• Division of Public Health, Department of Family and Preventive Medicine, and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT.
• Department of Internal Medicine, and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT.
• Branch of Medical Statistics, Biometry and Epidemiology "G. A. Maccacaro", Department of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy.

Although the protective role of dietary fiber on cancer risk has been reported in several epidemiological studies, the association of fiber intake on head and neck cancer (HNC) risk is still unclear. We investigated the association between fiber intake and the risk of HNC using data from the Prostate, Lung, Colorectal and Ovarian (PLCO) cancer screening trial. Among 101,700 participants with complete dietary information, 186 participants developed HNC during follow-up (January 1998 to May 2011). Dietary data were collected using a self-administered food-frequency questionnaire (1998-2005). We estimated hazard ratios (HRs) and the corresponding 95% confidence intervals (CI), using the Cox proportional hazards model. Higher intake of total fiber, insoluble fiber and soluble fiber was associated with decreased HNC risks, with a significant trend. The HRs of highest vs. the lowest tertile of intake were 0.43 (95%CI: 0.25-0.76) for total fiber, 0.38 (95%CI: 0.22-0.65) for insoluble fiber, and 0.44 (95%CI: 0.25-0.79) for soluble fiber. These inverse association were consistent in oral cavity and pharyngeal cases, but the impact of fiber intake was weaker in laryngeal cases. We did not observe any significant interaction of potential confounders, including smoking and drinking, with total fiber intake on HNC risk. These findings support evidence of a protective role of dietary fiber on HNC risk.