Given the popularity of coffee worldwide, it is unsurprising that it is a highly researched topic regarding health outcomes, including its relationship to cancer. In 2016, the International Agency for Research on Cancer (IARC) updated its 1991 statement that coffee is possibly carcinogenic to humans to “not classifiable as to its carcinogenicity to humans,” based on inadequate evidence of carcinogenicity, and the fact that most epidemiologic studies suggest a reduced risk for many cancers.1
Several meta-analyses of epidemiologic studies suggest that coffee consumption is associated with a decreased risk of all-cause mortality and is not associated with cancer-related mortality.2-5 Several meta-analyses also suggest that coffee consumption may decrease the risk of many types of cancers, but for some cancers, the data remain mixed or indicate an increased risk.
Digestive Tract Cancers
A meta-analysis that included over 3 million patients from 15 case-control and cohort studies found that high levels of coffee consumption significantly decreased the risk of oral cancer compared with low levels of use (odds ratio [OR], 0.63; 95% CI, 0.52-0.75), with the association remaining among both case-control and cohort studies.6 A meta-analysis of laryngeal cancer, however, suggested that coffee consumption significantly increased cancer risk compared with non-coffee drinkers (RR, 1.47; 95% CI, 1.03-2.11), though a subgroup analysis showed that this association was significant among Europeans (RR, 1.63; 95% CI, 1.01-2.61) but not for the Americas (RR, 1.18; 95% CI, 0.7-1.99).7 Another meta-analysis found no association between coffee consumption and esophageal cancer, though a subgroup analysis found a decreased risk among an East Asian cohort (OR, 0.64; 95% CI, 0.44-0.83).8
The association between coffee consumption and gastric cancer is less clear, with several meta-analyses suggesting an increased risk for some populations. Overall, the meta-analyses indicate no increased risk of gastric cancer with coffee consumption, even among groups who drank at least 3 cups per day.9-13
For the United States population, however, 2 meta-analyses suggested an increased risk for gastric cancer.11,12 One analysis included 13 prospective cohort studies and 20 independent reports that encompassed 3368 cases of gastric cancer with a follow-up period ranging from 4.3 to 8.0 years. For the United States cohort, high levels of coffee consumption were significantly associated with an increased risk of gastric cancer (RR, 1.36; 95% CI, 1.06-1.75).11 The second analysis included 15 prospective cohort studies with 2019 cases of gastric cancer with a follow-up period ranging from 8 to 18 years.12 In the United States cohort, the risk of gastric cancer was significantly higher with 6.5 cups per day or more (RR, 1.36; 95% CI, 1.05-1.75).
Several studies indicate that coffee consumption is not associated with the risk of colorectal cancer,14-17 and may decrease risk with 4 or 5 cups per day.15,17 A meta-analysis of 19 prospective cohort studies that included over 2 million patients demonstrated that for every 4 cups of coffee per day, colon cancer risk was reduced by 7% (RR, 0.93; 95% CI, 0.88-0.99).15 An analysis of the
CALGB 89803 (ClinicalTrials.gov Identifier: NCT00003835) study of 953 patients with stage III colon cancer undergoing adjuvant chemotherapy found that consuming at least 4 cups of coffee per day reduced the risk of colon cancer recurrence or mortality (hazard ratio [HR], 0.58; 95% CI, 0.34-0.99) compared with never drinkers.17 There was no association between nonherbal teas or decaffeinated coffee.