Everywhere you go, you hear about the benefits of sunscreen. When I was younger, I wore sunscreen when I needed it, but I also rubbed the dark tanning oil (SPF 6) all over myself in order to get a better tan. Now, I don’t go anywhere without sunscreen at least on my face.
But how do you know what the best sunscreens are? What’s the difference between SPF 15 and 50? Do all sunscreens block both UVA and UVB rays? What the heck are UVA and UVB rays? And why do we care??
I did a little research and found that in June 2011, the FDA changed some of the regulations for sunscreen. With these new regulations, the FDA recognizes that sunscreens (as long as they are approved by the FDA) help to prevent sun burns, skin cancer, and early skin aging- all the things you want from a sunscreen! Also, no new sunscreen can be labeled as SPF (sun protection factor) higher than 50. If it’s lower than 15 it must carry a warning that it may not prevent skin cancer or skin aging. These changes will take effect in December 2012.
All new sunscreens are going to be ‘broad spectrum’. What this means is that the lotion will block both UVA and UVB rays. In general, UVA rays are thought to contribute to skin again while UVB rays are the ‘bad’ ones that cause burning and cancer. But, now we know that UVA rays over time can contribute to skin cancer as well. You might wonder how exactly the sun rays are causing all these problems like aging, cancer, and sunburns. Here’s a simplified explanation:
When sunlight hits your skin, there is energy in the light particles (photons) that can do a few different things. The light energy from UVA rays doesn’t penetrate your skin as deeply as UVB and therefore doesn’t directly damage DNA. But it does cause indirect damage. It does this by creating free radicals and reactive oxygen species. If chemistry class was 10 years ago for you, all that means is that the light hits different molecules in your body, knocks off electrons and causes molecules to become charged. These charged particles are super reactive and run around injuring proteins, cell membranes, and even causing strand breaks in your DNA.
UVB rays can directly hit your DNA and cause nearby base pairs to form thymine dimers. Thymine what? A thymine dimer means that 2 bases in your DNA pair next to each other instead of across from each other and form a little bulge out of the side of your DNA. That mis-pairing causes your DNA to function improperly. When your body tries to repair these dimers, it can accidentally replace the bases with different ones and suddenly you have a mutation in your DNA! When enough of these little mutations add up, your risk for skin cancer sky rockets.
Many people are concerned about the potential negative health effects from the ingredients in sunscreen. PABA, Oxybenzone, and other chemicals have raised public attention for some negative side effects seen in animal studies. These studies were done using extremely high oral doses and therefore don’t represent the risk to humans from topical application. As of today, the FDA considers these ingredients to be safe at the doses authorized for sunscreen. It’s great to be wary of chemicals and what you put into and on your body- but the benefits of using sunscreen definitely outweigh the risks.
Some eye-opening statistics:
1 in 5 Americans will develop skin cancer in their lifetime
13 million people are living with a history of either squamous or basal cell carcinoma
58 million Americans are affected by actinic keratosis (a pre-cancerous lesion)
Current risk for developing invasive melanoma is 1 in 58
Many people say that because sunscreen reduces sunburns, it encourages people to stay outside longer and therefore increases the risk of cancer. In 2010, a study by Green et al. followed 1,621 Australians over 4 years. Half of the participants were instructed to apply sunscreen daily and the other half were instructed to apply sunscreen at their discretion. 10 years after the 4 year study was complete, there was a 50% reduction in melanoma in the group that applied sunscreen daily.
Vitamin D has been shown in countless studies to benefit one’s health in about a billion ways- it’s basically the new wonder vitamin. So does wearing sunscreen deprive you of all that great D?? This is actually a huge topic and one that I’d like to write about in another science post.
What do you think?
Do you wear sunscreen every day? Do you worry about skin cancer or skin aging? Do you worry about harmful chemicals in sunscreen?
Let me know!!
Making Sense of Sunscreen Controversies from Medscape Education Dermatology
Archives of Dermatological Research: DNA Damage After Acute Exposure of Mice Skin to Physiological Doses of UVB and UVA light
Halliday GM, Byrne SN, Damian DL (Dec 2011). “Ultraviolet A radiation: It’s role in immunosuppression and carcinogenesis”. Semin Cutan Med Surg 30 (4):214-21