The Latest Science in Sunscreens and Protection: What You Need To Know

For this third post, I thought I would pass on interesting and relevant scientific news from recent meetings I attended with my wife, Dr. Sharyn Laughlin. The Annual Meeting of the Photomedicine Society and the Annual Meeting of The American Academy of Dermatology were held in March 2014.

More evidence was presented by Dr. Thomas Ruenger for the role of UVA in inducing enzymes that promote the breakdown of collagen and elastin as an important mechanism for photoaging. The findings presented also show that the effect of longwave UVA is the most pronounced and much greater than the effect of UVB. Over the past decade, there has been a volume of evidence from scientific studies that confirm the important effect that UVA has on photoaging and the induction of cellular damage, leading to all forms of skin cancer. This should come as no surprise to anyone – including those who still do not acknowledge the inherent dangers of UVB-biased sunscreens that give unbalanced protection, and allow the effects of UVA to be mostly unabated and cumulative.

Our Skin: A Work of Art Worth Saving

Not everything in science needs a study. Many definitive studies cannot be done in humans for ethical and practical reasons. Sometimes critical thinking, cognitive analysis, deductive reasoning – fancy terms for common sense – is all that is required. UVA penetrates to the deeper dermis where the important elements regulating genetics, immunity, and cell function reside, while UVB barely penetrates through the epidermis. UVA is ubiquitous, essentially the same at any latitude and time of day, and is 15-16 times more potent than the dose of UVB that only accounts for 5% of the UV band. It should be logical that the adverse effects of UV radiation may have more to do with UVA than UVB. Erythema or redness of the skin, the first sign of sunburn, and the eventual sunburn, is commonly believed by many people (even some physicians), to be UVB (290-320 nm) mediated skin damage, with a minor contribution from UVA-2 (320-340 nm). It is the basis of the sun protection factor (SPF) that is a label standard that indicates the degree to which a sunscreen reduces the sunburn reaction. The new labelling rules to be adopted in N. America changes the meaning of SPF to denote sunburn protection factor, a more accurate definition. It should convey to the consumer that SPF is a measure of the sunscreen’s ability to reduce or protect from sunburn but is not an adequate measure of protection to other adverse effects of the sun. The erythema-sunburn reaction and its genesis is actually more complex and is also related to UVA-1 effects.

Anyone who has had a sunburn by not applying a sunscreen on a very cloudy day has experienced a UVA sunburn. It is a deeper burn and much more painful that the usual sunburn that starts with UVB initiation. A sunscreen that completely blocks only UVB will not always prevent sunburn and over time a gradual or delayed sunburn develops to the UVA part of the sun. UVB is more efficient in causing sunburn and produces the immediate redness. UVA accounts for 95% of UV exposure and this higher absolute amount contributes to erythema. The early or mainly UVB initiated sunburn reaction, is a protective response telling you to get out the sun when the damage is early and more superficial. Continued sun exposure, even with a sunscreen of high SPF, but minimal UVA-1 protection, eventually leads to a more severe sunburn and the deeper damage that causes irreversible consequences- photoaging and the DNA changes that may lead to cancer many years down the road. SPF values > 15 can only be attained if the UV filters used are reducing transmission of UVA-2 and UVA-1, but is primarily a measure of UVB attenuation.

Industry consultants continue to push the trend arguing for high SPF sunscreens with values > 50 even approaching 100. There is a minor photometric basis for using a higher SPF. Looking at the transmission, rather than what is blocked does show that SPF 30 gives twice the protection than SPF 15, a SPF 60 twice that of SPF 30 and four times SPF 15. An SPF 15 blocks 93.3% of incident UV compared to 96.6% with SPF 30, a difference of 3.3% for doubling the concentration of filters. However, considering what gets through by counting photons of light shows that only half the amount gets through with the higher SPF. The higher SPF also compensates for the lower application amounts used by consumers in practice than the amount applied for laboratory SPF testing. There is some truth in a consumer thinking that a higher SPF allows you better protection and a SPF 30 allows you to stay out twice as long as a SPF 15. The danger is that the higher SPF will have some UVA protection but not nearly enough, if it does not contain one of the limited number of filters that give adequate UVA-1 protection. I am cynical enough to think that industry pushes high SPF sunscreens knowing that the public assumes they are better in every respect. Given a choice between a SPF 30 and a SPF 50, always select the more balanced sunscreen with better UVA-1 protection. This is easy to do in the UK or Europe. Look for Boots 4 or 5 stars in the UK or a UVA-PF to SPF ratio of > 1/3 in Europe. The more this ratio approaches 1, the better the sunscreen is for affording you balanced and proper protection. North American consumers have no such ability  to use the label metrics for selection. The new rule of using a Critical Wavelength (CW) of 370 nm or greater as proof of truly broad spectrum activity, particularly the most important UVA-1 extinction, will not necessarily be valid.

