Vitamins are organic compounds that are essential, in small quantities in our food, for life and good health. They play important roles in many biochemical processes, but they are not used directly for energy or for the material of body tissues. (Minerals are also important in our diet. But minerals are just chemical elements, not organic molecules.)
The word "vitamine" was created in 1912 by biochemist Casimir Funk, who discovered vitamins. He believed that they were all amines (containing the —NH2 group) that were vital to health. Although these "vital amines" are all vital to our health, only some of them are actually amines.
There are two broad categories of vitamins. The fat-soluble vitamins (vitamins A, D, E, and K) are more soluble in fats, hydrocarbons, and nonpolar solvents than they are in water. The water-soluble vitamins include vitamin C (ascorbic acid) and the B complex of vitamins. The eight vitamins in the B complex are thiamine (B1), riboflavin (B2), pyridoxine (B6), cobalamin (B12), biotin, folic acid, niacin, and pantothenic acid.
Vitamin Structures and Functions
The table below shows the structures of these vitamins and describes their functions.| WATER-SOLUBLE
VITAMINS | STRUCTURE
(Note that water-soluble vitamins have polar molecules.) | FUNCTION |
| Ascorbic Acid
(Vitamin C) | Strong blood vessels, collagen maintenance, resistance to infection, and healthy gums | |
| Biotin | Carbohydrate, fat, and protein metabolism, formation of fatty acids, utilization of B vitamins | |
| Cobalamin
(Vitamin B12) | Carbohydrate, fat, and protein metabolism, maintenance of nervous system, blood cell formation | |
| Folic acid
Folate Folacin | Red blood cell formation, protein metabolism, growth and cell division | |
| Niacin
Nicotinic Acid | Carbohydrate, fat, and protein metabolism, health of digestive system, blood circulation, nerve function, appetite | |
| Pantothenic Acid | Convertion of nutrients into energy, vitamin utilization, nerve function | |
| Pyridoxine
Pyridoxal Pyridoxamine (Vitamin B6) | Carbohydrate and protein metabolism, formation of antibodies, red blood cells, nerve function | |
| Riboflavin
(Vitamin B2) | Carbohydrate, fat, and protein metabolism, needed for cell respiration, mucous membranes | |
| Thiamine
(Vitamin B1) | Carbohydrate metabolism, appetite maintenance, nerve function, growth & muscle tone | |
| FAT-SOLUBLE
VITAMINS | STRUCTURE
(Note that fat-soluble vitamins have nonpolar molecules.) | FUNCTION |
| Cholecalciferol
(Vitamin D3) | Calcium and phosphorus metabolism (bone and tooth formation) | |
| Retinol
Carotene | Growth and repair of body tissue, immune functions, night vision | |
| alpha-Tocopherol | Protects cell membranes and red blood cells from oxidation, may be active in immune function | |
| Vitamin K | Formation of blood clotting agents and bone |
Dietary Sources of Vitamins
Information on dietary sources for the various vitamins is listed in the table below.| WATER-SOLUBLE
VITAMINS | DIETARY SOURCE | |||||||||||||||
| Ascorbic Acid
(Vitamin C) | Fruits (especially citrus) and vegetables | |||||||||||||||
| Biotin | Various foods | |||||||||||||||
| Cobalamin
(Vitamin B12) | All foods of animal origin | |||||||||||||||
| Folic acid
Folate Folacin | Meat, leafy green vegetables, citrus fruits and juices, legumes, and whole grain products | |||||||||||||||
| Niacin
Nicotinic Acid | Meat, legumes, and grains | |||||||||||||||
| Pantothenic Acid | virtually all foods |
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