When the weather gets hot, conversations with patients often turn to which sunscreen is best and whether it’s always necessary. I am even asked if sunscreens can cause – or prevent – cancer.
This may be a surprising question given public awareness regarding the danger of solar radiation and the growth of the sunscreen industry, but it is a question that has been investigated extensively over the past three decades due to the tripling of cases of melanoma.
In its annual report on sunscreen, the Environmental Working Group (EWG), a research organization committed to protecting human health and the environment, states that there is little scientific evidence to suggest that sunscreen alone reduces cancer risk, particularly for melanoma, the most deadly type of skin cancer. EWG strongly disagrees with the FDA decision to allow sunscreens to claim that their products prevent cancer.1
It has been established that sunscreen can prevent sun damage and squamous cell carcinoma (another type of skin cancer), but there are no studies that report decreased melanoma incidence with sunscreen use, and some studies actually suggest increased risk.2
One explanation for this finding is that lack of sunburn when using sunscreen properly inadvertently causes people to extend their time in the sun. This exposes them to more cumulative ultraviolet radiation, which causes DNA damage leading to mutations in tumor suppressor genes and arrest of DNA repair.3
Sunscreen ingredients may also play a role in cancer formation. Titanium dioxide is used in sunscreens and has been modified from a fine particle to a nano-particle to reduce its opaque white appearance. These nano-particles produce tumors in animal experiments, and the International Agency for Research on Cancer has therefore classified this substance as possibly carcinogenic to humans.4 Retinoic acid and retinyl palmitate, two types of topical vitamin A, are also known to cause tumor growth and skin damage in animals and yet are present in hundreds of sunscreens, skin lotions and lipsticks.5
Another hypothesis is that daily use of sunscreen leads to suboptimal vitamin D levels associated with various types of cancer including those of the skin, breast, colon and prostate.6,7
Given this information, it is best not to rely on sunscreen alone to protect yourself from skin cancer. Use sunscreen when you expect to experience prolonged time in the sun, but avoid sunburn by seeking shade and using clothing as sun protection. Choose a sunscreen free of retinoids, nano-particles and parabens (a class of preservatives that may increase sun damage). And finally, ensure adequate vitamin D through brief periods of daily sun exposure on bare skin and/or by taking a vitamin D supplement.
Dr. Jessica Needle is a naturopathic doctor practicing at Optimal Health Center in Palm Desert and can be reached at (760) 568.2598.
References: 1) https://www.ewg.org/sunscreen/report/executive-summary/; 2) Chemoprevention of melanoma. Adv Pharmacol. 2012; 65: 361-398; 3) Cancer-preventive effects of sunscreens are uncertain. Scand J Work Environ Health 2000; 26(6):529-531.; 4) Titanium dioxide nano-particles: a review of current toxicological data. Part Fibre Toxicol. 2013; 10: 15; 5) Photocarcinogenesis Study of Retinoic Acid and Retinyl Palmitate. http://ntp.niehs.nih.gov/go/36130; 6) Vitamin D and skin cancer. Photochem Photobiol. 2015 Jan-Feb; 91(1):201-9; 7) An estimate of premature cancer mortality in the United States due to inadequate doses of solar ultraviolet-B radiation. Cancer, 2002b; 94:1867-75.