Sun Exposure: Skin Aging and Skin Damage
Intro
According to the Skin Cancer Foundation, “photoaging is a direct result of cumulative sun damage you’ve been exposed to throughout your life.” With the cumulative sun damage, photoaging can eventually lead to the appearance of fine lines, wrinkles, and pigmentation. Beyond the development of fine lines, wrinkles, and pigmentation, research also says that chronic exposure to sunlight can lead to the development of skin cancers. With all of this, looking at ways to protect the skin from sun damage is useful.
Despite having these negative effects on skin, sunlight exposure plays an important role in human health since sunlight is necessary for vitamin D production. And, vitamin D is an essential nutrient that’s been implicated with bone health, heart health, cognitive health, autoimmunity, and more. So, there are pros and cons to sunlight exposure, and many people may argue that having a bit of sunlight exposure is helpful. With all of the noise in the wellness world, I aim to provide a balanced & evidence-based perspective on sun exposure on skin health for people to feel more educated about the effects of sun exposure and for them to feel empowered to make the best choices for their personal health and wellness.
In this blog, we are going to dive into the effects of sunlight on skin health, specifically skin damage and skin aging. 4 topics that will be covered:
How sunlight affects skin health
Sun protection to prevent photo-aging
Different types of sunscreen UV filters and tips on how to best use sunscreen
How antioxidants may protect against sun damage
NOTE: THIS BLOG POST IS MEANT TO BE EDUCATIONAL ONLY, AND IS NOT MEANT TO DIAGNOSE, PREVENT, TREAT, OR CURE. PEOPLE SHOULD ALWAYS CONSULT THEIR TRUSTED LICENSED PROVIDER BEFORE TRYING ANY NEW TREATMENTS
How sunlight affects skin health
In this section, we are going to nerd out a bit and go into the science of what sunlight does to the skin.
First, we are going to dive into what a sunburn is to understand the acute effects of sun damage and why certain populations are more susceptible to sunburn. Then, we are going to dive into the biochemistry behind sunlight exposure on fine lines, wrinkles, and pigmentation. And lastly, we are going to look at how chronic exposure could lead to skin cancer.
What is a sunburn & why are some people more susceptible?
Sunburn can be defined as “a radiation burn to the skin caused by too much exposure to the sun’s ultraviolet (UV) rays or artificial sources such as tanning beds.” There are many factors that can contribute to the development of sunburn, such as: Medications, Excessive exposure during hours when UV radiation is at its peak, Tanning, Fitzpatrick skin phototype, and more.
The Fitzpatrick skin phototype scale classifies 6 different types of skin types according to the amount of pigmentation in the skin and the skin’s tanning ability. This scale can help dermatologist explain to their patients why they are more susceptible to sunburn (and skin cancer) and helps dermatologists understand their patient’s risk for skin cancer.
Fitzpatrick skin types:
Type I: Pale white skin with blue or green eyes and blond or red hair. Burns easily and does not tan.
Type II: White skin with blue eyes. Burns easily and tans with difficulty.
Type III: White skin. May burn, but tans easily. Tans after initial burn.
Type IV: Light brown or olive skin. Burns hardly and tans easily.
Type V: Brown skin. Rarely burns and tans easily.
Type VI: Dark brown or black skin. Never burns and always tans easily, and becomes darker with UV radiation exposure.
Now, that we know that sunburn is a radiation burn and that people with fair skin (types I-III) are more susceptible to sunburn, how could chronic sun exposure lead to photoaging and skin cancer?
How sunlight causes photoaging:
From a biochemical standpoint, sunlight’s ultraviolet (UV) radiation affects skin health through the production of reactive oxygen species (ROS), which are also called free radicals. And, these free radicals trigger biochemical processes to active enzymes that degrade collagen to lead to the appearance of fine lines and wrinkles. Additionally, sunlight can directly activate pigment-producing cells (called melanocytes) to release melanin, leading to pigmentation.
Chronic sunlight exposure & skin cancer
According to a 2017 scientific review, keratinocyte cancer is the most common cancer worldwide, especially amongst people with white skin. And, the authors from this review say that 75-80% of keratinocyte cancers are basal cell carcinoma (BCC) and 20-25% are squamous cell carcinomas (SCC), with UV exposure being the major cause of these cancers.
