I want to share with you my response to the CDC’s request for comments on its policy related to UV exposure. My comment would not have been possible without information I first learned about right here on the Vitamin D Council website. Many of the studies I cite here I know about only because of my Vitamin D Council membership.
Comment on anticipated Office of the Surgeon General statement on the public health problem of skin cancer.
AGENCY: Centers for Disease Control and Prevention (CDC), Department of Health and Human Services (HHS).
DOCKET NUMBER: CDC–2013–0014
FROM: Tom Weishaar, Program in Health Education, Department of Health and Behavior Studies, Teachers College, Columbia University
HHS/CDC and the Office of the Surgeon General are interested in receiving information on the following topics: (1) Barriers to reducing UV exposure from the sun and from indoor tanning devices…
The primary barrier to a public health policy of reducing UV exposure is that it ignores the overall impact of UV exposure on human health.
Creating public health policy based solely on the relationship between UV exposure and skin cancer while ignoring all of the other relationships between UV exposure and human health is ill-advised. Moreover, as I will show, it is in opposition to one of the four overarching goals of HHS/CDC as stated in Healthy People 2020 , to achieve health equity, eliminate disparities, and improve the health of all groups.
To begin, let’s look at the bigger picture of UV exposure and human health. Since 1934 anthropologists have been discussing, and in recent years have accepted, the theory that human skin color is an evolutionary adaptation to UV exposure [2-7].
They note that our evolutionary ancestors had dark skin that was protective against the high UV levels found near the equator. However, as human population groups moved away from the equator and its intense UV radiation, skin tones in those groups gradually became lighter because individuals with lighter skin had the evolutionary advantage of better health.
The primary mechanisms through which UV impacts health are skin damage leading to skin cancer and the production of vitamin D in the skin. There are additional mechanisms that we know about  and there may be others that are still unknown to us.
In humans, light skin requires less exposure to UV to synthesize the same amount of vitamin D as darker skin. The primary source of vitamin D in humans is synthesis in the skin as a result of UV exposure. The only food source with significant amounts of vitamin D is wild ocean fish. Because of these factors, at the latitude of the United States there are vitamin D disparities related to skin color. Moreover, many of the same diseases and health conditions are associated with both inadequate vitamin D status and with health disparities [9-11].
From a public health perspective, the theory of the evolution of human skin color implies that there will be health disparities in any population with diverse skin colors. In low UV areas, including parts of the U.S., those with dark skin will be relatively less healthy because of a lack of UV exposure, while in high UV areas, including parts of Australia, those with light skin will be relatively less healthy because of overexposure to UV. It is the work of public health professionals to solve both of these problems, not to pick one at the expense of the other.
Using data from NHANES, my colleague Joyce Vergili and I have recently demonstrated that vitamin D status is a biological determinant of health disparities . Our study replicated earlier findings using health care costs as the dependent variable . When you ask Americans to rate their health, on average, non-Hispanic blacks and Mexican-Americans both rate their health worse than non-Hispanic whites. A discrepancy remains even after controlling for socioeconomic status and other reasonable covariates. However, when you additionally control for vitamin D status, the difference in how blacks and whites rate their health disappears and the difference between the ratings of Mexican-Americans and whites is greatly reduced.
While our study was not a randomized controlled trial, other researchers have already demonstrated causal relationships between vitamin D status and specific diseases and conditions [14-16]. Our study, while epidemiological, is similar to studies that have been used in the past to set health policy, for example, on the health effects of smoking. Our study demonstrates that it will not be possible for public health authorities to eliminate health disparities without eliminating the skin-color based disparities in vitamin D nutriture.
While HHS/CDC has repeatedly stated that one of its overarching goals is to eliminate health disparities, a policy to reduce UV exposure in Americans will have exactly the opposite effect – it will increase health disparities. It is particularly inequitable to broadly recommend reduction of UV exposure to Americans when, according to the American Cancer Society, Melanoma is rare among African Americans; the lifetime risk of developing melanoma is 23 times higher among whites than among African Americans (page 21). 
