Consultant plastic surgeon Mr Paul Banwell explores the latest research and evidence in suncare
The mantra that sun protection factor (SPF) is the most important antiageing manoeuvre available at our disposal is now firmly entrenched within the aesthetics specialty; yet, surprisingly, this has only been accepted within the last decade. Prior to this there was a disconnect between the use of SPF and its impact on ageing; it was only associated with skin cancer prevention by aesthetic practitioners and the public alike. Hughes and colleagues’ 2013 randomised study confirming the link between use of sunscreen and prevention of skin ageing was truly a seminal event and cemented the connection.1 Indeed, within the last five years especially there has been an explosion in advancements in sunscreen technologies and in the whole concept of photoprotection. Clinicians and cosmetic scientists have developed new strategies and products to include standalone SPFs, topical antioxidants, topical immune protectants, solar botanicals from extremophile plants, oral supplements in capsule or drinkable form (nutraceuticals) or combinations of all of these. This article will describe the latest developments in suncare and how they can be used in practice.
Our traditional understanding that ultraviolet radiation (UV-A and UV-B) was the only form of deleterious energy causing damage to the skin has now been supplemented by the evidence that the other solar constant components of infrared (IR) radiation and visible light (recently dubbed high energy visible light ‘HEVL’) are also heavily implicated in photodamage too.2,3
The relative proportions of these energy forms and wavelengths are highlighted in Figures 1, 2 and 3, as well as the specific importance of ultraviolet radiation. These insights have spawned a huge proliferation of sunscreen manufacturers changing their formulations and marketing claims, meaning our patients can now benefit from this advancing knowledge. Interestingly, certain innovators in Australia (which leads the way in photoprotection knowledge and research) have been ahead of the game and have offered this for some years, however the rest of the medical community have been slower to adopt these ideas.
Unfortunately, the human skin is a very susceptible target organ to UV radiation (UVR). The acute photochemical reactions that occur in the skin secondary to UVR (280-400 nm) are characterised by various inflammatory cascades that are mediated by several possible mechanisms including (a) direct action of photons on DNA, (b) generation of reactive free radicals and reactive oxygen species (ROS) and (c) generation of inflammatory mediators e.g. prostaglandins, histamine and leukotrienes. In turn, repeated acute responses result in adaptive and chronic changes within the skin. These are manifested clinically as classical signs of photoageing and as actinic lesions or skin cancers.4
Sunburn inflammation (erythema) is the most conspicuous and well-recognised acute cutaneous response to UVR, particularly in fair-skinned individuals, and is associated with the classic signs of inflammation, namely redness, warmth, pain and swelling. It is well established that UVR exposure suppresses cutaneous cell-mediated immunity in humans. The depletion of Langerhans cells (the principal antigen-presenting cells in the epidermis), recruitment of macrophages into the dermis and epidermis, and release of inflammatory mediators such as TNF-a area, are all important events in the initiation of the concept of photoimmunosuppression (PIS).5
It is known that sustained episodes of cutaneous PIS play an important role in the emergence and growth of skin cancers. This concept is supported by evidence of transplant patients on (chemo)-immunosuppressive therapy who display an elevated risk of both non-melanoma and melanoma skin cancer formation.6
Sun (UV) creams have traditionally been the first defence against these UV-mediated processes and PIS. Professor Franz Greiter is generally credited with introducing the concept of Sun Protection Factors (SPF) in 1962, after Schulze had already experimented with commercial sunscreens in 1956. The SPF metric is a measure of the ability of the sunscreen to protect against sunburn; interestingly, the FDA proposed defining the SPF as the ‘Sunburn’ Protection Factor to increase clarity as to what the test actually measures.7
For the lay person, SPF is popularly interpreted as how much longer skin covered with sunscreen takes to burn compared with unprotected skin.
