Higher dietary fiber intake associated with better survival in male but not female cancer patients: Evidence from National Health and Nutrition Examination Survey 1999–2014

Recent studies have found that dietary fiber improves prognosis in cancer patients. However, few subgroup analyses exist. Subgroups can differ greatly in terms of different factors such as dietary intake, lifestyle, and sex. It is unclear whether fiber benefits all of the subgroups equally. In this study, we examined differences in dietary fiber consumption and cancer mortality between subgroups, including sex. This trial was conducted using eight consecutive National Health and Nutrition Examination Surveys (NHANESs) cycles data between 1999 and 2014. Subgroup analyses were used to investigate the results and heterogeneity within subgroups. Survival analysis was performed using the Cox proportional hazard model and Kaplan-Meier curves. Multivariable Cox regression models and restricted cubic spline analysis were applied to examine the association between dietary fiber intake and mortality. In total, 3504 cases were included in this study. Among the participants, the mean age (SD) was 65.5 (15.7) y and 1657 (47.3%) of the participants were men. Subgroup analysis found that men differed significantly from women (P for interaction < 0.001). We found no significant differences in the other subgroups (all P for interaction > 0.05). During an average follow-up of 6.8 y, 342 cancer deaths were recorded. The Cox regression models found that fiber consumption was associated with a lower cancer mortality rate in men (model I: hazard ratio [HR] = 0.60; 95% CI, 0.50–0.72; model II: HR = 0.60; 95% CI, 0.47–0.75; and model III: HR = 0.61; 95% CI, 0.48–0.77). However, there was no relationship between fiber consumption and cancer mortality in women (model I: HR = 1.06; 95% CI, 0.88–1.28; model II: HR = 1.03; 95% CI, 0.84–1.26; and model III: HR = 1.04; 95% CI, 0.87–1.50). The Kaplan-Meier curve illustrates that male patients who consumed higher levels of dietary fiber survived significantly longer than those who consumed lower levels of fiber (P < 0.001). However, there were no significant differences between the two groups in terms of female patients (P = 0.84). A dose-response analysis found an L-shaped relationship between fiber intake and mortality among men. This study found that higher dietary fiber intake was only associated with better survival in male cancer patients, not in female cancer patients. Sex differences between dietary fiber intake and cancer mortality were observed.