Fat and dietary fiber intake and colon cancer mortality: a chronological comparison between Japan and the United States.

To estimate the role of dietary fiber (DF) and fat in the striking growth of colon cancer mortality in Japan after World War II, we analyzed relations between the above variables in comparison with those in the United States. In the United States, fat intake grew by only one-third over the past 70 years (from 124 g in 1909-1913 to 166 g in 1984), whereas colon cancer mortality increased fourfold (from 5 to 20 per 100,000). In Japan, although fat intake roughly doubled during the 40 years after World War II (from 20 to 38 g), colon cancer mortality grew 5.5-fold (from 2 to 11 per 100,000). It is difficult to give a consistent explanation for the growth patterns of colon cancer mortality in both countries on the basis of fat consumption as a cancer promoter. In the United States, DF intake continuously dwindled at a level always less than in Japan throughout this century. DF intake in Japan also declined rather steadily, except for war time, over the past 80 years. However, with regard to the growth pattern of colon cancer mortality, it began rising steeply around the period when the daily DF intake diminished below 20 g, suggesting the presence of a threshold level in this neighborhood in preventing the development of colon cancer.