Vitamin D

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and is available as a dietary supplement. It is also produced endrogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis [1,2]. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol.

Vitamin D Deficiency

Nutrient deficiencies are usually the result of dietary inadequacy, impaired absorption and use, increased requirement, or increased excretion. A vitamin D deficiency can occur when usual intake is lower than recommended levels over time, exposure to sunlight is limited, the kidneys cannot convert vitamin D to its active form, or absorption of vitamin D from the digestive tract is inadequate. Vitamin D-deficient diets are associated with milk allergies, lactose intolerance, and strict vegetarianism [47].

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