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Saturday, May 18, 2013

The Real Risks and Benefits of Sun Exposure and Sunscreen


Widespread vitamin D deficiency has caused some experts to recommend spending more time in the sun, while others maintain that we should spend less time in the sun. To make matters more complicated, reports suggest that sunscreen products designed to prevent skin cancer can actually cause skin cancer. So before you head outdoors this summer, understand the real risks and benefits of sun exposure and sunscreen products, and learn how to use them wisely.

Sunscreen Safety

Sunscreen products can contain ingredients that may trigger allergic reactions, disrupt hormones in the body, and damage DNA. Damaged DNA doesn't always cause cancer, but does increase the risk of developing cancer.

Additives to be concerned about include sulisobenzone, ensulizole, octocrylene, octinoxate, methoxycinnamate, octyl methoxycinnamate, hemosalate, PABA and PABA esters, Padimate O, 4-methylbenzylidene camphor, 3-benzylidene camphor, and benzophenone-2, -3, and -4.

Concerns have also been raised about nanoparticles which may be added to sunscreen products that use minerals like zinc oxide and titanium dioxide to protect skin from damaging UVA and UVB radiation. These ingredients give sunscreens a white color, which can give skin a white color too. To minimize this effect, zinc oxide and titanium dioxide may be used in the form of nanoparticles, which are so small, they're measured in nanometers. (It takes a billion nanometers to make a meter.) Their smaller size makes them invisible, so the sunscreens become invisible too.

Reports suggest that nanoparticles could interact with sunlight to increase the risk of skin cell damage but research studies have had mixed results. Lab studies using cell cultures show that zinc oxide and titanium dioxide nanoparticles exposed to UV radiation generate free radicals and damage DNA, while human studies have found no evidence that nanoparticles damaged DNA in the presence or absence of UV irradiation. And in 15 out of 16 studies, nanoparticles only penetrated the outer layer of skin, composed of dead skin cells, and never penetrated living skin cells.

While sunscreen products can prevent sunburn, they can't prevent skin damage from sun exposure and in most cases, they don't prevent cancer. Studies show that regular use of sunscreen can reduce the risk of one type of skin cancer, squamous-cell carcinoma, but it doesn't reduce the risk of the most common type, basal-cell carcinoma, or the most deadly type, malignant melanoma.

Because people who wear sunscreen are less likely to become sunburn, they are more likely to spend prolonged periods of time in the sun. More time in the sun means more cancer risk, so using sunscreen can indirectly increase risk of developing cancer, regardless of any potentially toxic additives.

Sun Therapy

Too much sun may be harmful but some sunshine is good for us. It sets off several beneficial biochemical pathways in the body which regulate our circadian rhythm, metabolism, and mood, and stimulate the production of vitamin D, which strengthens our bones as well as our immune systems.

If you don't spend enough time in the sun, or if you wear too much sunscreen, your skin doesn't make enough vitamin D. Low levels of vitamin D are a risk factor for developing cancer. A Chinese study found that people who had more exposure to sunshine were less likely to die from cancer and suggested that higher levels of vitamin D played an important role in prevention. Sun exposure not only reduced rates of skin cancer. It was also associated with lower rates of most major cancers including those of the lung, breast, bladder, esophagus, stomach, liver, colon, and rectum.

Besides vitamin D, our bodies have another built-in mechanism for protecting us from the sun: melanin. It's a pigment in our skin that acts as an antioxidant and neutralizes unstable free radicals generated by ultraviolet radiation that can damage DNA and turn cells cancerous. People with darker skin naturally make more melanin than people with lighter skin. Melanin production is also higher in people who have regular exposure to sunlight. We call this a sun tan. More melanin means fewer free radicals, less DNA damage, and a lower cancer risk.

Sunshine Safety

Some sun exposure is just as important for good health as fresh air, clean water, and regular contact with the earth. Follow these five tips to sunbathe safely, get your vitamin D, and minimize your risk of cancer at the same time.

#1  Check the UV index and spend time outside when the sun's rays are least intense.

The UV index is a scale from 1 to 11 that estimates the risk of harm that the sun's rays can have on unprotected skin:
  • 1 and 2 = low risk
  • 3, 4, 5 = moderate risk
  • 6 and 7 = high risk
  • 8, 9, 10 = very high risk
  • 11 = extremely high  risk 
The UV index is highest in the summer and in the middle of the day. It's lowest in the winter and during early morning and late afternoon hours. When the UV index is low, it's safe to be outside without using sunscreen. When the UV index is moderate, wear sunscreen outdoors. When the UV index is high, stay out of the sun. If you can't seek shade, cover your skin with long sleeves, long pants, and a hat. Strong sun can also damage your eyes and increase the risk of macular degeneration, so it’s also a good idea to wear sunglasses, especially when the UV index is moderate or high.

