I'm Dr Kavita Mariwalla, director of Mohs and dermatologic surgery at St Luke's-Roosevelt Hospital Center and Beth Israel Medical Center and an assistant professor of dermatology at Stony Brook University. I practice in New York. I'd like to welcome you to this Medscape video lecture titled "Making Sense of Sunscreen Controversies."

In recent years, the topic of skin cancer has received a lot of attention in the United States, and attention to the use of sunscreens has followed. It is my hope that at the end of this video lecture you will be able to speak knowledgeably with patients about sunscreen protection and answer some of the more common questions they may have.

Today we will outline the 3 main controversies involving sunscreen products. First we will review the new US Food and Drug Administration (FDA) guidelines governing sunscreen use. Next we will discuss whether sunscreen use actually protects against skin cancer. Finally we will evaluate whether sunscreen use has a negative impact on vitamin D levels.

In June 2011, the FDA released new guidelines for sunscreen manufacturers.^[1] The intent was to help consumers decide how to buy and use sunscreen. The guidelines are an effort to reduce confusion and allow consumers to more effectively protect themselves and their families from sun-induced damage. The FDA recognized in these guidelines that when used with other sun protection measures, sunscreen use can reduce the risk of skin cancer and early skin aging as well as help prevent sunburn. Let's review the new labeling requirements that manufacturers must comply with by June 2012.

One of the main changes is that all sunscreens must be broad spectrum. In other words, the product must demonstrate efficacy against both ultraviolet A (UVA) and ultraviolet B (UVB) rays. We traditionally think of UVB rays as those that cause burning and UVA rays as those that cause aging. Although this is true, we now know that over time cumulative ionizing radiation from UVA rays can contribute to the formation of skin cancer as well.

The next change is that manufacturers will only be allowed to use the term "water resistant" (not waterproof) and must specify the time of water resistance (40 or 80 minutes). To qualify as water resistant, the product has to demonstrate retained efficacy in preventing sunburn when applied to skin that is subsequently immersed in water. In essence, human subjects apply the product to their skin and then immerse themselves for either 2 or 4 20-minute periods in a whirlpool or tub of water. If the sunscreen manufacturer performs these tests and documents that the sun protection factor (SPF) value is retained after these periods of water immersion, the manufacturer is allowed to label the product as water resistant for 40 minutes or water resistant for 80 minutes. Terms like "sweatproof," "waterproof," and "sunblock" are no longer allowed.

In addition to the changes already mentioned, sunscreen products will have a maximum SPF of 50+ because the FDA did not think that there are adequate data to show that SPF values higher than 50 provide any additional, significant protection. To be categorized as broad spectrum, the SPF, which is actually a measure of protection against UVB, must be at least 15. In that case, the label on the back of the bottle will read, "If used as directed with other sun protection measures, decreases the risk of skin cancer and early skin aging caused by the sun." If the product has an SPF lower than 15, the label will read, "Skin Cancer/Skin Aging Alert: Spending time in the sun increases your risk of skin cancer and early skin aging. This product has been shown only to help prevent sunburn, not skin cancer or early skin aging."

The FDA sunscreen monograph applies to sunscreen protection in the form of oils, creams, lotions, gels, butters, pastes, ointments, sticks, and sprays. The FDA currently considers wipes, towelettes, powders, body washes, and shampoos ineligible for the monograph; therefore, these products cannot be marketed without an approved application. For spray products, the FDA has requested additional data to establish efficacy as a sun protection product and to determine whether sprays present a safety concern if inhaled unintentionally.

What does this mean for your patients? They should be using a broad spectrum sunscreen product with an SPF of 30, at least. Encourage them to reapply every 3 hours.

The monograph creates a more level playing field for sunscreen protection products. The FDA recognized the benefits of sunscreen in preventing skin cancer and also answered some questions about ingredients. Let's take a moment to examine that controversy.