The CW is a measure of the wavelength at which 90% of the area under the absorption or extinction curve occurs. This relates to broad spectrum activity as to achieve this CW of 370 nm, usually requires a significant UVA absorbance. However, the threshold of 370 nm can be attained by some sunscreens with little overall UVA-PF, particularly in the more problematic UVA-I spectrum approaching 400 nm. Sunscreens with low UVA-PF  and those with moderate UVA-PF can both have the same CW of 370 nm. The shape of the extinction curve is a factor and a UVB biased sunscreen SPF 30, with inadequate or a low UVA-PF  < 10 can attain the same CW of 370 nm as a sunscreen with UVA-PF of ≥ 10. One would fail the EU criteria but both would pass in the USA and Canada, under new regulations being enforced this year. My preference for adequate UVA protection is that SPF 30 values should have a UVA-PF exceeding 20 with the ratio approaching 1. More about these considerations in a later post.

The other important topics discussed at these meetings included the use of anti-inflammatory(AI) agents

Can a diet rich in anti-oxidants protect you from the sun?

or antioxidants (AO) in sunscreens, and the role for oral photoprotection as a component of a sun protection strategy. The use of AI ingredients will be discussed in detail in a future post. Dr. Salvador Gonzales  reviewed the present status of oral nutrients that afford some measure of UV protection, and its use in oral photoprotection is increasing in Europe at an annual rate of about 5%. He also reminded us that a lifetime UV radiation exposure is attained 1/3 through vacation, compared to 2/3 from every day or non-vacational time. This supports our view that a balanced sunscreen is for daily use all year round. In addition 70-80% of sunburns occur can occur in your backyard. Dr. Mary Matsui presented evidence that certain nutrient and botanical ingredients applied on the skin are a source of non-sunscreen photoprotection. The list of useful agents for oral or topical photoprotection is extensive. Some of these and other agents also may reduce skin damage from visible light (400-770 nm) and near infrared (IRA at 770 -1400 nm), now shown to be relevant in addition to UV in the genesis of adverse effects from sunlight. This an area I am presently researching at CyberDERM. While developing a balanced sunscreen that mimics the UV protection afforded by black clothing or shade, we are identifying the single best antioxidant to add to the formula. Some of the effects of UV and IRA on inducing immune suppression may also be reduced by oral therapy. Longer wavelengths UVA-1 near 400 nm and visible through IRA at 400- 1400 nm, tend to produce deeper damage to the dermis. Oral antioxidants may be more rational and efficient than topical application. The concept of skin therapy from within via the dermal blood vessels is not new. I recall an ad-campaign from many years ago- “have you taken your skin care today”? For therapy to cell damage in the dermis, ingestion and delivery by the dermal blood supply seems more logical than topical administration, which requires absorption through the epidermis, and the agent is not always sure to reach the deep dermis. We are also working on an antioxidant mix for oral supplementation that best achieves all the objectives. For now it appears that taking 2 Gms. of Vitamin C and 1200 IU of Vitamin C increases the minimal erythema dose –  the visible sign of sun damage – by 20% after 1 week and 40% at 3 months (Gonzales et al). Flavonoids and the subgroups- anthocyandins, catechins, flavonols, and isoflavones – all play important roles in modulating and inhibiting the various adverse effects. A diet rich in blue and red berries, red or purple grapes, 1-2 glasses of red wine/day, dark chocolate, green and white teas, apples, broccoli, onions and scallions, kale, soybeans, hot peppers, apricots and celery, provides Flavonoids. This diet with Vitamin C and E as described above may be a useful adjunctive measure to using a balanced sunscreen and sun avoidance  for those at greater risk of cancer and photodamage. These nutrients, along with ingesting curcumin, resveratrol, and pomegranate, are already recommended for a myriad of health benefits. Skin cancer is considered an occupational disease in some provinces of Germany, and in Canada we need a National Occupational Strategy for those involved in outdoor work. For these workers and anyone at higher risk for skin cancer, a dietary approach as outlined is a complementary and responsible self- help initiative.

