Life Extension Magazine June 2005
Why Sunscreens Do Not Fully Prevent Skin Cancer
By Dale Kiefer
By Dale Kiefer
For decades, the public has been told that sunscreens help guard against skin cancer.
One would think that a lotion that reduced solar ray penetration would be protective. Recent scientific studies, however, suggest that sunscreen use may not reduce the risk of melanoma, the deadliest of skin cancers.1
Commercial sunscreens fail to adequately protect the skin because they have little impact on reducing the free radicals generated in response to solar radiation exposure. One study showed that an SPF 20 sunscreen provided a “free radical protection factor” of only 2!2 In other words, while sunburn-inducing ultraviolet-B rays can be blocked, other kinds of solar radiation continue to inflict DNA damage that can result in skin cancer.2,3 These same free radicals also contribute to skin aging.3,4
Since 1983, the Life Extension Foundation has maintained that it takes more than conventional sunscreens to protect the skin from DNA-damaging solar rays. The encouraging news is that an abundance of newly published data provides a basis for enhanced skin protection against ultraviolet light that greatly exceeds what is available in commonly used over-the-counter sunscreens.
Considering that skin cancer (malignant melanoma, basal cell carcinoma, and squamous cell carcinoma) is the cancer with the highest incidence worldwide, those who follow obsolete recommendations are setting themselves up for lethal disease or premature aging of the skin.5
In this article, Life Extension challenges conventional wisdom about how you can protect yourself against damaging solar rays. Alternatives to outmoded, topical sun-blocking agents are provided.
Misconceptions can be deadly. If you think you can safely lie out in the sun as long as you are covered with a commercial sunscreen, the science indicates you are mistaken. Increasingly, studies suggest that no commonly available sunscreen prevents photodamage.3
Even if you choose to avoid sunbathing, typical everyday exposure (30 four-minute exposures over the course of a week) is equivalent to spending over two hours every week at the beach. In fact, everyday sun exposure is a causative factor in skin aging.2,4
With the onset of the long, sunny days of summer and the ongoing depletion of the Earth’s protective ozone layer, protecting your skin against solar radiation should be a priority. As the incidence of skin cancers and premature aging of the skin continues to increase to epidemic levels, taking aggressive steps to guard against sunlight-induced free radicals is of paramount importance.
An estimated 90% of all skin cancers result from long-term exposure to UV radiation from the sun.6 Fair-skinned Caucasians and redheads, usually of northern European descent, are at highest risk of suffering UV-induced damage.
Melanoma Incidence Rising
Melanoma is highly treatable when detected and treated early. It is also largely preventable, if you scrupulously avoid sun exposure throughout your life. However, studies show that Americans have received up to 50% of their lifetime dose of UV radiation by the time they reach the age of 21.7 If you are of Caucasian descent and a certain age, you likely are at increased risk of developing this dangerous cancer of the skin’s pigment cells, which are known as melanocytes.
In fact, according to the National Cancer Institute, the incidence of skin melanoma among Caucasians in North America has steadily increased for about the last 30 years. Diagnoses increase dramatically after the age of 50, especially among men.8 Scientists at the Boston University School of Medicine report that in the US, melanoma diagnoses are increasing at a rate faster than those of any other preventable cancer.9
The American Cancer Society estimates that the mortality rate from melanoma has increased 50% since 1973. While the annual rate of increase has slowed somewhat since the early 1980s, nearly 60,000 new cases are expected to be diagnosed this year, and nearly 8,000 Americans will die of the disease.10 Those statistics pertain only to melanoma, the deadliest of skin cancers. If we also include basal cell and squamous cell carcinomas (two less deadly but still worrisome cancers of the epidermis), various skin cancers account for more than 50% of all cancer cases.
Melanoma may be deadly, but basal and squamous cell carcinomas are considerably more common. In fact, “Basal cell carcinoma is as common as dirt,” says Dr. Brett Coldiron, an expert on skin cancer treatment. Basal and squamous cell carcinomas respond well to relatively simple treatment, but repeat carcinomas likewise are common.
Why Tanning Is Damaging
Tanning results when melano-cytes generate pigment in an apparent effort to protect the skin. Efficiency at pumping out melanin confers darker skin, and darker skin traditionally has been associated with greater protection from the sun, primarily because darkly pigmented skin is at lower risk of photocarcinogenesis, or UV-induced cancer. By the time a tan develops, however, tissue damage has already occurred.
Recently, some scientists have suggested that melanin production is triggered by DNA damage and subsequent cellular efforts to repair that damage. According to this hypothesis, photoprotection against the redness and DNA damage caused by UV exposure does not correlate with level of skin pigmentation; instead, darker-skinned Caucasians may simply be better at repairing damage than are lighter-skinned individuals.11 Growing public awareness of the dangers of a “healthy tan”—and of the importance of regular use of sunscreen with a sun protection factor (SPF) of 15 or greater, in combination with skin-protective phytochemicals—may help to slow the incidence of skin cancer.
