Fiber and whole grain intakes in relation to liver cancer risk: An analysis in two prospective cohorts and systematic review and meta-analysis of prospective studies

Background and aims The association between fiber or whole grain intakes and risk of liver cancer remains unclear. We assessed the associations between fiber or whole grain intakes and liver cancer risk among two prospective studies, and systematically reviewed and meta-analyzed these results with published prospective studies. Approach and results A total of 111,396 participants from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) and 26,085 men from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC) were included. Intakes of total fiber and whole grains were estimated from validated food frequency questionnaires. Study-specific hazard ratios (HRs) and 95% confidence intervals (CI) with liver cancer risk were estimated using multivariable-adjusted Cox regression. We systematically reviewed existing literature and studies were combined in a dose-response meta-analysis. A total of 277 (median follow-up=15.6 y) and 165 (median follow-up=16.0 y) cases of liver cancer were observed in PLCO and ATBC, respectively. Dietary fiber was inversely associated with liver cancer risk in PLCO (HR10g/day:0.69; 95%CI:0.55-0.86). No significant associations were observed between whole grain intakes and liver cancer risk in either study. Our meta-analysis included 2,383 incident liver cancer cases (seven prospective cohorts) for fiber intake and 1,523 cases (five prospective cohorts) for whole grain intake; combined HRs for liver cancer risk were 0.83 (0.76-0.91) per 10 g/day of fiber and 0.92 (0.85-0.99) per 16 g/day (1 serving) of whole grains. Conclusions Dietary fiber and whole grains were inversely associated with liver cancer risk. Further research exploring potential mechanisms and different fiber types is needed.