THe Hierarchy of Sun Smart Behaviour

The first post dealt with rising skin cancer rates in N. America. Up to 4 million Americans and 120,000 Canadians will develop a skin cancer this year. One in six Canadians and one in five Americans will develop a skin cancer within their lifetime. More alarming, is the rising rate for all skin cancer but particularly the rate for melanoma.  The last post dealt with the public health and economic dimensions of the problem. Scarce health care resources are spent on a  preventable disease and costs continue to rise. In Canada up to 1/4 million cases of skin cancer could cost over one billion by 2030. Collectively, we need a new strategy. There is a need for new public health policy, but after years of trying to engage public officials, I have come to the conclusion that they are either unable or unwilling to frame effective solutions. Each of us must adopt our own public health measures and educate or encourage our entire circle of friends, relatives and contacts.

The Basics:

Figure 1: The Iconic Coppertone Baby

Everyone can adopt a simple approach to sun safety motivated by wanting to lower your risk for skin cancer, to reduce photoaging and retain a younger appearance, or simply do it for public responsibility. First, an understanding of basic photobiology. Sunlight contains visible light at 400-760 nm and  ultraviolet (UV) at wavelengths 290-400 nm. Longer infra-red beyond 760 nm gives you the feeling of warmth on your skin and also has negative effects. However, most sun-damage comes from UV that accounts for 5% of total sunlight. Sunscreens are supposed to absorb, scatter, or reflect this entire range of invisible UV energy - UVB (290-320nm) and UVA (320-400nm), which is split into shortwave UVA (UVA-II at 320-340nm) and longwave UVA (UVA-I at 340-400nm). Most  Canadians will be using sunscreens that filter UVB and provide inadequate or no protection to harmful UVA radiation, particularly in the UVA-I band. UVA accounts for 95% of the UV radiation reaching a person and is 15 times more potent on earth than UVB. It is illogical for sunscreens to be UVB-biased, as they are in N.America, providing most protection against UVB. Sunscreens need to provide balanced protection aiming for equal attenuation at every wavelength. The word ‘balanced’ will be a recurring refrain in this series. Your ability to identify and use a sunscreen with balanced UV protection will be the ultimate part of a smart sun protection hierarchy. The iconic Coppertone ad (Figure1) shows the graphic profile of the UVB sunscreen that allowed tanning without burning – UVB biased. Newer sunscreens give some more UVA-II protection but the ideal and safest sunscreen would be balanced, depicted by the profile at the right- similar to the lady shaded by a parasol. This is defined as balanced protection or spectral homeostasis – where a sunscreen affords virtually equal protection at every wavelength across the entire UV spectrum from 290-400 nm.

What to do?

