Coffee: Even Better Than You Thought

Drink up: Coffee is officially off the “Naughty List.”

The World Health Organization International Agency for Research on Cancer has declared that coffee should no longer classified as a carcinogen to humans. It received its absolution in a report titled “Carcinogenicity of Drinking Coffee, Mate, and Very Hot Beverages,” published in the journal The LANCET Oncology.

Java got the bad rap back in 1991 when the working group classified coffee as “possibly carcinogenic” to humans. They say the error was “based on limited evidence of an association with cancer of the urinary bladder from case-control studies, and inadequate evidence of carcinogenicity in experimental animals.”

Now, after analyzing 10 cohort studies and several population-based studies, researchers have concluded there is “no consistent evidence” linking coffee drinking and bladder cancer.

“The working group concluded that positive associations reported in some studies could have been due to inadequate control for tobacco smoking, which can be strongly associated with heavy coffee drinking,” wrote study author Dana Loomis, PhD., deputy head of the section of IARC monographs at the International Agency for Research on Cancer.

But wait, it gets better: Some cancers, such as endometrial and liver cancer, were found to have an inverse association with coffee consumption, with a particular meta-analysis reporting a decrease of 15 percent in the risk of liver cancer per daily cup of coffee.

“More than 40 cohort and case-control studies and a meta-analysis including nearly 1 million women consistently indicated either no association or a modest inverse association for cancer of the female breast and coffee drinking,” Loomis and colleagues wrote. “Similarly, numerous cohort and case-control studies of cancers of the pancreas and prostate consistently indicated no association between these cancers and coffee drinking.”

The team reviewed data related to more than 20 types of cancer, including colorectal, lung, ovarian, and brain cancers. They noted, “Although the volume of data for some of these cancers was substantial, the working group judged the evidence to be inadequate for all of the other cancers reviewed for reasons including inconsistency of findings across studies, inadequate control for potential confounding, potential for measurement error, selection bias or recall bias, or insufficient numbers of studies.”

The same pattern of inadequate evidence was also extended to the potential carcinogenicity of mate — caffeine-rich drink consumed primarily in South America.