Findings refute earlier health warning issued by the Environmental Working Group
Despite previous concerns about the cancer-causing potential of sunscreens containing retinyl palmitate (vitamin A), an independent analysis published online in the Journal of the American Academy of Dermatology (JAAD) determined that there is no evidence that the inclusion of retinyl palmitate in sunscreens can cause cancer in humans.
"Earlier this year, the Environmental Working Group issued a health warning that sunscreens containing retinyl palmitate could pose a cancer risk," said dermatologist Henry W. Lim, MD, FAAD, chairman of the department of dermatology at Henry Ford Hospital in Detroit. "This warning garnered significant media attention and caused considerable confusion among the public. Our report should help dismiss the misinformation that sunscreens are not safe, as sunscreens are vitally important in reducing your risk for skin cancer, not causing it."
Retinyl palmitate is approved by the Food and Drug Administration (FDA) for use in over-the-counter and prescription drugs, and it is also used as a food additive (e.g., to fortify low-fat milk, dairy products and breakfast cereals with vitamin A). When used in sunscreen, retinyl palmitate is not an active drug ingredient (unlike sunscreen filters), but rather a cosmetic ingredient. In sunscreen, it can serve as an antioxidant to improve product performance against the aging effects of UV exposure or to enhance the aesthetic qualities of sunscreen.
In the commentary published in JAAD entitled "Safety of retinyl palmitate in sunscreens: A critical analysis," lead investigator and dermatologist Steven Q. Wang, MD, FAAD, director of dermatologic surgery at Memorial-Sloan Kettering Cancer Center in New York, explains that although retinyl palmitate was selected for testing by the National Toxicology Program (NTP), mere selection does not mean that the chosen compounds are dangerous or unsafe. He explained that retinyl palmitate was mainly selected because of its widespread use in cosmetic and sunscreen products. Many common ingredients, such as aloe vera, nanoscale titanium dioxide, and zinc oxide are currently under review by the NTP.
One of the primary concerns about retinyl palmitate cited by the Environmental Working Group in its annual sunscreen report is that when the compound is exposed to ultraviolet A (UVA) radiation, it can result in the generation of oxygen radicals, or free radicals. Since 2002, there have been eight in vitro (test tube) studies using mouse lymphoma cell and human skin Jurkat T-cell cultures demonstrating that retinyl palmitate can produce free radicals, which can disrupt cell function.
"Despite the concerns raised by these non-human studies, retinyl palmitate operates within the skin as only one component of a complex antioxidant network," said Dr. Wang . "For example, when a sunscreen with retinyl palmitate is applied to the skin, a number of antioxidants work together to alleviate the risk of free radical formation seen in these in vitro experiments. If studied on its own – outside of this environment – its antioxidant properties can rapidly be exhausted, allowing the production of oxygen radicals. In these non-human studies, retinyl palmitate was the only compound studied – making the biological relevance of these findings to humans unclear."
In addition, a large animal study testing whether hairless and albino mice developed tumors sooner when coated in retinyl palmitate versus a placebo cream was conducted by the NTP. At this time, the findings have not been published in peer-reviewed literature. After critically analyzing the available data, Dr. Wang and his team of investigators determined that there is no conclusive evidence to indicate the combination of retinyl palmitate and UV radiation causes increased rates of skin cancer.
"It is important to note that the mice in the NTP study are highly susceptible to the effects of UV radiation and can develop skin cancer or other skin abnormalities within weeks of UV exposure, even in the absence of retinyl palmitate," said Dr. Wang. "That is why extreme caution is needed when extrapolating these animal study results to humans."
Although there are no published human studies on the potential of retinyl palmitate or other retinoids to cause cancer, the commentary concludes that observations from decades of clinical practice do not support the notion that retinyl palmitate in sunscreen causes or promotes skin cancer. First, dermatologists routinely prescribe various forms of topical and oral retinoids to treat a number of skin conditions (e.g., acne, psoriasis and photoaging). Dr. Wang explained that there is no published evidence to suggest that topical or oral retinoids increase the risk of skin cancer in these patients. He added that oral retinoids (e.g., acitretin) also are used to prevent skin cancers in high-risk individuals, such as organ transplant patients.
"Based on the current available data from in vitro, animal and human studies, there is no convincing evidence to support the notion that retinyl palmitate in sunscreens causes cancer," said Dr. Wang. "On the contrary, years of research suggests that retinoids are helpful in reducing your risk for skin cancer. The bottom line is that people should continue vigilantly using sunscreens along with other sun-safe practices – such as limiting sun exposure, seeking shade, and wearing sun-protective clothing, hats and sunglasses – to reduce the risk of skin cancer and premature aging."
SOURCE American Academy of Dermatology