UV exposure’s role in skin cancer has always been a hot topic in vitamin D research. As you can pick up on all of our blogs this week, research in the area is contradictory, so much is still to be learned on the topic of sun exposure and skin cancer.
Professor Moan and colleagues recently studied UVA and UVB exposure and incidence rates of cutaneous malignant melanoma (CMM) and squamous cell carcinoma (SCC) in Norway and Sweden to lo see if there is a relationship.
Moan and company reviewed data from the Cancer Registries from Norway and Sweden to find the incidence of CMM and SCC in different counties, as well as collect data on UVA and UVB. They found:
- Incidence of CMM and SCC among men and women are increasing in Norway and Sweden.
- The incidence rates of CMM in both sexes increase with decreasing latitude.
- The incidence rates for CMM in people under 50 years of age have decreased or stayed constant after about 1990, notably in the southern region of Norway.
- The UVA/UVB ratio decreases with decreasing latitude, as does the CMM/SCC ratio of incidence rates.
Based on the last finding, the authors suggest that UVA may contribute to melanoma more so than to squamous cell carcinoma. In other words, there are a higher percentage of UVA rays at higher latitudes than at lower latitudes and that could explain why there are relatively more CMM cases to SCC cases at the higher latitudes compared to lower latitudes.
They recommend future research confirm their findings, and if confirmed, they suggest better UVB to UVA ratios in sunbeds. They also denounce the use of sunscreens that block UVB but not UVA. And they acknowledge the importance of keeping vitamin D levels sufficient year round.
“Sun-like sunbeds, with less UVA than those used now, would act as summer sun and might, carefully used, improve the winter levels of vitamin D. Keeping a constant vitamin D level throughout the year might be optimal.”
This is in line with what the Vitamin D Council recommends: exposure to sunlight or low pressure tanning beds that focus on the UVB spectrum, which allows your skin to produce vitamin D.