Vitamin B complex

A group of watersoluble vitamins comprising thiamine (vitamin B), riboflavin (vitamin B), niacin, pantothenic acid, pyridoxine (vitamin B), 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.