The article “Dietary fiber intake is inversely associated with risk of pancreatic cancer: a meta-analysis” was published in the January 2017 issue of the Asia Pacific Journal of Clinical Nutrition. Mao, et al., conducted a meta-analysis of epidemiological studies to review evidence of the association between dietary fiber intake and the risk of pancreatic cancer and to quantify the potential dose-response relationship. Data from 3,287 cases of pancreatic cancer published in thirteen case-control studies and one cohort study were included in the analysis of dietary fiber intake. The studies included populations from North America (n=6), Europe (n=5), Asia (n=2) and Australia (n=1). Information regarding the participants’ fiber intake was obtained by interview or self-administered questionnaire. In this analysis, high fiber intake was inversely associated with pancreatic cancer with an odds ratio of 0.52 (95% CI 0.44-0.61) for the highest versus lowest categories of fiber intake. Following data analysis by subgroups to evaluate the role of study design, sex, geographical region, study quality, and exposure assessment, the researchers report that fiber intake was consistently associated with reduced risk of pancreatic cancer. Furthermore, Hao, et al., report no evidence of heterogeneity or publication bias was identified. In evaluating a possible dose-response relationship between dietary fiber and the risk for pancreatic cancer, the pooled odds ratio of pancreatic cancer risk per 10 g/day increment in total dietary fiber was 0.88 (95% CI 0.84-0.92). The researchers suggest that the findings that the risk of pancreatic cancer was reduced by 48% in a comparison of the highest with the lowest category of dietary fiber intake and the by 12% for every 10 g/d increment of dietary fiber intake support the hypothesis that dietary fiber intake is inversely associated with the risk of pancreatic cancer.
The authors present several limitations of their study including:
- Residual confounders in meta-analysis of observational studies could distort the analysis and results regarding the association between dietary fiber intake and risk of pancreatic cancer
- Data from case control studies may have greater selection and recall bias while data from the single cohort study was conducted in a population with high risk for pancreatic cancer.
- Dietary fibers differ greatly and may have different roles in modifying cancer risk. Two possible mechanisms including modulation of insulin resistance pathways and inflammation are discussed as areas of continued research interest.
- Generalizability may be limited as most studies were conducted in Western populations.
- Relative fiber intake was evaluated rather than absolute intake which may have influenced the study findings.
- Bias and inaccurate data may have been introduced by including intake provided by surrogates of participants that were included to do poor survival of participants with pancreatic cancer.
The authors state “In conclusion, in the present meta-analysis, we demonstrated that an increased fiber intake is associated with a reduced risk of pancreatic cancer. Considering the limitation of included studies, further well-designed prospective studies are needed to confirm the inverse association and to identify the dietary fiber types involved.”