There are two main types of sun cream – chemical (organic) and mineral (which may also be known as physical or inorganic). The main difference is that chemical suncare products contain UV-filtering ingredients that take time to be absorbed by the skin – hence people using the 20 minute rule before sun exposure. By contrast, mineral sunscreens contain inert UV protective ingredients such as zinc oxide and titanium dioxide and form a protective barrier on top of the skin, and these have an immediate effect.8
What is more, some people who suffer allergies or sensitivities to chemical UV filters find that mineral sun creams do not irritate their skin. Zinc is also known to be a potent anti-inflammatory agent and does not block pores.9 Chemical sunscreens offer good protection from both UVA and UVB rays. The most popular UVA and UVB filters include benzophenone, avobenzone, parsol and cinnamates. However, the chemical filters parsol and cinnamates may sometimes irritate sensitive skin but the main skin irritant – the UVB-filtering ingredient PABA (para-aminobenzoic acid) – has been phased out of most sunscreens.9 Some small in vitro studies demonstrating that some of these filters passed through the skin was picked up by the international media creating a backlash on sunscreen use, despite the FDA declaring them as safe and having been used for many years.9
In contrast, mineral sunscreens such as zinc oxide or titanium dioxide now form the cornerstone of most SPF preparations – they afford excellent physical protection and they are also less sensitising than chemical filters. However, opaque inorganic oxide formulations lack cosmetic acceptability, with a reported trend towards lower and insufficient application rates.9
Making the particles smaller using micronised or nanonised formulations has therefore become common – nanoparticles of titanium and zinc are transparent in formulations spread on the skin surface. This transparency provides the cosmetic elegance that is just not achievable with larger-particle formulations. However, a few years ago some authorities claimed that as dermally-administered nanoparticles are known to localise to regional lymph nodes via skin macrophages and Langerhans cells, they were dangerous and should not be used. Subsequent studies have revealed lack of penetration of such nanonised formulations. While they are generally considered safe, ongoing research is required.10
Taking the concept of cosmetic elegance further in sunscreens is the concept of superfluid-like formulations. These take their origins from the ideas of superfluids (helium) discovered in the 1930s by Leitner. Superfluidity is the characteristic property of a fluid with zero viscosity, which therefore flows without any loss of kinetic energy. This discovery defied the conventional laws of physics and has spawned further research in multiple industries. These ideas have also recently been adopted in the arena of cosmetic science for the development of liquid microfilms, which spread rapidly over the skin and, in the case of SPFs, provide improved coverage and protection as well as the ability to integrate multiple other actives. Rationale skincare in Australia was the first to champion this concept (e.g. B3-T, Beautiful Skin SPF) but other companies including La Roche Posay (e.g. Anthelios) and Kiehls (e.g. Superfluid SPF) have developed similar products.
One of the key sequelae of UV exposure is the generation of oxygen-free radicals and reactive oxygen species. As explained, these cause both photoageing and skin cancer. Antioxidants are powerful molecules which can safely interact with free radicals and terminate the chain reaction before vital molecules are damaged. Although there are several enzyme systems within the body that ‘scavenge’ free radicals, the principal micronutrient (vitamin) antioxidants are vitamins A, C and E. Additionally, selenium, a trace metal that is required for proper function of one of the body’s antioxidant enzyme systems, is sometimes included in this category.11
In the past decade the role of antioxidants in medical skincare has been well established via a multitude of high-quality studies.12 There are two types of antioxidants we can use – those found naturally in the body (endogenous) and those found outside the body (exogenous), either derived from nature or synthesised in a laboratory. Of all the exogenous antioxidants, the most popular is green tea extract, and it has been utilised in cosmeceuticals for some time. Fortunately, the skin also has its own antioxidant system, and I believe this is where we should direct our search in terms of the most effective antioxidants.11
The so-called Human Skin Antioxidant Complex comprises vitamins A, C and E together with a group of enzymes, predominately superoxide dismutase, glutathione S-transferase and catalase. In young skins, these antioxidants are found in abundance, but as we age, our natural levels almost half with each decade of life. Unfortunately, our reserves are also easily diminished by even a single exposure to UVR. For example, after 30 minutes in the sun, the vitamin A and C levels in an average 40 year old are depleted by almost 90%.13 Vitamins A, C and E must be included at a dosage high enough to ensure effective antioxidant protection, and these levels have been well elucidated. One of the most recent findings about vitamins A, C and E is that they are synergistic, meaning that they recycle each other as they are used up, ensuring a constant return to ground state where they are able to reload and fire again and again (so-called ‘redox’ reaction).13 Interestingly, enzyme antioxidants are more problematic as they are usually highly unstable outside the human body. However, recent innovations in biotechnology have provided us with skin identical enzymes such as glutathione, catalase and CoEnzyme Q (ubiquinone) which function as full-strength antioxidants.11
Whilst the endogenous antioxidant system comprising vitamins, enzymes and chromophores are extremely powerful, there are also a host of recently-discovered botanical antioxidants that are many times more potent and equally effective.14
In my experience, the best topical products contain all of these biomolecules as they are all equally important and synergistic. The difficulty is that these substances are inherently unstable and dose dependent, making precise formulation imperative.
