Cancers of the digestive tract

Coffee and cancer of the oesophagus

The research to date has not found an association between oesophageal cancer risk and the amount of coffee consumed^5,15-17, with a number of analyses suggesting that there may be an inverse association, i.e. a reduced risk of oesophageal cancer^5,16,17. In fact, a 2016 review from the International Agency for Cancer Research (IARC) concluded that the majority of the evidence shows no association between coffee consumption and oesophageal cancer¹.

However, the temperature of coffee beverages seems to be important – the IARC review classified beverages consumed at very high temperatures (defined as over 65°C) in Group 2A: “probably carcinogenic to the human oesophagus”¹. The temperature of 65°C is significantly hotter than the temperature at which most people can comfortably drink coffee without scalding their mouth and tongue^18,19; coffee is typically drunk at temperatures below 60°C.

• A 2011 large meta-analysis of 59 studies found that coffee consumption was inversely associated with oesophageal cancer (relative risk 0.55)⁵

• A 2011 Norwegian prospective study, of 389,624 middle-aged men and women followed up for over 14 years, found no relationship between coffee intake and cancer of the oesophagus¹⁵

• A 2013 meta-analysis of 7,376 oesophageal cancer cases concluded that both coffee and green tea, but not black tea, have protective effects on oesophageal cancer risk¹⁶.
• A 2018 meta-analysis of 457,010 participants and 2,628 incident cases suggested that there was an inverse association between coffee consumption and incidence of oesophageal cancer in East Asians, but not in Euro-Americans¹⁷.

Coffee and stomach cancer

A series of meta-analyses on associations between coffee consumption and risk of stomach cancer have shown variable results, with the majority suggesting that there is no association between coffee consumption and risk of stomach cancer^20-26. In 2016, IARC concluded that there was inadequate evidence to suggest any association between coffee consumption and stomach cancer¹. As with many cancers, smoking may be a confounding factor, and additionally ethnicity may affect the outcome^20,21.

• A 2014 meta-analysis of 12 studies with 840,651 subjects and 2,688 gastric cancer cases concluded that coffee consumption is not associated with risk of gastric cancer, although the authors suggested that smoking may confound some positive results and needs further investigation²⁰

• Five, 2015 meta-analyses were published^21-25. Of these, two concluded that coffee was not associated with the risk of gastric cancer^21,22 and three suggested that coffee consumption was associated with the development of gastric cancer^23-25‍

• Some studies reported varying results in participants from the United States compared to Europeans and Asians as well as those followed up for 10 years or less²¹, whilst others suggested that coffee consumption may be a risk factor for gastric cardia cancer^22,24 (cancer occurring in the upper portion of the stomach); therefore further research is required to provide clarification

• A 2016 meta-analysis of 22 studies with 1,019,693 subjects and 7,631 cases of gastric cancer concluded that coffee consumption was associated with a decreased risk of gastric cancer, showing a greater effect at higher coffee intakes (up to 3 – 4 cups per day)²⁶.

Coffee and cancer of the upper aero-digestive tract

Research reviewing associations between coffee consumption and cancers of the upper digestive tract, such as the buccal cavity, pharynx and larynx, have shown variable results^5,27-29. Although some research has suggested an inverse association between coffee consumption and risk of oral cavity/pharynx cancers, the 2016 IARC review concluded that the current evidence is inadequate to suggest such an association¹.

• Two meta-analyses in 2011 and 2015 respectively found that coffee consumption was inversely associated with buccal and pharyngeal cancer (relative risk 0.49)^5,27

• A 2011 Norwegian prospective study, of 389,624 middle-aged men and women followed up for over 14 years, also found no relationship between the amount of coffee consumed and the risk of cancer of the buccal cavity and pharynx; however, the authors could not exclude a weak inverse association¹⁵

• Two, 2014 meta-analyses reviewing associations between coffee consumption and laryngeal cancers give conflicting results, one suggesting that tea and coffee consumption was not associated with laryngeal cancer²⁸, whilst the other suggests coffee consumption, but not tea consumption, is associated with an increased risk²⁹

Coffee and liver cancer

Studies looking at the relationship between coffee consumption and risk of liver cancer have consistently found an inverse association^30-37. In its 2016 review, IARC concluded that the evidence shows a consistent and statistically significant inverse association between coffee consumption and liver cancer. In addition, the WCRF 2015 Liver Cancer Report lists coffee under a probable decrease in risk³⁸. A dose response association has been noted in some reviews, with the effect being notable in those who drank more than 3 cups of coffee a day³⁷.

• Two 2013 and two 2017 meta-analyses reported a significant reduction in the risk of developing liver cancer^30-33. One of these meta-analyses suggested a 40% reduction in risk of hepatocellular cancer for any coffee consumption compared to no coffee consumption³¹

• A 2016 dose response meta-analysis of prospective cohort studies suggested a linear association between coffee consumption and a reduced risk of liver cancer, also concluding that coffee drinking is inversely associated with liver cancer risk³³

• Results from a 2015 multicentre prospective European cohort study further strengthened the existing research regarding the association between coffee/tea and a reduced risk of hepatocellular cancer³⁴

• A 2015 study investigated the association between liver cancer and biological markers, concluding that the inverse association of coffee intake with hepatocellular cancer risk was partly accounted for by biomarkers of inflammation and hepatocellular injury³⁵

• A 2019 meta-analysis of six cohort studies from Japan concluded that coffee consumption among Japanese people has a significant role in preventing liver cancer³⁶

• A 2020 systematic review of 20 studies published between 1996 and 2019 concluded that the risk of developing liver cancer was reduced by 31% in coffee drinkers, with the effect being notable in those who drank at least 3 cups of coffee a day³⁷

The potential mechanisms involved in the association between coffee intake and  a reduced risk of developing liver cancer and slower progression of liver disease are still being investigated. It has been suggested that an effect on inflammation, innate immunity and hepatocellular injury may be important³⁵. Coffee also contains many different compounds such as caffeine, diterpenes, chlorogenic acids and flavonoids, which may also be involved³⁴.

