Researchers who conducted the world's first study to assess the molecular impact of sunscreen found it offers 100% protection against all three types of skin cancer - basal cell carcinoma, squamous cell carcinoma and malignant melanoma. They also found sunscreen prevents damage to a key anti-cancer gene known as p53.
There is lots of evidence that sunscreen stops skin from getting sunburn, but not much is known - although there is much speculation - about whether it can prevent skin cancers.
In the journal Pigment Cell & Melanoma Research, researchers from Australia's Queensland University of Technology (QUT) report how they looked at the molecular effect of sunlight on human skin, both with and without sunscreen.
They found that when sunscreen (SPF30+) was properly applied to exposed skin, there was no evidence of UV-induced damage.
Protecting the p53 gene
But they also found sunscreen has another effect - it protects the p53 gene from DNA damage that mutates it into a form where it can no longer do its job of repairing skin cells whose DNA has been damaged by the sun. Once skin cells have DNA damage, there is a higher risk of skin cancer.
Lead researcher Dr. Elke Hacker says:
"Melanoma is the most lethal form of skin cancer with research showing damage of melanocytes - the pigment-producing cells of the skin - after sun exposure plays a role in the development of skin cancer."
For their study, the researchers recruited 57 patients who were having a series of skin biopsies and assessed molecular changes in their skin before and after exposure to UV, with and without sunscreen.
They first took biopsies of two sites on unexposed skin, then applied sunscreen to one site and left the other site bare while they exposed them to UV light. They then took biopsies of both sites again.
Then, after 24 hours, they took another set of biopsies and compared the skin samples, says Dr. Hacker, who explains what they found:
"... after 24 hours where the sunscreen had been applied, there were no DNA changes to the skin and no impact on the p53 gene."
She says this is an important discovery because they found something about sunscreens and their effect on skin that goes beyond protecting against the redness of sunburn.
Findings set a benchmark
The study "looks beyond the redness to determine whether UV exposure when using sunscreen causes molecular changes to the skin, as these changes have been linked to basal cell carcinoma, squamous cell carcinoma and malignant melanoma. When there are changes in the molecular structure it can enhance skin cancer development," says Dr. Hacker.
The researchers believe their findings also set a benchmark for investigating "super sunscreens" that help repair skin damaged from sun exposure.
The study was funded by Cancer Council Queensland, who recommend before going out in the sun, people put on SPF30 or above, broad-spectrum, water-resistant sunscreen, and reapply it every 2 hours.
Spokesperson Katie Clift says:
"Adults should apply more than half a teaspoon of sunscreen to each arm and the face, neck and ears - and just over one teaspoon to each leg, and front and back of the torso.
It's also important to complement sunscreen with sun protective clothing, a broad-brimmed hat, to seek shade and slide on wraparound sunglasses for best protection."
Researchers in Denmark reported in JAMA Dermatology recently that melanoma patients increase sun exposure in the 3 years following their diagnosis.
Written by Catharine Paddock PhD
Ref:
The effect of MC1R variants and sunscreen on the response of human melanocytes in vivo to ultraviolet radiation and implications for melanoma; Hacker, E., Boyce, Z., Kimlin, M. G., Wockner, L., Pollak, T., Vaartjes, S. A., Hayward, N. K. and Whiteman, D. C.; Pigment Cell & Melanoma Research Published online first 9 September 2013; DOI:10.1111/pcmr.12157;