It's time for sunscreen! Or is it?

Sunscreens prevent sunburns, but beyond that simple fact surprisingly little is known about their safety and efficacy. The Environmental Working Group's  review of the latest research discovered troubling facts that might tempt you to give up on sunscreens altogether. That’s not the right answer. Despite the unknowns about sunscreens’ efficacy, public health agencies still recommend using them, just not as your first line of defense against the sun.

There’s no consensus that sunscreens prevent skin cancer

The FDA’s 2011 sunscreen rules allow sunscreen makers to advertise that using their products can decrease the risk of skin cancer and sun-related skin aging. But a wide range of public health agencies – including the FDA – have found very little evidence that sunscreen prevents most types of skin cancer. In reviewing the evidence, the FDA said that the available clinical studies “do not demonstrate that even [broad spectrum products with SPF greater than 15] alone reduce the risk of skin cancer and early skin aging.” The agency also said that it is “not aware of any studies examining the effect of sunscreen use on the development of melanoma.”

The International Agency for Research on Cancer recommends clothing, hats and shade as primary barriers to UV radiation. It says that “sunscreens should not be the first choice for skin cancer prevention and should not be used as the sole agent for protection against the sun."

A newly published study of a group of sun-savvy Australians found that the daily use of a SPF 15 sunscreen with good UVA protection along with other protection strategies reduced risk of melanoma diagnosis over a 10-year follow-up period.  But other studies have concluded that sunscreen users are at increased risk of melanoma because they tend to subject themselves to more intense sun exposure.  No one has the final answer.

There’s some evidence that sunscreens might increase the risk of the deadliest form of skin cancer for some people

Some researchers have detected an increased risk of melanoma among sunscreen users. No one knows the cause, but scientists speculate that sunscreen users stay out in the sun longer and absorb more radiation overall, or that free radicals released as sunscreen chemicals break down in sunlight may play a role. One other hunch: Inferior sunscreens with poor UVA protection that have dominated the market for 30 years may have led to this surprising outcome. All major public health agencies still advise using sunscreens, but they also stress the importance of shade, clothing and timing.

The International Agency for Research on Cancer (IARC) is one of many public health agencies that recommend taking other measures before using sunscreens:

• “Sunscreens should not be the first choice for skin cancer prevention and should not be used as the sole agent for protection against the sun.” – IARC 2001

The agency’s experts have noted that people wearing sunscreens may be tempted to stay in the sun longer than is safe. They write: “The use of sunscreens can extend the duration of intentional sun exposure, such as sunbathing. Such an extension may increase the risk for cutaneous melanoma." 

There are dozens of high-SPF products — but no proof they’re better.

There is little difference in sunscreens beyond SPF 15. Consider the following:

• SPF 15 will allow 7% of UVB radiation through to the skin
• SPF 30 will allow 4% of UVB radiation through to the skin
• SPF 60 will allow 2% of UVB radiation through to the skin

SPF values are calculated based on a dose of about 1oz (30mL, or 2 tablespoons) for the entire body — much more than is typically used.  In general, insufficient amounts of sunscreen are applied to achieve the labeled UV protection.  The EWG  illustrates the consequences of inadequate use of sunscreens, based on applying one-quarter of the recommended amount:

SPF on label	Average SPF of users at(0.5 mg/cm2)	% UV transmission (amount reaching skin)
15	2	50%
30	2.3	43%
50	2.6	38%
100	3.2	31%

The FDA has proposed prohibiting the sale of sunscreens with SPF values higher than “50+.” The agency has written that values higher than 50 would be “misleading to the consumer,” given that there is an “absence of data demonstrating additional clinical benefit, "and that “there is no assurance that the specific values themselves are in fact truthful."

Scientists are also worried that high-SPF products may tempt people to stay in the sun too long, suppressing sunburns (a late, key warning of overexposure) while upping the risks of other kinds of skin damage.

More than 1 in 7 products now lists SPF values higher than 50+, compared to only 1 in 8 in 2009. It’s a fair statement that higher SPF products are more about marketing, rather than meaningful differences in potential sun protection. You get better protection using a sunscreen properly.

Too little sun might be harmful, reducing the body’s vitamin D levels.

Sunshine serves a critical function in the body that sunscreen appears to inhibit — producing vitamin D. The main source of vitamin D in the body is sunshine, and the compound is enormously important to health – it strengthens bones and the immune system, reduces the risk of various cancers (including breast, colon, kidney and ovarian cancers) and regulates at least a thousand different genes governing virtually every tissue in the body (Mead 2008). About one-fourth of Americans have borderline low levels of vitamin D, and 8% have a serious deficiency (CDC 2012). Particular groups are at the highest risk – breast-fed infants, people with darker skin and people who have limited sun exposure (NIH 2012).  See my post http://wellenough.blogspot.com/2012/05/sunlight-can-reduce-cancer-risks.html to learn more.

Some people can make enough vitamin D from 10 to 15 minutes of unprotected sun exposure several times a week. But many others cannot. The right amount depends on the individual’s age, skin tone, the intensity of sunlight, time outdoors and skin cancer risk. Check with your doctor to see if you should get a vitamin D test or if you should take seasonal or year-round supplements.

The common sunscreen ingredient vitamin A may speed development of cancer

Recently available data from an FDA study indicate that a form of vitamin A, retinyl palmitate, may speed the development of skin tumors and lesions when applied to skin in the presence of sunlight. This evidence is troubling, because the sunscreen industry adds vitamin A to 25% of all sunscreens.  However, the research that gave us this information can be misleading. 

