Heliophobia: Fear of the Sun
By Jacob Schor, ND
Here in Colorado, the month of May is when we go to the beach. By "beach," we mean the parking lot at the base of Arapahoe Basin Ski Area, commonly called "The Basin."By long tradition, a day of spring skiing at The Basin requires a lounge chair, barbecue, ice chest and a few end-of-season ski runs, but the emphasis is to work on your tan. It's a party lasting from sunup to sundown. Between the warm weather, the high altitude and the late spring sun reflecting off the snow-covered peaks, the "beach" turns into a magnificent ultraviolet reflector oven. Sunscreen should be mandatory, but this year, I'm wondering if that's really a good idea.
Medical authorities encourage us to use more and more sunscreen each year. As friends are having bits of their faces frozen, cut and burned off, there is little wonder why we become fearful of skin cancer and are becoming conscientious about applying sunscreen. Yet reading the research on skin cancer and sun exposure raises questions about this approach. Are we doing the right thing?
Over the past half-dozen years, scientists have established a link between sun exposure, vitamin D production and cancer prevention. Sunscreen, by blocking ultraviolet light penetration into the skin, limits vitamin D production. Thus, sunscreen and the precautions people take to prevent sun exposure and to lower the risk of skin cancer, increase the risk for other cancers.
A Map-Reading Man
William Grant was one of the first to report the link between vitamin D and cancer. Grant is an atmospheric ozone physicist with NASA. He noticed that mortality from many common cancers, including colon, breast and prostate, is higher in the northeast U.S. than in the rest of the country. The standard explanation for this phenomenon is that people in colder areas eat more fat. This explanation wasn't adequate for Grant to account for the 150 percent difference in cancer rates from the northeast to the southwest. He recognized that a map of cancer incidence looked similar to one depicting geographical variations in ultraviolet exposure. Grant realized the regional cancer variations were better explained by varying levels of vitamin D in the populations of these different areas, as a result of varying UV exposure.
In his early calculations, Grant figured that at least 23,600 Americans die of cancer every year through lack of sunshine.1 To put that into perspective, about 9,800 people die each year from skin cancer. He has since increased his estimate to 100,000 people developing skin cancer and 40,000 deaths per year result from vitamin D deficiency, or four times the death rate of skin cancer.
The classic risk factors for developing prostate cancer – being old, African-American and living in the northern latitudes – all point to vitamin D deficiency. In an elegant study published in 2005, researchers measured the skin pigmentation on a person's forehead and on the inner arm, figuring that forehead pigmentation was a good measure of lifetime sun exposure and inner arm a baseline of skin coloration.2 The ratio of these two measurements allowed them to rate a man's lifetime sun exposure. Comparing the measurements of 450 Caucasian men with advanced prostate cancer against 455 matched controls without disease produced striking data. Men with the most sun exposure were 49 percent less likely to develop prostate cancer than those with the palest forehead pigmentation. In other words, adequate sun exposure or vitamin D levels cut prostate cancer by half. In the U.S., there are currently 240,000 new prostate cancers diagnosed each year. In theory, providing adequate D could prevent 120,000 prostate cancers a year.
Cedric Garland and his colleagues at the University of California, San Diego, have concluded that 1,000 IU of vitamin D a day decreases risk of colorectal cancer by half.3 Garland calculated that this would prevent 28,000 colon cancer deaths a year. Sun exposure may be worth the risk of skin cancer. Yet sun exposure isn't needed to make vitamin D. It can be taken as an oral supplement. Using sunscreen and taking vitamin D in pill form could lower colon, prostate and other cancer rates while still providing skin cancer protection. That is, if life were simple. There are a few problems with this idea.
In February 2007, a short summary of a recent article in Nature Immunology raised some interesting questions:
Skin produces the inactive form of vitamin D3 in response to sun exposure. Now Eugene Butcher of Stanford University in California and his colleagues have shown that immune cells in the skin known as dendritic cells convert the inactive vitamin D3 into its active form. The active form then causes T-cells – immune cells that destroy damaged and infected cells, and regulate other immune cells – to change the receptors on their surfaces to enable them to migrate to the upper layers of the skin. Here, they can help repair sun-induced damage and fight off pathogens."4
This new information suggests oral vitamin D may not suffice, at least in preventing skin cancer. The vitamin D made in the skin as a result of sun exposure attracts immune protection to the skin. One possible solution is to enrich sunscreens and other topical lotions with high doses of vitamin D. To match the natural vitamin D production that a day's use of sunscreen blocks, thousands of IUs of vitamin D per dollop of sunscreen should be considered.
