Abstract 5318: Intake of tea and tea flavonoids, coffee and caffeine in relation to risk of lung cancer - the Singapore Chinese Health Study
Authors: Seow Wei Jie , Jin Aizhen , Yuan Jian-Min , Koh Woon-Puay 
Published: July 2017

Abstract
Background: Coffee and tea are widely consumed beverages. Tea flavonoids have been shown to inhibit lung tumorigenesis in in-vitro and animal models. Conversely, coffee contains complex mixtures of biochemically active compounds that may have genotoxic and mutagenic properties. However, previous epidemiologic studies have shown inconsistent results on tea and coffee in relation to lung cancer risk.
Methods: The association between intake of tea and coffee, and their active compounds, and risk of lung cancer was investigated in the Singapore Chinese Health Study, a population-based prospective cohort of 63,257 Singaporean Chinese men and women aged 45-74 years at enrollment from 1993 through 1998. Information on demographic, lifestyle and habitual diet was collected through in-person interviews using a structured questionnaire which included a validated food-frequency questionnaire. The intake of caffeine and tea flavonoids was estimated for each participant based on the Singapore Food Composition Database, which was developed for this cohort and provided 96 nutritional and non-nutritional values per 100 grams of the edible portion for each of 165 surveyed foods and beverages specific for the study population. Flavonoids predominantly from black tea included theaflavin, thearubigin, theaflavin-3-3’-digallate, theaflavin-3’-gallate and theaflavin-3-gallate while those predominantly from green tea included catechin, epigallocatechin, epicatechin, epicatechin-3-gallate and epigallocatechin-3-gallate. Incident lung cancer cases were identified via record linkage with the nationwide cancer registry through 31 December 2013. Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations with adjustment for potential confounders.
Results: Compared to non-daily coffee drinkers, HR (95% CI) of lung cancer for those consuming 1 and 2 or more cups of coffee per day was 1.16 (1.00-1.34) and 1.29 (1.02-1.64), respectively (P for trend=0.029). Among ever smokers, black tea was inversely associated with risk of lung cancer (P for trend=0.037). HR (95% CI) was 0.83 (0.69-1.00) for the highest third of consumers (average 1.5 cups/day) compared to non-black tea drinkers. Consistently, flavonoids predominantly from black tea were also inversely associated with lung cancer risk (P for trend=0.045). This risk reduction with black tea and their major flavonoids was only observed in ever smokers and not in never smokers. There was no statistically significant association for lung cancer risk with total caffeine, green tea or flavonoids predominantly from green tea, regardless of smoking status.
Conclusions: Coffee may increase the risk of developing lung cancer, and this effect does not seem to be mediated by its caffeine content. Conversely, black tea and flavonoids found mainly in black tea may reduce the risk of lung cancer among ever smokers.
Citation Format: Wei Jie Seow, Aizhen Jin, Jian-Min Yuan, Woon-Puay Koh. Intake of tea and tea flavonoids, coffee and caffeine in relation to risk of lung cancer - the Singapore Chinese Health Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5318. doi:10.1158/1538-7445.AM2017-5318