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Green tea consumption reduced lung cancer risk
Lin IH. PLoS One. 2012;doi:10.1371/journal.pone.0030951.
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Drinking at least one cup of green tea a day may significantly decrease a person’s risk for lung cancer, according to study results.
Based on prior laboratory studies indicating that the polyphenols in green tea could halt the growth of cancer cells, researchers analyzed the correlation between green tea consumption, smoking, genetic factors, including insulin-like growth factors (IGFs), and lung cancer risk. In particular, researchers examined IGF-I and IGF-II, peptide hormones with strong mitogenic effect on normal and cancerous cells, as well as their major binding protein, IGF-binding protein-3.
From 2004 to 2008, 170 patients with lung cancer were enrolled from Changhwa Christian Hospital in Taiwan. All patients received a series of examinations of pathologic stages by board-certified pathologists, and tumor types and stages were determined according to WHO classification. Questionnaires were administered to the patients with lung cancer, as well as 340 healthy controls, to ascertain characteristics such as smoking habits and green tea consumption.
Among the patients with lung cancer, cell types included 93 adenocarcinoma (54.7%), 46 squamous cell carcinoma (27.1%) and 31 others, including small cell carcinoma, neuroendocrine carcinoma, mixed cell carcinoma and unspecific malignant cell.
Customarily, tea is most commonly made in a small earthenware teapot and served in small cups (30-50 mL). For the study, researchers defined a standardized cup of tea as 100 mL to 120 mL. For lung cancer patients, the period of exposure was assessed from birth to the day when lung cancer was first diagnosed. For the control group, the period of exposure was assessed from birth to when the interview was performed.
Patients with lung cancer exhibited a higher proportion of smoking, green tea consumption of less than one cup per day, exposure to cooking fumes and family history of lung cancer than controls, according to the study results. An elevated risk was observed in smokers who never drank green tea, as compared with smokers who drank more than one cup of green tea per day (OR= 13.16; 95% CI, 2.96-58.51).
The relationship between smoking and green tea consumption regarding lung cancer risk was also observed. Those with IGF-I genotypes who drank green tea for at least 10 years exhibited a significantly reduced lung cancer risk (OR=0.34; 95% CI, 0.12-0.95). However, no significant decrease in risk for lung cancer was found for green tea drinkers with IGF-II and IGF-binding protein-3 genotypes.
“Our study suggests a protective effect of green tea on lung cancer elicited by cigarette smoking,” the researchers said. “Green tea drinkers with susceptible IGF-I genotypes have a reduced risk of lung cancer. Heavy smokers carrying susceptible IGF-I, IGF-II and [IGF-binding protein-3] have a higher risk of lung cancer. This result may indicate that smoking-induced pulmonary carcinogenesis may be modulated by green tea consumption and the growth factor environment.”
Disclosure: The researchers report no relevant financial disclosures.