Figure 2: The Fitzpatrick Skin Type Classification

Figure 3: Time To Burn Based on Skin Type

The next step is to be aware of the harmful effects of UV radiation. All types of skin cancer can occur in areas never exposed to the sun, but the majority are related to effects of UV radiation. It is estimated sun damage causes 90% of non melanoma skin cancer and 65% of melanomas, and most are potentially preventable. Sunburn and the erythema effect (the visible warning sign of UV skin damage) is caused almost entirely by UVB and UVA-I (290-340nm). Figure 2 gives the classification dermatologists use and Figure 3 shows the time for unprotected skin to burn. Unprotected white skin (Type I) can show mild erythema and sunburn after 1-2 minutes under the tropical summer sun at noon.  UVA radiation may be more harmful than UVB with a wider scope of skin damage- immune suppression, accelerated photoaging, and skin cancer. UVA as a longer wavelength penetrates deeper than UVB.  20 times more UVA, particularly the deeper penetrating UVA-I, reaches fragile proliferating cells in the basal layer of the epidermis and harmful effects even extend below the dermis (Figure 4). UVB triggers the sunburn and tanning response. UVA that penetrates deeper and stimulates the melanin response in the dermis responsible for the deeper and longer lasting tan. That is why the early sunscreens were formulated to prevent sunburn but to allow tanning by being UVB-biased. They blocked UVB and inhibited sunburn but allowed harmful UVA rays to stimulate a tan in melanin-competent skin- usually Skin Types III-V.   Do not consider a tan as UV protection. It is a protective response that says damage to your skin has occurred. The role of harmful UVA rays in tanning is also the reason why dangerous tanning beds use pure UVA light. This ill-advised way to tan is linked to the dramatic rise in melanoma rates in younger patients, particularly females under 30.

Figure 4: Detrimental Effects of UV to Human Skin

What does it mean to be Sun Smart?

The hierarchy of Sun Smart or Sun Safety Campaigns begins with being aware of the UV-Index and linking your dress and sun-avoidance behaviour accordingly. See Figure 5&6, for what the index means and sensible measures you should adopt. We recommend a daily balanced sunscreen every day to exposed skin. The UVA band is ubiquitous- almost constant with time of day or at any latitude- 70-80% penetrates clouds or fog, and window or auto glass. UV radiation dose increases by 5% for every 1000’ rise in altitude.  Winter can actually be worse as snow can increase your exposure by 80% due to reflection by snow – as does sand and concrete. The UV Index is global but my informal study suggests that < 30% of Canadians know what it means and actively look for it every day. In contrast, 96% of Danes know what the UV-Index is and 89% know how to interpret it. Up to 50%% key the index to behaviour and decisions about sun-protection, particularly for children living at home. Our only added precaution is that even when the index is low, you should use a balanced sunscreen everyday to prevent UVA exposure that is difficult to limit any other way. A UVA burn is deep and painful as many who go sailing or recreate on cloudy days can confirm. It is harder to reduce your UVA exposure by just staying out of the sun. The best way is to add every morning use of a balanced sunscreen to sun avoidance measures (there is that word- balanced again). This will reduce your risk of skin cancer and retard photoaging by up to 25 years. Used from the teenage years this can mean that when you are 70 it is possible to look like you are 45. We recommend use of a daily balanced sunscreen with filters that do not enter the body, in every person over 6 months of age.

Figure 5: Deciphering the UV Index System

Choosing the best sunscreen:

We can now make balanced sunscreens that give as much UVA protection as UVB. I am presently working with scientists in Europe to make such a sunscreen that will mimic the protective effects of shade or black clothing. The benefits are exciting compared to the limitations and dangers of unbalanced UVB-biased sunscreens, with minimal UVA protection that now dominate the market in N. America. A few UV filters are able to achieve a balanced UVB to UVA protection approaching unity. These include zinc oxide, Tinosorb S™ and Tinosorb M™, and Mexoryl XL™, in tailored combinations. Interestingly, these filters also belong to a group of 7 filters with large molecules that do not enter the skin. This gives them the best safety profiles favored by consumer groups. Look for these agents in combination with each other or titanium dioxide, and no other active ingredients. Many products that use these agents add the other organic filters with small molecular weights that quickly penetrate your skin into blood and all your tissues. There are several potential dangers – links to cancers and hormone disruption and photoallergy. A prudent approach would be to avoid these risks and use filters that do not enter the body.

Figure 6: How Best To Protect Yourself

 Zinc oxide is the only single agent used in concentrations of 15% and over that gives adequate SPF values, and relatively balanced protection. New formulas can be very aesthetic and go on clear. Look for EWG preferred sunscreens such as our Simply Zinc Sun Whip, if you can pardon the plug but these are the concepts we used to formulate it. 

 The next post will deal with details of UV effects and the benefits of reducing your lifetime exposure. Later posts will show the differences in UVA protection between a balanced and a UVB biased sunscreen, and assist the reader in selecting a balanced product from among  the minority of those available in N. America.