Some groups have expressed concern that chemicals used in sunscreen products are dangerous, in particular oxybenzone, a synthetic estrogen, and retinyl palmitate, which breaks down in sunlight to photomutagenic compounds. The FDA monograph lists 16 compounds that adhere to the GRASE (Generally Recognized as Safe and Effective) conditions for sunscreens, taking into account the active ingredients at approved concentrations. Among these 16 compounds are para-aminobenzoic acid, which many people refer to as PABA, avobenzone, cinoxate, dioxybenzone, ensulizole, homosalate, meradimate, octinoxate, octisalate, oxybenzone, sulisobenzone, trolamine salicylate, and zinc oxide.

One of the controversial ingredients that has received much media attention is oxybenzone. Certain consumer advocates cited animal studies which suggest that oxybenzone may cause endocrine disruption.^[2,3] However, the studies involved high-dose oral administration of the medication rather than topical application. The results of the studies were not shown to be reproducible, so the FDA determined that there was no conclusive evidence that oxybenzone is a safety concern.

The other controversial ingredient is retinyl palmitate. It should be noted that retinyl palmitate is not an approved active ingredient in sunscreen products and when it is used it is added as an emollient, skin conditioner, or antioxidant. One of the concerns raised by consumer advocates was the role of retinyl palmitate in photocarcinogenesis. It should be noted that the specific study cited involved application of the chemical to mice that were genetically susceptible to developing skin cancer and then exposing these mice to sunlight.^[4] The formulation of the chemical was not a sunscreen product, nor did it include an active sunscreen ingredient. It is interesting that the control group of mice that received sunlight exposure without the application of topical retinyl palmitate also developed a high number of skin cancers. Therefore, evidence of retinyl palmitate as a photocarcinogen is unproven.

Here is the take-home message: The risk of not using sunscreen is much greater than any potential risk associated with sunscreen ingredients.

This brings us to our next controversy: Does sunscreen use actually prevent skin cancer formation? Let's look at the incidence of skin cancer. In the United States, 1 in 5 Americans will develop skin cancer in the course of a lifetime.^[5] Nearly 13 million people are living with a history of either basal cell or squamous cell carcinoma, and more than 58 million Americans are affected by the precancerous lesion actinic keratosis.^[6] The current lifetime risk of developing invasive melanoma is 1 in 58 in the United States.^[7]

Those who advocate sunscreen use believe that sunscreen protects against the formation of skin cancer, in particular melanoma. Those who believe that sunscreens cause skin cancer think that sunscreen use protects against sunburn and, as a result, may lead to longer sun exposure and thus increase the risk of skin cancer. It is also believed that results of epidemiologic studies on sunscreen use and skin cancer have been mixed.

However, new data are available. In a study published in December 2010, Green and colleagues^[8] followed 1621 Australians aged 25 to 75 years. One group was asked to apply sunscreen daily for 4 years; the other group applied sunscreen at their discretion over the same 4-year period. Ten years after trial cessation, the authors showed that there was a 50% reduction in primary melanoma in the group that applied sunscreen daily.

Darlington and colleagues^[9] demonstrated that study participants who applied sunscreen daily had a 24% reduction in actinic keratosis counts after 2 years of sunscreen use. This reduction had the effect of preventing, on average, 1 additional actinic keratosis per person during the 2-year period. Similar data are available for basal cell and squamous cell cancer reduction.

Here is the take-home message. The rate of skin cancer in the United States, both melanoma and nonmelanoma, is on the rise. Regular sunscreen use has been shown to reduce this risk and should be advocated, particularly in women and in patients with skin of color -- 2 populations in whom melanoma rates continue to climb steadily.

This brings up our last controversy. Does wearing sunscreen regularly hinder the production of vitamin D?

