WHO: Coffee itself isn't cancerous, but watch out for 'very hot' beverages

If you're like many around the world who enjoy a cup of coffee in the morning, you'll be happy to know that the World Health Organisation has released its long-anticipated report on the drink, and its findings bode well for your health.

In reviewing the most recent scientific evidence over the 25 years since its last analysis on coffee, the WHO concluded that coffee should no longer be considered a carcinogen and that it may actually have positive effects for your body when it comes to liver and uterine cancers.

Now before you start ordering that second steaming cup, it's important to know that the WHO report wasn't all good news. There was another significant finding: "Very hot" beverages "probably" cause cancer. This is mostly based on studies related to the consumption of a traditional drink called mate or cimarron in South America where the tea can be taken at temperatures around 70C. That's significantly hotter than people in North America or Europe usually consume their drinks.

The findings were published in The Lancet Oncology on Wednesday.

"These results suggest that drinking very hot beverages is one probable cause of esophageal cancer and that it is the temperature, rather than the drinks, that appears to be responsible," said Christopher Wild, director of the International Agency for Research on Cancer (IARC).

Wild and other officials were unable to quantify the risk - "We can't put a number on it at this stage," they said - but they had some practical advice for people who consume hot beverages.

"Certainly wait a few minutes more before drinking," the IARC said.

The decision to reclassify coffee is a major victory for the industry, which has been aggressively lobbying for such an action. For organisations, such as the WHO, that are charged with protecting the public's health, it's often politically trickier to say a product causes no harm than to say a product causes harm - even for one as beloved as coffee. In the United States, when a federal advisory committee issued recommendations regarding the Dietary Guidelines for Americans last year and said coffee could be part of a "healthy diet", there was a significant backlash. The new US recommendations, officially issued in January, say that up to five 240ml cups a day is fine.

The National Coffee Association cheered the WHO finding, pointing out that it's the first time scientists have positively reclassified a foodstuff or beverage.

"Coffee drinkers have known for a long time that their go-to beverage is a super food," said association president Bill Murray. "Today we can brew or buy a cup with even more confidence, thanks to science."

"More confidence" are the key words here as science is a moving target, especially in terms of food, as bodies making recommendations about what people consume have tended to flip-flop in recent years.

The WHO working group said that it reviewed more than 1000 studies in humans and animals in making its decision, and that there was "inadequate evidence" for the carcinogenicity of coffee drinking. It noted that epidemiological studies mentioned no impact of coffee drinking, specifically on cancers of the pancreas, prostate and female breast. Reduced risks were seen for cancers of the liver and uterine endometrium. For more than 20 other types of cancer, the evidence was inconclusive.

Although the WHO's coffee decision was carefully thought out and involved countless hours of research by some of the top minds in nutrition science, it's just a snapshot in time in terms of what we know. Meat was once thought to be good and important for your health, but the WHO told us last year that it now thinks hot dogs and bacon cause cancer and red meat "probably does", too. Many other changes have taken place over just the past few months: cholesterol, the boogieman of our diets since the 1960s, suddenly became less harmful in January when the new Dietary Guidelines for Americans came out - as did salt.

The coffee issue is also far from definitively resolved. Early work shows that there may be at least one place in your genes that may determine whether you process caffeine quickly or slowly, and that there is a roughly 50-50 split among humans. That has led some experts to wonder whether a general rule about the good or ill effects of a food means anything to individuals.

"A one-size-fits-all recommendation for coffee won't work. Some people just can't tolerate it," Marilyn Cornelis, a Northwestern medical school professor, said at the time.