Vitamin

Vitamins are organic substances essential to human health. They are enzymes, complex proteins which act as catalysts for temperature sensitive biological reactions. Vitamins are also essential parts of hormones.

The term vitamin does not encompass other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids, nor is it used for the large number of other nutrients that merely promote health, but are not strictly essential.

Vegetables are an important source of vitamins

Types of Vitamins

Vitamins can be classified as either water soluble, which means they dissolve easily in water, or fat soluble, which means they are absorbed through the intestinal tract with the help of lipids.

In humans, there are thirteen vitamins, divided into two groups, the four fat-soluble vitamins (A, D, E and K) and the nine water-soluble vitamins (eight B vitamins and vitamin C).

Vitamin name	Chemical name	Solubility	Deficiency disease	Overdose	Estimated Average Minimum Daily Requirement (male, aged 19–30)
Vitamin A	Retinol	Fat	Night-blindness, Keratomalacia	7.5 mg	620 μg
Vitamin B1	Thiamine	Water	Beriberi	n/a	1000 μg
Vitamin B2 (G)	Riboflavin	Water	Ariboflavinosis	n/a	1100 μg
Vitamin B3 (PP)	Niacin	Water	Pellagra	2500 mg	12000 μg
Vitamin B5	Pantothenic acid	Water	Paresthesia	n/a	10000 μg
Vitamin B6	Pyridoxine	Water	n/a	400 mg	1100 μg
Vitamin B7 (H)	Biotin	Water	n/a	n/a	30 µg
Vitamin B9 (M)	Folic acid	Water		1 mg	320 μg
Vitamin B12	Cyanocobalamin	Water	Pernicious anemia	n/a	2 µg
Vitamin C	Ascorbic acid	Water	Scurvy	n/a	75000 μg
Vitamin D1–D4	Lamisterol, Ergocalciferol, Calciferol, Dihydrotachysterol, 7-dehydrositosterol	Fat	Rickets	1.25 mg	2 µg (for all Vitamin D)
Vitamin E	Tocopherol	Fat	n/a	33000 mg	12000 μg
Vitamin K	Naphthoquinone (not to be confused with Ketamine)	Fat	Bleeding diathesis	n/a	75 µg

Retinol (Vitamin A)

History

The value of eating certain foods to maintain health was recognized long before vitamins were identified. The ancient Egyptians knew that feeding a patient liver would help cure night blindness, now known to be caused by a vitamin A deficiency. In 1747, the Scottish surgeon James Lind discovered that citrus foods helped prevent scurvy, a particularly deadly disease in which collagen is not properly formed, and characterized by poor wound healing, bleeding of the gums, and severe pain. In 1753, Lind published his Treatise on the Scurvy. His recommendation of using lemons and limes to avoid scurvy was adopted by the British Royal Navy, resulting in the nickname Limey for sailors of that organization. His discovery, however, was not widely accepted by individuals; In the Royal Navy's Arctic expeditions in the 19th century, for example, it was widely believed that scurvy was prevented by good hygiene on board ship, regular exercise, and maintaining the morale of the crew, rather than by a diet of fresh food, so that Navy expeditions took all the amenities of 'sophisticated' society, like silk sheets, spices, expensive food and drink, and almost nothing of any use beyond the Arctic Circle. As a result, these expeditions continued to be plagued by scurvy and other deficiency diseases. At the time Robert Falcon Scott made his two expeditions to the Antarctic in the early 20th century, the prevailing medical theory was that scurvy was caused by "tainted" canned food.

In 1881, Russian surgeon Nikolai Lunin fed mice upon an artificial mixture of all the separate constituents of milk known at that time, namely the proteins, fats, carbohydrates, and salts. They died, while the mice fed by milk itself developed normally. He made a conclusion that "a natural food such as milk must therefore contain besides these known principal ingredients small quantities of unknown substances essential to life" [1] However, his conclusion was rejected by other researchers who were unable to reproduce his results. One difference was that he used table sugar (sucrose), while other researchers used milk sugar (lactose) which still contained small amounts of vitamin B.

In 1905, William Fletcher discovered that eating unpolished rice instead of polished helped prevent the disease beriberi. The following year, Frederick Hopkins postulated that foods contained "accessory factors"—in addition to proteins, carbohydrates, fats, etc.—that are necessary to the human body.