By definition, topical antioxidants will therefore confer many benefits from not only an antiageing perspective, but just as importantly from an anti-skin cancer perspective and thus should be used as part of a daily skincare regime for UV protection. Daily use of vitamin A and synergistic formulations of vitamins C and E remain essential (e.g. Antioxidant ACE from Rationale, CE Ferulic from SkinCeuticals and C-Tetra Intense from Medik8).
Niacinamide is a key ingredient in cosmeceutical practice and, like vitamin A, is beginning to be hailed as another wonder vitamin in skincare due its wide-ranging effects. Topically, niacinamide includes benefits for ageing such as increased collagen and glycosaminoglycan production, acne with its anti-inflammatory effects, as well as demonstrating a reduction in sebum production and pore size, and dry skin by increasing the production of ceramides in the epidermis and pigmentation, through its effects on the melanin pathway.15 Gansara et al. also suggests that nicotinamide may influence telomere length through multiple mechanisms and have additional antiageing effects.16 In addition, emerging evidence shows that nicotinamide also acts as an adaptogen, with beneficial effects on sleep.17 However, the key action for niacinamide is that it is a powerful photo-immunoprotectant. UV irradiation depletes keratinocytes of cellular energy and niacinamide, which is a precursor of nicotinamide adenine dinucleotide (NADP) and niacinamide may act, at least in part, by providing energy repletion to irradiated cells.18 Relatively inexpensive with little toxicity, niacinamide has been shown to have powerful photoprotective effects against carcinogenesis and immune suppression in animals and is photo-immunoprotective in humans when used topically or orally. A formative study published in the New England Journal of Medicine by Professor Damian’s group confirmed in a randomised study that twice daily oral nicotinamide is effective in skin cancer chemoprevention.19
Resveratrol, a component in grape skin (and found in red wine), is a well-studied agent with a potential role in skin cancer chemoprevention, as well having other health benefits.20
Whilst resveratrol has come to the cosmeceutical skincare market mainly as a topical antageing (antioxidant) product, there is a growing body of evidence detailing its effects as an anticancer agent and recognition that it could play an important role in skin cancer management.21 Resveratrol suppresses metabolic activation of pro-carcinogens to carcinogens by modulating the metabolic enzymes responsible for their activation, and induces phase II enzymes, thus, further detoxifying the effect of procarcinogens. Furthermore, studies reveal that resveratrol also inhibits cell growth and induces cell death in cancer cells by targeting cell survival and cell death regulatory pathways. These effects are on top of its role in activating antioxidant enzymes and preventing inflammation.21
The phytochemical Polypodium leucotomos (PL or commercially known as Fernblock) is another immune photoprotectant that exhibits a number of benefits including inhibition of photo-immunosuppression, DNA photoprotection, anti-inflammatory effects, anti-skin cancer properties and remodelling of the dermal extracellular matrix.22 Importantly, it also inhibits the generation of reactive oxygen species (ROS) production induced by UV, including superoxide anion, and causes a marked decrease of UV-mediated cellular apoptosis and necrosis.22 It is a remarkable ingredient and has been incorporated into sunscreen preparations commercially (e.g. Heliocare).