Even this might not be adequate. What may be even more relevant news comes from a study published in the March 9, 2007 issue of Cell, which discloses that the tumor-suppressor gene called p53 is the gene responsible for initiation of tanning.5 Tanning is a reaction to ultraviolet light exposure. Melanin pigment production is increased and the melanin concentrated in skin cells. Melanin then protects skin cells from DNA damage caused by UV exposure. Researchers had explained most of this tanning process already, but not what initiated tanning. This current paper reveals that UV light activates the p53 gene, which in turn, activates the tanning pathway. Skin cells without the p53 gene will not tan. We typically think of the p53 gene in relation to cancer protection and as the trigger to apoptosis (cellular suicide) of cancer cells. Cells without p53 genes can't protect themselves against cancer. Cells with a working p53 gene usually will kill themselves if they become cancerous. Turning on the p53 gene through sun exposure also may turn on the cancer-fighting potential of both the skin and the body.
Sun exposure protects our skin against cancer by stimulating vitamin D production. Sun also may protect against skin cancer by stimulating p53 activity. Sunscreen blocks both effects. How sure are we that sunscreen offers protection against skin cancer? Apparently, not as sure as we have been led to believe.
Martin Weinstock has studied this question for years. In 1999, he published the results after he reviewed 13 epidemiological studies on the relation of sunscreen use to melanoma risk. Three showed a decreased risk of melanoma. Four showed an increased risk and six were inconclusive.6
A 2002 review published in the British Journal of Dermatology asked the same question and yielded no more convincing an answer.7 The authors described their results as "discordant." To quote their abstract: "Two case-control studies show a protective effect of sunscreen use, while three studies showed a significant risk associated with sunscreen use." At least they don't think sunscreen causes melanoma, even if the data appear to suggest it: "The lack of dose-effect relationship and the numerous biases, especially the uncertainty that exposure (sunscreen use) preceded melanoma, do not suggest a causative association between sunscreen use and melanoma."
Saying that sunscreen doesn't cause melanoma hardly convinces this reader that it prevents melanoma. I need to say this: There is no strong research that says using sunscreen prevents skin cancer.
There may be a smarter approach to preventing skin cancer. Ultraviolet light increases the reactive oxygen species in skin cells, and the resultant oxidative damage may be to blame for causing skin cancer. A number of plant extracts with strong antioxidant action that reduces ROS damage from UV light have been shown to prevent skin cancer in animals.8,9 Green tea extracts10 and pomegranate extracts11 are two examples. Using topical antioxidants instead of, or along with, sunscreen might go a long way in preventing cancer.
What about people who don't tan? An interesting paper appeared last fall that suggests the supplemental forskolin can help induce a tan. Here is a New Scientist summary:
The ability to tan is largely controlled by a hormone called melanocyte-stimulating hormone, which binds to the melanocortin 1 receptor (MC1R) on the outside of melanocytes. Many people with red hair and fair skin have a defect in this receptor, meaning they find it almost impossible to tan and are prone to skin cancer.
John D'Orazio of the University of Kentucky College of Medicine in Lexington, US, used depilated mice with defective MC1Rs to show that applying forskolin to the skin can restore their ability to produce the skin pigment melanin. When it was applied for four weeks before mice were exposed to UV light, they were subsequently able to tan.
In a second experiment, a particularly cancer-prone strain of mice, also bred to lack effective MC1Rs, were exposed to the equivalent of 1 to 2 hours of midday Florida sunlight each day for 20 weeks. Nine control mice developed 11 tumors and showed other evidence of skin damage, while nine mice treated with forskolin developed just six tumors. Their skin also showed less evidence of damage (Nature, vol 443, p 340).
"We see no logical reason why it shouldn't work in humans too," says D'Orazio, although no clinical trials have yet taken place. Because forskolin stimulates melanin production, it could give fair-skinned people a natural tan that would also afford some protection from the sun. Unlike UV-blocking creams, the forskolin tan would have the added benefit of not washing off.12
Does sunscreen protect us from cancer or does it cause cancer? The truth is probably somewhere in between. If using sunscreen, my choice is to use one loaded with vitamin D and plant antioxidants. Who sells this sunscreen? Absolutely no one that I've researched. We may have to make it ourselves. If this thought interests you, check out the Web site http://skinactives.com/products/productlist1.htm. This company sells a wide range of ingredients you can use to make your own skin creams. Say you want a skin cream enriched with ellagic acid, resveratrol, betulinic acid and green tea. This company is the source for all your ingredients. At this point, it doesn't sell vitamin D3. My solution is to empty our tubes of sunscreen, mix in several 100,000 IUs of vitamin D and then figure out how to put all the goop back into the tube. I'll keep you posted.
About the Author: Dr. Jacob Schor graduated with a bachelor of science degree from Cornell University and received his naturopathic training at National College of Naturopathic Medicine. He currently practices at the Denver Naturopathic Clinic. E-mail Dr. Schor at email@example.com.
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Date Last Modified - Friday, 17-Oct-2008 12:11:10 PDT