Vitamin D has gained significant attention in recent years because vitamin D deficiency has been linked to myriad diseases ranging from brittle bones and heart disease to diabetes, cancer, and certain autoimmune diseases. We do know that vitamin D offers dose-dependent protection against fractures.^[10] It reduces the occurrence of falls in the elderly population^[11], and, in the case of vitamin D₃, has been shown to decrease mortality in women.^[12] Vitamin D deficiency may place adults at risk for developing cancer of the breast, colon, and prostate, but optimal levels of vitamin D are not clear cut. The Institute of Medicine recommends 600 IU for everyone aged 1 to 70 years, and 800 IU for adults older than 70 years.^[13] The Endocrine Society recommends that adults at risk for vitamin D deficiency may need at least 1500 IU daily to maintain blood levels above 30 ng/mL.^[14]

Levels of 25-hydroxyvitamin D₃ (25[OH]D) range from sufficient to toxic. Keep in mind that vitamin D is a fat-soluble vitamin, so it is possible to have too much. Information has now become available to indicate that a level of at least 80 nmol/L might be necessary to provide the full range of health benefits of vitamin D.

The term vitamin D refers to either vitamin D₂ or vitamin D₃. Vitamin D₃, also known as cholecalciferol, is either made in the skin or obtained in the diet from fatty fish. Vitamin D₂, also known as ergocalciferol, is obtained from irradiated fungi such as yeast. Both products are used to supplement food or are contained in multivitamins.

The first step in the production of the biologically active form of vitamin D, which is known as 1,25-dihydroxyvitamin D₃, (1,25[OH]D) is the conversion of 7-dehydrocholesterol, also known as provitamin D, in the skin to previtamin D₃ following exposure to UV radiation. This reaction occurs in the UVB waveband, which is 290 to 315 nm, with a maximum efficiency at approximately 300 nm. Vitamin D₃ is then formed from previtamin D₃ by a gradual thermal isomerization in the skin.

In the skin, the main component of vitamin D production is the formation of previtamin D_3, and that's why we're concerned about it and discussing it in this video. Factors that affect production include age, skin color, clothing, area of skin exposed, latitude, season, weather, and time of day. Let's look at some of the data.

Marks and colleagues conducted a randomized, double-blind, controlled trial involving 113 subjects aged 40 and older.^[15] Half of the volunteers applied SPF 15 sunscreen to the head, neck, and forearms; the other half applied placebo cream. Blood samples were collected at the beginning and end of the study, and the concentration of 25(OH)D rose in both groups by a similar amount. Thus sunscreen use could not be interpreted as a risk factor for vitamin D deficiency.

Another study by Farrerons and colleagues followed 24 elderly sunscreen users and 19 controls on 5 occasions throughout a period of 24 months.^[16] Serum 25(OH)D and 1,25(OH)D levels were measured along with several bone markers and parathyroid hormone. All subjects were vitamin D sufficient at the beginning of the study; 1,25(OH)D levels did not change significantly in either the sunscreen or the control groups with the season of the year, nor were there any changes in osteoporosis markers.

Lastly, Kimlin and colleagues assessed 25(OH)D serum status in 124 healthy adults aged 18 to 87 years who were living in Queensland, Australia, at the end of the winter months to find out whether there was a phenotypic characteristic or sun behavior pattern that was important in determining vitamin D levels.^[17] The mean 25(OH)D level increased with increasing frequency of sunscreen use, and participants who regularly used sunscreens not only had sufficient levels but some of the highest concentrations. The authors surmised that people who wear sunscreen actually go out in the sun and are using the sunscreen to avoid a burn when sunbathing.

The take-home message is that the evidence described above demonstrates that in real-life situations the regular use of sunscreen is unlikely to affect vitamin D status and indeed may even enhance it.

So what should you do? The sensible approach is best. This is what I tell my patients. Wear sunscreen with an SPF of 30 and reapply every 3 hours. For golfers, this means every 9 holes; for athletes it means at halftime. If my patient reports not going in the sun at all, I check the vitamin D level and supplement only if needed. I talk about sunscreen with patients during their cosmetic dermatology visits, and I use sunscreen to massage the skin [after injection of filler products while I educate patients about the importance of sunscreen use]. I also talk about sunscreen use during total body skin examinations when I'm looking through the scalp. When people ask me for moisturizer recommendations, I tell them that in the summer sunscreen alone can work as a moisturizer. I hope my tips help.

Thank you for joining us for this Medscape video lecture. Remember to complete the post-test in order to earn credit for this program.