Chronological changes and inter-regional differences in dietary fiber intakes among middle-aged Japanese women

Dietary fiber intake was estimated by the total food duplicate method, using a computerized system for fiber calculation recently developed by this study group. Collection of food duplicates were conducted twice, once in 1979-83 and then in 1990-95, in 20 sites across Japan. Altogether 294 and 384 nonsmoking, nonhabitually drinking adult women offered the samples, in the first and second survey, respectively. The average intake of total fiber was 20.7 g/day in the first study, and it was 18.7 g/day in the second survey with a significant reduction. Soluble fiber accounted for 18 to 19%, and the reduction was more marked in soluble fiber than in insoluble fiber. There was an inter-regional difference in fiber intake which was more evident in the first survey than in the second; farmers in Okinawa took less soluble, insoluble and total fiber than in Hokkaido and Honshu farmers and also urban residents. Throughout the four groups, the leading fiber sources were vegetables, followed by cereals, fruits and pulse in the decreasing order. Intakes of these foods diminished during the two survey period, and the reduction of fiber from cereals was most evident in Honshu and Okinawa farmers. International comparison showed that the current level of fiber intake in Japan is essentially similar to the levels in Europe and USA, despite the long-term trend of reduction.