Trends in Dietary Intake of Folate, Vitamins B(6), and B(12) among Japanese Adults in Two Rural Communities from 1974 through 2001

BACKGROUND: The 5th edition of the Japanese food composition table enables us to evaluate intakes of folate and vitamins B(6) and B(12), which are associated with risk of chronic diseases. METHODS: We investigated long-term trends in dietary intake of those nutrients in two rural communities; Ikawa from 1974 through 2000, and Kyowa from 1982 through 2001. The 24-hour recall method was adopted. Intake of green tea interviewed from 1994 was used to examine food sources for these nutrients in the latest period, but not to evaluate long-term trends. Reduced intakes of nutrients due to cooking were not taken into account. RESULTS: Age-adjusted mean folate intake increased by 30% in Ikawa between the 1970’s and 1980’s, and then leveled off to the latest survey, while that in Kyowa did not change throughout the survey periods. The increased folate intake was primarily due to green/yellow vegetables. Mean vitamin B(6) intake did not change except that it increased for Ikawa women in the 1980’s and decreased for Kyowa men in the latest period. No secular trend was found for mean vitamin B(12) intake. The largest source for folate intake was total vegetables (38-58% of total intake) and the second largest source was alcohol/beverages including green tea (11-24%). Fish/shellfish was the largest source for vitamins B(6) (16-23%) and B(12) (77-84%). CONCLUSIONS: Dietary intakes of folate, vitamins B(6) and B(12) showed no notable long-term trend, except for an increased folate intake between the 1970’s and 1980’s due to an increased intake of green/yellow vegetables.