Vitamins are substances which, in small amounts, are necessary to sustain life. They must be obtained from food as they are either not made in the body at all, or are not made in sufficient quantities for growth, vitality and well-being. A deficiency of a particular vitamin causes disease symptoms which can only be cured by that vitamin.
Vitamins are chemically unrelated substances and all are organic. Organic substances are those that contain carbon and come from materials that are living, such as plants and animals, or that were once living, for example petroleum or coal.
It is impossible to sustain life without all the essential vitamins.
What Vitamins Do
Vitamins have many functions and influence the health of nearly every organ in the body. Their combination with other substances such as minerals, proteins and enzymes brings about certain chemical reactions. Individual vitamins have specific functions which vary widely and can overlap. They are involved in growth, the ability to produce healthy offspring and the maintenance of health. They play a role in metabolism, enabling the body to use other essential nutrients such as carbohydrates, fats, proteins and minerals. Vitamins are important for a normal appetite, in digestion, mental alertness and resistance to bacterial infections.
In addition to satisfying the body’s daily needs and preventing deficiency diseases, vitamins have several therapeutic effects. For example, niacin can be used to lower cholesterol and vitamin A derivatives can be used to treat acne. Large doses of vitamins may slow, or even reverse many diseases previously thought an inevitable part of aging, such as cancer, heart disease, osteoporosis, impaired immunity, nerve degeneration and other chronic health problems.
In the USA the following are officially listed as vitamins:
The B vitamin complex containing:
Vitamin B1 (thiamin)
Vitamin B2 (riboflavin)
Vitamin B3 (niacin)
Vitamin B6 (pyridoxine)
Vitamin B12 (cobalamin)
There are other substances whose vitamin status has not been established. Some researchers consider these to be vitamins but this is not generally accepted. Such substances include choline, inositol, para-aminobenzoic acid (PABA) and coenzyme Q10.
Vitamins are usually divided into two categories: fat soluble and water soluble.
Vitamins A, D, E and K are fat soluble. They require an adequate supply of minerals and fats to be absorbed in the digestive system and are stored in the liver. The remaining vitamins are water soluble with any excess being excreted in the urine. These need to be replenished frequently.