Sun Avoidance and the “Sunshine Vitamin”
How to achieve a public health message that benefits all?
Anthony J. Alberg, PhD, MPH, Hollings Cancer Center and Department of Public Health Sciences, Medical University of South Carolina, Charleston, SC
In this issue of Progressnotes are two articles that may at first appear to be unrelated but are in fact closely intertwined. One is on malignant melanoma, a form of skin cancer, and the other is on vitamin D. What is the common ground? Exposure to sunlight is critical to both topics, but in directly opposing ways: sunlight is the major risk factor for skin cancer, but it also catalyzes vitamin D synthesis in the skin.
Skin cancer (including both melanoma and nonmelanoma) is the most common type of cancer, and its major environmental cause is exposure to ultraviolet light, mostly from sunlight but also from tanning beds. Consequently, skin cancer prevention strategies emphasize reducing sunlight exposure through sun avoidance and skin-protection behaviors, such as use of sunscreens and skin-protective clothing.
Conversely, exposure to sunlight induces the skin to produce vitamin D, which in turn benefits bone health and, as described in the Progressnotes article, the health of pregnant mothers and breast-fed infants. Vitamin D is also hypothesized to have health benefits that extend well beyond these endpoints to include a broad spectrum of health outcomes.
The public health dilemma is that sun avoidance to prevent skin cancer may compromise vitamin D sufficiency, leading some to speculate that the benefits of unprotected exposure to sunlight to increase cutaneous vitamin D synthesis may outweigh the risks of skin cancer. This is clearly a controversial stance. Also, rest assured that there is an industry with a vested interest in the topic: the tanning bed industry. Further complicating matters, the public is aware of the claims regarding vitamin D as reports touting the health benefits of the “sunshine vitamin” have received extensive media coverage.
Developing a policy based on advocating for unprotected sun exposure is also challenged by the fact that the level of sun exposure required to achieve optimal concentrations of vitamin D is uncertain. The relationship between sun exposure and vitamin D synthesis in the skin is complex, as individuals produce different amounts of vitamin D for a given dose of sunlight, and the dose of sunlight depends on factors such as the season of the year, the time of day, and the latitude.
The heightened awareness of vitamin D in the general population accentuates the public health importance of resolving this controversy. The public needs clear guidance on how best to navigate the challenging terrain between the mixed medical and media messages that range from sun avoidance for skin cancer prevention to the sun-seeking, pro–vitamin D message.
A prudent public health strategy is proposed in the vitamin D article: using vitamin D supplements to maintain optimal vitamin D levels. This is a “win-win” strategy that avoids advocating for exposure to the predominant cause of skin cancer while still enabling health-enhancing levels of vitamin D to be achieved. This is also an increasingly viable strategy, as more is learned about the high supplemental vitamin D doses that humans can tolerate. Vitamin D supplementation represents a path forward that allows patients and the public to benefit from vitamin D’s health-enhancing effects–both those that are known and those yet to be proven–while remaining vigilant to prevent skin cancer.