Is there a cancer risk with coffee?
Trouble is brewing for coffee lovers in California, where a judge ruled that sellers must post scary warnings about cancer risks. But how frightened should we be of a daily cup of joe? Not very, some scientists and available evidence seem to suggest.
“At the minimum, coffee is neutral. If anything, there is fairly good evidence of the benefit of coffee on cancer,” said Dr. Edward Giovannucci, a nutrition expert at the Harvard School of Public Health.
The World Health Organization’s cancer agency moved coffee off the “possible carcinogen” list two years ago, though it says evidence is insufficient to rule out any possible role.
The current flap isn’t about coffee itself, but a chemical called acrylamide that’s made when the beans are roasted. No one knows what levels are safe or risky for people.
“A cup of coffee a day, exposure probably is not that high,” said Dr. Bruce Y. Lee of Johns Hopkins Bloomberg School of Public Health. “If you drink a lot of cups a day, this is one of the reasons you might consider cutting that down.”
Here’s what’s known about the risks.
The chemical
Start with the biggest known risk factor for cancer — smoking — which generates acrylamide. In the diet, french fries, potato chips, crackers, cookies, cereal and other high-carbohydrate foods contain it as a byproduct of roasting, baking, toasting or frying.
Food and Drug Administration tests of acrylamide levels found they ranged from 175 to 351 parts per billion (a measure of concentration for a contaminant) for six brands of coffee tested. By comparison, french fries at one fast food chain ranged from 117 to 313 parts per billion, depending on the location tested. Some commercial fries had more than 1,000.
What’s the risk?
The “probable” or “likely” carcinogen label is based on studies of animals given high levels of acrylamide in drinking water. But people and rodents absorb the chemical at different rates and metabolize it differently.
Scientists convened by the WHO’s cancer agency in 2016 looked at coffee — not acrylamide directly — and decided coffee was unlikely to cause breast, prostate or pancreatic cancer, and that it seemed to lower the risks for liver and uterine cancers.
The California law
Since 1986, businesses have been required to post warnings about chemicals known to cause cancer or other health risks — more than 900 substances are on the state’s list today — but what’s a “significant” risk is arguable.
Coffee sellers and other defendants in the lawsuit that spurred Thursday’s ruling have a couple of weeks to challenge it or appeal.