Sun Exposure: The Bright and Dark Sides

By Dr. David M. Brady and Danielle Moyer, MS

Summer is here and the sun is out!

Being cooped up in our homes for the last year has made many of us seek every opportunity to step outside and experience the fresh air.

If you ask yourself, “Do I have to wear sunscreen?” before stepping outside – you are not alone!

There are both health benefits and risks, and it is challenging to know what actions to take to protect yourself.

The “bright” sides to sun exposure:

The best-known benefit of sunlight is vitamin D. When ultraviolet (UV) rays hit our skin, it allows our liver and kidneys to create the active form of vitamin D. Vitamin D improves bone health, reduces inflammation, enhances the immune and nervous systems, and may even regulate blood sugar. It is difficult to get enough vitamin D from food sources alone (fatty fish, mushrooms, tofu, eggs, and fortified milks and cereals), making the sun a much more reliable source [1].

2. Serotonin & mental health

Getting enough vitamin D from the sun has been shown to enhance serotonin production in the brain! Serotonin ,the “happy hormone”, helps stabilize mood and helps with sleeping, eating, and digestion [2].

This helps to explain seasonal affective disorder (SAD). SAD is a specific type of depression and a chronic disease that happens during darker, colder months. Researchers have said that SAD is the most intense during January and February, and affects around 1.5 to 9% of the US population [3]. Studies have shown that a root cause of this disease is the reduction of sun exposure, vitamin D, and serotonin, all of which can be reversed during the sunnier months [4-5]. 

3. Skin, bone, and other health benefits 

Doctors have used UV radiation exposure to treat or help multiple skin diseases, including psoriasis, eczema, dermatitis, or vitiligo, as well as improve bone health by lowering the risk of bone fractures [6]. Sun exposure has also helped treat rheumatoid arthritis, lupus erythematosus, thyroiditis, and inflammatory bowel disease [7]. These benefits can largely be due to vitamin D’s role in inflammation and the immune system.

4. Cancer protection

Research from recent decades shows that the three main forms of skin cancer (melanoma, basal cell carcinoma, and squamous cell carcinoma) can be attributed to excess sun exposure. In fact, skin cancer is one of the most common forms of cancer worldwide.  However, there are some cancers that can result from too little sun. Higher latitude countries with little sunshine tend to have higher rates of Hodgkin lymphoma as well as breast, ovarian, colon, and pancreatic cancers compared to sunnier countries [8-10].

The dark sides to sun exposure:

Unfortunately, UV radiation can also be a carcinogen, meaning an agent that causes cancer in humans. UV radiation is linked with skin cancer. More than one million people in the United States are diagnosed with skin cancer each year. An estimated 90% of non-melanoma skin cancer and 65% of melanoma skin cancers are associated with the exposure to UV radiation from the sun [11]. UV radiation also contributes to premature aging of the skin, eye damage, and skin color changes [12].

A person’s skin type affects the degree to which people burn. Those with fair skin tend to burn more rapidly and more severely, whereas those with darker skin do not burn as easily. Furthermore, those with a large number of freckles or moles tend to have higher risks of developing skin cancer. However, regardless of race or ethnicity, everyone is subject to the potential adverse effects of overexposure to the sun. Other factors that increase a person’s risk can be their disease and medication status. Certain diseases, such as lupus, can make a person more sensitive to sun exposure, as well as medications such as antibiotics and antihistamines [13].

How do you find the balance?

Many of the health benefits of the sun come from vitamin D. Therefore, the key is to get it safely.

It is best to avoid direct sunlight without protection when the sun’s rays are strongest, usually between 10 AM to 4 PM. If you are outdoors during those hours without sunscreen, the World Health Organization states that 5 to 15 minutes of casual sun exposure to hands, face, and arms two to three times a week during the summer months is sufficient to keep vitamin D levels in the normal range [12]. However, this does not imply that this will allow your vitamin D levels to reach more optimal ranges, prompting many to recommend longer duration (15-30 minutes) of casual sun exposure prior to application of sunscreen. If you live closer to the equator where UV levels are higher, shorter periods of time may suffice. On the other hand, if you have a darker skin tone, you may need more time in the sun (20-30 minutes, two to three times a week) to obtain sufficient vitamin D levels [13]. It is best to check the UV index of your area to help you plan your outdoor activities in a way to prevent sun overexposure.

