Webster's New World Medical Dictionary

niacin
Vitamin B3.
nicotinic acid
Vitamin B3.
pantothenic acid
Vitamin B5.
pyridoxine
Vitamin B6.
retinol
Vitamin A.
riboflavin
Vitamin B2.
thiamin
Vitamin B1.
vitamin A
An oil-soluble vitamin that is also known
as retinol. Carotene compounds are gradually con-
verted by the body to vitamin A. A form of vitamin A
called retinal is responsible for transmitting light sen-
sations in the retina of the eye. Vitamin A is found in
egg yolk, butter, cream, leafy green vegetables, yellow
fruits and vegetables, cod-liver oil, and similar fish-
liver oils. Deficiency of vitamin A leads to night blind-
ness and to diseases that affect the eyes and mucous
membranes. Overdose of vitamin A can cause insom-
nia, joint pain, fatigue, irritability, headache, and
other symptoms. The daily adult requirement is 900
micrograms.
vitamin A2
A form of vitamin A that is found only
in the flesh of freshwater fish.
vitamin B1
Thiamin, a water-soluble vitamin,
which acts as a coenzyme and is essential for a num-
ber of reactions in body metabolism. Vitamin B1 is
found primarily in liver and yeast, and it is easily
destroyed by cooking. Deficiency of vitamin B1 leads
to beriberi, a disease of the heart and nervous sys-
tem. The daily adult requirement is 1.2 milligrams.
vitamin B2
Riboflavin, a water-soluble vitamin,
which is a component of two coenzymes in the oxi-
dation-reduction processes that are important to
body metabolism. Vitamin B2 is found primarily in
liver and yeast, and it is easily destroyed by cooking.
Deficiency of vitamin B2 causes inflammation of the
lining of the mouth and skin. The daily adult require-
ment is 1.5 milligrams.
Appendix C
Vitamins
The term vitamin was coined in 1911 by the Warsaw-born biochemist Casimir Funk. Working at the Lister
Institute in London, Funk isolated a substance that prevented nerve inflammation (neuritis) in chickens raised
on a diet deficient in that substance. He named the substance “vitamine” because he believed it was necessary to
life and it was a chemical amine. The e at the end was later removed when it was recognized that vitamins need
not be amines. Vitamins soon became identified, as they were noted to be associated with vitamin deficiency dis-
eases. The letters (A, B, C, and so on) were assigned to the vitamins in the order of their discovery. The one
exception was vitamin K, which was assigned its K (from Koagulation) by the Danish researcher Henrik Dam. 
Vitamins are known to play a major role in both health maintenance and the treatment of certain diseases. The
classic vitamins are divided into two categories, oil-soluble and water-soluble, based on how they are absorbed
with the food we eat. The oil-soluble vitamins are vitamins A, D, E, and K and are absorbed with fats. There are
nine water-soluble vitamins, thiamine (vitamin B1), riboflavin (vitamin B2), pyridoxine (vitamin B6),
cyanocobalamin (vitamin B12), ascorbic acid (vitamin C), biotin, folic acid, niacin, and pantothenic acid. Other
vitamins have more recently been described and are included below. Beta carotene is a plant pigment that is a
precursor of vitamin A. Vitamins can be dangerous in overdose. The vitamins include:
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