Did You Know Just That Many Cancers Are Linked To A Vitamin Deficiency?
Vitamins: Definitions And Classifications
There are 13 known vitamins of which four are fat-soluble,
and the remaining nine are water-soluble. A fat-soluble
vitamin is absorbed with the help of fat. Vitamins A,D,E
and K are fat-soluble. The nine water-soluble vitamins are:
B-1 (Thiamin), B-2 (Riboflavin), B3 (Niacin), Folic Acid,
B-6 (Pyridoxine), B-12, Pantothenic Acid, Biotin and Vitamin
C.
The History Of Vitamins
The discoveries of which vitamins are present in food, and
what effects those vitamins have upon human health, began
to develop in about 1905 when an English doctor, William
Fletcher, experimented on asylum inmates in Kuala Lumpur.
He showed that nearly 25 percent of those who received polished
rice developed beriberi, while less than 2 percent of the
123 patients who received unpolished rice fell victim to
beriberi. This disease was common in the rice cultures of
Asia. Beriberi is characterized by weakness in the legs,
hands and arms. Later, weakening of the cardiac muscles
leads to heart failure.
Then, in 1912, while working at the famed Lister Institute
in London, the Polish-born biochemist Casimir Funk, took
Fletcher's thinking a few steps further. He isolated the
active substances in rice husks of the unpolished rice that
were preventing beriberi. He named these missing dietary
links 'vitamines' (vital amines), in the belief that they
were "amines," which were compounds derived from
"ammonia." (The "e" on the end was dropped
in 1920 when it became clear that not all vitamins were
"amines.")
In 1913, attention turned to finding and isolating the vitamins
themselves. Thomas Osborne and Lafayette Mendel showed in
rat experiments conducted at Yale Univeersity that butter
contained a growth-promoting factor necessary for development.
Soon known as fat-soluble Vitamin A, its chemical character
was established in 1933, and it was synthesized in 1947.
Other vitamin discoveries came along in the early 20th century.
Cow's milk was found to contain another growth-promoting
factor, the water-soluble Vitamin B, which was isolated
in pure form in 1936. (We now know there are several different
types of Vitamin B.) In 1922, while looking for a solution
to the problem of rickets, Edward Mellanby dicovered Vitamin
D. In the United States, the enrichment of milk with Vitamin
D was extremely effective against rickets.
Experiments with rats in 1922 showed that rats reared exclusively
on whole milk grew normally but were sterile and could not
reproduce. Herbert Evans and Katherine Bishop, at the University
of California, showed that the missing factor was abundant
in green leaves and wheat germ. The fat-soluble Vitamin
E had been discovered.
In the early 16th century, observations that citrus fruits
could prevent scurvy on long sea voyages later led Harriet
Chick of the Lister Institute to begin a series of painstaking
investigations during the 1930s into the antiscorbutic qualities
of various foods. Meanwhile, in 1932, Albert Szent-Gyorgyi
isolated a substance from the adrenal glands. He called
it hexuronic acid. At the same time in history, W.A. Waugh
and Charles King isolated a vitamin from a lemon and showed
it was identical to hexuronic acid. In 1932, this vitamin
became the first to be synthesized in a laboratory. It was
Vitamin C. By the 1930s, vitamin sales were already making
huge profits for pharmaceutical companies.
http://iml.jou.ufl.edu/projects/
Spring2000/Kimpel/vitamins.html