The best way to assess your vitamin D levels is through a blood test called 25-Hydroxy Vitamin D. Most experts define vitamin D deficiency as a level of less than 20 ng/mL. Whereas the “optimal range” of vitamin D levels has been debated, but many agree upon the range of 40-60 ng/mL [14]. There are also advocates in the integrative medical community of vitamin D levels being maintained in the 60-100 ng/mL range, but evidence for these levels is somewhat scant. 

A lot of individuals are starting to take supplements to ensure proper vitamin D levels. Though you should speak with your doctor or nutritionist about what dosage is right for you, the Recommended Dietary Allowance for adults 19+ years old is 600 IU, and for adults 70+ years old is 800 IU daily. The maximum daily intake for most individuals is 5,000 IU [1], although higher dosages are sometimes used for specific medical reasons under supervision. Supplements are commonly taken in doses varying from 1,000-2,000 IU/day safely (in addition to sunlight) During the winter months, this dosage can be increased. Note that vitamin D is a fat-soluble vitamin, so it must be taken with food for proper absorption. Always consult with your doctor and/or nutritionist before taking any supplements.

How do you choose the right sunscreen?

“Sunburns significantly increase the lifetime risk of developing skin cancer, especially for children,” says the US Environmental Protection Agency [13]. In addition to shade and protective clothing and accessories , sunscreen is essential for protection. Sunscreen contains chemicals that absorb or reflect both types of UV radiation (UVA and UVB) to protect you from the sun’s rays.

In 2019, the FDA released a goal of updating sunscreen regulations for the first time since 2011, but had to withdraw their plans. In the FDA’s proposed statement, they recognized only two ingredients as safe and effective in sunscreen: Zinc oxide and titanium dioxide. These two ingredients are classified as “Mineral Product” sunscreens [15-16]. 

Other common sunscreen ingredients (oxybenzone, avobenzone, homosalate, octinoxate, octisalate, octocrylene) used in about 60% of the sunscreens have more questions regarding their safety and efficacy. Though they are not flagged as “unsafe”, the FDA requested additional safety information from the sunscreen industry to consider in their upcoming policy. 

The FDA has flagged one particularly concerning sunscreen ingredient called oxybenzone. The FDA is concerned that oxybenzone could interfere with normal functioning of a number of hormones, including estrogen. Because of this and other potential health concerns, the American Academy of Pediatrics (AAP) advises parents to avoid using sunscreens with oxybenzone on children [15-16]. If you don’t want it on your children, you probably don't want it on you either. 

SPF (sun protection factor) rates how well the sunscreen can block the UV rays. While no sunscreen’s SPF protects you fully from the sun, an SPF of 15 or below must carry a label that it only protects against sunburn, not skin cancer or skin aging. Therefore, it is recommended by the American Cancer Society to use an SPF of 30 or higher. SPF ratings mainly apply to UVB rays, so sunscreen manufacturers that contain SPF that protect against UVB and UVA are labeled “Broad Spectrum” and are highly recommended [17]. 

Sunscreen must be reapplied at least every 2 hours, and maybe more frequently depending on how much you are swimming, sweating, and whether the sunscreen is “water resistant”. Read the label of each sunscreen to know how long it lasts specifically [17]. 

The Environmental Working Group (EWG) is a third-party group that provides a great guide to sunscreen, where you can even “search” your sunscreen brand and see how they rate the ingredients.

