A judge in Los Angeles has ruled that Californian law requires companies to warn consumers that coffee could cause cancer. If the ruling stands, that means a Starbucks coffee cup in California could feature an unsightly cancer warning, a bit like a packet of cigarettes.

So, what’s the deal with this? Is your morning tradition of sinking a few coffees going to kill you?

The short answer is no, not exactly.

Currently, there is no scientific research that directly says drinking coffee gives humans cancer at all. On the contrary, numerous studies have sung the praises of coffee (see here, here, and here). The World Health Organization's (WHO) cancer agency has previously said that coffee has “no conclusive evidence for a carcinogenic effect." In fact, a panel of experts from the WHO has also said that regularly drinking coffee might actually protect against certain types of cancer.

However, here’s where it gets a bit hazy. Coffee does contain the chemical acrylamide, a byproduct of roasting coffee beans that can be found in many foods, from french fries, toasted bread, and many roasted or fried foods. Usually, it’s produced when starchy foods are heated to high temperatures, giving the food its characteristic brown color and flavor. It’s the same culprit that led to sensational headlines saying “Burned Toast Will Give You Cancer!!!” last year.

Laboratory tests show that high doses of acrylamide can cause cancer in animals, so it is presumed to do the same to people. That link has not been proven in humans though.

This current situation in California is the result of an eight-year legal battle between an obscure non-profit group, The Council for Education and Research on Toxics (CERT), and 90 coffee companies including Starbucks, the Associated Press (AP) reports. The law in California requires warnings on a wide range of chemicals that can cause cancer. CERT argues that the coffee industry must not be exempt from this law because coffee contains acrylamide and this has been linked to cancer. The judge ruled that the defendants hadn't proven that benefits from drinking coffee outweighed any risks. In an earlier part of the trial, he ruled that they had failed to show the threat from chemicals found in coffee weren't insignificant.

CERT’s lawyer Raphael Metzger, who drinks a few cups of coffee daily according to the AP, also argued that the industry should remove acrylamide from its production, although the coffee companies say that changing the roasting process isn't really an option.

Basically, it's just a fiddly legal thing. While consumers should certainly be aware of what can be found in their morning brew, others argue that labeling it a carcinogen is excessive.

“Cancer warning labels on coffee would be misleading,” the National Coffee Association said in a statement. 

"Study after study has provided evidence of the health benefits of drinking coffee, including longevity – coffee drinkers live longer.”