While a number of studies have suggested an inverse association between coffee consumption and risk of renal cell carcinoma (RCC), few have examined variations based on caffeinated versus decaffeinated coffee. Now, research carried out at the Mayo Clinic suggests the type of coffee consumed has a significant effect on the relationship.
Among a cohort of 669 incident RCC cases and 1,001 frequency-matched controls, those who drank caffeinated coffee had a reduced risk of developing RCC compared to those who did not drink any coffee. After adjusting for age, institutional site, sex, smoking, BMI, hypertension, and alcohol consumption, regular consumption of caffeinated coffee was associated with a 26 per cent reduced risk of RCC. There was a trend towards increased risk with consumption of decaffeinated coffee.
Decaffeinated coffee consumption was also associated with an increased risk of developing clear cell RCC subtype, particularly the aggressive form of ccRCC. In fact, the risk of developing aggressive ccRCC was almost doubled in those who drank decaffeinated coffee compared to non-coffee-drinkers.
The authors theorise that the effects could be related to the decaffeinating process which may reduce the levels of antioxidants in the coffee or involve exposure to toxic solvents.