The association between the frequency of eating ready-made meals (RMM) or eating out (EO) during pregnancy and postpartum depression remains unclear. We aimed to explore the association between the frequency of RMM or EO use during pregnancy and the incidence of postpartum depression. This study included 639 community-dwelling pregnant women who were recruited between 2019 and 2022. Data on the frequency of RMM and EO use, as well as sociodemographic, economic and lifestyle factors, were obtained using self-administered questionnaires. Data on dietary intake were obtained using a validated brief self-administered diet history questionnaire. Postpartum depression was assessed using the Japanese version of the Edinburgh Postnatal Depression Scale (EPDS). The incidence of postpartum depression (EPDS score of ≥9) based on the frequency of RMM or EO use was analysed using multiple logistic regression analysis. After adjusting for potential confounders, there was limited evidence suggesting an association between consuming RMM 3 times/week or more and the likelihood of experiencing postpartum depression, with an adjusted OR (aOR) and 95 % CI (95 % CI) of 4·16 and 1·68–10·27 (Pfor trend = 0·017) compared with consuming RMM less than 1 time/week. There was no evidence for an association between consuming EO 3 times/week or more and postpartum depression (aOR: 1·20, 95 % CI: 0·14, 10·04 and Pfor trend = 0·283). Accordingly, the present study presented weak evidence of an association between RMM and postpartum depression. Further studies with large and diverse samples are needed to overcome any potential selection bias.

This study aimed to compare the differences in the intake of food groups and nutrients between Japanese adults who consumed the recommended daily vegetable intake (350 g/day) and those who did not. Dietary information was obtained from one-day dietary records collected from the 2016 National Health and Nutrition Survey, which was conducted in 46 prefectures in Japan. The participants aged ≥20 years (n = 21,606; 53.8% women) were classified into the < and ≥350 g/day groups. Inter-group differences for 17 food groups and 27 nutrients were assessed as percentages of consumers (food groups only) and energy-adjusted intake (units/MJ/d or % of total energy intake). Overall, 29% of participants consumed ≥350 g/day of vegetables. The ≥350 g/day group had a higher percentage of consumers and energy-adjusted intakes for all vegetable subgroups than the <350 g/day group. For other food groups, the ≥350 g/day group had higher percentages of consumers for all food groups, except for cereals, eggs, and condiments and seasonings, which showed no significant differences. However, the ≥350 g/day group had a significantly higher energy-adjusted intake for potatoes and other tubers, mushrooms, meats, and condiments and seasonings but a significantly lower value for cereals, eggs, savoury snacks and confectionaries, and beverages. The ≥350 g/day group had a significantly higher intake of almost all (25/27) nutrients, including sodium, than the <350 g/day group. Participants with vegetable intake ≥350 g/day might have a more favourable intake of food groups and nutrients; however, watching for salt intake is necessary when promoting vegetable intake.

This scoping review aimed to identify questionnaire-based dietary assessment methods for use in the National Health and Nutrition Survey (NHNS) in Japan. The search was conducted in three databases (PubMed, Web of Science, and Ichushi) to identify questionnaire such as food frequency questionnaire and dietary history questionnaire validated against dietary recalls or food records for the intakes of both food groups and nutrients among Japanese adults. Study quality was assessed based on previously developed criteria. We extracted the questionnaire characteristics and the design and results of the validation studies. We identified 11 questionnaires, with the number of food items ranging from 40 to 196, from 32 articles of good quality. In the validation studies, participants were aged 30–76 years and 90% of the articles used ≥3 d dietary records as reference. The number of nutrients and food groups with a group-level intake difference within 20% against the reference method ranged from 1 to 30 and 1 to 11, respectively. The range of mean correlation coefficients between questionnaire and reference methods were 0.35–0.57 for nutrients and 0.28–0.52 for food groups. When selecting a survey instrument in the NHNS from the 11 existing questionnaires identified in this study, it is important to select one with high group-level comparison and correlation coefficient values on the intended assessment items after scrutinizing the design and results of the validation study. This review may serve as a reference for future studies that explore dietary assessment tools used for assessing dietary intake in specific representative populations.

