No preventive effect of dietary fiber against colon cancer in the Japanese population: a cross-sectional analysis

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

The role of dietary factors in the outcome of colorectal cancer (CRC) has been the subject of many studies, but results are inconclusive. Presented here are the results of a systematic review of studies published on dietary factors and CRC outcome in the English literature between March 2002 and March 2012. Studies were subdivided into survival studies in CRC patients and CRC mortality studies in the general population. Sixteen of the 636 studies identified--5 on survival and 11 on mortality--met the predefined inclusion criteria. No consistent association between individual dietary components and CRC outcome was detected in the survival studies. In the mortality studies, an association between meat intake and increased CRC mortality was found in two ecologic studies; however, two prospective cohort studies did not confirm this association. An inverse association between cereal intake and CRC mortality was found in two ecologic studies. In conclusion, published studies investigating dietary factors and outcome in CRC are heterogeneous in design and findings. No dietary component was conclusively and consistently associated with survival in CRC patients. The results of mortality studies seem to indicate that meat intake has an adverse effect on CRC mortality, while cereal intake may be protective.

Diet and vitamin or mineral supplementation and risk of colon cancer by subsite in Canada

The study assesses the association of diet and vitamin or mineral supplementation with risk of proximal or distal colon cancer. Mailed questionnaires were completed by 1723 newly diagnosed, histologically confirmed colon cancer cases and 3097 population controls between 1994 and 1997 in seven Canadian provinces. Measurement included information on socio-economic status, physical activity, smoking habits, alcohol use, diet and vitamin or mineral supplementation. Odds ratios and 95% confidence intervals were derived through unconditional logistic regression. Linear regression was used to examine that dietary factors affect body mass index. The strongest positive associations between colon cancer risk and increasing total fat intake were observed for proximal colon cancer in men and for distal colon cancer in both men and women. Increased consumption of vegetables, fruit and whole-grain products did not reduce the risk of colon cancer. A modest reduction in distal colon cancer risk was noted in women who consumed yellow-orange vegetables. Significant positive associations were observed between proximal colon cancer risk in men and consumption of red meat and dairy products, and between distal colon cancer risk in women and total intake of meat and processed meat. We also saw strong associations between bacon intake and both subsites of colon cancer in women. When men were compared with women directly by subsite however, the results did not show a corresponding association. A significantly reduced risk of distal colon cancer was noted in women only with increasing intake of dairy products and of milk. Among men and women taking vitamin and mineral supplements for more than 5 years, significant inverse associations with colon cancer were most pronounced among women with distal colon cancer. These findings suggest that dietary risk factors for proximal colon cancer may differ from those for distal colon cancer.

Ecological study of solar radiation and cancer mortality in Japan

Geographic observation of the increased mortality of some cancers at higher latitudes has led to a hypothesis that vitamin D produced after exposure to solar radiation has anti-carcinogenic effects. However, it is unclear whether such association would be observed in countries like Japan, where fish consumption, and therefore dietary vitamin D intake, is high. Pearson correlation coefficients were calculated between averaged annual solar radiation levels for the period from 1961 through 1990 and cancer mortality in the year 2000 in 47 prefectures in Japan, with adjustments for regional per capita income and dietary factors. A moderate, inverse correlation with solar radiation was observed for cancers of the esophagus, stomach, colon, rectum, pancreas, and gallbladder and bile ducts in both sexes (correlation coefficient, ranging from -0.6 to -0.3). The results of this study support the hypothesis that increased exposure to solar radiation reduces the risk of cancers of the digestive organs.