A recent study from Australia highlights the difficulties of a public health policy to reduce UV exposure . The study targeted dark-skinned women who had moved to Australia as humanitarian refugees from Horn of Africa countries – mostly Somalia – and mostly within the last five (none more than ten) years. One participant said, When we were in our countries, we were exposed to the sun a lot. Our sun is very healthy. We don’t have cancer in the skin…[but here in Australia]…there are some rays in the sun. Skin cancer, so sometimes we compare, we say is it better to have lack of vitamin D or to have skin cancer? You compare the both, which one is safer. We think vitamin D [deficiency] is safer (p. 295).
While it is not too late to adjust a statement from the Surgeon General to make it equitable to all groups, the HHS/CDC and other health policy expert panels currently support health inequities through a double standard for evidence regarding UV’s health impacts.
When the policy concerns improving the health of those with light skin, there is no requirement for evidence from randomized controlled trials. All of the available scientific evidence that UV has a negative impact on health is epidemiological. For example, in the discussion section of the U.S. Preventative Services Task Force supporting article on screening for skin cancer, the task force reports:
The literature on screening for skin cancer has several limitations. A major limitation is the lack of direct evidence linking skin cancer screening to improved health outcomes. An adequately powered, population-based RCT of screening demonstrating mortality outcomes would require approximately 800,000 participants because of the relatively low melanoma-related mortality rate in the United States. 
To fully understand this statement, it helps to realize that in the U.S., deaths related to skin cancer represent only 2% of all deaths related to cancer .
On the other hand, when the policy concerns improving the health of those with dark skin by increasing vitamin D levels, epidemiological evidence is not considered adequate – only randomized controlled trials will do. This was the policy when the Institute of Medicine raised the recommended daily allowance of vitamin D in 2011  and it is the policy that the U.S. Preventative Services Task Force uses when examining issues related to the health effects of vitamin D deficiency .
This double standard is inequitable, harms the health of vulnerable groups, and is not a worthy foundation for U.S. public health policy.
In its RCT-based nutritional recommendation regarding vitamin D, the IOM recommended that, for bone health, 20 ng/mL is the optimal population level of the marker used to determine vitamin D status – serum 25-hydroxyvitamin D or 25(OH)D. While the average 25(OH)D levels for the U.S. as a whole are above that level, the average for non-Hispanic blacks in the U.S. in 2003-2006 (the most recent data available) was 15.0 ng/mL . Meanwhile, the mean level for traditionally-living people in equatorial Africa is 46 ng/mL .
The background for the IOM’s RCT-based recommendation was the classic understanding of vitamin D – that vitamin D is activated in the kidney and passed into the blood stream as a hormone to control blood calcium levels. In this understanding vitamin D has an endocrine function – it is created at one place in the body and is used to send signals to cells in other parts of the body. In the classic understanding, vitamin D impacts bone health and nothing more .
There is also a modern understanding of vitamin D, which the IOM acknowledged by noting it has possible roles in carcinogenesis, cardiovascular disease, diabetes, falls, immune response, neuropsychological functions, physical performance, and preeclampsia. The modern understanding includes this endocrine signaling, but also acknowledges that vitamin D is activated inside many other cells, where it is used to signal the DNA machinery inside that cell (autocrine signaling) or inside adjacent cells (paracrine signaling) to up- or down-regulate genes that code for specific proteins [16, 22]. The IOM said that optimal vitamin D levels for these other functions of vitamin D were unknown, however, many other experts, who – like skin cancer researchers – review epidemiological and biological studies as well as RCTs, disagree with this assessment [15, 23].
Continuing the current public health policy of reducing UV exposure without attending to the effects of that policy on people of color is inequitable and borders on public health malpractice. Moreover, HSS/CDC must put an end to the double standard for evidence regarding UV’s impact on health. At an absolute minimum, an equitable policy regarding UV exposure must include policies and targeted behavior change programs to increase the mean serum 25(OH)D level of U.S. subpopulations with darker skin colors above the IOM recommended level of 20 ng/mL.