A. Alice H. Lichtenstein, DSc, senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging and executive editor of Tufts Health & Nutrition Letter, answers: “The so-called ‘B vitamins’ are actually a diverse group of compounds. When the first vitamins were discovered, the fat-soluble compounds were called ‘A’ and the water soluble were called ‘B.’ Each new vitamin discovered after that was given the next letter in the alphabet, up to vitamin E. Vitamin K was named after the German name for its function in blood, Koagulation (coagulation). However, it soon became apparent that what had been designated as ‘vitamin B’ was actually a mixture of compounds (as was fat soluble vitamin A). The first and second vitamins identified within the B grouping were thiamine and riboflavin, given the designations vitamin B1 and B2, respectively. More followed, some of which are commonly referred to by their chemical name (like niacin), and others by their numerical nomenclature (like vitamin B12), for reasons that are lost to history. Hence, the term B vitamins, plural, represents a wide range of heterogeneous compounds. At the Tufts Health & Nutrition Letter, we try to avoid using the term ‘B vitamins’ unless absolutely appropriate and refer to individual B vitamins by their common names.”
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