Coffee and cancer of the pancreas

The majority of reviews do not support an association between coffee consumption and an increased risk of pancreatic cancer^5,39-43. Whilst some studies suggest an inverse association^5,39-42, one of the reviews did suggest an increased risk with increasing coffee consumption⁴³. The World Cancer Research Fund (WCRF) 2012 Pancreatic Cancer Report lists coffee under ‘Substantial Effect on Risk Unlikely’⁴⁴. IARC’s 2016 review stated that cohort and population-based case-control studies together showed no association between coffee consumption and pancreatic cancer¹.

• A 2011 meta-analysis of 14 cohort studies looking at coffee consumption and risk of pancreatic cancer, found a significant inverse relationship (relative risk 0.82)⁵

• A further 2011 meta-analysis of 14 cohort studies, covering Europe, the United States and Japan and including 671,080 individuals (1,496 cancer events) followed up for over 14 years, also identified an inverse association between coffee consumption and risk of pancreatic cancer in men³⁹. 18% lower risk in regular coffee consumption; 14% lower risk in low to moderate consumption; and 32% lower risk in high coffee consumption vs. abstention. Overall, an additional cup of coffee per day was associated with a 4% lower risk of pancreatic cancer

• A 2011 pooled-analysis of two Italian case-control studies (688 pancreatic cancer cases and 2,204 controls) found no association between the quantity of coffee consumed, the duration of exposure, and pancreatic cancer risk. These studies suggested that there was no causal association between coffee and pancreatic cancer⁴⁰

• A 2012 meta-analysis of 37 case-control and 17 cohort studies with 10,594 cases of pancreatic cancer showed that, overall, coffee consumption was not convincingly related to pancreatic cancer risk once smoking was taken into account, even at high intakes⁴¹

• A 2020 meta-analysis study of 12 cohort studies (3,230,053 participants) concluded that there was no association between coffee consumption and pancreatic cancer risk, and no significance in the dose response relationship⁴²

• A 2019 systematic review and dose response analysis with 959,992 participants concluded that coffee consumption was related to an increasing risk of pancreatic cancer in a dose-response manner⁴³

Coffee and colorectal cancer

A series of meta-analyses have been undertaken on coffee consumption and colorectal cancer risk, some of which suggest an inverse association^45-52. The WCRF 2018 Colon and Rectum Report does not mention coffee as a risk factor⁵³.

In addition, IARC’s 2016 review concluded that most informative cohort studies show no association between coffee consumption and increased risk of colorectal cancer¹. Variable results between different ethnic groups, and between sexes suggest that further work is required to clarify the associations.

• Two meta-analyses in 2011 and 2012 respectively, were published. One, of 15 cohort studies looking at coffee consumption and colorectal cancer, found an inverse association between coffee intake and the risk of colorectal cancer⁵. The second, including 15,522 cases, also suggested that coffee consumption could significantly decrease the risks of colorectal cancer and colon cancer, especially in Europeans and females⁴⁵

• A 2016 population-based study in northern Israel of 5,145 cases and 4,097 controls from the Molecular Epidemiology of Colorectal Cancer (MECC) study concluded that coffee consumption was associated with a 26% lower risk of developing colorectal cancer⁴⁶

• A 2018 meta-analysis of 26 studies suggested that moderate coffee consumption may not be associated with colorectal cancer, but may be weakly inversely associated in the Japanese population⁴⁷

• A 2018 pooled analysis of 320,322 participants in a Japanese population suggested that coffee drinking was not materially associated with colorectal cancer risk in men or women. Analysis by subsite showed a lower risk of colon cancer among female drinkers of ≥3 cups coffee/day but this was not seen in men⁴⁸

• A 2019 systematic review and meta-analysis of 26 prospective studies concluded that overall there was no significant relationship between coffee intake and colorectal cancer. Ethnicity seems to be an important variable in the relationship between coffee consumption and the risk of developing colorectal cancer⁴⁹

• A 2019 meta-analysis did not find evidence for the association between coffee consumption and colorectal cancer risk. However further evaluations suggested that coffee consumption was related to a decreased risk of colon cancer in those who have never smoked and in Asian countries, and with an increased risk of rectal cancer in an analysis of the general population and after restriction to women, never-smokers, and European countries⁵⁰

• A 2020 further meta-analysis suggested that increasing coffee consumption by 150ml per day (about one cup) may be related to a reduced risk of colon adenoma⁵¹.
• A 2020 meta-analysis suggested that coffee consumption is not associated with the risk of colon cancer in Asian men and women⁵².

The inverse association between coffee consumption and colorectal cancer risk has been attributed to a number of factors^49,54-56 including:

• The potential anti-carcinogenic properties of coffee diterpenes, phenolic phytochemicals and chlorogenic acid^49,54,55

• Coffee’s capacity to induce the excretion of biliary acids and neutral sterols in the colon⁵⁵.
• The stimulation of colon motility, reducing the length of time mutagens are in contact with the intestinal mucosa⁵⁵

• Caffeine’s inhibition of colon cancer cell growth⁵⁶