Beyond these keratinocyte cancers, melanoma is another skin cancer that can arise from UV exposure. A 2020 article indicated that melanoma is the most common form of cancer in young adults, and is also found in high numbers in elderly populations. And, the authors of this 2020 article write that young adult females are more likely to experience melanoma than males “due to the greater use of sunbeds, as well as intentional sun exposure among girls and, in general, risky behaviours in seeking to suntan, due to socially-determined aesthetic needs.”
So, how could chronic sunlight exposure lead to these conditions?
Basal cell carcinoma and sunlight: Research indicates that chronic exposure to UV radiation from sunlight (specifically UV-B radiation) leads to DNA mutations in skin cells that lead to excessive growth and eventually leading to BCC.
Squamous cell carcinoma and sunlight: A 2007 study completed on animal models indicated that UV-B radiation plays a role in the development of SCC. Additionally, according to the American Cancer Society, UV rays can alter the DNA of skin cells, and further literature entails that genetic mutations in genes responsible for healthy cellular division and DNA repair with UV-B radiation play roles in the development of SCC.
Melanoma and sunlight: Literature indicates that UV radiation plays a role in the development of melanoma, with UV radiation causing DNA changes that lead to excessive cellular division.
So, chronic sunlight exposure can alter DNA in skin cells that lead to DNA mutations that play a role in the development of various UV-induced skin cancers.
Addressing photoaging: Sun protection
Protecting the skin from UV radiation is one of the pillars in preventing and addressing photoaging and photodamage. The more-common way to protect the skin from UV exposure is going to be through sunscreens. In addition to this, other strategies spoken about in research for sun protection include: seeking shade when outdoors, wearing wide-brimmed hats and photoprotective clothing, and wearing sunglasses. Additionally, many individuals are speaking about the importance of antioxidants when addressing photo-protective measures. In this section, we are going to go over sunscreen and antioxidants.
Sunscreen
Sunscreen products are meant to act as a topical barrier on the skin to prevent the damaging effects of UV radiation from sunlight. Sunlight contains UV-A and UV-B radiation, and research indicates that UV-B is mainly absorbed at the upper layers of the skin (epidermis) due to its short wavelength and that UV-A can penetrate deeper into the skin (dermis) due to its longer wavelength. And, since UV-B is mainly absorbed in the epidermis, it is the main driver for sunburn and skin cancers, and since UV-A can go into the dermis, it is the main driver of photoaging. So, using a sunscreen that has both UV-A and UV-B protection would be of great importance with scientific research indicating that daily sunscreen use plays an important role in preventing photoaging.
Types of UV filters
In regards to sunscreen, there are physical UV filters and chemical UV filters.
Physical UV filters, also called inorganic filters, are usually mineral-based. FDA-approved inorganic UV filters are zinc oxide and titanium dioxide. And literature says that zinc oxide and titanium dioxide provide protection against UV-A, UV-B, and visible light. Additionally, the FDA has proposed to categorize zinc oxide and titanium dioxide as category I-GRASE (generally recognized as safe and effective).
With sunscreens containing zinc oxide and titanium dioxide, they have the potential to leave a “white cast,” which means that these products can make the user look pale. And, this effect is usually more-pronounced in people of color, and is why people of color may use chemical UV filters instead.
Chemical UV filters, also known as organic filters, can also be found in sunscreen products. The more-common organic filters people may find are oxybenzone, octinoxate, and octocrylene. However, there are many more organic filters that can be found in sunscreen products. In regards to UV filtering, oxybenzone, octinoxate, and octocryline have been shown to protect against UV-A and UV-B, but the FDA has proposed to categorize these organic filters as category III-non-GRASE, meaning “insufficient safety data to make a positive GRASE determination.”
As spoken earlier, organic filters are usually the sunscreen of choice for people of color since it does not leave a white cast. And with personal experience, I have found that chemical sunscreens truly blend in well and look “invisible” on the skin. And compared to zinc oxide and titanium dioxide, sunscreens with organic filters feel less heavy on the skin. However, with the proposed category of these organic UV filters, I personally choose mineral-based sunscreens. And, from my own experience, I have found that sunscreens tinted with iron oxide usually do not leave a white cast on my skin.
