Sunshine, Sunscreen, or Shade - What is Optimal for Our Skin?

In the eternal debate over sun exposure and skin protection, the question of what's truly best for our health remains a topic of considerable discussion. While some people may defend the benefits of sunshine for its role in vitamin D synthesis, mood regulation, and sleep-wake cycle, others emphasize the importance of hiding from the sun for skin cancer prevention. While both sides have strong arguments, in the end, consumers just want to know what to do and understand if their sunscreen choice and routine of application is correct. Let's delve into the science behind this discussion and unravel the complexities of sunshine, sunscreen, and shade, aiming to discover the ideal strategy for promoting overall health and skin wellness.

Sunshine: Friend or Foe?

To make it easier to understand, firstly we need some background information. When it comes to solar UV radiation, we usually think primarily about the down pits of it, such as photoaging, sunburn, and skin cancer. Ultraviolet (UV) radiation comprises UVA, UVB, and UVC categories. UVC radiation, with the shortest wavelength, is largely absorbed by the ozone layer and doesn't reach the skin significantly. UVB radiation, slightly longer in wavelength, penetrates the epidermis, causing sunburn and contributing to skin cancer. UVA radiation, with the longest wavelength, penetrates deeper into the skin, reaching the dermis and causing premature aging and skin damage. Protection against UV radiation, particularly UVA and UVB, is crucial to prevent skin damage and maintain skin health.

However, solar UV radiation plays a crucial role in maintaining our overall health. Exposure to sunlight stimulates serotonin production, often referred to as the "feel-good" neurotransmitter in the brain. Serotonin synthesis occurs from the amino acid tryptophan in the presence of UVB radiation, leading to heightened levels associated with improved mood and well-being. Additionally, sunlight influences melatonin production, a hormone integral to regulating the sleep-wake cycle. During daylight hours, sunlight suppresses melatonin production, while darkness stimulates its release, impacting sleep patterns and circadian rhythms. Furthermore, melatonin plays a role in activating pathways related to oxidative stress protection, hair growth cycles, and pigmentation physiology, highlighting the multifaceted effects of sunlight on our bodies.

Vitamin D emerges as the key player in our health reliant on sunlight. Its production initiates when UVB radiation penetrates the skin, starting the synthesis process by converting 7-dehydrocholesterol into pre-vitamin D3 (cholecalciferol). This compound undergoes a complex multi-organ process, ultimately culminating in the synthesis of Vitamin D. Vitamin D plays a crucial role in various bodily functions, including intestinal calcium absorption, bone health, and metabolic processes, serving as an immunoregulator as well. Serum 25(OH)D serves as the primary indicator of vitamin status, although there is no universal consensus on its optimal value. Recommendations vary widely, ranging from 25 nmol/L to >100 nmol/L. However, the most widely accepted threshold for defining insufficiency versus sufficiency is 50 nmol/L.

Sunscreens: Do they diminish the sun’s benefits?

Now that we understand the dual nature of sunlight, serving as both a friend and a potential foe when in excess, let's explore the role of sunscreens. Firstly, it's essential to recognize that our skin doesn't solely act as a sunblock but also functions as a natural sunscreen. Comprised of chromophores like keratin and melanin, our skin inherently filters sunlight to some extent. However, under certain circumstances, additional protection is necessary to shield ourselves from the sun's harmful effects.

Sunscreens are products applied to the skin that contain chemicals to protect against the sun's ultraviolet radiation. They are rated by their Sun Protection Factor (SPF), which measures their effectiveness in preventing sunburn. When applied correctly, sunscreen can block a significant amount of UV radiation, reducing the risk of sunburn and long-term skin damage. Regulatory bodies worldwide typically require sunscreens to provide balanced protection against both UVA and UVB rays to ensure comprehensive photoprotection. However, studies show that people often apply sunscreen inadequately, leading to less protection than advertised. As a result, while sunscreen is an essential part of sun protection strategies, other measures like seeking shade and wearing protective clothing also play a vital role in preventing sun damage, depending on the conditions that you are exposed to.

However, does sunscreen usage affect vitamin D levels? Studies indicate that sunscreen application is unlikely to have a significant impact on vitamin D status, despite the overlapping UVB wavelengths responsible for both vitamin D synthesis and sunburn. This is partly attributed to the suboptimal application of sunscreen, which diminishes its efficacy. Additionally, the quantity of vitamin D produced by the skin is influenced not only by sunscreen application, but by various factors such as intrinsic metabolic characteristics, skin type, geographic location, and season. In summary, broad-spectrum sunscreens are unlikely to detrimentally affect vitamin D status in healthy individuals.

Guidelines for sun protection

In conclusion, prolonged exposure to the sun without proper protection can result in sunburn, premature skin aging, and an increased risk of skin cancer. Hence, the importance of sunscreen in preventing these adverse effects cannot be overstated. It's reassuring to note that daily sunscreen application, particularly using products with low SPF and high UVA protection, is unlikely to impede the production of vitamin D and serotonin/melatonin. Numerous studies have failed to establish a significant link between sunscreen use, even with SPF greater than 15, and vitamin D deficiency.

Findings by Passeron and colleagues (2019) underscore the need for a personalized approach to sun protection, considering factors such as climate, UV radiation levels, and outdoor activities. In moderate climates with relatively low UVB exposure, experts recommend using sunscreen with a low SPF (15 or higher as per WHO guidelines) along with UVA protection to combat photoaging. Conversely, in regions with intense UVB radiation, such as lower latitudes and high altitudes, a higher SPF of 30 or above is advisable year-round. During outdoor recreational pursuits in the sun, it's essential to opt for high SPF and UVA protection, coupled with appropriate clothing and seeking shade whenever possible.

To strike a balance between skin protection and vitamin D synthesis, healthcare professionals advocate for a holistic approach. This includes using sunscreen with adequate SPF, minimizing sun exposure during peak hours, and ensuring sufficient intake of vitamin D through dietary sources or supplements. Regular skin assessments and consultations with healthcare providers are also pivotal in maintaining optimal skin health and vitamin D levels. Ultimately, achieving radiant skin and overall well-being hinges on striking the right balance between sunshine, shade, and sunscreen.

References:

Passeron, T., Bouillon, R., Callender, V., Cestari, T., Diepgen, T. L., Green, A. C., van der Pols, J. C., Bernard, B. A., Ly, F., Bernerd, F., Marrot, L., Nielsen, M., Verschoore, M., Jablonski, N. G., & Young, A. R. (2019). Sunscreen photoprotection and vitamin D status. The British journal of dermatology, 181(5), 916–931. https://doi.org/10.1111/bjd.17992

Raymond-Lezman, J. R., & Riskin, S. I. (2023). Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels. Cureus, 15(5), e38578. https://doi.org/10.7759/cureus.38578

Slominski, A., Wortsman, J., & Tobin, D. J. (2005). The cutaneous serotoninergic/melatoninergic system: securing a place under the sun. FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 19(2), 176–194. https://doi.org/10.1096/fj.04-2079rev