Vitamin B complex consists of several vitamins that are grouped together because of the loose similarities in their properties, distribution in natural sources, and physiological functions. All the B vitamins are soluble in water. Most of the B vitamins have been recognized as coenzymes, and they all appear to be essential in facilitating the metabolic processes of all forms of animal life. The complex includes B1 (thiamine), B2 (riboflavin), niacin (nicotinic acid), B6 (a group of related pyridines), B12 (cyanocobalamin), folic acid, pantothenic acid, and biotin.
Vitamin B1, or thiamine, helps the body convert carbohydrates into energy and helps in the metabolism of proteins and fats. Vitamin B1 deficiency affects the functioning of gastrointestinal, cardiovascular, and peripheral nervous systems. Beriberi and Wernicke-Korsakoff syndrome (often seen in alcoholics) are the primary diseases related to thiamine deficiency. General symptoms of beriberi include loss of appetite and overall lassitude, digestive irregularities, and a feeling of numbness and weakness in the limbs and extremities.
Vitamin B2, or riboflavin, is required to complete several reactions in the energy cycle. Reddening of the lips with cracks at the corners of the mouth, inflammation of the tongue, and a greasy, scaly inflammation of the skin are common symptoms of deficiency.
Niacin, or nicotinic acid, helps the metabolism of carbohydrates. Prolonged deprivation leads to pellagra, a disease characterized by skin lesions, gastrointestinal disturbance, and nervous symptoms.
A form of Vitamin B6 is a coenzyme for several enzyme systems involved in the metabolism of proteins, carbohydrates, and fats. No human disease has been found to be caused by a deficiency of this vitamin. Chronic use of large doses of vitamin B6 can create dependency and cause complications in the peripheral nervous system.
Vitamin B12, or cyanocobalamin, is a complex crystalline compound that functions in all cells, but especially in those of the gastrointestinal tract, the nervous system, and the bone marrow. It is known to aid in the development of red blood cells in higher animals. Deficiency most commonly results in pernicious anemia
Folic acid is necessary for the synthesis of nucleic acids and the formation of red blood cells. Folic-acid deficiency most commonly causes folic-acid-deficiency anemia. Symptoms include gastrointestinal problems, such as sore tongue, cracks at the corners of the mouth, diarrhea, and ulceration of the stomach and intestines. Large doses of folic acid can cause convulsions and other nervous-system problems.
Pantothenic acid promotes a large number of metabolic reactions essential for the growth and well-being of animals. Deficiency in experimental animals leads to growth failure, skin lesions, and graying of the hair. A dietary deficiency severe enough to lead to clear-cut disease has not been described in humans
Biotin plays a role in metabolic processes that lead to the formation of fats and the utilization of carbon dioxide. Biotin deficiency results in anorexia, nausea, vomiting, inflammation of the tongue, pallor, depression, and dermatitis.