Vitamin D is a fat-soluble
steroid hormone, which is essential to health and for which epidemiological studies suggest a role in
autoimmune disease,
infections, cardiovascular disease and
cancer. It is ingested in foods such as oily fish and supplements, so that average levels vary between countries, but most individuals worldwide make most of their
vitamin D as a result of the effects of sun exposure on the skin. Many studies in different populations around the world have in recent years shown that sub-optimal levels of
vitamin D (<70 nmol/L) are common. A series of epidemiological studies have suggested that low
vitamin D levels increase the risk of
cancers, particularly of the breast and gastrointestinal tracts, so that there has been much interest in understanding the effects of
vitamin D on
cancer cells.
Vitamin D binds to the
vitamin D receptor (VDR) resulting in transcription of a number of genes playing a role in inhibition of MAPK signalling, induction of apoptosis and cell-cycle inhibition, and therefore
vitamin D has anti-proliferative and pro-apoptotic effects in cells of many lineages. It also has suppressive effects on adaptive immunity and is reported to promote innate immunity. Here we review data on
vitamin D and
melanoma. There are in vitro data, which suggest that
vitamin D has the same anti-proliferative effects on
melanoma cells as have been demonstrated in other cells. We have reported data to suggest that
vitamin D levels at diagnosis have a role in determining outcome for
melanoma patients. There is a curious relationship between
melanoma risk and sun exposure where
sunburn is causal but occupational sun exposure is not (at least in temperate climes). Seeking to understand this, we discuss data, which suggest (but by no means prove) that
vitamin D might also have a role in susceptibility to
melanoma. In conclusion, much remains unknown about
vitamin D in general and certainly about
vitamin D and
melanoma. However, the effects of avoidance of suboptimal
vitamin D levels on
cancer cell proliferation are likely to be beneficial to the
melanoma patient. The possible results of high
vitamin D levels on the immune system remain unclear however and a source of some concern, but the data support the view that serum levels in the range 70-100 nmol/L might be a reasonable target for
melanoma patients as much as for other members of the population.