Vitamin D is a conditionally essential micronutrient and an endocrine messenger that maintains a healthy cellular growth.
There are two primary forms of vitamin D, vitamin D3 and vitamin D2.
Vitamin D3, or cholecalciferol, is formed in the skin upon UV exposure. The cholecalciferol form of vitamin D derives from the conversion of 7-dehydroxycholesterol to vitamin D3 via UV radiation from the sun.
Recent research has focused on the effects of 1,25 (OH) D3, the active metabolite of vitamin D, which has been shown to hold antiapoptotic, antiproliferative and antiangiogenic potentials.
Low levels of 1,25 (OH) D3 have conversely been associated with increased incidence of breast, colon and prostate cancer.
Vitamin D is both a fat-soluble vitamin and a hormone. Its synthesis and catabolism of is a highly regulated multi-step process.
On entering the circulation from either the diet or the skin, vitamin D is bound to vitamin D-binding protein and transported to the liver.
The molecule produced by this photochemical reaction is converted in the liver to 25, hydroxy cholecalciferol (25 – (OH) D3). The kidneys then convert 25-(OH) D3 to 1,25 dihydroxy cholecalciferol, the active form of vitamin D.
Low plasma concentration of vitamin D has been associated with increased cancer risk and increased disease progression.
For example, one study associated low plasma concentrations of vitamin D with increased disease progression in breast cancer patients. In another, the risk of palpable prostate cancer in men aged 57 or above was greater in those with low vitamin D plasma concentrations.
In a study of 620 healthy volunteers, the risk of developing colon cancer decreased threefold in subjects with moderate vitamin D plasma concentrations as opposed to those with low concentrations.
Furthermore, low vitamin D3 concentrations have been implicated as a risk factor in cancers of the breast, colon and prostate.
Taken together, these studies indicate that high normal plasma level of vitamin D may reduce cancer risk and inhibit cancer progression.
Thus, it would seem prudent to maintain at least normal to high-normal plasma concentration of vitamin D which could be accomplished through adequate sun exposure or taking vitamin D3.
References
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6. Majewski S., Marzak M., Szmurlo A., et al. Retinoids, interferon alpha, 1,25 dihydroxyvitamin D3 and their combination inhibit angiogenesis induced by non-HPV- harboring tumour cell lines. Cancer Letter. 1995; 89(1): 117-24
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