Recently, everyone from the major news networks to local newspapers to bloggers have been featuring the latest in research from the Environmental Working Group
, stating that the vitamin A (as retinyl palmitate) in sunscreens may not be safe and may actually accelerate the rate of cancer growth. The Environmental Working Group mentions that over 41 percent of the sunscreens in the United States feature the compound. The EWG also added that high levels of SPF (those above 50) offer a "false sense of security" to consumers.
What the Medical/Scientific Community Knows For Sure at this Point
At this point, the EWG has made a request to the FDA
to review the use of retinyl palmitate in sunscreens. The reasons for this were at least three-fold:
- Vitamin A increases photosensitivity in the skin. This means that vitamin A tends to make the skin more susceptible to UV exposure. This is a fact that has been well-established within the dermatological community for years (as stated in this 2004 study in The International Journal of Environmental Research and Public Health), and for this reason, many dermatologists have consistently recommended to use retinoids at night.
- Vitamin A breaks down in sunlight, and forms free radicals in the presence of UVA and UVB radiation, according to a 2007 study in Vitamins and Hormones. The EWG cited this particular study in making its request for further review to the FDA. Obviously, it is not beneficial to have free radicals forming on the surface of your skin - preventing oxidation is one of the reasons you use UV protection in the first place! For the sake of caution, this fact alone is reason enough to switch to a sunscreen without vitamin A. However, if it makes you feel any better for using retinyl palmitate-containing sunscreens in the past, many of these sunscreens contain other antioxidants, which were likely to have neutralized some (if only some) of the oxidative compounds that were released onto your skin. I'm certainly not saying to use them now - I'm just trying to make you feel a little better, :-) .
- High SPF is more effective UVB protection than lower SPF, though no form of protection is 100%. In brief, UVA is longer-wavelength and not rated on sunscreens in the U.S.; UVB is shorter-wavelength and is the number on the bottle. According an algorithm from Dr. Rachel Herschenfeld, SPF 30 allows 1/30 UVB rays, or 3.3% through, meaning it blocks about 96.6% of UVB rays; SPF 50 allows 1/50 UVB rays, or 2.0% through, meaning it blocks 98.0% of UVB rays. I personally prefer higher ratings - why pay for 97% when you can get 99%? However, I do see the Environmental Working Group's point in advising the public that high SPF's are not synonymous with perfect protection. For one, higher UVB ratings do not necessarily mean higher UVA protection (for instance, compounds like Mexoryl and Tinosorb are excellent UVA protection, but are sometimes available with UVB protection of SPF 30). For another, sunscreen ratings are made from a rating scale using about 1 gram of product per cubic centimeter area, which is quite a bit higher than the average person uses. Lastly, sunscreen tends to wear off with sweat, water exposure, UV exposure, and daily wear and tear - so unless you are using a bottle a day and reapplying every 2 hours, you are getting more than 2.0% of the UVB rays from your SPF 50 sunscreen application. I personally see a dermatologist, wear a wide-brimmed hat and clothing with a UPF of 30-50, and, yes, still maximize my sunscreen use!
What Needs to be Evaluated Closely
- Vitamin A accelerates the growth of cancer...or can it prevent it? The idea that vitamin A causes cancer, featured on many popular headlines this week, is mostly backed by the Environmental Working Group's recent research, which found that skin tumors and lesions developed up to 21% faster in mice treated with a 0.1-0.5% retinyl palmitate-containing cream than without. This is certainly alarming, but raises questions: For instance, is this effect shared by other vitamin A- related compounds, such as retinol or prescription tretinoin? How much of the 0.1-0.5% vitamin A cream was applied to the mice (g/kg of body weight), and is this a fair comparison with the amount of 0.1-0.5% vitamin A cream per body weight a human would use? If yes, then - and this is much harder to test - does this effect occur in humans? Conversely, a 2007 study of nearly 2300 individuals found that taking 2500 IU of vitamin A daily prevented the development of squamous cell carcinoma (SCC), a form of skin cancer, although it did not prevent the development of basal cell carcinoma, another prevalent form of skin cancer. Further, consuming vitamin A-rich foods, such as carrots, spinach, and green beans, is often a recommendation in cancer prevention diets, and just about everyone has consumed vitamin A (and hence had it in their bloodstream and in their skin) before going into the sun. Could the negative effect limited to retinyl palmitate?
- Vitamin A interferes with drug-drug interactions. A 2005 study in the journal Toxicological Sciences demonstrated that retinoids activate a pathway (retinoid X receptor (RXR)/steroid and xenobiotic receptor (SXR)). This pathway regulates the transcription of certain genes, including CYP3a4, an enzyme responsible for drug metabolism (of, you guessed it, xenobiotics). However, what has made headlines was that RXR/SXR-mediated CYP3a4 (drug metabolism) activity was increased in a line of liver cancer cells, Huh7, though it was not stated that vitamin A accelerated liver cancer cell growth and proliferation. Nevertheless, more studies need to be done to see if the same altered drug metabolism effect is exhibited in cells in vivo (within the body), as this study was conducted in vitro (on a line of cells outside the body). Still very promising and interesting!
The Bottom Line
These are exciting times in the medical/scientific community, and the FDA is scheduled to make a decision on the safety of vitamin A in Fall 2010. In the meantime, here are some guidelines:
- Visit your dermatologist. As I always say, I am a medical student, not a physician yet. As I am growing and learning, I love to write about exciting thoughts and findings in this blog, but the key words here are that I am learning. Please consult your dermatologist! (Or, conversely, if you are a scientist and would like to contribute something to this piece, please feel free to comment below).
- You may wish to use your vitamin A-based products only at night. Retinoids have long been considered a gold standard in anti-aging within the dermatological community, and they still have vast clinically proven benefits. However, because it appears that retinyl palmitate breaks down to produce free radicals in the skin following UV exposure, it may not be advisable to use products that contain retinyl palmitate during the day. Furthermore, because retinoids in general tend to make the skin more susceptible to photodamage, it may be wise to use retinoids during the day. I personally use retinol-containing products at night.
- Give the EWG and the FDA a break! After talking to some friends and family members outside of the medical community, there seems to be a lot of distrust in the EWG and FDA right now. Whether due to the current trend for "all natural" products (the prevalent belief that all things "natural are good, chemical are bad," while neither is entirely true) or actual viable complaints, many consumers tend to think that neither side is seeing the big picture (one being overprotective, the other not enough), and that is beside the point. We are living in exciting times, and the scientific and medical communities are full of brilliant people who are constantly increasing our knowledge base and reflecting the advancements in our research journals. With that said, until the FDA makes its decision in the Fall of 2010, I'm seeing my dermatologist, using - and often reapplying- retinyl palmitate-free sunscreen (with Mexoryl or Tinosorb for UVA protection and high SPF for UVB protection), and donning a big ol' hat! :-)
Have any thoughts on this hot issue? Please feel free to comment below!
Photo courtesy: Kailua Vacancy Originally uploaded by Bright Tung