Researchers have long tried to determine if a link exists between coffee consumption and cancer, but have had trouble separating results from people's other potentially cancer-causing habits, like smoking cigarettes.
A new study, presented on March 31 to the American Association for Cancer Research (AACR), looks at coffee and tea consumption in both smokers and non-smokers — and it has found that a link could exist between the beverages and lung cancer risk.
The study is still ongoing and the results aren't finalized yet, but based on preliminary findings, researchers believe there could be an increased risk of lung cancer in people who drink at least two cups of coffee or tea a day.
Read more: 4 drinks you consume every day that might raise your risk of cancer
Researchers performed a meta-analysis of over 1.2 million people, using data from previous studies on US and Asian populations. They evaluated participant information including coffee and tea intake, demographics, and lifestyle factors like smoking in each of the 17 studies. "These populations have different consumption patterns and genetic makeups. Such study would be more informative than a single population study," Dr. Xiao Ou Shu, lead author of the study, told INSIDER.
To better understand whether smoking affected results, the researchers looked at people who had never smoked, previously smoked, and currently smoke cigarettes. So far, researchers have found that people who reported drinking two or more cups or coffee or tea a day, whether caffeinated or decaffeinated, had an increased risk of lung cancer.
This was true for both smokers and non-smokers, suggesting the beverages could have been the cancer risk factor.
The study has some caveats. According to Dr. Shu, most of the data came from studies where smoking information was collected only once. If a person's smoking status changed during that study, it could have affected results. Secondhand smoke could have also played a role in increased cancer risk. "Only few studies [we used] have collected detailed information on passive smoking," Dr. Shu said.
Previous research has also suggested acrylamide, a chemical found in coffee due to the roasting process, could be cancer-causing if consumed in large amounts. But the amount of acrylamide in coffee is negligible, even for a person who sips on multiple cups per day.
The temperature of coffee has also been studied as a potential cancer risk factor. In two studies, researchers found that people who drank piping-hot beverages had slightly higher risks of developing esophageal or throat cancer.
Still, since existing research on coffee and cancer is largely inconclusive, skipping your morning cup of Joe isn't a surefire way to lower your cancer risk. So good news, coffee fiends: you don't have to part ways with your brew just yet.
