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8.1: Vitamins

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    1112
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    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.

    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