When Casimir Funk in 1912 isolated the water-soluble complex of micronutrients whose bioactivity Fletcher had identified, he proposed that it be named "Vitamine". Vita in Latin is life and the -amine suffix is for amine; at the time it was thought that all vitamins were amines. The name soon became synonymous with Hopkins' "accessory factors", and by the time it was shown that not all vitamins were amines, the word was already ubiquitous. In 1920, Jack Cecil Drummond proposed that the final "e" be dropped, to deemphasize the "amine" reference, after the discovery that vitamin C had no amine component, and the name has been "vitamin" ever since.

The reason the alphabet soup of vitamins seems to skip from E to the rarely-mentioned K is that most of the "letters" were reclassified, as with fatty acids, discarded as false leads, or renamed because of their relationship to "vitamin B", which became a "complex" of vitamins. Vitamin G, Riboflavin, for example, is now known as B₂.

Throughout the early 1900s, scientists were able to isolate and identify a number of vitamins by depriving animals of them.

NUTRITION

Why we need vitamins

Vitamins are not a source of energy nor a source of structural tissue components. They give living cells the ability to conduct and control chemical reactions. They are essential for normal growth and development. Vitamins are necessary for the body to use the calories provided by the food that we eat and help process proteins, carbohydrates, and fats. Vitamins are also involved in building cells, tissues, and organs.

Vitamins are available by eating a balenced diet including fruits, vegetables, grains, nuts, meat, eggs, fish, and milk.

Vitamin deficiencies

Deficiencies of vitamins are either primary or secondary. A primary deficiency occurs if a person does not get enough of the vitamin in the food he eats. A secondary deficiency may be due to a lifestyle factor, such as smoking, excessive alcohol consumption, or the use of certain medications that interfere with the absorption or the body's use of the vitamin. Prolonged use of antibiotics will kill off the useful gut flora that make vitamin K. Vitamin deficiencies may also be due to an underlying problem, such as an intestinal disorder, that prevents or limits the absorption or use of the vitamin.

According to the World Health Organization vitamin A deficiency is the most serious vitamin deficiency disease in the world today. It is the leading cause of preventable childhood blindness in developing countries. It also increases the risk of death from measles, malaria, worms, and other diseases. It can be prevented by diet improvements and supplementation for children and mothers.[2]

Well-known vitamin deficiencies are thiamine (beriberi), niacin (pellagra), vitamin C (scurvy) and Vitamin D (rickets). In north America today, however, such deficiencies are rare due to an adequate food supply for most people, and food fortification programs that add vitamins and minerals to common foods.

Scientists now have shifted their focus to discovering ways in which vitamins can promote health, prevent disease, boost the body's protection against infection and even slow down the aging process. At the same time, public interest in vitamins has heightened. This has been prompted by headlines in the media and widespread advertising by the manufacturers of nutrient supplements.

Vitamin overdosing

The likelihood of consuming too much of any vitamin from food is remote, but overdosing from vitamin supplementation can occur. For example, many people take large amounts of vitamin C, usually in the belief that this will relieve or "cure" a cold. However, overdosing on vitamin C can lead to diarrhea or kidney stones. If you take vitamin supplements, you should always do so at the advice of your doctor or dietitian, and first consider whether your diet could be improved instead.

References

ISBN links support NWE through referral fees

• Stedman's Medical Dictionary. Ed. Maureen Barlow Pugh et.al. 27th ed. Baltimore: Lippincott Williams & Wilkins, 2000.
• Donatelle, Rebecca J. Health: The Basics. 6th ed. San Francisco: Pearson Education, Inc. 2005.
• Funk, C. and H. E. Dubin. The Vitamines. Baltimore: Williams and Wilkins Company, 1922.
• The History of Vitamin Discovery. Retrieved 1 Feb 2005.
• Bellis, Mary. History of Vitamins. Retrieved 1 Feb 2005.
• Challem, Jack (1997). The Past, Present and Future of Vitamins. Retrieved 1 Feb 2005.
• Leonhardt, David (2004). Vitamin A - The Glow in the Dark Vitamin. Retrieved 1 Feb 2005.
• A Brief Update on Ubiquinone (Coenzyme Q10), Journal of Orthomolecular Medicine 2000; 15(2):63-68.
• Murray, R., Granner, K., et al, Harper's Illustrated Biochemistry 26th Edition, New York : Lange Medical Books 2003 ISBN 0071389016

External links

• USDA RDA chart in PDF format
• The lab which discovered the enzyme associated with PQQ
• Health Canada Dietary Reference Intakes Reference Chart for Vitamins

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

• Vitamin  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Vitamin"

Note: Some restrictions may apply to use of individual images which are separately licensed.