growth, for the formation of bones and teeth, for cell structure, for night vision, and for protecting the linings of the respiratory, digestive, and urinary tracts against infection.

Vitamin A is absorbed by the body in the form of retinol. This is found in liver, fish-liver oils, egg yolk, dairy produce, and is added to margarines. Carotene, which the body converts into retinol, is found in various vegetables and fruits.

Vitamin A deficiency is rare in developed countries. In most cases, it is due to malabsorption. Vitamin A deficiency may also result from long-term treatment with certain lipid-lowering drugs. Deficiency is common in some developing countries due to poor diet. The first symptom of deficiency is night blindness, followed by dryness and inflammation of the eyes (see xerophthalmia), keratomalacia, and eventually blindness. Deficiency also causes reduced resistance to infection, dry skin, and, in children, stunted growth.

Prolonged excessive intake of vitamin A can cause headache, nausea, loss of appetite, skin peeling, hair loss, and irregular menstruation. In severe cases, the liver and spleen become enlarged. Excessive intake during pregnancy may cause birth defects. In infants, excessive intake may cause skull deformities, which disappear if the diet is corrected.

The drug tretinoin (a derivative of vitamin A) is used to treat severe acne.... vitamin a

See vitamin B; vitamin B complex.... vitamin b

A water-soluble vitamin that plays an essential role in the activities of various enzymes. Vitamin C is important for the growth and maintenance of healthy bones, teeth, gums, ligaments, and blood vessels; in the production of certain neurotransmitters and adrenal gland hormones; in the response of the immune system to infection; in wound healing; and in the absorption of iron.

The main dietary sources are fruits and vegetables. Considerable amounts of vitamin C are lost when foods are processed, cooked, or kept warm.

Mild deficiency of vitamin C may result from a serious injury or burn, major surgery, the use of oral contraceptives, fever, or continual inhalation of carbon monoxide (from traffic fumes or tobacco smoke). It may cause weakness, general aches, swollen gums, and nosebleeds. More serious deficiency is usually caused by a very restricted diet. Severe deficiency leads to scurvy and anaemia.

If the daily dose of vitamin C exceeds about 1g, it may cause nausea, stomach cramps, diarrhoea, or kidney stones

(see calculi, urinary tract).... vitamin c

The collective term for a group of substances that help to regulate the balance of phosphate and calcium in the body, aid calcium absorption in the intestine, and promote strong bones and teeth.

Good sources include oily fish, liver, and egg yolk; vitamin D is also added to margarines. In the body, vitamin D is synthesized by the action of ultraviolet light on a particular chemical in the skin.

Deficiency may occur in people with a poor diet, in premature infants, and in those deprived of sunlight. It can also result from malabsorption. Other causes include liver or kidney disorders and some genetic defects. Prolonged use of certain drugs, such as phenytoin, may also lead to deficiency. Deficiency in young children causes rickets; long-term deficiency in adults leads to osteomalacia.Excessive intake of vitamin D may lead to hypercalcaemia and abnormal calcium deposits in the soft tissues, kidneys, and blood vessel walls.

In children, it may cause growth retardation.... vitamin d

The collective term for a group of substances that are essential for normal cell structure, for maintaining the activities of certain enzymes, and for the formation of red blood cells. Vitamin E also protects the lungs and other tissues from damage by pollutants and is believed to slow aging of cells. Sources include vegetable oils, nuts, meat, green vegetables, cereals, and egg yolk.

Dietary deficiency is rare; deficiency is most common in people with malabsorption, certain liver disorders, and in premature infants. It leads to the destruction of red blood cells, which eventually leads to anaemia. In infants, deficiency causes irritability and oedema.

Prolonged excessive intake of vitamin E may cause abdominal pain, nausea, and diarrhoea.

It may also reduce intestinal absorption of vitamins A, D, and K.... vitamin e

A water-soluble vitamin that plays a vital role in the activities of several enzymes in the body. Vitamin B12 is important in the production of the genetic material of cells (and thus in growth and development), in the production of red blood cells in bone marrow, in the utilization of folic acid and carbohydrates in the diet, and in the functioning of the nervous system. Foods rich in vitamin B12 include liver, kidney, chicken, beef, pork, fish, eggs, and dairy products.Deficiency is almost always due to the inability of the intestine to absorb the vitamin, usually as a result of pernicious anaemia (see anaemia, megaloblastic). Less commonly, deficiency may result from gastrectomy, malabsorption, or veganism. The effects of vitamin B12 deficiency are megaloblastic anaemia, a sore mouth and tongue, and symptoms caused by damage to the spinal cord, such as numbness and tingling in the limbs. There may also be depression and memory loss. A high intake of vitamin B12 has no known harmful effects.... vitamin b12

A group of watersoluble vitamins comprising thiamine (vitamin B1), riboflavin (vitamin B2), niacin, pantothenic acid, pyridoxine (vitamin B6), biotin (vitamin H), and folic acid. Vitamin B12 is discussed above.

Thiamine plays a role in the activities of various enzymes involved in the utilization of carbohydrates and thus in the functioning of nerves, muscles, and the heart. Sources include whole-grain cereals, wholemeal breads, brown rice, pasta, liver, kidney, pork, fish, beans, nuts, and eggs.

