Vitamins

Vitamins are organic compounds (substances that contain carbon) found in food that all animals need in small amounts. Although they usually cannot be made by the body, they are essential to its proper functioning. Vitamins are not a source of energy, but instead serve to help enzymes (proteins that act as catalysts and speed up chemical reactions in living things) make important chemical reactions occur.

Vitamins are essential to life. Although all animals need them for proper metabolism (the chemical processes that take place in a living thing), different animals need different types or varying amounts. All animals need some vitamins in their systems, since most vitamins are necessary coenzymes. A coenzyme is something that helps an enzyme speed up a chemical reaction in the body. Specifically, it helps regulate the chemical reactions that take place inside an organism when an organism converts food into energy. Some enzymes cannot work at all by themselves and require a vitamin to do their job.

Vitamins are named by letters, and there are thirteen vitamins that have been identified as being necessary for human health. They are vitamins A, C, D, E, K and eight B vitamins. Since the B vitamins were originally thought to be one vitamin, they were first given different numbers, like B₁, B₂, etc. Later, all but B₆ and B₁₂ were given actual names. The deficiency, or lack, of one certain vitamin usually shows itself in a very specific condition that is described as a deficiency-related disease.

TYPES OF VITAMINS

There are two types of vitamins: water-soluble vitamins and fat-soluble vitamins. Something is soluble if it is capable of being dissolved. Fat-soluble vitamins are stored in the body in the fats and oils that are taken in. Water-soluble vitamins are not able to be stored, and any excess passes out of the body. Vitamins A, D, E, and K are fat-soluble vitamins. Vitamin A is essential for the sense of sight, and a lack of Vitamin A is a common cause of blindness in developing countries. Vitamin D is important for healthy bones and teeth (a lack causes the disease rickets), and is found mainly in fish and eggs. It is also formed in the skin when it is exposed to sunlight. Vitamin E plays a major role in the reproductive system, and Vitamin K helps the blood to clot.

FREDERICK GOWLAND HOPKINS

English biochemist Frederick Hopkins (1861–1947) discovered the existence of "accessory food factors"—now known as vitamins—which are needed in animal diets to maintain health and life. He also laid the foundation for the concept of essential amino acids (those that cannot be made by the body and must be supplied in the diet).

Frederick Hopkins was born in Sussex, England, and had an especially lonely and unhappy childhood being raised by a widowed mother and an unmarried uncle who ignored him. When he was seventeen, his uncle found him a job in the insurance business. Despite doing this for several years, he managed to take part-time courses at the University of London and eventually earned a degree in chemistry when he was twenty-seven. By then he had received a small inheritance and was able to attend medical school at Guy's Hospital in London. After receiving his medical degree at the age of thirty-three, he finally began his real career at Cambridge University when he was thirty-seven years old. Although a very late starter, Hopkins made up for lost time, and in 1900 made his first discovery in his area of dietary research. He found that rats fed only gelatin would not live and grow, despite the fact that gelatin was a protein. He then found that the important amino acid called tryptophan was missing in gelatin. Additional research revealed that tryptophan (as well as several other amino acids) could not be manufactured in the body. He discovered that this amino acid had to be supplied in the diet. In doing this, Hopkins thus laid the foundation for the concept of the essential amino acid, which was detailed by others a generation later.

Hopkins then went on to study diet and its effect on metabolism (all of the chemical processes that take place in a living thing). At this point in time, nutritional science was not very advanced, and most scientists believed that such diet-related diseases as scurvy, beriberi, or rickets were caused by some sort of toxic substances in food. Hopkins' research soon led him to have serious doubts about this thinking, and his experiments only confirmed this. He had already noticed that his laboratory rats failed to grow when fed a diet of artificial nutrients. However, those whose artificial nutrients contained a tiny amount of cow's milk grew rapidly. This led him to suspect that normal food must contain substances missing from the artificial nutrients that contained only pure fats, proteins, and carbohydrates. Hopkins never was able to isolate them or find out what these trace substances were, but in 1906 he wrote a paper in which he described them as "accessory food factors." He pointed out that whatever they were, they were obviously essential for growth. This paper is considered to be the first explanation of the concept of vitamins. In 1925, the young man who started life as an insurance man and whose determination got him his first teaching job at thirty-seven, was knighted and thereafter was called "Sir." Four years later he was awarded the Nobel Prize in physiology and medicine for being the first to suggest what became known as the "vitamin concept."

The other nine vitamins are water-soluble vitamins. Vitamin B₁ is called thiamin and is found in the outer layer of cereal grains. It helps break down carbohydrates (group of naturally occurring compounds that are essential sources of energy for all living things). B₂ is known as riboflavin and is necessary for cellular respiration (the breaking down of food into energy). B₃ is called niacin and also works in cellular respiration. B₅ is pantothenic acid which helps convert carbohydrates, fats, and proteins into energy. B₆ does not have a commonly used name, although it is technically called pyridoxine, and it helps break down fatty acids and amino acids (the building blocks of proteins). B₁₂ can be called cobalamin and helps make proteins. Biotin also is a B vitamin and is necessary for the formation of some fatty acids. Folic acid is needed to help make nucleic acids (genetic material). Finally, Vitamin C, also called ascorbic acid, is needed for healthy teeth, gums, and bones as well as for healing. While each of these thirteen vitamins plays a very specific role in the body, each also fills a more general need in promoting overall wellbeing or good health.

HOW TO OBTAIN VITAMINS

Most physicians say that the best way to get the right amounts of vitamins into our systems is to eat a regular balanced diet. This means that a variety of foods from each of the basic food groups (fats, carbohydrates, proteins, and minerals) should give people the relatively small amounts of the thirteen vitamins they need. Today, however, many people take vitamin supplements just to be sure they are getting enough. Recent trends in taking what are called megadoses of certain vitamins are more controversial, and some physicians warn that large doses can be dangerous. While some of the water-soluble vitamins people take are simply excreted in their urine, if they take too many fat-soluble vitamins they will not pass the body and can accumulate to harmful levels.

Humans' knowledge about vitamin deficiency diseases is fairly certain. For example, it is known that Vitamin C cures scurvy and Vitamin D can cure rickets. However, we do not yet fully understand all of the biochemical roles played by vitamins, nor are all of the interactions among vitamins and other nutrients known.

[See alsoMalnutrition; Nutrition ]