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^1,16, with a number of analyses suggesting that there may be an inverse association, i.e. a reduced risk of oesophageal cancer¹⁶.

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 Europeans and Americans¹⁶.

The 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 as discussed in the previous section.

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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^17-19. 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^17-19.

• 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)¹⁷

• Two 2022 systematic reviews assessed coffee consumption and gastric cancer risk^18,19. Both showed no association at moderate intakes with one study suggesting that moderate coffee consumption was associated a reduced risk of gastric cancer. However, in one study heavy coffee consumption (7 or more cups per day) showed differing results¹⁸

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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 buccalcavity, pharynx and larynx, have shown variable results^20-22. 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.

• A 2015 meta-analysis found that coffee consumption was inversely associated with buccal and pharyngeal cancer (relative risk 0.49)²⁰

• 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 cancer²¹, whilst the other suggests coffee consumption, but not tea consumption, is associated with an increased risk²²

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Coffee and liver cancer

Studies looking at the relationship between coffee consumption and risk of liver cancer have consistently found an inverse association^23-26. In its 2016 review, IARC concluded that the evidence shows a consistent and statistically significant inverse association between coffee consumption and liver cancer¹. In addition, the WCRF 2015 Liver Cancer Report lists coffee under a probable decrease in risk²⁷. 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 day²⁵.

• A 2019 meta-analysis of six cohort studies from Japan concluded that coffee consumption among Japanese people has a significant role in preventing liver cancer²⁴

• A 2020 systematic review 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 day²⁵, with similar results presented in a 2023 meta-analysis²⁶

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 important²³. Coffee also contains many different compounds such as caffeine, diterpenes, chlorogenic acids and flavonoids, which may also be involved²³.

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Coffee and cancer of the pancreas

The majority of research do not support an association between coffee consumption and an increased risk of pancreatic cancer^28,29. Whilst some studies suggest an inverse association, one of the reviews did suggest an increased risk with increasing coffee consumption²⁸. The World Cancer Research Fund (WCRF) 2018 Revised Pancreatic Cancer Report lists coffee under ‘Substantial Effect on Risk Unlikely’³⁰. IARC’s 2016 review stated that cohort and population-based case-control studies together showed no association between coffee consumption and pancreatic cancer¹.

• 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 manner²⁸

• 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 relationship²⁹

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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^31-37. The WCRF 2018 Colon and Rectum Report does notmention coffee as a risk factor³⁸.

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 isrequired to clarify the associations.

• 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 population³¹

• 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 men³²

• 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 cancer³³

• 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 countries³⁴

• A 2020 meta-analysis suggested that increasing coffee consumption by 150ml per day (about one cup) may be related to a reduced risk of colon adenoma³⁵

• A further 2020 meta-analysis suggested that coffee consumption is not associated with the risk of colon cancer in Asian men and women³⁶

• A 2023 umbrella review concluded that, whilst coffee consumption is associated with a reduced risk of colorectal cancer, the data is variable. However the authors suggested that the protective effect of coffee drinking seems evident at higher levels of coffee intake (5 or more cups per day)³⁷. Moderate coffee consumption is typically defined as 3-5 cups per day, based on the European Food Safety Authority’s (EFSA) review of caffeine safety¹⁰.

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The inverse association between coffee consumption andcolorectal cancer risk has been attributed to a number of factors including:

• The potential anti-carcinogenic properties of coffee diterpenes, phenolic phytochemicals and chlorogenic acid^33,39,40

• Coffee’s capacity to induce the excretion of biliary acids and neutral sterols in the colon⁴⁰

• The stimulation of colon motility, reducing the length of time mutagens are in contact with the intestinal mucosa⁴⁰

• Caffeine’s inhibition of colon cancer cell growth⁴¹