Eating frequency has been associated with nutrient intake and diet quality. The aim of this study was to examine the association between daily nutrient and food group intake and consumption of breakfast and/or snacks among young Japanese adults, as secondary analysis of the 2012 National Health and Nutrition Survey in Japan involved 1420 men and 1659 women aged 20–39 years. Dietary intake data were collected using a one-day semi-weighed household dietary record. Participants were classified into four groups based their breakfast and snack consumption, defined as the consumption of any food or beverage that contained energy based on participant-defined eating occasions; both breakfast and snack consumption (B+S+), breakfast consumption without snacking (B+S–), breakfast skipping and snack consumption (B–S+) and breakfast skipping without snacking (B–S–). The proportion of breakfast skippers among men and women was 11·8 % and 6·6 %, whereas that of snack consumers among men and women was 55·3 % and 68·2 %, respectively. Energy, Mg potassium (in both sexes), vitamin B2, Ca, (only men) and folate and dietary fibre (only women) intakes were higher among breakfast and snack consumers than in the B+S– group. The nutrient intake level of the B+S– group was similar to that of the B–S+ group, whereas the B–S– group had lower energy (both sexes), Cu, dietary fibre and potassium (only women) intakes than the B+S– group. Snack consumption could supplement nutrients that may not be adequately consumed by three meals among young Japanese adults.

Identifying trends in dietary salt sources is essential for effectively reducing salt/Na intake. This study aimed to examine the trends in dietary salt sources among Japanese adults using the 2007–2019 National Health and Nutrition Survey data collected from 95 581 adults aged ≥ 20 years. Dietary intake was estimated using the 1-d household-based dietary record. Foods reported as potential sources of salt intake in Japan and other countries were categorised into twenty-one groups. Salt intake for each food group was adjusted using the density method based on the energy intake. Trends in dietary salt intake based on food sources by sex and age groups (20–39 years, 40–59 years and ≥ 60 years) were analysed using the Joinpoint Regression Program. Salt intake for each age group in both men and women decreased from 2007 (5·3 g/1000 kcal–6·4 g/1000 kcal) to 2019 (4·9 g/1000 kcal–5·6 g/1000 kcal). The major dietary source of salt continued to be seasonings such as soya sauce and soyabean paste (approximately 70 %). Salt intake from seasonings decreased over time in adults aged ≥ 40 years but did not change in those aged 20–39 years. Additionally, a decreasing salt intake from unprocessed fish and shellfish and an increasing salt intake from unprocessed meat were observed across all age categories for both sexes. This study demonstrated that a strategy targeting different age groups may be needed to reduce salt consumption from seasonings among the Japanese population. Further studies on salt content in seasonings and continued monitoring of trends in dietary salt sources are required.

The influence of free sugar intake on nutrient intake remains unclear in Japanese children and adolescents with relatively low free sugar intake. This cross-sectional study aimed to investigate the relationship between free sugar and selected nutrient intakes using data from the 2016 National Health and Nutrition Survey, Japan, based on the WHO recommendations (<5 % or <10 % of energy (%E)) for free sugar intake. A 1-d weighed dietary record was assessed in Japanese children and adolescents (aged 1–19 years; n 2919). Mean intakes for selected nutrients and food groups were compared according to free sugar intake categories (<2·5 %E, 2·5 to <5 %E, 5 to <10 %E and ≥10 %E) with adjustment for sex, age and weight status. Inverse associations were observed between intakes of free sugars and twenty-one of twenty-four micronutrients assessed, except for vitamins A and C and Ca. Significantly reduced intakes were identified for twenty-two and fourteen micronutrients in the ≥10 %E and 5 to <0 %E categories, respectively, compared with the lower categories. Mean micronutrient intakes at the <2·5 %E category did not differ from those at the 2·5 to <5 %E category. Free sugar intake had positive associations with intakes of sugars and jams, confectioneries, fruit and vegetable juices, and soft drinks and negative associations with intakes of pulses and nuts and vegetables. This study showed that nutrient dilution was associated with higher free sugar intake among Japanese children and adolescents. The findings suggest that the WHO recommendations might help prevent nutrient dilution in Japanese children and adolescents.

