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8.1: Vitamins

The name vitamin comes from Casimir Funk, who in 1912 thought vital amines (NH3) were responsible for preventing what we know now are vitamin deficiencies. He coined the term vitamines to describe these compounds. Eventually it was discovered that these compounds were not amines and the 'e' was dropped to form vitamins1.

Vitamins are classified as either fat-soluble or water-soluble. The fat-soluble vitamins are:

Vitamin A

Vitamin D

Vitamin E

Vitamin K

The water-soluble vitamins are vitamin C and the B vitamins, which are shown in the table below.

Table 8.11 The B vitamins and their common names

Vitamin

Common Name

B1

Thiamin

B2

Riboflavin

B3

Niacin

B5

Pantothenic Acid

B6*

Pyridoxine

B7

Biotin

B9

Folate

B12*

Cobalamin

*Normally used instead of common name

A common question from students about B vitamins is: “Why are there so many B vitamins? It is not like they ran out of letters in the alphabet to name them.”

Before they even knew that vitamins existed, a scientist named E.V. McCollum recognized that a deficiency in what he called ‘fat-soluble factor A’ resulted in severe ophthalmia (inflammation of the eye). In addition, a deficiency in ‘water-soluble factor B’ resulted in beriberi (a deficiency discussed more later)1.

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Figure 8.11 Factor A deficiency led to ophthalmia, factor B deficiency led to beriberi

Factor A is what we now know as vitamin A. However, researchers soon realized that factor B actually consisted of two factors that they termed B1 and B2. Then they realized that there are multiple components in B2, and they began identifying the wide array of B vitamins that we know today1.

You might be thinking “but the numbers on the B vitamins still do not add up." You are right, vitamins B4, B8, B10, and B11 were discovered and then removed leaving us with the B vitamins shown in Table 8.11.

Relative to other scientific milestones, the discovery of vitamins is a fairly recent occurrence, as shown in the table below.

Table 8.12 Vitamin, year proposed, isolated, structure determined, and synthesis achieved up to 19441

Vitamin

Year Proposed

Isolated

Structure Determined

Synthesis Achieved

Thiamin

1901

1926

1936

1936

Vitamin C

1907

1926

1932

1933

Vitamin A

1915

1939

1942

-

Vitamin D

1919

1931

1932

1932

Vitamin E

1922

1936

1938

1938

Niacin

1926

1937

1937

1867*

Biotin

1926

1939

1942

1943

Vitamin K

1929

1939

1942

1943

Pantothenic Acid

1931

1939

1939

1940

Folate

1931

1939

-

-

Riboflavin

1933

1933

1934

1935

Vitamin B6

1934

1936

1938

1939

* Was established long before it was known to be a vitamin

A number of B vitamins serve as cofactors/coenzymes. The following table lists the cofactors/coenzymes formed from B vitamins that will be discussed in more detail in the following subsections.

Table 8.13 Cofactors/coenzymes formed from B vitamins

Vitamin

Cofactors/Coenzymes

Thiamin

Thiamin Pyrophosphate (TPP)

Riboflavin

Flavin Adenine Dinucleotide (FAD),

Flavin Mononucleotide (FMN)

Niacin

Nicotine Adenine Dinucleotide (NAD),

 Nicotine Adenine Dinucleotide Phosphate (NADP)

Pantothenic Acid

Coenzyme A

Vitamin B6

Pyridoxal Phosphate (PLP)

Biotin

-

Folate

Tetrahydrofolate (THF)

Vitamin B12

Adenosylcobalamin, Methylcobalamin

References & Links

  1. Carpenter K. (2003) A short history of nutritional science: Part 3 (1912-1944). J Nutr 133(10): 3023-3032