There is no officially recognized Vitamin Z, nor are there Vitamins F, G, or I in the standard alphabet of essential nutrients. A vitamin is defined as an organic compound required in small amounts for normal metabolic function. Crucially, the body cannot synthesize these compounds in sufficient quantities, meaning they must be obtained through diet. The existence of a “Vitamin Z” is hypothetical, as the naming convention ended long before the letter Z.
The Recognized Essential Vitamins
The scientific community recognizes thirteen essential vitamins required for human health, categorized based on how the body absorbs and stores them. These fall into two classes: fat-soluble and water-soluble. The four fat-soluble vitamins (A, D, E, and K) are absorbed with dietary fats and can be stored in the liver and fatty tissues for extended periods. Fat-soluble vitamins have diverse regulatory functions, such as Vitamin A’s role in cell growth, Vitamin D’s function in mineral metabolism, and Vitamin K’s necessity for blood coagulation.
The remaining nine essential nutrients are water-soluble, including Vitamin C and the eight compounds that make up the B-complex. These vitamins dissolve easily in water and are not stored in the body, requiring a consistent daily intake to prevent deficiency. The B-complex group collectively functions as coenzymes, playing a significant role in cellular metabolism to help convert food into energy. The B-complex vitamins are:
- B1
- B2
- B3
- B5
- B6
- B7
- B9
- B12
The Historical Reason for Skipping Letters
The gaps in the alphabetical sequence resulted from the early, unsystematic nature of nutritional science in the early 20th century. Researchers initially assigned letters based on the order of discovery, starting with A and B. This system quickly became problematic because many substances given a letter designation were later found to be non-essential, duplicates, or complex mixtures rather than single compounds.
For example, the letter F was assigned to Essential Fatty Acids, which do not fit the strict definition of a vitamin. The letter G was originally used for Riboflavin, which was later renamed Vitamin B2 and grouped with the other water-soluble B vitamins. Vitamin H was similarly reclassified as Biotin, or Vitamin B7.
The alphabetical sequence was permanently abandoned when Vitamin K was discovered. It was named after the German word for coagulation, Koagulation, due to its role in blood clotting. This non-sequential naming, coupled with reclassification, ensured that no systematic progression to Z would ever occur. This is why letters like I and J were simply bypassed.
Compounds Mistakenly Labeled as Vitamins
Public confusion often stems from compounds misleadingly marketed as vitamins. These substances are often bioactive but do not meet the scientific criteria because the human body can synthesize them in adequate amounts. For instance, Choline, Inositol, and Para-aminobenzoic acid (PABA) are sometimes referred to as “vitamin-like substances,” but they are not true vitamins.
Two of the most notorious examples are the pseudo-vitamins B15 and B17, which have no legitimate place in nutritional science. “Vitamin B15,” or pangamic acid, was promoted as a beneficial compound for various ailments but is not recognized as having any proven nutritional value. The lack of a standardized chemical identity and the presence of potentially harmful chemicals in some formulations have raised safety concerns.
“Vitamin B17,” also known as amygdalin or laetrile, is perhaps the most dangerous misnomer. It is a toxic compound that releases cyanide upon digestion. It was fraudulently named a vitamin for marketing purposes to promote it as an alternative treatment for cancer. The use of such substances highlights the importance of the strict scientific definition of a vitamin.