1346 
Oesophageal cancer risk is causally associated with genetically-predicted coffee consumption and this effect might be temperature-related
Oesophageal cancer risk is associated with genetically predicted coffee consumption even after adjustment for factors such as body mass index (BMI), smoking initiation and alcohol intake according to the findings of a Mendelian randomisation study by UK and Swedish researchers.
Coffee contains a wide range of compounds, some of which including kahweol that has been reported to exert anti-cancer properties. Moreover, coffee has been associated with a significant decrease in the risk of colorectal cancer and colon cancer with a higher intake of the beverage also linked to a lower risk of prostate cancer.
Nevertheless, much of the data has been derived from epidemiological studies which can be subject to confounding and reverse causality, i.e., where the direction of causality between to factors is the opposite of what might be expected.
A Mendelian randomisation (MR) study is designed to avoid the problems due to confounding and reverse causality and assesses whether the genetically-predicted levels of a risk factor, for instance, coffee consumption, and a disease outcome, such as oesophageal cancer are associated.
Since genetic variants are present at birth, MR studies reduce the potential for reverse causality and confounding and are therefore more likely to generate a causal interpretation.
In the present study, researchers investigated the association of genetically-predicted coffee consumption and the risk of 22 different cancers which, for example, included those affecting the ovary, thyroid and bladder.
There were a total of 15 single nucleotide polymorphisms (SNPs) identified to be associated with coffee consumption although only 12 of these were used in the analysis. Most of the SNPs were in gene regions (one for example was near a locus linked to the smell/test perception of coffee) that were likely to affect coffee drinking behaviour or behaviour indirectly by altering the metabolism of caffeine.
The researchers tested the association using data from the UK Biobank and also tested these for replication in the FinnGen consortium. The results were then adjusted for differences in genetically-predicted body mass index, smoking and alcohol consumption.
The effect sizes of the associations between genetically-predicted coffee consumption and cancer risk were scaled to a 50% increase in coffee consumption.
Oesophageal cancer risk and coffee consumption
Using a sample of 367,561 European participants, 59,647 had one of the 22 site-specific cancers. However, genetically-predicted coffee consumption was not associated with the risk of any cancer in the main analysis (odds ratio, OR = 1.05, 95% CI 0.98 – 1.14, p = 0.183) even after adjustment for BMI, smoking and alcohol intake.
But when the team looked at digestive system cancers overall, there was an increased risk (OR = 1.28, 95% CI 1.09 – 1.51, P = 0.003) and which remained significant after adjustment for BMI, smoking initiation and alcohol consumption.
This higher risk was largely driven by oesophageal cancer (OR = 2.79, 95% CI 1.73 – 4.50) in the Biobank and remained after adjustment for the effect of BMI, smoking and alcohol intake. In the FinnGen consortium, genetically predicted coffee consumption was associated with a non-significant increase in oesophageal cancer (OR = 2.01, 95% CI 0.57 – 7.05, p = 0.27) and which was attenuated after adjustment for BMI.
Coffee consumption was also associated with an increased risk of multiple myeloma in the Biobank data (OR = 2.25) even after adjustment and a reduced risk of ovarian cancer.
Interestingly, when the researchers looked at coffee consumption and individual’s preferences for drinking, they found that a preference for drinking warm (OR = 2.74) and hot (OR = 5.45) coffee was also significantly associated with a higher risk of oesophageal cancer but, surprisingly, not for very hot.
In a further subgroup analysis based on self-reported coffee intake, the risk of oesophageal cancer was similar among those drinking 1 – 3 cups/day compared with those who did not drink coffee and which the authors suggested might be due to consumption of tea.
The authors concluded that their study found evidence that coffee consumption was causally associated with a risk of oesophageal cancer and that there was some evidence that this was related to a temperature effect.
Citation
Carter P et al. Coffee consumption and cancer risk: a Mendelian randomisation study Clin. Nutr 2022
