A "vitamin" is also a pill that contains vitamins, eaten regularly to keep one healthy.
Fruits and vegetables are a source of vitamins
A vitamin is a chemical compound that is needed in small amounts for the human body to work correctly. They include Vitamin A, many B vitamins (like B1, B2, B3, B6, and B12), Vitamin C, Vitamin D, Vitamin E, and Vitamin K. For example, citrus fruits such as oranges and lemons contain vitamin C.
The term was coined in 1912 by biochemist Casimir Funk, who isolated a complex of micronutrients and proposed the complex be named vitamins. By convention, the word vitamin does not include other essential nutrients, such as certain minerals, essential fatty acids, and essential amino acids.
Thirteen vitamins are recognized at present. Vitamins are classified by their biological and chemical activity, and not their structure. Each vitamin name (the word vitamin followed by a letter) refers to a number of vitamer compounds which all show the same biological activity. For example, vitamin A refers to several different chemicals. Vitamers convert to the active form of the vitamin in the body. They are sometimes inter-convertible to one another as well.
The body does not make these chemicals. They come from other places, usually food. A short term lack of a certain vitamin is usually not a problem, because the body can store vitamins for a short time. Not having a certain vitamin for a longer period of time can lead to different diseases, depending on the vitamin. Probably the best-known of these diseases is scurvy, which results from not having enough Vitamin C. Beriberi and rickets are others.
Today, many drug companies make inexpensive pills that contain various vitamins. They help people avoid those diseases.
Vitamins can be either fat-soluble or water-soluble. Fat-soluble vitamins (A, D, E, and K) can be stored in the body, and are used when needed. Water-soluble ones only stay in the body for a short time.
Vitamins are a group of substances that are needed for normal cell function, growth, and development.
There are 13 essential vitamins. This means that these vitamins are required for the body to work properly. They are: