109 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 names
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).
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