Cancer

Coffee and skin cancer

There is no evidence that coffee consumption is linked to skin cancer. Caffeine, however, may protect skin cells against the harmful effects of UVB radiation.

• In 2008, a study in mice reported that caffeine added to drinking water, or placed directly onto the skin, induced the death of cells damaged by UVB irradiation. In 2009, the same work performed on human skin cell cultures showed that caffeine doubled the mortality of the cells damaged by UVBs, hence decreasing the risk of cancer⁴².
• The underlying molecular mechanism is similar in both species, which led the authors to hypothesize that caffeine, or a substance with a similar mode of action, could protect human skin from the deleterious action of UVBs when applied topically⁴³.

Coffee and lung cancer

High consumption of coffee (more than 5 cups a day) may increase the risk of lung cancer. However, the residual confounding effects of smoking, or other factors, may still exist. Hence these results should be interpreted with caution.

• A recent meta-analysis⁴⁴, including 5 prospective and 8 case-control studies involving 5,347 lung cancer cases and 104,911 non-cases, reported a positive association between the highest coffee intake (at least 5-7 cups a day) and lung cancer i.e. those who consumed the most coffee had a 27% higher risk of developing lung cancer (relative risk 1.27). The increase in coffee consumption of 2 cups per day led to a 14% increased risk for lung cancer (relative risk 1.14).
• This coffee-related increased risk was significantly associated with high coffee intake (over 5-7 cups a day) in prospective studies, American and Japanese studies, but borderline significantly associated with decreased risk of lung cancer in non smokers. Decaffeinated coffee drinking was associated with decreased lung cancer risk⁴⁴.

Coffee and brain tumours

Coffee consumption may be linked to a reduced risk of brain tumours, in men in particular.

• The data from a synthesis of 3 cohort studies conducted in the USA, including 335 cases, showed that the consumption of at least 5 cups of coffee and tea daily, compared with no tea or coffee, was associated with a 40% lower risk of glioma (relative risk 0.60)⁴⁵. No association was observed between decaffeinated coffee and glioma risk. Among women, the significant inverse association observed was weaker than among men.
• A recent European study⁴⁶ of 343 cases of glioma newly diagnosed in 9 countries, showed the same results, i.e. a significant 34% lower risk of glioma among subjects consuming over 100 mL (one cup) coffee and tea per day compared with those consuming less than 100 mL/day (relative risk 0.66). In this study, the association was also slightly stronger in men than in women⁴⁶.

More studies are needed to confirm this inverse association.