Many vitamins, though treated as single substances, are actually groups of structurally related compounds that exhibit similar physiological behaviors. However, the physiological function of these vitamins is often limited to one active form to which the related compounds are converted. For instance, vitamin D exists in multiple forms, but its most active form is calcitriol, which is crucial for calcium absorption and bone health.
Whether a substance must be supplied intact to the cell or can be synthesized by the cell depends on the specific enzymes present in the cell species. Therefore, a substance might be a vitamin for one species but not for another. For example, humans cannot synthesize vitamin C due to the absence of the enzyme L-gulonolactone oxidase, making it essential in our diet. Conversely, many animals can produce their own vitamin C, illustrating how the requirement for dietary vitamins varies across species.
Understanding these distinctions is crucial for nutrition science, informing dietary recommendations and health strategies to prevent deficiencies and promote optimal metabolic function. The latest research continues to explore the nuanced roles of vitamins, highlighting their importance in maintaining health and preventing chronic diseases.
The Essential Role and Classification of Vitamins in Human Health
