Drinking coffee does not change a person's risk of being diagnosed with or dying from cancer, a new Queensland study has found, with researchers saying the results could have public health implications worldwide.
The study, released by QIMR Berghofer Medical Research Institute, analysed data from more than 300,000 coffee drinkers using previous international observational studies and a genetic-based technique called Mendelian randomisation.
Associate Professor Stuart MacGregor said the findings were conclusive.
"Using a genetic-based approach to assess whether coffee increases cancer risk is a really powerful approach, and we've used it to show that ultimately your risk won't be changed if you drink coffee," Associate Professor Macgregor said.
"Genetics don't lie. For other diseases, the jury's still out — we need to do more work.
"What we found was that irrespective of specific compounds that were there, in terms of the relationship between the coffee they drink every day and whether they ultimately get cancer, we found that essentially there is no link."
Coffee consists of both potentially carcinogenic biochemical compounds, as well as antioxidants that might help prevent cancer — as shown in animal studies.
The health benefits, or otherwise, have long been the subject of heated debate among the scientific and medical communities.
The report's lead researcher, Jue-Sheng Ong, was surprised by the results, given the confusion and conflicting data surrounding coffee's carcinogenic risks.
"That is something that was a bit shocking for us, because we always thought either coffee is associated to some kind of therapeutic benefit, or coffee might be associated with increased risk for many cancers, and that's clearly not the case here," Mr Ong said.
About 2 billion cups of coffee are consumed every day around the world and an international controversy was stirred when a US court in California ruled a multinational coffee chain and other retailers did not have to place warning labels on cups about coffee's carcinogenic risk.
It declared the beverage did not pose a "significant" cancer risk, despite containing a chemical listed by the state as being carcinogenic.
This came in response to a Los Angeles judge ruling Starbucks and other companies failed to show that benefits from drinking coffee outweighed risks from a chemical by-product of the roasting process called acrylamide.
The chemical is "formed in certain plant-based foods during cooking or processing at high temperatures, such as frying, roasting, grilling, and baking," according to the California government and is on a list that California says causes cancer, though other groups classify it as a "probable" carcinogen.
Foods affected include potato chips and French fries, canned black olives, roasted nuts, toast — and roasted coffee beans.
The QIMR Berghofer researchers believed their study could have public health implications worldwide.
"Government policy doesn't need to be affected," Associate Professor Stuart MacGregor said.
"If there really was an effect there, from a big policy level, then that would be something we'd need to change, whether we'd need to regulate things.
"This gives us confidence there's no detrimental effects from people enjoying a cup of coffee."
The research findings have been published in the International Journal of Epidemiology.
