Sunday, June 26, 2011

Screening Our Sunscreens for Potential Endocrine Disruptors

Recent research about sunscreens had questioned their safety. The FDA is in charge of regulating products and claims that sunscreen manufacturers make and the last time they were reviewed claims and efficacy was in the 1970’s. Labeling is expected to change for next summer. So what are the current problems associated with some sunscreens and what do consumers do for now until greater regulation and review takes place?

Let’s take a look at one potential problem and that is the chemicals in sunscreen. Oxybenzone is commonly used in sunscreens and may actually be very problematic. In addition to being known to produce free radicals (also known as pro-oxidants), recent research done on fish actually found that oxybenzone can have endocrine disrupting estrogenic effects as well. In this study, the researchers took two different groups of fish. When exposed to high levels of oxybenzone, the fish’s blood levels of estrogen was 75 times greater than those fish not exposed to oxybenzone. Researchers also evaluated the reproductive success of the fish. The ability of females to produce viable eggs was significantly lower after just 7 days of exposure and the number of fertilized eggs that ended up hatching was also significantly lower. This research suggests that there may be an estrogen like activity of the chemical oxybenzone and may alter normal hormonal function.

Knowing this information, what are safe ingredients in sunscreens? Look for sunscreens that are mineral based and contain either zinc oxide or titanium dioxide as the main sun protective ingredients. According to the environmental working group, Mexoryl SX is another good option, but it’s sold in very few formulations. Tinosorb S and M could be great solutions but are not yet available in the U.S. Sunscreens with avobenzone are also okay.

Label reading can also be a hurdle when selecting a sunscreen. SPF measures a sunscreen's ability to prevent sunburn, which is caused by ultraviolet B (UVB) light. If your skin would normally burn after 10 minutes in the sun, for example, wearing an SPF 15 sunscreen would theoretically allow you to stay in the sun for 150 minutes (10 x 15) without burning. This means that the person should re-apply after 2.5 hours in the sun. Scientists now also know that ultraviolet A (UVA) is a major cause of aging and also contributes to skin cancer. SPF can be misleading because products with less than SPF 15 might not protect against the UVA effects, but may prevent sunburn. There is little data if products greater than SPF 50 provide any additional benefit. A tan offers the equivalent protection to a sunscreen with SPF 3 or 4. A white long sleeve tee is SPF 7 and dark, heavy denim has an SPF of 1,700.

To learn more about chemical components of sunscreen, take a look at environmental working group’s 2011 sunscreen report. This group reports on the health effects of chemicals in our environment. Their online resource allows you to see how your current sunscreen (makeup, moisturizer or lip balm) ranks and gives their recommendation for the safest products to use. It actually breaks down all the ingredients in a product so you can see how each may be influencing your health.

It’s difficult to talk about the sun without talking about vitamin D. You need at least 20 minutes of full body sun exposure between the hours of 10 am until 2 pm  to make your daily allowance of vitamin D. Darker skinned individuals may need up to one hour. Anything over SPF 8 blocks the body’s ability to make vitamin D. So you can see the problem here-- many people burn with just 10 minutes in the sun and we want to protect our skin from damaging rays. This is where the importance of taking supplemental vitamin D comes in to play. Vitamin D deficiency is very common in Wisconsin and individual need is widely variable. I have seen similar body and age matched patients need anywhere from 2000 units a day to 10,000 units a day to get to an optimal blood vitamin D levels. Vitamin D is an easy blood test that your doctor can to o that you can ensure that you are getting the correct supplemental amount of D.

Here are the key take home points:
  1. Avoid oxybenzone. Look for mineral lotion sunscreen with zinc oxide or titanium dioxide.
  2. Look for full spectrum: UVA (A for Aging) and UVB (B for Burn) with at least SPF 15.
  3. Consider that most sunscreens are water resistant at best, waterproof claims are not well substantiated, and therefore you need to re-apply every few hours. Clothing and shade are likely the best bets for complete protection from the sun.
  4. Wait about 20 min after going outside before applying sunscreen or take supplemental vitamin D and have your levels checked.

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