No Preventive Effect of Dietary Fiber Against Colon Cancer in the Japanese Population: A Cross-Sectional Analysis

Abstract

The report of Fuchs et al. in 1999 on the protective effects of dietary fiber (DF) against colon carcinogenesis has led many researchers to question the benefits of DF. We analyzed the relationship between dietary intake and mortality from colon cancer in Japan cross-sectionally. Dietary data were taken from the National Nutrition Survey. The standardized mortality ratio (SMR) was calculated using data from "Vital Statistics" and "the Population Census in Japan." Multiple regression analysis (stepwise variable selection method) was performed with the SMR of colon cancer as the objective variable and intake of DF, nutrients, and food groups in 1966 as the explanatory variables. The beta regression coefficient was significantly positive for intakes of fat, protein, and vitamin C and significantly negative for intakes of calcium and vitamin A to the SMR of colon cancer. However, no significant correlation was observed for DF or for any of the various food groups analyzed. In conclusion, our data do not demonstrate any protective effect of DF on colon cancer in subjects with a low fat intake (Japanese subjects), which supports Fuchs' findings in subjects with high fat intake (U.S. subjects).

Role of dietary factors in survival and mortality in colorectal cancer: a systematic review

“…This study was sponsored by the manufacturer of the fiber product (Madaus Laboratories, Cologne, Germany) . Another prospective follow‐up study from Japan found no association between fiber consumption and CRC mortality . This study had a longer follow‐up time than the 5‐year Spanish study …”

“…Five studies examined the influence of dietary factors on outcome in CRC patients, which are referred to as survival studies . The remaining 11 studies investigated the influence of dietary factors on CRC outcome in the general population, which were referred to as mortality studies …”

“…Two studies investigated the association between fiber consumption and CRC mortality in the general population (Table ) . A Spanish ecologic study reported that a higher fiber intake ( Plantago ovata ) was associated with decreased CRC mortality, which was statistically significant when comparing the top quintile of fiber consumption with the bottom quintile (RR = 0.75, 95%CI = 0.42–0.91).…”

“…This review included studies with different study populations, five of which investigated survival of patients who had already been diagnosed with CRC (survival studies) and 11 of which were mortality studies that examined CRC mortality in the general population. In these studies, CRC mortality depended on the risk of developing CRC, the risk of recurrent CRC, and CRC survival.…”

“…Besides differences in study populations, differences were found in the study designs, which varied between ecologic studies and prospective cohort studies 11,12,14‐16,19‐21,24–26. The type of study design is important for the reliability of the evidence obtained.…”