#2  Choose non-toxic sunscreens with a sun protection factor (SPF) between 30 and 50 that block both UVA and UVB light. 

Use the Environmental Working Group's Sunscreen Guide to find products free of harmful additives. Also opt for creams and lotions over sprays and powders, which can be accidentally inhaled and absorbed directly into the bloodstream. I don't recommend sunscreens with SPF higher than 50 because they can convey a false sense of security, enticing users to stay longer in the sun.

#3  Apply sunscreen liberally.

Use two to three tablespoons of sunscreen lotion every two hours and apply it everywhere including your hands, feet, and ears. Use lip balm with SPF protection as well.

#4  Be extra cautious at high altitudes and around water, snow, ice, and glass.

UV radiation increases with elevation, penetrates glass and water, and is reflected from glass, water and sand, which magnify its intensity. Be extra cautious when sitting on the beach, swimming and ice skating outdoors, participating in snow sports, spending time at high altitudes, and sitting next to windows inside planes, trains, and automobiles.

#5  Consume plenty of colorful, antioxidant-rich foods including berries, tomatoes, cruciferous vegetables, and green tea (hot or iced).

Studies show that certain compounds found in fruits, vegetables, green tea, and herbs like rosemary can protect skin against damage from the sun's ultraviolet radiation without interfering with vitamin D production. These foods have anti-inflammatory and antioxidant effects in the skin which minimize damage associated with aging and modulate the immune system, helping to prevent cancerous changes. If you don't eat them regularly already, start now.

References:

Afaq F. and Mukhtar H. 2006. Botanical antioxidants in the prevention of photocarcinogenesis and photoaging. Experimental Dermatology 15(9):678-84.

Aiyer H.S. et al. 2008. Dietary berries and ellagic acid prevent oxidative DNA damage and modulate expression of DNA repair genes. International Journal of Molecular Sciences 9(3):327-41.

Australian Government. 2009. A review of the scientific literature on the safety of nanoparticulate titanium dioxide or zinc oxide in sunscreens. Department of Health and Aging, Therapeutic Goods Administration. www.tga.gov.au/pdf/review-sunscreens-060220.pdf

Chen W., Clements M., Rahman B., Zhang S., Qiao Y., and Armstrong B.K. 2010. Relationship between cancer mortality/incidence and ambient ultraviolet B irradiance in China. Cancer Causes Control 21(10):1701-9.

Dennis L.K. et al. 2003. Sunscreen use and the risk for melanoma: a quantitative review. Annals of Internal Medicine 139(12):966-78.

Dinkova-Kostova AT. 2008. Phytochemicals as protectors against ultraviolet radiation: versatility of effects and mechanisms. Planta Medica 74(13):1548-59.

Evans J.A. and Johnson E.J. 2010. The role of phytonutrients in skin health. Nutrients 2(8):903-28.

Green A. et al. 1999. Daily sunscreen application and betacarotene supplementation in prevention of basal-cell and squamous-cell carcinomas of the skin: a randomised controlled trial. Lancet. 354(9180):723-9.

Offord E.A. et al. 2002. Photoprotective potential of lycopene, beta-carotene, vitamin E, vitamin C and carnosic acid in UVA-irradiated human skin fibroblasts. Free Radical Biology and Medicine 32(12):1293-303.

Plourde, Elizabeth. 2012. The false promises of sunscreens: the real consequences of their use. Part 1. Townsend Letter 348:108-111.

Rizwan M. et al. 2011. Tomato paste rich in lycopene protects against cutaneous photodamage in humans in vivo: a randomized controlled trial. British Journal of Dermatology 164(1):154-62. doi: 10.1111/j.1365-2133.2010.10057.x.

Stahl W. et al. 2006. Lycopene-rich products and dietary photoprotection. Photochemical and Photobiological Sciences 5(2):238-42.

Stahl W. and Sies H. 2012. Photoprotection by dietary carotenoids: concept, mechanisms, evidence and future development. Molecular Nutrition and Food Research 56(2):287-95. doi: 10.1002/mnfr.201100232.

1 comment:

Erin Youngerberg said...

Thanks for sharing! I just did an interview with everyday health on melanoma. So good to share info! http://m.everydayhealth.com/skin-cancer/thinking-about-sitting-in-the-sun-think-again