New, Improved Zinc Oxide
Various chemicals act as UV screens, and commercial sunscreen products may incorporate several of these to achieve a given SPF level. One of the oldest, best-known sunscreen agents is zinc oxide. Although perhaps none-too-fondly recalled as a white paste sported by lifeguards at the beach, zinc oxide has come a long way in recent years. New manufacturing processes can produce zinc oxide with microfine particles that block UV radiation effectively while appearing invisible on the skin.12,13 The FDA classifies microfine zinc oxide as a Category I skin protectant.
Also important for immune health is inorganic zinc, which is found in at least 300 proteins, hormones, and enzymes,14 including one of the body’s most important natural antioxidants, superoxide dismutase (SOD).15,16 Topical zinc apparently promotes healthy skin by at least two mechanisms besides UV protection. Animal studies have shown that topical zinc oxide prompts the release of insulin-like growth factor and increases the mitotic index of basal cells, while also promoting wound healing.17,18 The mitotic index measures the rate at which cells divide in order to repair tissues.
Like zinc oxide, titanium dioxide is an inorganic metal. While previous research suggested that these micronized oxides act as physical sun shields by scattering or reflecting UV light, recent findings suggest that zinc oxide and titanium dioxide mobilize electrons within their atomic structure while absorbing UV radiation.13 Thus, while these agents are not inert as was previously assumed, they are still safe, stable, non-toxic, and highly efficient sunscreens.13 Titanium dioxide offers a high level of protection against both UVA and UVB radiation, and scientists report that “products containing microfine titanium dioxide are likely to offer superior photoprotection.”19
Octinoxate and Oxybenzone
Octinoxate and oxybenzone are highly efficient ultraviolet shields that the FDA has qualified as Category I sunscreens. These compounds primarily offer protection against UVB waves. Investigators have found that octinoxate, also known as octyl methoxycinnamate, protects the skin against not only sunburn but also UV light-induced DNA alterations.20,21 Titanium dioxide also demonstrated this DNA-protective effect.21 When scientists compared the efficacy of several sunscreen agents, they found that preparations containing oxybenzone yielded the highest SPF values.22 Thus, octinoxate and oxybenzone may help protect against UV-light induced DNA changes and boost the SPF of sunscreen products.
Sunscreen agents including transparent microfine zinc oxide, titanium dioxide, octinoxate, and oxybenzone are clearly a boon to sun worshipers. For some people, however, the judicious use of sun blockers may simply be too little, too late, as sun damage is cumulative.23 Skin can be thought of as a kind of radiation dosimeter, such as an X-ray technician might wear. Although daily exposure may be minimal, invisible damage accumulates gradually. Like the X-ray technician, we need to keep cumulative dosage in mind when venturing into the sun.
Sunscreen: How Much, How Often?
A sunscreen with an SPF of 15 should prevent sunburn from an all-day exposure to tropical sunlight. Behavioral studies show, however, that sunscreens of SPF 15 or greater do not always prevent sunburn.24 Several factors may account for this discrepancy in sun protection, including the type of sunscreen applied, resistance to water immersion and sand abrasion, and how often sunscreen is reapplied.
A number of studies suggest that many people do not use enough sunscreen to obtain maximum sun protection. The FDA determines the SPF of a sunscreen based on an application thickness of 2 mg/cm2. A study from Denmark showed that when 42 volunteers on a beach applied their own sunscreen all over their bodies, the average amount applied was only 0.5 mg/cm2, or one quarter of the recommended amount.25 The application thickness of sunscreen has a significant effect on its sun protection factor. In fact, an English study showed that most people apply only enough sunscreen to achieve 20-50% of the sun protection factor expected from the product label.26 Underprotection due to inadequate application may explain the reports suggesting that sunscreen use is a risk factor for melanoma.26
While ample application of sunscreen is important, consistent daily use may be just as critical. Researchers from Boston and Cincinnati examined the effects of daily versus intermittent sunscreen application in preventing skin damage. Twenty-four subjects were exposed to two daily doses of UV radiation for four consecutive days. Three sunscreen products were applied to areas of each subject’s skin. A product with an SPF of 15 was applied daily before UV exposure.
To simulate intermittent product use, an SPF-15 product or SPF-29 product was applied to another area on three of the four days, with one missed application on days two, three, or four. The researchers found a significant increase in inflammation and sunburn in the intermittently protected areas compared to skin that was not exposed to UV light and skin that was treated daily with the SPF-15 product. The researchers concluded, “daily use of a sunscreen reduces the skin damage produced by UV exposure compared with intermittent use of equal or higher SPF products. The daily application of sunscreens in appropriate quantities reduces the harmful effects of solar UV radiation on skin.”27