Flavonoids intake and risk of lung cancer: a meta-analysis.

Objective: A number of studies have evaluated the association between flavonoids intake and lung cancer risk. However, results were inconsistent. To clarify the role of flavonoids in lung cancer, we conducted a meta-analysis on this topic.

Methods: Two authors independently searched PubMed and EMBASE for studies regarding the association of flavonoids intake with lung cancer risk. Summary relative risks (RRs) with their corresponding 95% confidence intervals (CIs) were calculated by using random-effects model.

Results: Eight prospective studies and four case-control studies involving 5073 lung cancer cases and 237 981 non-cases were included in this meta-analysis. The combined results indicated a statistically significant association between highest flavonoids intake and reduced risk of developing lung cancer (RR = 0.76, 95% CI = 0.63-0.92). Furthermore, an increase in flavonoids intake of 20 mg/day was associated with a 10% decreased risk of developing lung cancer (RR = 0.90, 95% CI = 0.83-0.97). In stratified analyses, the highest flavonoids intake was significantly associated with decreased lung cancer risk in prospective studies, studies conducted in Finnish population, studies without adjustment for fruits and vegetables or vitamins, males, smokers and studies using dietary history interview for flavonoids intake estimation. Most subclasses of flavonoids were inversely associated with lung cancer except for hesperetin.

Conclusions: Our data indicate that high or an increased intake of flavonoids is associated with reduced risk of lung cancer in some population but not in other population.