Hence, formerly in western diets VD was added to food and beverage products such as milk, soft drinks, and bread, to increase its nutritional value. Due to the very limited dietary sources of VD and insufficient exposure to sunlight in northern regions, between 30 and 60% of the European and North American population suffer from VD deficiency. Still, vitamin D deficiency is a worldwide well-recognized problem with health consequences. Also, several studies support that VD may play a major role in tumor’s pathogenesis, progression, and therapy. For example, this hormone has the ability to suppress prostaglandin actions and enhance pro-inflammatory cytokines production, displaying a role in ceasing inflammatory process. Calcitriol is nowadays associated with many additional actions including antiproliferative, pro-differentiating, anti-inflammatory, and immunomodulatory effects. ĭespite its well-known regulation of calcium homeostasis and bone mineralization functions, in the late 1970s VD was found in tissues not previously considered targets of VD action, which came to disclose that this hormone may carry out several other functions. Due to their structural similarities, calcitriol acts like classical steroid hormones binding to the vitamin D receptor (VDR) regulating target gene expression via both genomic and nongenomic pathways. As cholecalciferol is inert, it must be metabolized in the liver and the kidney through two hydroxylation processes to be converted to its active form, calcitriol. However, VD does not remain in circulation for a long time as it is almost instantly stored on the adipose tissue or metabolized in the liver.
Once produced, VD is translocated into the bloodstream. In the epidermis, VD is produced in the form of cholecalciferol due to the action of sunlight. VD is a precursor to its active and biologically functional metabolite, a lipophilic seco-steroid hormone known as calcitriol. Vitamin D (VD) was firstly identified as a vitamin and now is recognized as a prohormone. In this chapter, an overview on vitamin D and its metabolic activity is presented, as well as a review of nanosystems for the encapsulation of vitamin D for different applications, such as food and pharmaceutical industries. Thus, the use of nanotechnology may overcome these problems associated with vitamin D administration, allowing to decrease its toxicity in healthy tissues and increasing its bioavailability. However, its administration presents some drawbacks such as high toxicity and low bioavailability. Also nowadays, vitamin D is recognized as a potential therapeutic agent in anticancer therapy. Thus, the awareness that vitamin D insufficiency/deficiency may be associated with various diseases has grown.
In addition to the traditional role of calcium homeostasis and bone mineralization, calcitriol, the active metabolite of vitamin D, also displays other metabolic activities as antiproliferative, pro-differentiating, anti-inflammatory, immunomodulatory, and antineoplastic effects.
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