CHICAGO — The increasing prevalence of Crohn's disease in Japan correlates closely with the decreasing consumption of rice, Ryosuke Shoda, M.D., said at the annual Digestive Disease Week.
Crohn's disease was once almost unknown in Japan, Dr. Shoda said in a poster presentation. In the early 1960s and before, rice was the main source of dietary fiber in Japan, providing the average citizen with about 28 g of fiber per day. Today, the average intake of fiber from rice is 12–15 g/day.
Meanwhile, the prevalence of Crohn's disease went from virtually nothing in the 1960s to 2.9 per 100,000 persons in the mid-1980s and about 14 per 100,000 today, said Dr. Shoda, chief of the department of general internal medicine at the International Medical Center of Japan, Tokyo.
Data on fiber consumption and Crohn's disease from the Japanese Ministry of Health, Welfare, and Labor from 1966 to 1993 show that the rising prevalence of Crohn's disease closely paralleled the decreasing intake of fiber and rice and the increasing intake of fiber from wheat and grains, Dr. Shoda said.
Of nine sources of fiber studied, rice was the only one that was independently correlated with the prevalence of Crohn's disease. When changes in the consumption of animal fat were included in the analysis, rice remained the only independent factor.
Breakfast is the meal that has changed the most in Japan and is probably the most responsible for the decline in rice consumption, Dr. Shoda said in an interview. Many people in Japan now eat bread rather than rice with breakfast.
Dr. Shoda declined to speculate on what might explain the association. “This is just statistics,” he told this newspaper. “No one knows about this for certain. There must be other factors.”