There are many food stories that sound factual but are actually myths. One good example of a myth is asking people to wait for about two minutes after opening a canned coffee. The apparent logic here is that leaving it open for around two to five minutes could reduce the furan levels in a canned coffee.

Furan is an aromatic compound produced when food is heated to a high temperature. The substance generates a sweet and savory aroma, often associated with caramel, fruit, and nuts.

Although no study on humans found a link between furan and cancer, furan is considered a potential carcinogen based on a study on animals.

Asking people to wait for two minutes after opening a canned coffee is partially reasonable. While you wait, furan volatilizes, and the furan level in the coffee decreases. According to a 2017 study by Dongguk University, doing so can lower the furan level by 2 percent at 4 degrees Celsius, and by up to 14 percent at 60 degrees Celsius.

Still, you don’t have to wait for two to five minutes after opening a canned coffee in real life. Furan levels in canned coffee and brewed coffee are different. Canned coffee or instant coffee tends to have low furan levels due to the manufacturing process.

The furan level in coffee brewed with a coffee maker is 110.73 ng/mL on average, and that of canned coffee, 28.08 ng/mL. Instant coffee dissolved in water has 8.55 ng/mL of furan. (1 ng is one billionth of a gram.)

You can understand this easily if you think about how a coffee's aroma is different depending on the type of coffee. The aroma of instant coffee or canned coffee is much lighter than that of brewed coffee or espresso made from freshly-ground beans. In contrast, coffee in air-tight capsules keeps the aroma better, having furan levels similar to those of expresso or much higher. Furan contained in canned coffee is only about one-fourth of that in brewed coffee.

You don’t have any reason to worry about the risk of furan, whether you drink brewed coffee, espresso, or capsule coffee. Furan is just one of the many substances in coffee that contains a thousand compounds. If you drink coffee, you drink not only one substance but all of them.

The World Health Organization classified coffee as a potential carcinogen in 1999 but removed it from the list in 2016. The decision came after study results increasingly showed that coffee had nothing to do with cancer.

Most of the latest research outcomes indicate that two or three cups of coffee a day are beneficial for health. Coffee drinkers have a lower risk of liver cancer, prostate cancer, type-2 diabetes, heart disease, and Parkinson's disease than non-drinkers.

A study, published on May 31 2022 analyzing data from 170,000 adults in the U.K., found that those who drank 1.5 to 3.5 cups of coffee a day had a 30 percent lower risk of death than those who did not. Even adding 1 teaspoon (5g) of sugar per cup of coffee reduced the risk of death. We cannot derive a causal relationship between coffee drinking and health from this study, but we can be sure that coffee drinkers do not have to worry about getting cancer.

We should stop worrying about the minutiae and look at the big picture. We don’t eat a single ingredient but whole food.

Jeong Jae-hoon is a food writer and pharmacist. He covers a variety of subjects, including trends in food, wellness and medications. This column was originally published in Korean in Joongang Ilbo on June 8. – Ed.