Coffee and cancer – a clearer picture

Coffee: a nice pick-me-up, but not a cancer buster

Coffee is a big part of many people’s lives, but it’s not thought to have many health benefits – it keeps you awake, and often has lots of sugar, milk or cream added, which can pile on the calories.

But lots of studies have looked into whether coffee could have greater effects on the body other than waking you up – including whether it could affect your chances of developing cancer.

The results of these studies have been conflicting – especially those that have looked at different types of cancer, with some indicating coffee could be beneficial, others that it could be harmful, and yet more showing that it has no effect on cancer risk or the risk of dying from cancer.

Among all this conflicting evidence, a new study has been published in the New England Journal of Medicine, following more than 400,000 people for up to 13 years, to search for links between the amount of coffee they drank and their likelihood of dying from any cause during the course of the study, including cancer.

The results showed that drinking coffee could reduce ‘all-cause mortality’ – the chance of dying from anything – and the risk of dying from certain other conditions, but it had no effect on the risk of dying from cancer.

What did they find?

The researchers looked into the risk of dying from several different diseases – cancer, heart disease, diabetes, lung disease, infections, stroke – and even accidents. Many of these causes of death were less likely among heavier coffee-drinkers, but not cancer. In fact, cancer death rates stayed pretty much the same, no matter how much coffee people drank.

There’s also an interesting observation buried in the statistics.

Although overall death rates were lower in coffee-drinkers, this was only apparent after the results had been adjusted to take into account all the other things that might affect the risk of dying.

In particular, smoking had such a strong effect that without adjusting the results to take it into account, the overall risk of dying initially seemed to be higher among coffee-drinkers, because people who drank the most coffee were also more likely to be smokers.

It might sound like an obscure statistical point, but it does serve as a useful reminder that coffee, like so many other aspects of our diet and lifestyle, isn’t a ‘magic bullet’ or a guarantee against disease. And small positive effects from one thing can easily be outweighed by other aspects of our lifestyles.

And here’s another important point – because this study just looks at the likelihood of dying for different levels of coffee-drinking, it can’t show anything about whether it’s the coffee itself causing the reduced risk of dying, or some other reason that’s linking the two things. In other words, it doesn’t show cause and effect, just a statistical link.

What does all this mean?

In essence, while drinking coffee tastes great, may help keep us awake, and might protect against other diseases, it doesn’t seem to protect us against cancer.

There are plenty of things you can do that are reliably known to reduce cancer risk – being a non-smoker, keeping a healthy weight and drinking less alcohol, to name but a few.

But as for coffee, it won’t be making it onto that list for now.

Jess

Reference

• Freedman, N. et al. (2012). Association of coffee drinking with total and cause-specific mortality New England Journal of Medicine, 366 (20), 1891-1904 DOI: 10.1056/NEJMoa1112010