Cohabitational effect of grandparents on dietary intake among young Japanese women and their mothers living together. A multicenter cross-sectional study.

We examined the cohabitational effect of the grandparents on dietary intakes among young Japanese women and their mothers, using data from a cross-sectional multicenter study conducted in 35 of 47 prefectures in Japan. Among a total of 2032 three-generation families, 1336 female dietetic students (18-20 years), 1336 of their mothers (36-59 years), and 1560 of their paternal or maternal grandmothers (59-94 years) were included. Intake of foods and nutrients was assessed with self-administered diet history questionnaires. The prevalence of students and their mothers living with the grandparents (GP) was 36%. Students living with GP had a higher intake of fruits, vegetables, total dietary fiber, β-carotene, vitamin C and potassium and lower intake of meats than those living without GP. For mothers, fish and shellfish and vitamin C intakes were higher and meat intake was lower among participants living with GP. The median correlation coefficients of food and nutrient intakes in the students-grandmothers living together was higher than in those living apart for both paternal grandmothers (PGM) and maternal grandmothers (MGM) (all P <0.01). The median values of mothers-PGM living together were also significantly higher than in those living apart (P <0.01). However, the values of mothers-MGM did not significantly differ between those living with and without MGM. These results may suggest that family members who live together tend to share similar dietary habits. Further, the mother's dietary habits might affect those of their children even after they live apart.