The research showed that even a even a single copy of a red hair-associated MC1R gene variant increased the number of mutations in melanoma skin cancer; the most serious form of skin cancer.
Many non-red haired people carry these common variants and the study shows that everyone needs to be careful about sun exposure.
Funded by Cancer Research UK, the study carried out by researchers at the University of Leeds and the Wellcome Trust Sanger Institute, analysed data on tumour DNA sequences from more than 400 people.
They found an average of 42 per cent more sun-associated mutations in tumours from people carrying the MC1R gene variant.
Professor Tim Bishop, joint lead author and Director of the Leeds Institute of Cancer and Pathology said that while a predisposition between red-haired people and skin cancer had been known for around 20 years, it is the first time the biological impact of the gene variant had been examined.
He said: “This is the first study to look at how the inherited MC1R gene affects the number of spontaneous mutations in skin cancers and has significant implications for understanding how skin cancers form. It has only been possible due to the large-scale data available. The tumours were sequenced in the USA, from patients all over the world and the data was made freely accessible to all researchers. “This study illustrates how important international collaboration and free public access to data-sets is to research.”
UV rays, either from sunlight or artificially generated for sunbeds, damage DNA. People with red hair have a skin pigment that is thought to allow more of the rays to penetrate their DNA, potentially increasing the risk.
The new study, published in the journal Nature Communications, confirmed that the MC1R gene variant raised the number of spontaneous mutations in the skin caused by UV rays.
Unexpectedly, it was also found to boost levels of other skin tumour mutations not related to UV exposure - suggesting involvement of the variant in cancer processes not driven by sunlight.
Dr Julie Sharp, head of health and patient information at Cancer Research UK, said: “This important research explains why red-haired people have to be so careful about covering up in strong sun.
“It also underlines that it isn’t just people with red hair who need to protect themselves from too much sun. People who tend to burn rather than tan, or who have fair skin, hair or eyes, or who have freckles or moles are also at higher risk.
“For all of us the best way to protect skin when the sun is strong is to spend time in the shade between 11am and 3pm, and to cover up with a T-shirt, hat and sunglasses.
“And sunscreen helps protect the parts you can’t cover; use one with at least SPF15 and 4 or more stars, put on plenty and reapply regularly.”