Sunscreen application Tips:
The Skin Cancer Foundation recommends using broad spectrum sunscreen that protects against both UV-A and UV-B radiation that is SPF 15 or higher for everyday occasional sun exposure and SPF 30 or higher for extended outdoor activities. They also recommend using 2 tablespoons (or 1 shot glass’ worth) to the exposed areas of the face and body, and that a nickel-sized amount is necessary for the face alone. In regards to application and going out, the Skin Cancer Foundation recommends applying sunscreen 30 minutes before sun exposure and to reapply every 2 hours.
antioxidants
Antioxidants are compounds that neutralize reactive oxygen species (ROS), also known as “free radicals”. Free radicals are compounds that are naturally made intrinsically by cells when doing normal biochemical processes, such as making cellular energy, but can also be formed when the cells and tissues are exposed to external factors, like sunlight. In regards to antioxidants and photo-aging, there are various studies that have looked at the effect of orally consumed antioxidants and topically applied antioxidants on skin health when exposed to UV radiation.
Oral antioxidants
A 2012 review suggested that there is a link between intake of antioxidants and skin aging. When looking at the the research for oral antioxidants, there have been studies completed on animal models and human subjects. A study completed in 2020 revealed that oral astaxanthin (a type of antioxidant from algae) “can protect against photoaging caused by UV irradiation.” With this evidence coming out, hopefully studies on human subjects are completed to understand how protective oral astaxanthin could be for photoaging in human skin. The studies completed on human subjects included a small study completed in 2012 that revealed that oral supplementation of french maritime pine bark (an antioxidant-rich extract) led to a “significant decrease in clinical grading of skin photoaging” and a “significant reduction in the pigmentation of age spots.” And, a 2021 longitudinal study looking at the long-term effects of oral consumption of foods with high antioxidant capacity on skin health showed that adults 45 years and older who ate foods with high antioxidant capacity “experienced approximately 10% less photoaging over 15 years than those who ate foods with low antioxidant capacity.”
With all of this, dietary/oral antioxidants appear to be protective against photoaging, but it is hard to say that dietary/oral antioxidants can replace sunscreen. So, it may be worthwhile to look into an antioxidant-rich diet while also regularly applying sunscreen to protect the skin from photoaging.
Topical antioxidants
Antioxidants can also be applied topically, and some common antioxidants found in skincare products include vitamin C (ascorbic acid), green tea extract, caffeine, and more. A 2017 review indicated that topical antioxidants may be helpful for reducing the effects of free radical damage in the skin. And, studies completed in 2011, 2017, and 2019 concluded that antioxidants add protection to sunscreen through a synergistic mechanism for improved photo-protection.
So, topical antioxidants can work alongside topically applied sunscreen for improved photo-protection, but there have been no studies that looked into how effect topical antioxidants are compared to sunscreen products. So, it may be worthwhile to look into sunscreen products that have antioxidants in them or to use skincare products with antioxidants before regular application of sunscreen.
Summary & Takeaways
Unprotected sun exposure can lead to acute and chronic skin effects. Acute effects can include sunburn, which is described as a radiation burn from too much exposure to the sun’s UV radiation; and chronic effects can include signs of photo-damage and photo-aging, such as fine lines, wrinkles, and pigmentation. In worst-case scenarios, chronic effects of unprotected sun exposure could lead to skin cancer, such as squamous cells carcinoma, basal cell carcinoma, and melanoma. With this, it is important that the skin is protected against the damaging and aging effects of sun exposure.
In regards to photo-protection against UV radiation, the mainstays have included topical sunscreen, going into the shade for protection, wearing wide-brimmed hats and photo-protective clothing, and wearing sunglasses. With topical sunscreen, we spoke about the different types of UV filters commonly used in sunscreen products (inorganic and organic UV filters), and why it is important to choose a broad-spectrum sunscreen product to protect against UV-A and UV-B radiation. In addition to this, we also spoke about the pros and cons of inorganic and organic chemical filters, such as their proposed safety with the new FDA classification system for sunscreen and how they look and feel when applied onto the skin.
Beyond topical sunscreens for photo-protection, we also looked at the evidence behind antioxidants for photo-protection. With what science indicates, there is a connection between dietary antioxidants and skin health, with animal and human studies showing that certain oral antioxidants maybe helpful for photoaging. And with topical antioxidants, science has shown that they work alongside topical sunscreen for photo-protection. However, it cannot be said that dietary or topical antioxidants are as effective as sunscreen for photo-protection against photo-damage and photo-aging.
All in all, unprotected sun exposure can increase one’s risk for developing signs of photo-aging. And, there are measures that can be taken to prevent the appearance of fine lines, wrinkles, and pigmentation from sun exposure.
In next week’s post, I am going to cover the evidence behind skincare actives claimed to address photo-aging and photo-damage. And later on this month, I will be addressing skin procedures claimed to address photo-aging and sun damage and addressing sunscreen myths that I have seen surface on social media.
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