Association between parents’ work hours and nutrient inadequacy in Japanese schoolchildren on weekdays and weekends

•Children whose mothers worked ≥40 h/wk had higher nutrient shortages of vitamins and minerals.•The children's nutrient shortages were more pronounced on weekdays than on weekends.•Notable differences were not shown based on fathers’ working hours. Evidence is sparse concerning whether the nutrient intake in schoolchildren differs according to parents’ work hours. The aim of this study was to investigate the relationship between parents’ work hours and nutrient inadequacy among Japanese primary schoolchildren using dietary reference intakes on days with and without a school lunch. Participants included 10- to 11-y-old children in grade 5 from 19 public primary schools in four prefectures of east Japan. Data for 699 children were analyzed. Participants completed 24-h dietary records with photographs of their meals for 4 d consecutively, which included of 2 d of weekdays and 2 d of weekends. Their mothers’ and fathers’ work hours were obtained from questionnaires that were completed by the participants’ guardians. Logistic regression analyses were used to estimate the odds ratios for whether participants had poor nutrient intake, with adjustment for confounders. Children whose mothers worked ≥40 h/wk had significantly higher rates of nutrient shortages for vitamins A, E, K, and B6, pantothenic acid, potassium, magnesium, and iron (P = 0.007, 0.003, 0.007, 0.023, 0.021, 0.045, 0.004, and 0.009, respectively) than those in the 0 h/wk group. These differences were not significant based on fathers’ working hours, with the exception of vitamin A (≥40 versus 0–39 h/wk, P = 0.032). Additionally, nutrient shortages for children were more pronounced on weekdays than on weekends. This evidence revealed the necessity to improve nutrition intake in children whose mothers work more than statutory working hours, which would enable children to have adequate nutrient intake, especially on weekdays.