Abstract 2680: Intake of whole grain and dietary fiber and risk of hepatocellular carcinoma among U.S. adults
Authors: Yang Wanshui , Ma Yanan , Liu Yue , Stephanie Smith-Warner , Simon Tracey G. , Chong Dawn , Meyerhardt Jeffrey A. , Giovannucci Edward L. , Chan Andrew T. , Zhang Xuehong 
Published: August 2019

Abstract
Background Higher intake of whole grain and dietary fiber has been associated with lower risk of insulin resistance, hyperinsulinemia, and inflammation, which are known predisposing factors for hepatocellular carcinoma (HCC). To our knowledge, no epidemiological study has yet examined the association between whole grain intake and HCC risk. Therefore, we hypothesized that long-term intake of whole grain and dietary fiber may be associated with lower risk of developing HCC.
Methods We tested this hypothesis by utilizing data from two large U.S. prospective cohorts, the Nurses’ Health Study and Health Professionals Follow-up Study. Intake of whole grain and its subcomponents (bran and germ), and dietary fiber (cereal, fruit, and vegetable) were collected and updated almost every 4 years using validated food frequency questionnaires. Time-varying Cox proportional hazards regression model was utilized to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of of HCC by tertiles of energy-adjusted whole grain and fiber, after adjusting for sex, race, age, body mass index, alcohol drinking, smoking, physical activity, regular aspirin use, and type 2 diabetes.
Results During up to 32 years of follow-up, we identified a total of 141 incident HCC cases. Higher whole grain intake was significantly associated with lower risk of HCC (the highest versus lowest tertile intake, HR=0.63, 95% CI: 0.41-0.96, Ptrend=0.04). A suggestive inverse HCC association was found for total bran (HR=0.70, 95% CI: 0.46-1.07, Ptrend=0.11), but not for germ. After mutual adjustment for bran and germ, the inverse association between total bran and HCC persisted (HR=0.66, 95% CI: 0.41-1.07, Ptrend=0.13). Increasing intake of cereal fiber (HR=0.68, 95% CI: 0.45-1.03, Ptrend=0.07), but not fruit or vegetable fiber, was also suggestively associated with reduced risk of HCC. In sensitivity analyses, the results did not materially change after excluding HCC cases with hepatitis B or C virus infections. In addition, we observed similar inverse associations for whole grain, bran and germ, or dietary fiber with risk of HCC subtypes by history of cirrhosis (i.e., cirrhotic versus non-cirrhotic HCC).
Conclusions Intake of whole grains, cereal fiber, and bran could be associated with reduced risk of HCC among U.S. adults. Future studies that carefully consider hepatitis B and C virus infections are needed to replicate our findings, to examine these associations in other racial or high-risk populations, and to elucidate the underlying mechanisms.
Citation Format: Wanshui Yang, Yanan Ma, Yue Liu, Smith-Warner Stephanie, Tracey G. Simon, Dawn Chong, Jeffrey A. Meyerhardt, Edward L. Giovannucci, Andrew T. Chan, Xuehong Zhang. Intake of whole grain and dietary fiber and risk of hepatocellular carcinoma among U.S. adults [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2680.