Coffee consumption and cancers of the digestive tract
Coffee and cancer of the oesophagus
Coffee consumption and cancers of the digestive tract
Coffee and cancer of the oesophagus
Overall, there is little evidence for an association between oesophageal cancer risk and the amount of coffee consumed, and indeed coffee may be protective, although further research is required.
- A literature survey pooled the data of 22 studies (17 case-control studies, 2 pooled analyses and 3 cohort studies; 14 originating from the USA and Europe), published between 1974 and 2008, looking at the relationship between the consumption of coffee and the risk of oesophageal cancer. Most studies reported an unchanged, or reduced, risk of oesophageal cancer with the consumption of 3 or more cups of coffee per day. However, the majority of studies stated an increased risk with the increase in the temperature of hot drinks. There are however possible biases since the exact temperature of coffee, and the quantity and frequency of consumption, as well as the exact type of oesophageal cancer are unknown.
- A large meta-analysis published in 2011 found that coffee consumption was inversely associated with oesophageal cancer (relative risk 0.55).
- In 2011, a further large 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 oesophagus.
- 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 risk.
- The 2007 Second Expert Report by the World Cancer Research Fund (WRCF), a review of the worldwide evidence on food, nutrition, physical activity and 17 cancers, does not mention coffee in relation to oesophageal cancer.
Coffee and stomach cancer
A series of meta-analyses on associations between coffee consumption and risk of stomach cancer have shown variable results. Although the majority suggest that there is no association between coffee consumption and risk of stomach cancer, some have shown variable results and further research is required to draw firm conclusions.
- A systematic review and meta-analysis of 23 studies found no association between coffee consumption and the development of stomach cancer in either cohort (relative risk 1.02) or case-control studies (relative risk 0.97).
- A 2014 meta-analysis 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 investigation.
- Of five meta-analyses published in 2015, two concluded that coffee was not associated with the risk of gastric cancer and three suggested that coffee consumption was associated with the development of gastric cancer. 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 less, whilst others suggested that coffee consumption may be a risk factor for gastric cardia cancer (cancer occurring in the upper portion of the stomach); therefore further research is required to provide clarification.
- The WCRF 2007 Second Expert Report lists coffee under ‘Limited Evidence – No Conclusion’ in relation to stomach cancer.
Research suggests an inverse association between coffee consumption and risk of oral cavity/pharynx cancers.
- A systematic meta-analysis of observational studies, published between 1989 and 2009, reported a 36% reduced risk for cancers of the oral cavity/pharynx (relative risk 0.64) between highest (3-5 and more cups per day) versus lowest (up to 1 cup per day) coffee drinkers, based on a total of 2,633 cases from one cohort and 8 case-control studies. On the other hand, there was no relation between coffee consumption and laryngeal cancer. There was no significant heterogeneity across studies.
- Two meta-analyses found that coffee consumption was inversely associated with buccal and pharyngeal cancer (relative risk 0.49).
- Additionally, a large 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 association.
- 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 cancers, whilst the other suggests coffee consumption, but not tea consumption, is associated with an increased risk.
- The WCRF 2007 Second Expert Report lists coffee under ‘Limited Evidence – No Conclusion’ for mouth, pharyngeal and laryngeal cancer.
Coffee and liver cancer
Liver cancer is the fifth most prevalent type of cancer worldwide, and the fourteenth most prevalent in Europe. Studies looking at the relationship between coffee consumption and risk of liver cancer have found an inverse association, and coffee consumption appears to be linked to a slower progression of liver disease.
Four meta-analyses reported a significant reduction in the risk of developing liver cancer. One of these meta-analyses suggested a 40% reduction in risk of hepatocellular cancer for any coffee consumption compared to no coffee consumption. Results from a 2015 multicentre prospective European cohort study further strengthened the existing evidence regarding the inverse association between coffee/tea and a reduced risk of hepatocellular cancer.
In addition, a case-control study in Hong Kong among chronic hepatitis B virus carriers (a group at higher risk of developing liver cancer) found that moderate coffee drinkers, who drank coffee four times a week or more, had a 59% lower risk of developing liver cancer than non-coffee drinkers. There was also a significant dose-response effect. Further work has suggested that the risk of evolution of hepatitis C to cancer was found to be reduced by 22% for each cup of coffee consumed, and for at least 3 cups daily the risk of disease progression is reduced by 62%.
A study published in 2015 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 injury. In addition, the WCRF 2015 Liver Cancer Report lists coffee under a probable decrease in risk.
There are two proposed mechanisms for coffee’s association with a reduced risk of developing liver cancer and slower progression of liver disease.
- Cirrhosis is a major risk factor for the development of liver cancer and coffee has been shown to inhibit the elevation of hepatic transaminases, markers of hepatic disease.
