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Friday, January 30, 2009

Will Coffee Crack your Chromosomes?

Bloggers were amused by the Daily Mail's latest crap science article - a scary cancer story about research that hadn't even been done yet. The article is about a study to be conducted by some University of Leicester scientists, which will investigate whether coffee intake by pregnant women is correlated with DNA changes in babies, similar to those seen in leukemia. In other words: coffee-drinking might be associated with some molecular changes which might point to a risk of leukemia. We should ban the stuff, clearly.

What did scare me though was this line:
Previous research has shown that caffeine damages DNA, cutting cells’ ability to fight off cancer triggers such as radiation.
Hold on, caffeine is genotoxic? That would be pretty worrying. It wouldn't mean that coffee causes cancer, but it would make it highly plausible. But does caffeine in fact damage DNA? That might sound like a simple question to answer. Sadly not. It turns out that caffeine is one of the most researched chemicals in all of genotoxicology, and after over 1000 studies there's no consensus on what, if anything, it does to DNA. The story is remarkably complex and has all the good elements of a scientific intrigue. This review by Steven D'Ambrosio , for example, convincingly argues that:
A number of [genotoxic] effects have been observed [in the lab]. However, they usually appear after very high doses (> 1 mM) of caffeine in combination with genotoxins, and are usually specific to certain cell types and/or cellular parameters. Humans, on the other hand, consume much less caffeine in the diet...thus, it is difficult to implicate caffeine, even at the highest levels of dietary consumption, as a genotoxin to humans.
That's a relief. But right at the end we find that "This work was supported by the National Coffee Association"! If the author was in the pocket of Big Java, how can we trust him? Was he being bribed, perhaps with sacks of top-grade Columbian beans...? There's good evidence that high concentrations of caffeine can enhance the DNA damage produced by genotoxic agents such as radiation. But most of these experiments used caffeine concentrations hundreds of times higher than most coffee-drinkers are likely to experience. And contrary to the Mail's claim, this doesn't mean that coffee damages DNA - it probably works by deregulating the cell replication cycle to prevent DNA repair, which means that in theory, caffeine could even make cancer cells more vulnerable to chemotherapy (but again, only at extreme doses.) There's little epidemiological evidence of any association between coffee drinking and cancer; what evidence there is seems to suggest that coffee might even protect against some cancers...

Still, one comforting lesson from all this is that it's not just neuroscience in which seemingly simple questions (like is there are an area of the brain for recognizing faces?) can turn out to be much more complicated than one might hope...

ResearchBlogging.orgS Dambrosio (1994). Evaluation of the Genotoxicity Data on Caffeine Regulatory Toxicology and Pharmacology, 19 (3), 243-281 DOI: 10.1006/rtph.1994.1023

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