Epidemiological data strongly support the photoprotective role of melanin in the skin as there exists an inverse correlation between skin pigmentation and the incidence of sun-induced skin cancers.23 It is not surprising, therefore, that researchers have tried to harness its power since Dr John Pawelek from Yale University patented the manufacture of synthetic melanin over 20 years ago. It has been used extensively in the cosmetics and biotechnology sectors and integrated as an important skin conditioning agent and component within sunscreens.24
In Scientific American in 2017 there was an interesting article reporting early results from synthetic nanoparticle melanosomes. Not only were the melanin-like nanoparticles transported and distributed throughout skin cells like natural melanin – they also protected the cells’ DNA. The researchers incubated skin cells with nanoparticles and then exposed them to UV radiation. After three days, 50% of the skin cells that absorbed the nanoparticles survived, compared with just 10% of those without nanoparticles, highlighting the photoprotective effects of nanoparticle synthetic melanin.25
On a bigger picture, vitamin D is essential for immune system health but we also know that optimum vitamin D3 levels are associated with protection against a number of malignancies; a strong body of evidence from animal and cell culture studies supports this protective role. However, evidence also indicates that vitamin D signalling protects the skin from cancer formation by controlling keratinocyte proliferation and differentiation, facilitating DNA repair, and suppressing activation of the hedgehog (Hh) pathway following UVR exposure. Many skin specialists therefore recommend regular use of oral vitamin D3 supplements for photoimmune protection.26,27,28
Many of the exciting and powerful ingredients now used in cosmetic skin science have a botanical origin, which has prompted researchers to look even further into the photoprotective benefits of compounds within the plant and marine worlds.29 In a post-COVID world there is also a profound and resurgent desire to use ‘natural’ ingredients wherever possible and boost the body’s (skin) immunity. Of note, extremophile plants have garnered much attention. Scientists have studied extracts from extremophile plants which are those that live and operate in the most challenging environments,
including the extreme heat and droughts in deserts, as well as those dominated by the extreme cold in Antarctica, or indeed in the salinity of the oceans.30 Australian SolarProtective Botanicals used by Rationale, Alpine Botanicals used by Albus and Flora and Desert Resurrection Plants by Hydraskin are just several examples of this.
In a similar vein, so-called adaptogens are also being incorporated into photoprotective strategies. An adaptogen is essentially a botanical that adapts to your body’s needs by reducing the effects of stress on the body – including inflammation (from UV exposure).31 These adaptogenic ingredients have been used for centuries in eastern modalities such as Chinese traditional medicine and Ayurvedic medicine and may be used topically or orally.
Ashwagandha, a particularly well-known adaptogen, is a herb that aims to alleviate many of the symptoms of a stressful modern life. It also contains potent antioxidant properties that help protect the skin against free radical damage and ageing.32
Schisandra (a medicinal berry) is another type of adaptogen which has multiple healing properties and small studies suggest it has photoprotective and environmental benefits for the skin. In Ayurvedic medicine, triphala is known as ‘three fruits’ and is made from the combination of three myrobalans, fruit-bearing trees: amalaki, bibhitaki and haritaki. In particular, amalaki is being investigated for its antioxidant properties and is said to contain 20 times the vitamin C of an orange, which is essential for collagen synthesis. Triphala can also be applied topically to aid in the healing of bruises and sunburn.33
The role of diet and nutraceuticals for skin health is a huge subject and outside the scope of this article, but these also offer other approaches to suppression of phototoxic responses. Whilst we know marine collagen should be part of a daily skin health regime, we also now know that biomarine extracts can significantly protect the skin from ultraviolet A-induced sun damage.34
The concept of photoprotection for ageing well and optimal skin health is now firmly entrenched in the aesthetics specialty. Recent innovations with superfluids, novel antoxidants and emerging botanicals with extremophile and adaptogenic properties provide more options to help educate patients and practitioners alike. Robust photoprotection skin regimes should form an essential part of our recommendations to patients to age well, alongside their other injectable and skin treatments.
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