Retinyl palmitate is a form of vitamin A commonly used in cosmetic products to reduce wrinkles and fine lines. The EWG points to a 2009 study of retinyl palmitate on mice as their main cause for concern. Treated mice, and a control group were exposed to the equivalent of nine minutes of noontime Florida sun daily, for a year. Compared to the control group, the RP group developed more tumors. The mice were treated with retinyl palmitate — not sunscreen that contained retinyl palmitate. It’s known that retinyl palmitate can be a photosensitizer.

So how relevant is this mouse study to human subjects, wearing sunscreens containing retinyl palmitate? It’s difficult to say. Study completion and peer review is expected. It’s not unreasonable to avoid it if desired, but there’s still no hard evidence to suggest its presence is directly linked to developing cancer.

Zoe Diana Draelos, editor of the Journal of Cosmetic Dermatology, has hypothesized that sunscreens may not be as safe as dermatologists contend and should be used only on exposed areas, like the hands, that cannot easily be covered with tightly woven clothing. She notes that wearing clothing “over most of the body, with sunscreen only applied to exposed areas, such as face and hands, might minimize systemic levels and prevent problems, which as of yet are poorly understood."

Free radicals and other skin-damaging byproducts of sunscreens.

Both UV radiation and many common sunscreen ingredients generate free radicals that damage DNA and skin cells, accelerate skin aging and cause skin cancer. An effective sunscreen prevents more damage than it causes, but sunscreens are far better at preventing sunburn than at limiting free radical damage. While typical SPF ratings for sunburn protection range from 15 to 50, equivalent “free radical protection factors” come in at about 2. When consumers apply too little sunscreen or reapply it infrequently – and that’s more common than not – sunscreens can cause more free radical damage than UV rays on bare skin.

Pick your sunscreen: nanomaterials or chemicals

 The major choice in the U.S. is between “chemical” sunscreens, which have inferior stability, penetrate the skin and may disrupt the body’s hormone systems, and “mineral” sunscreens (zinc and titanium), which often contain micronized- or nanoscale particles of those minerals.

Mineral sunscreens have the best safety profile of today’s choices. They are stable in sunlight and do not appear to penetrate the skin. They offer UVA protection, which is sorely lacking in most of today’s sunscreen products.

Some scientists have urged parents to avoid using oxybenzone on children due to penetration and toxicity concerns.  Oxybenzone hasn’t been linked conclusively to negative health effects. But absence of evidence isn’t evidence of absence, so should there be cause for concern? The CDC notes, “Human health effects from benzophenone-3 at low environmental doses or at biomonitored levels from low environmental exposures are unknown.” Luckily, when it comes to oxybenzone and sunscreens, the myriad of alternatives available mean that it’s possible to avoid oxybenzone if desired, while still finding products that provide good UV protection.

Europe’s sunscreens

According to the EWG, sunscreen makers and users in Europe have more options than in the United States. In Europe, sunscreen makers can select from among 27 chemicals for their formulations, compared to 17 in the US. Companies selling in Europe can add any of seven UVA filters to their product, but they have only three available for products marketed in the US.  Sunscreen chemicals approved in Europe but not by the FDA provide up to five times more UVA protection; US companies have been waiting five years for FDA approval to use the same compounds. Until the FDA approves these ingredients and lifts restrictions on combining certain active ingredients, strong UVA protection will be scarce in US sunscreens.

Sunscreen – within reason

A 2009 article in the British Journal of Dermatology suggested that “despite the lack of evidence demonstrating the efficacy of modern sunscreens in preventing melanoma… it would be irresponsible not to encourage their use, along with other sun protection strategies, as a means of combating the year-on-year rise in melanoma incidence.” Similarly, the American Academy of Dermatology said in a 2009 statement: “To protect against skin cancer, a comprehensive photo-protective regimen, including the regular use and proper use of a broad-spectrum sunscreen, is recommended.”

But don’t shut out the sun

Many scientists warn against overreacting, because sunlight stimulates the skin to produce vitamin D, which enhances overall well being and possibly lowers skin cancer risks. As well, according to scientists at the Los Angeles County Department of Public Health, “avoiding sun exposure by staying indoors more may come at the cost of adequate physical activity. The consequences of overweight and obesity, cardiovascular disease, and, yes, potentially many non-skin types of cancer indicate that there are important trade-offs between messages to reduce sun exposure and messages to get regular sun exposure to stimulate the production of vitamin D and to get adequate physical exercise.”

Bottom line

The uncertainties surrounding sunscreens might tempt people to give up on them altogether. That’s not the right answer. Research is inconclusive about the possible dangers of sunscreen and public health agencies still recommend using them.

We need sun every day and we also need to avoid the most harmful of its rays.  Both UVA and UVB are now implicated as cancer-causing, and UV radiation is considered a carcinogen.  Acutely, we see the effects of UVB. Sunburns can range from mild redness to life-threatening situations. Long term, the skin will show signs of both UVA and UVB damage. Degenerative changes including skin thickening as well as fibrous tissue and circulatory changes follow chronic exposure.

So seek shade, wear sunscreen if you or your children are outside in the midday sun and get some vitamin D and exercise. 

Sources:
Environmental Working Group
http://breakingnews.ewg.org/2012sunscreen/sunscreens-exposed/sunscreens-exposed-9-surprising-truths/

New England Journal of Medicine
http://www.nejm.org/doi/full/10.1056/NEJMra070553

British Journal of Dermatology
http://laboratoires-spirig.com/upload/news/docs/81Daylong_Ac_dans_le_BJD.pdf

JNCI Journal of the National Cancer Institute Advance Access published March 23, 2010http://jnci.oxfordjournals.org/content/early/2010/03/23/jnci.djq056.full.pdf

Science-Based Medicine.org
http://www.sciencebasedmedicine.org/index.php/the-great-sunscreen-cover-up/

US National Library of Medicine
http://www.ncbi.nlm.nih.gov/pubmed/8695238