The takeaway

Balance is key! Both the benefits and risks of sun exposure encourage everyone to find a reasonable “middle-ground”. You can keep yourself safe by wearing appropriate sun-protecting clothes and accessories, applying safe sunscreen, sitting in shade, checking your city’s UV ray index, and timing your sun exposure. Additionally, checking your vitamin D levels at least once a year (ideally once during the winter and once during the summer) can determine what actions are needed to achieve an optimal vitamin D status. 

Safe sun exposure is possible! So, get out there, enjoy the outdoors, and protect your skin. 

References: 

1. Vitamin D. National Institute of Health website. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. Updated March 26, 2021. Accessed June 15, 2021. 
2. Bancos I. What is Serotonin? Hormone Health Network website. https://www.hormone.org/your-health-and-hormones/glands-and-hormones-a-to-z/hormones/serotonin. Updated December 2018. Accessed June 15, 2021. 
3. Nussbaumer-Streit B, Forneris CA, Morgan LC, et al. Light therapy for preventing seasonal affective disorder. Cochrane Common Mental Disorders Group, ed. Cochrane Database of Systematic Reviews. Published online March 18, 2019. doi:10.1002/14651858.CD011269.pub3
4. Penckofer S, Kouba J, Byrn M, Ferrans CE. Vitamin D and Depression: Where is all the Sunshine? Issues Ment Health Nurs. 2010;31(6):385-393. doi:10.3109/01612840903437657
5. Patrick RP, Ames BN. Vitamin D hormone regulates serotonin synthesis. Part 1: relevance for autism. FASEB J. 2014;28(6):2398-2413. doi:10.1096/fj.13-246546
6. Rathod DG, Muneer H, Masood S. Phototherapy. In: StatPearls. StatPearls Publishing; 2021. Accessed June 15, 2021. http://www.ncbi.nlm.nih.gov/books/NBK563140/
7. Schwalfenberg GK. Solar Radiation and Vitamin D: Mitigating Environmental Factors in Autoimmune Disease. Journal of Environmental and Public Health. 2012;2012:e619381. doi:10.1155/2012/619381
8. Holick MF. Vitamin D and Sunlight: Strategies for Cancer Prevention and Other Health Benefits. CJASN. 2008;3(5):1548-1554. doi:10.2215/CJN.01350308
9. Baggerly CA, Cuomo RE, French CB, et al. Sunlight and Vitamin D: Necessary for Public Health. Journal of the American College of Nutrition. 2015;34(4):359-365. doi:10.1080/07315724.2015.1039866
10. Hoel DG, Berwick M, de Gruijl FR, Holick MF. The risks and benefits of sun exposure 2016. Dermatoendocrinol. 2016;8(1). doi:10.1080/19381980.2016.1248325
11. Kim I, He Y-Y. Ultraviolet radiation-induced non-melanoma skin cancer: Regulation of DNA damage repair and inflammation. Genes Dis. 2014;1(2):188-198. doi:10.1016/j.gendis.2014.08.005
12. Radiation: The known health effects of ultraviolet radiation. World Health Organization website. https://www.who.int/news-room/q-a-detail/radiation-the-known-health-effects-of-ultraviolet-radiation. Published October 16, 2017. Accessed June 15, 2021. 
13. The Burning Facts. United States Environmental Protection Agency website. https://www.epa.gov/sites/production/files/documents/sunscreen.pdf. Published September 2006. Accessed June 15, 2021. 
14. Mead MN. Benefits of Sunlight: A Bright Spot for Human Health. Environ Health Perspect. 2008;116(4):A160-A167.
15. EWG’s Sunscreen Guide. Environmental Working Group website. https://www.ewg.org/sunscreen/report/executive-summary/. Accessed June 15, 2021. 
16. Wadyka S. What You Need to Know About Sunscreen Ingredients. Consumer Reports website. https://www.consumerreports.org/sunscreens/what-you-need-to-know-about-sunscreen-ingredients/. Updated May 22, 2019. Accessed June 15, 2021. 
17. Choose the Right Sunscreen. American Cancer Society website. https://www.cancer.org/latest-news/choose-the-right-sunscreen.html. Accessed June 15, 2021. 

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