Those susceptible to deficiency include elderly people on a poor diet, and people who have hyperthyroidism, malabsorption, or severe alcohol dependence. Deficiency may also occur as a result of severe illness, surgery, or injury.

Mild deficiency may cause tiredness, irritability, and loss of appetite. Severe deficiency may cause abdominal pain, constipation, depression, memory impairment, and beriberi; in alcoholics, it may cause Wernicke–Korsakoff syndrome. Excessive intake is not known to cause harmful effects.

Riboflavin is necessary for the activities of various enzymes involved in the breakdown and utilization of carbohydrates, fats, and proteins; the production of energy in cells; the utilization of other B vitamins; and hormone production by the adrenal glands. Liver, whole grains, milk, eggs, and brewer’s yeast are good sources. People who are susceptible to riboflavin deficiency include those taking phenothiazine antipsychotic drugs, tricyclic antidepressant drugs, or oestrogen-containing oral contraceptives, and those with malabsorption or severe alcohol dependence. Riboflavin deficiency may also occur as a result of serious illness, surgery, or injury.

Prolonged deficiency may cause soreness of the tongue and the corners of the mouth, and eye disorders such as amblyopia and photophobia.

Excessive intake of riboflavin is not known to have any harmful effects.

Niacin plays an essential role in the activities of various enzymes involved in the metabolism of carbohydrates and fats, the functioning of the nervous and digestive systems, the manufacture of sex hormones, and the maintenance of healthy skin. The main dietary sources are liver, lean meat, fish, nuts, and dried beans. Niacin can be made in the body from tryptophan (an amino acid). Most cases of deficiency are due to malabsorption disorders or to severe alcohol dependence. Prolonged niacin deficiency causes pellagra. Excessive intake is not known to cause harmful effects.

Pantothenic acid is essential for the activities of various enzymes involved in the metabolism of carbohydrates and fats, the manufacture of corticosteroids and sex hormones, the utilization of other vitamins, the functioning of the nervous system and adrenal glands, and growth and development. It is present in almost all vegetables, cereals, and animal foods. Deficiency of pantothenic acid usually occurs as a result of malabsorption or alcoholism, but may also occur after severe illness, surgery, or injury. The effects include fatigue, headache, nausea, abdominal pain, numbness and tingling, muscle cramps, and susceptibility to respiratory infections. In severe cases, a peptic ulcer may develop. Excessive intake has no known harmful effects.Pyridoxine aids the activities of various enzymes and hormones involved in the utilization of carbohydrates, fats, and proteins, in the manufacture of red blood cells and antibodies, in the functioning of the digestive and nervous systems, and in the maintenance of healthy skin. Dietary sources are liver, chicken, pork, fish, whole grains, wheatgerm, bananas, potatoes, and dried beans. Pyridoxine is also manufactured by intestinal bacteria. People who are susceptible to pyridoxine deficiency include elderly people who have a poor diet, those with malabsorption or severe alcohol dependence, or those who are taking certain drugs (including penicillamine and isoniazid). Deficiency may cause weakness, irritability, depression, skin disorders, inflammation of the mouth and tongue, anaemia, and, in infants, seizures. In very large amounts, pyridoxine may cause neuritis.

Biotin is essential for the activities of various enzymes involved in the breakdown of fatty acids and carbohydrates and for the excretion of the waste products of protein breakdown. It is present in many foods, especially liver, peanuts, dried beans, egg yolk, mushrooms, bananas, grapefruit, and watermelon. Biotin is also manufactured by bacteria in the intestines. Deficiency may occur during prolonged treatment with antibiotics or sulphonamide drugs. Symptoms are weakness, tiredness, poor appetite, hair loss, depression, inflammation of the tongue, and eczema. Excessive intake has no known harmful effects.

Folic acid is vital for various enzymes involved in the manufacture of nucleic acids and consequently for growth and reproduction, the production of red blood cells, and the functioning of the nervous system. Sources include green vegetables, mushrooms, liver, nuts, dried beans, peas, egg yolk, and wholemeal bread. Mild deficiency is common, but can usually be corrected by increasing dietary intake. More severe deficiency may occur during pregnancy or breastfeeding, in premature or low-birthweight infants, in people undergoing dialysis, in people with certain blood disorders, psoriasis, malabsorption, or alcohol dependence, and in people taking certain drugs. The main effects include anaemia, sores around the mouth, and, in children, poor growth. Folic acid supplements taken just before conception, and for the first 12 weeks of pregnancy, have been shown to reduce the risk of a neural tube defect.... vitamin b complex

A group of dietary preparations containing 1 or more vitamins. Most healthy people who have a balanced diet do not need them. Supplements are used to treat diagnosed vitamin deficiency. They are also given to prevent vitamin deficiency in susceptible people, such as those who have increased requirements (for example, women who are pregnant or breastfeeding); those who follow a restricted diet (in veganism, for example); those with severe alcohol dependence; and people who have malabsorption, liver disorders, kidney disorders, or another serious illness or injury. In addition,vitamins are used to treat certain disorders.

For example, vitamin D is used to treat osteomalacia, and vitamin A derivatives are given for severe acne.... vitamin supplements