- Coffee could reduce the circulating level of iron, and hence reduce the risk of hepatic carcinogenesis.
The role of antioxidants and other coffee components warrant further investigation.
Coffee and cancer of the pancreas
Scientific evidence does not support an association between coffee consumption and an increased risk of pancreatic cancer, and indeed some, but not all, studies suggest an inverse association.
- In 1990, the International Agency for Research on Cancer (IARC) considered that the evidence for a link between coffee and pancreatic cancer was inadequate. The positive results of the first studies, published in 1970 and 1981, were attributed to confounders. Moreover, the control subjects of these studies were patients who suffered gastro-intestinal problems likely to affect, i.e. reduce their coffee consumption.
- Since the IARC Monograph, a report from the World Cancer Research Fund (WCRF) included a meta-analysis of 37 case-control and 18 cohort studies, which found a relative risk of 1.04 and 1.00, respectively, in coffee drinkers versus non-coffee drinkers. In other words, there was no increase in risk of developing pancreatic cancer with coffee consumption.
- Since this meta-analysis, a large Japanese cohort study, involving 102,137 participants followed over 11 years, did not observe an increased risk with coffee consumption. The study even reported a reduced risk in men consuming 3 cups of coffee daily compared to non-coffee drinkers.
- A further meta-analysis, which included 14 cohort studies looking at coffee consumption and risk of pancreatic cancer, found a significant inverse relationship (relative risk 0.82).
- Another 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 drinking and risk of pancreatic cancer in men. Regular coffee drinkers had an 18% lower risk of cancer than non-drinkers; low to moderate coffee drinkers had a 14% lower risk; and high coffee drinkers had a 32% lower risk. Overall, an additional cup of coffee per day was associated with a 4% lower risk of pancreatic cancer.
- A further 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 intakes.
- In addition, two Italian case-control studies found no association between the quantity of coffee consumed, the duration of exposure, and pancreatic cancer risk, suggesting that there is no causal association between coffee and pancreatic cancer.
- The WCRF 2012 Pancreatic Cancer Report lists coffee under ‘Substantial Effect on Risk Unlikely’.
Coffee and colorectal cancer
There appears to be a modest, favourable effect of moderate coffee consumption on colorectal cancer risk, consistent across study designs (hospital vs. population-based), geographical areas, and various confounding factors. A series of meta-analyses have been undertaken on coffee consumption and colorectal cancer risk, the majority of which suggest an inverse association. However, one suggests that no protective effect is observed, but equally there is no adverse association with coffee consumption in relation to colorectal cancer:
- A 2004 meta-analysis on coffee and colorectal cancer included 3 cohort and 15 case-control studies from Japan, eight European countries, Argentina and the USA, and included 8,713 cases of cancer occurring in 147,227 subjects. The authors reported heterogeneity linked to the design of the studies. Cohort studies did not observe any association, while case-control studies did generally find a relative risk below 1.
- Another meta-analysis of 5 cohort and 12 case-control studies, including 6,192 cases of colorectal cancer, found a 24% lower risk (relative risk 0.76) in those with a high coffee consumption (at least 4 cups/day) compared to non-coffee drinkers. However a further meta-analysis concluded that whilst there was no observed protective effect on colorectal cancer of coffee consumption, there was no adverse effect either.
- A 2010 meta-analysis, including 24 case-control studies, reported a risk reduction of 17% in coffee drinkers compared to non-coffee drinkers, with risk falling by 6% for each cup of coffee consumed, and a 30% lower risk (relative risk 0.70) of colorectal cancer in the highest consumers.
- A further meta-analysis, including 15 cohort studies looking at coffee consumption and colorectal cancer, found an inverse association between coffee intake and the risk of colorectal cancer, a conclusion also found by a 2012 meta-analysis of observational studies including 15,522 cases, which suggested that coffee consumption can significantly decrease the risks of colorectal cancer and colon cancer, especially in Europeans and females.
- Two Japanese cohort studies, including 31,550 and 96,000 subjects respectively, reported a risk reduction of 56% with 3 or more cups per day, but only in women.
- A 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 cancer.
- The WCRF 2011 Colon and Rectum Report does not mention coffee as a risk factor.
Only one meta-analysis shows a dose-response relationship, which suggests either a threshold effect or a difference between coffee drinkers and non-coffee drinkers. It could indeed represent a confounding factor linked to the decrease in coffee consumption in patients after the onset of symptoms.
The inverse association between coffee consumption and colorectal cancer risk has been attributed to a number of factors, including:
- The anti-carcinogenic properties of coffee diterpenes and antioxidants.
- Coffee’s capacity to induce the excretion of biliary acids and neutral sterols in the colon.
- The stimulation of colon motility, reducing the length of time mutagens are in contact with the intestinal mucosa.
- Caffeine’s inhibition of colon cancer cell growth.