Few studies have reported associations between the Na:K ratio and risk factors related to CVD among the general population in Asian countries. This study aimed to investigate the dietary Na:K ratio association with CVD risk factors among Japanese adults. This retrospective cross-sectional study included 48 800 Japanese participants (19 386 men and 29 414 women) aged ≥20 years, registered in the 2003–2017 National Health and Nutrition Survey. Multivariate OR and 95 % CI for risk of hypertension, high glycated HbA1c levels, hypercholesterolaemia, low serum levels of HDL-cholesterol and high non-HDL-cholesterol levels according to the Na:K ratio were estimated using logistic regression models. Dietary Na:K ratio decreased for both men and women from 2003 to 2017. Higher Na:K ratio and higher hypertension prevalence were observed (multivariate OR (fifth v. first quintiles) 1·27, 95 % CI 1·15, 1·40; Pfor trend < 0·001 for men and 1·12, 95 % CI 1·01, 1·23; Pfor trend = 0·007 for women). Higher Na:K ratio was associated with higher prevalence of high HbA1c levels in men (multivariate OR 1·56, 95 % CI 1·24, 1·96). Prevalence of low HDL-cholesterol levels was increased with higher Na:K ratio (Pfor trend =0·002 for men and <0·001 for women). No significant associations were found between Na:K ratio and hypercholesterolaemia in men or high non-HDL-cholesterol levels in both men and women. Our findings suggest that dietary Na:K ratio is associated with several CVD risk factors among Japanese adults.

Few studies have reported the association between the Japanese diet as food score and mortality. This study aimed to investigate adherence to the Japanese food score associated with all-cause, CVD and cancer mortality. A total of 58 767 (23 162 men and 34 232 women) Japanese participants aged 40–79 years, who enrolled in the Japan Collaborative Cohort Study between 1988 and 1990, were included. The Japanese food score was derived from the components of seven food groups (beans and bean products, fresh fishes, vegetables, Japanese pickles, fungi, seaweeds and fruits) based on the FFQ. The total score ranged from 0 to 7, and participants were divided into five categories based on scores (0–2, 3, 4, 5 and 6–7). Hazard ratios (HR) and 95 % CI for all-cause, CVD and cancer mortality based on sex were estimated using Cox proportional models. During the follow-up period until 2009, 11 692 participants with all-cause, 3408 with CVD and 4247 with cancer died. The multivariable HR in the 6–7 and 0–2 Japanese food score groups were 0·93 (95 % CI 0·86, 1·01) in men and 0·82 (95 % CI 0·75, 0·90) in women for all-cause mortality and 0·89 (95 % CI 0·76, 1·04) in men and 0·66 (95 % CI 0·56, 0·77) in women for CVD mortality. Our findings suggest that adherence to the Japanese food score consisting of food combinations characterised by a Japanese diet may help in preventing all-cause and CVD mortality, especially in women.

Monitoring nutritional status of the population is essential in the development and evaluation of national or local health policies. In this study, we aimed to demonstrate analysis on the trends in dietary intake of energy and macronutrients, as well as Na, in Japanese population using the data of series of cross-sectional national surveys – the National Nutrition Survey (NNS) and the National Health Nutrition Survey (NHNS) – during the period from 1995 to 2016. The NNS and NHNS participants aged 20–79 years were included in the analysis. Dietary intake was estimated using 1-d household-based dietary record. The trend in total energy intake, energy intake from macronutrients (fat and protein), Na intake and energy-adjusted Na intake were analysed using regression models adjusted to 2010 age distribution and anthropometry status. A total of 94 270 men and 107 890 women were included the analysis. Total energy intake showed a decreasing trend in both men and women. Similarly, energy intake from protein decreased, but energy intake (%) from fat increased in both sexes. Energy-adjusted Na intake showed a decreasing trend in both men and women. This study identified the decrease in total energy intake and energy intake from protein, whereas there were inverse trends in energy intake from fat among Japanese adults. Continued monitoring of trends in dietary intake will be needed, and there should be efforts to increase the accuracy of current survey procedures.