It is a strange paradox of nature that the wavelengths of solar UV light that drive cutaneous vitamin D photosynthesis are the very same ones that cause DNA damage and skin cancer. That conjunction of healthful and harmful effects has caused a good bit of consternation in medical circles in recent years.
As we’ve learned more about the importance of vitamin D, the extent of vitamin D insufficiency, and the negative effects of low D levels, some physicians now oppose skin cancer prevention efforts focused on avoiding sun exposure and diligent sunscreen use. They argue that on a population basis, gains in reducing skin cancers are outweighed by increased risk of colorectal cancer, diabetes, heart disease, depression, MS and osteoporosis associated with low vitamin D.
Since vitamin D is easily obtained from oral supplements, is there real cause for concern or is this a “pseudo-controversy”? We think it is the latter.
Be aware that arguments against UV protection are heavily promoted by the $5 billion/year indoor tanning industry that encourages tanning bed use as a way to obtain vitamin D. Such a claim is illegal and is currently being litigated, but it is still prevalent. Indoor tanning does not focus on the frail elderly or inner-city ethnic minorities who are at greatest risk of vitamin D deficiency, but rather on healthy Caucasian teens and young adults, who are at highest risk of UV photodamage and subsequent skin cancer later in life.
A Pseudo-Controversy
The basis of the pseudo-controversy is the assumption that vitamin D sufficiency is best achieved from UV exposure, even though all intervention studies showing benefit from increasing 25(OH)D were done with oral vitamin D, not increased sun/UV exposure (Wolpowitz D, Gilchrest BA. 2006 Feb; J Am Acad Dermatol. 54(2): 301–317).
Unfortunately, evolution has not kept up with civilization. Life expectancy was less than 40 years when we humans evolved the capacity for cutaneous vitamin D production; long-term photodamage was not a concern, and vitamin D deficiency, in the form of rickets, was fatal in early life.
To be sure, the notion of relaxing in the sun and making one’s own vitamin D has a back-to-nature holistic appeal. But the fact is, most people can obtain ample vitamin D levels from a combination of diet, supplements, and incidental protected sun exposure. (For more on this, visit www.holisticprimarycare.net, and read “Vitamin D: New Findings, New Questions,” Vol. 9, No. 2, Summer 2008.)
What Should We Tell Our Patients?
The preponderance of medical literature and common sense indicate that light-skinned people benefit from regular, lifelong, safe sun practices. People who apply high-sun protection factor (SPF) sunscreen probably synthesize vitamin D maximally in exposed areas during incidental sun exposure (Gilchrest BA. J Natl Cancer Inst. 2008; in press).
Although some claim that sunscreens block all UV and all vitamin D photosynthesis, this is not the case. Sunscreens allow continuous transmission of a fraction of incident UV photons equal to 1/SPF. In other words, an SPF 15 product still allows 1/15 or 7% of UV photons into the skin.
Sunscreen users typically apply half or less of the FDA-stipulated amount of product needed to obtain the advertised protection level (Bech-Thomsen N, Wulf HC. Photodermatol Photoimmunol Photomed. 1992; 9(6): 242–244). Observation of people at parks and gardens, golf courses, tennis courts, pools and beaches showed a high degree of unprotected UV exposure, especially on golf courses (Dixon HG, et al. Cancer Epidemiol Biomarkers Prev. 2008 Feb; 17(2): 428–434).
If people require 2–8 minutes of unprotected summer sun exposure to maximize vitamin D synthesis, they could attain this in approximately 10–20 minutes after applying SPF 15–30 sunscreens. But let’s not forget that oral vitamin D can completely compensate for any lack of cutaneous vitamin D photosynthesis.
We are often asked to recommend a “safe” sunscreen. The Centers for Disease Control published a national survey of 2,500 Americans, age 6 and up, showing that the UV filter oxybenzone readily absorbs into the skin and is present in 97% of Americans tested (Calafat AM, et al. 2008; Environ Health Perspect. 116(7): 893–897).
The problem is, oxybenzone, AKA, benzophenone-3, has been linked to allergies, hormone disruption, and cell damage (Schlumpf M, et al. Toxicology. 2004; 205(1–2): 113–122). Typically, women and girls had higher levels than men and boys, probably due to greater use of body care products and sunscreens.
Oxybenzone is none-too-healthy for the environment. It can trigger outbreaks of viral infection in coral reefs; up to 10% of coral reefs are threatened by sunscreen-induced bleaching (Danovaro R, et al. Environ Health Perspect. 2008; 116(4): 441–447).
We can all minimize our negative impact on our inner and outer ecology by using sunscreens with physical filters, which reflect instead of absorb ultraviolet radiation; and choosing eco-friendly chemical sunscreens. One such product is Soleo, an organic, water-resistant, biodegradable formulation of 22.3% zinc oxide and other natural ingredients. Other paraben-free physical sun blockers (zinc and/or titanium) we recommend are: MyChelle Sun Shield SPF 28 and DDF Organic Sun Protection SPF 30.
Lastly, don’t forget UV-protective clothing, hats, sunglasses, and lip protection!
Michael Traub, ND, DHANP, FABNO, past-president of the American Association of Naturopathic Physicians, practices on the Big Island of Hawaii. He is designing a study to compare the relative efficacy of an emulsified liquid vitamin D with encapsulated vitamin D. Interested parties may contact him at michaeltraub@earthlink.net.
Monica Scheel, MD is a dermatologist at Kaiser Permanente Kona Clinic. They are collaborating on a book about natural medicine for skin disorders.
