Coffee-leukaemia headlines based on research that hasn’t been done yet

No strong evidence linking coffee to leukaemia

A headline in the Daily Mail today proclaimed “Coffee may raise child cancer risk: New evidence that caffeine could damage babies’ DNA”.

The Daily Record ran with “New fears over leukaemia link to coffee”, while the Metro said “Coffee ‘raises risk’ of leukaemia in babies”.

So what is this new research that has prompted such alarming headlines?

In short, it doesn’t exist. It hasn’t been done yet.

There is no data – no “new evidence” or “new fears”. All that exists are a series of plans and ideas in the heads of a group of scientists.

These stories were based on a press release issued by the University of Leicester, about the upcoming work of researcher Dr Marcus Cooke. Cooke has recently received funding to study how drinking caffeine during pregnancy might affect an unborn baby’s risk of leukaemia during childhood.

That is the critical point. Like any scientist, this group have sensed an interesting question and have designed a study to test their ideas. But they haven’t done anything yet.

The press release

Here’s a quote:

“We want to find out whether consuming caffeine could lead to the sort of DNA changes in the baby that are linked to risk of leukaemia,” said Dr Cooke. “This is an important area of research because it is vital that mothers are given the best advice possible.”

Although there are currently no convincing links between caffeine and cancer risks [emphasis ours], previous studies have found a link between alterations to DNA, which are sometimes found in newborn babies, to an increased risk of leukaemia. Caffeine has been shown to cause these kinds of changes to DNA.”

Now this is a research proposal. If – and it’s a big ‘if’ – the study uncovers a link between drinking coffee and having a child who gets leukaemia, the results may well have an impact on future public health advice. But that is a debate for several years down the line, when Cooke and his team have actually completed their work.

While the press release makes it clear that the research is yet to happen and talks about the current state of evidence, one might question the wisdom of publicising studies like this before they have even begun. Realistically, it seems almost inevitable that someone’s going to jump to the wrong conclusion.

Coffee and cancer

So what of this potential link between coffee and cancer? There has been a lot of research in this area, but for the most part, it’s failed to arrive at a consistent answer. The extensive evidence summary from the World Cancer Research Fund (who are funding Cooke’s work) concluded that coffee is unlikely to affect the risk of either pancreatic or kidney cancer.

Other studies have investigated potential links between coffee and ovarian, breast, prostate and bowel cancers, again with many mixed results.

Some studies have even suggested that coffee could protect against some types of cancer, such as liver cancer and womb cancer.

What about leukaemia?

So far, a couple of French studies have looked into this issue. The first of these, published in 2005, compared 280 children with leukaemia to 288 healthy children. The researchers asked the mothers of these children to say how much coffee they drank while they were pregnant. They concluded that children whose mums drank more than 8 cups of coffee a day had a greater risk of leukaemia.

However, the result of this first study was only just about statistically significant – this means that the scientists couldn’t rule out the chance that it was a fluke. And it was later contradicted by a second study, published in 2007 by the same research group.

This one looked at a larger number of children – 472 with leukaemia, and 567 without it. This study found that children whose mothers drink three or more cups of coffee a day are no more likely to develop leukaemia than those whose mums avoid coffee entirely.

Based on these studies, there is no solid evidence to believe that coffee can raise an unborn child’s future risk of cancer. Now, it’s entirely possible that Cooke’s planned study will add some new evidence into the mix. But obviously, we won’t know until the results are actually in.

Until then, it’s a good idea to avoid promoting the research of tomorrow as the scare-story of today.

NB Cancer risk aside, drinking too much caffeine during pregnancy could have other effects on your health. For this reason, the Food Standards Agency advises pregnant women not to drink more than 200mg of caffeine a day, which is about the same as two cups of coffee.

Image: by Julius Schorzman, sourced from Wikipedia