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Vitamins are nutrients required in small amounts to maintain life. Vitamins are called essential because they cannot be made by the human body. They must be obtained from foods or supplements.

What food source is the nutrient found in? 
Vitamins are organic compounds. They are rich in carbon. Vitamins are found in all the organic components of diets. This includes everything eaten from plant or animal sources. Unlike protein, fat and carbohydrate, which are the main ingredients of all foods, vitamins occur in much smaller amounts in food.

How does the nutrient affect the body? 
Vitamins are important to many vital functions in the body. One of their main roles is to act as enzymes or enzyme helpers. Enzymes act like keys that turn on reactions in the body. Every reaction has a distinct enzyme to start the process.

The word vitamin was made up in the early 1900s after the first vitamin, thiamine or B1, was discovered. Some of the harmful diseases of the past century were caused by vitamin deficiencies. These included beriberi, rickets and scurvy. Generally, such diseases can be reversed by just taking the missing vitamin. Because of improvements in understanding health, nutrition and vitamins, these deficiency diseases are very rare.

The Recommended Dietary Intakes (RDI) are currently under review. In the past, the guidelines were concerned with preventing deficiency diseases like beriberi and scurvy. Now scientists are learning how vitamins may help prevent disease. Future guidelines will reflect this information.

Vitamins are divided into two groups: fat soluble and water soluble. The fat-soluble vitamins are A, D, E, and K. These vitamins dissolve in fat and are transported by fat. They are found in fatty foods, such as dairy foods, fat and oils and the fat-containing parts of grains and vegetables.

Water-soluble vitamins dissolve in water-based fluids. These include the eight B vitamins, B1, B2, B3, B6, B12, folate, biotin and pantothenic acid, and vitamin C. Water-soluble vitamins are more common in fruits, vegetables and grains. Because these vitamins dissolve in water, care must be used during food preparation to keep the vitamins from dissolving into cooking water. For example, boiled vegetables lose a lot of their water-soluble vitamins to the cooking water. Steaming vegetables helps keep the vitamins intact. Microwaving uses less water as well.

Most vitamins are safe when taken as low dose supplements. Some can cause problems when taken in excess, particularly the fat-soluble vitamins, which tend to be stored in fat rather than excreted in urine like the water-soluble vitamins.

When a nutrient is supplemented at levels several times the RDI, it is called a megadose. Supplementing at RDI levels generally mimics levels that could be obtained through food. Megadoses of vitamins are considered therapeutic, in some cases acting more like a drug than a nutrient. Megadoses are not always beneficial or safe.

A number of scientists believe that megadosing vitamin E may protect the heart from some diseases. There are many claims about the benefits of megadosing different vitamins. There is not much good research that supports the claims. Megadoses of vitamins C and E have been the most widely studied, with mixed results. People interested in taking megadoses of vitamins or minerals should discuss it with a doctor. For more information on recommended safe and adequate intakes of specific vitamins, see articles under those headings.

Author: Clare Armstrong, MS, RD
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 7/03/2005
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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