Objectives: Incidence rates for colorectal cancer are universally high in western countries while values in theorient are very variable. Japan is one of the oriental countries with a high incidence but any association with foodcomponents remains to be clarified. To explore specific nutrient effects on risk of colorectal cancer in Japan, we hereconducted a correlation analysis between change in the diet and incidence rates.
Methods: Incidence data for 1976-1996 and national values for per capita daily food nutrient intake in 1956-1995were used. We first analyzed chronological changes of food nutrients and colorectal cancer, and then calculatedcorrelation coefficients with time lags of 5, 10, 15 or 20 years. To adjust for the confounding effects of total energy, wealso performed a partial correlation analysis.
Results: Incidences of colorectal cancer gradually increased during 1976-1996 with the highest incidence ratesfor colon and rectal cancers, 25.31 and 13.75 per 100,000, respectively, in 1996. Food nutrient intake also demonstratedmajor variation during 1956-1995, total fats and oils increasing most, followed by animal protein and animal fats.Incidences of colorectal cancer were positively associated with fat and oil intake, of both plant and animal types; apositive link was noted with animal protein but the association with plant protein consumption was inverse, as wasalso the case for carbohydrate and cereals; no simple association was evident with total energy intake.
Conclusions: Food nutrients play roles in risk of colon and rectal cancers. Lower animal protein and fat intake,and higher carbohydrate and cereal consumption might reduce the risk of colon and rectal cancers.