RAY A. MATULKA
Director of Toxicology, Burdock Group Consultants, Orlando, USA

Vitamin D may be considered a nutrient that has been long recognized for its benefits to bone health, but recent research has found that vitamin D likely also has positive aspects in many bodily systems, and does not function like any other “vitamin”. The Oxford dictionary defines vitamins as “any of a group of organic compound which are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be synthesized by the body”(1). Vitamin D was originally found to be essential when consumption of cod liver oil (a good source of vitamin D) or exposure to sunlight prevented the formation of rickets (2). UVB radiation from sunlight converts 7-dehydrocholesterol in the skin to a pre-vitamin form of vitamin D (D3), which is then enzymatically metabolized to the active form of vitamin D (1,25-dihydroxy-vitamin D3, also called calcitriol). Certain plants and fungi also produce vitamin D, but start with ergosterol, forming vitamin D2 (ergocalciferol) that is also metabolized by humans to form calcitriol (3). As vitamin D is produced in the body, it does not fit the definition of a vitamin, but is actually a hormone (“a regulatory ...