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Stick with shade, clothes and sunscreen to prevent skin cancer – not coffee

by Jess Kirby | Analysis

16 August 2011

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A cup of coffee

Our verdict: a hat is a wiser choice

Today, a new study has led to headlines claiming that adding caffeine to sunscreen could improve its effectiveness in preventing skin cancer.

But don’t chuck away the sunscreen just yet, nor pour your coffee into it – this was an interesting study in mice, but it doesn’t prove that adding caffeine to sunscreen would have any effect on skin cancer.

Let’s look at what the researchers did, and what they found.

They didn’t use caffeine

In the study, published in the Proceedings of the National Academy of Science, US-based researchers used a specially bred strain of mouse, in which the genes of a specific biological pathway had been switched off.

The pathway – which affects how cells repair damaged DNA – was chosen because previous studies had suggested that caffeine obstructs this pathway, which makes tumour cells particularly sensitive to radiation and DNA-damaging chemicals.

When the mice were exposed to UV rays, they developed fewer skin tumours, and developed them later, than the normal mice.

This gave the research team evidence that reducing the effects of this signalling pathway could make cells less likely to become cancerous.

But this is a far cry from saying that applying caffeine to human skin could protect our cells from sun damage. And it’s even further from saying anything about the effects of drinking coffee, as some news outlets seemed to suggest.

More research is needed to find out whether this pathway works in a similar way in humans, and whether caffeine has any effect on human skin – and if so, whether it would stand any chance of making sunscreens more effective.

So could drinking coffee have an effect?

The link to drinking coffee isn’t quite as far-fetched as it sounds. There have been a large number of previous studies (for example, this one, this one and this one)  that have looked into whether drinking coffee could have an effect on reducing the risk of different types of cancer.

But the results from these studies have been conflicting and confusing – in short, as our former colleague Ed has said, they’re “all over the place”. Many studies have found no link between coffee and cancer, some have found that it may be associated with a reduced risk, and yet others have found links between coffee and higher risks of cancer.

So what should people do?

We can’t say for sure whether coffee has any effect on cancer risk.

If anything, the overall evidence tends to suggest that it might reduce the risk of cancer risk, but this isn’t a certainty yet – and if there is a link, it would probably be a relatively small effect among heavy coffee-drinkers.

So all in all, there’s no reason to suggest a change from people’s current level of coffee-drinking – and certainly no reason to recommend that people should start (as some news articles suggested) rubbing coffee into their skin. Doing that would be more likely to make you look silly than reduce the risk of skin cancer.



Kawasumi, M. et al (2011). Protection from UV-induced skin carcinogenesis by genetic inhibition of the ataxia telangiectasia and Rad3-related (ATR) kinase Proceedings of the National Academy of Sciences, 108 (33), 13716-13721 DOI: 10.1073/pnas.1111378108

Image: Wikimedia Commons