To (i) examine the consumption of highly processed foods (HPF) in relation to diet quality among Japanese adults and (ii) compare the results when dishes prepared away home are disaggregated into food ingredients before classification by processing levels and the results when they are not.

Cross-sectional analysis using 4-day dietary record data. Foods were categorised by level of processing using the framework developed by the University of North Carolina at Chapel Hill. Specifically, dishes prepared away from home were classified at both the food level (classified after disaggregation into ingredients) and dish level (classified without disaggregation). Diet quality was assessed using the Healthy Eating Index-2015 and Nutrient-Rich Food Index 9·3.

Twenty areas in Japan.

Adults aged 20–69 years (n 388).

Energy contribution of HPF was higher when dishes prepared away from home were classified at dish level than food level (48·3 % v. 32·9 %, P < 0·0001). Regardless of the classification method, cereals and starchy foods were the top food groups contributing to total energy intake from HPF. After adjusting for potential confounders, participants in higher tertiles of the energy contribution of HPF had lower total scores for Healthy Eating Index-2015 and Nutrient-Rich Food Index 9·3 (P for trend ≤ 0·007 for all), irrespective of the food- or dish-level classification.

HPF accounted for at least one-third of energy intake of Japanese adults. Regardless of the classification methods for dishes prepared away from home, higher consumption of HPF was associated with lower diet quality.

As the world’s population is ageing, improving the physical performance (PP) of the older population is becoming important. Although diets are fundamental to maintaining and improving PP, few studies have addressed the role of these factors in adults aged ≥ 85 years, and none have been conducted in Asia. This study aimed to determine the dietary patterns (DP) and examine their relationship with PP in this population.

This cross-sectional study (Kawasaki Aging and Wellbeing Project) estimated food consumption using a brief-type self-administered diet history questionnaire. The results were adjusted for energy after aggregating into thirty-three groups, excluding possible over- or underestimation. Principal component analysis was used to identify DP, and outcomes included hand grip strength (HGS), timed up-and-go test, and usual walking speed.

This study was set throughout several hospitals in Kawasaki city.

In total, 1026 community-dwelling older adults (85–89 years) were enrolled.

Data of 1000 participants (median age: 86·9 years, men: 49·9 %) were included in the analysis. Three major DP (DP1: various foods, DP2: red meats and coffee, DP3: bread and processed meats) were identified. The results of multiple regression analysis showed that the trend of DP2 was negatively associated with HGS (B, 95 % CI –0·35, –0·64, –0·06).

This study suggests a negative association between HGS and DP characterised by red meats and coffee in older adults aged ≥ 85 years in Japan.

To examine the association between the amount of time spent at childcare and diet quality in 668 Japanese children aged 1·5–6 years.

A cross-sectional design was used. Dietary information was collected using dietary records (1 d for children aged 1·5–2 years and 2 d for children aged 3–6 years). Diet quality was assessed by counting the number of nutrients not meeting the Japanese Dietary Reference Intakes (DRI). Each child’s guardian reported the average amount of time spent at childcare per d for the previous 1 month.

In total, 315 childcare centres located in twenty-four areas in Japan.

In total, 753 children aged 1·5–6 years who attend childcare facilities.

After adjustment for potential confounders, OR for the low diet quality (≥ 5 of twenty nutrients not meeting DRI) in long (≥10 h/d) v. medium (8–10 h/d) childcare hours was 4·81 (95 % CI 1·96, 11·8) among children aged 5–6 years. There was no significant association in children aged 1·5–2 and 3–4 years.

This study showed that long time spent at childcare was strongly associated with low diet quality among children aged 5–6 years, but not those aged 1·5–2 and 3–4 years. More research is needed to clarify different associations in each age group.

To characterise different meal types by examining the contribution of specific meals to the total intakes and the nutritional quality of each meal.

A cross-sectional analysis was conducted based on dietary data collected using 4-d dietary record. Diet quality was assessed by the Healthy Eating Index-2015 and Nutrient-Rich Food Index 9.3.

Japan.

Adults aged 20–81 years (n 639).

Diet quality was, on average, highest for dinner, followed, in order, by lunch, breakfast and snacks. Breakfast, lunch, dinner and snacks, on average, accounted for 21 %, 32 %, 40 % and 11 % of total energy intake, respectively. For many nutrients, the percentage contribution to total intake did not vary within each meal, broadly in line with that for energy: 18–24 % for breakfast, 26–35 % for lunch, 35–49 % for dinner and 4–15 % for snacks. However, intakes of many foods largely depended on one meal type. The foods mainly eaten at dinner were potatoes, pulses, total vegetables, fish, meat and alcoholic beverages (52–70 %), in contrast to noodles (58 %) at lunch and bread (71 %) and dairy products (50 %) at breakfast. The foods mainly eaten at snacks were confectioneries (79 %) and sugar-sweetened beverages (52 %). Conversely, rice and eggs were more evenly distributed across three main meals (19–41 % and 30–38 %, respectively), while fruit and non-energetic beverages were more evenly distributed across all meal types (17–30 % and 19–35 %, respectively).

These findings provide the background information on each meal type in Japanese and may help inform the development of meal-based guidelines and public health messages.

Recent research supports the importance of PUFA intake in children, particularly of EPA and DHA; however, few verified methods to assess whether PUFA intake is adequate are available.

We assessed the correlation between serum PUFA and lipid concentrations with seafood and PUFA intake measured using a brief-type self-administered diet history questionnaire for Japanese preschool children (BDHQ3y).

Single centre birth cohort in Japan.

A total of 152 36-month-old Japanese children.

Average dietary intake of daily seafood, EPA and DHA was 13·83 (sd 10·36) g, 49·4 (sd 43·5) mg and 98·3 (sd 64·6) mg, respectively. Significant weak-to-moderate correlations were observed between dietary intake and serum EPA (Spearman rho = 0·41, P < 0·001; Pearson r = 0·44, P < 0·001); DHA (Spearman rho = 0·40, P < 0·001; Pearson r = 0·42, P < 0·001) and AA (arachidonic acid) (Spearman rho = 0·33, P < 0·001; Pearson r = 0·32, P < 0·001), whereas no significant correlation was observed for dihomo-γ-linolenic acid (DGLA) (Spearman rho = 0·06, P = 0·484; Pearson r = 0·07, P = 0·387). Correlations between seafood intake and serum EPA and DHA were also moderate (0·39–0·43). A negative correlation between serum TAGs and serum EPA, as well as positive correlations between serum cholesterol (total cholesterol, LDL and HDL) with serum EPA and DHA were observed, whereas no significant correlations between seafood intake and serum lipid profiles. Based on this model, we estimated 61–98 g/week of seafood intake is required to meet current EPA/DHA intake recommendations by the WHO (100–150 mg/d).

For children of 2–4 years of age, weekly intake of 61–98 g of seafood is required to meet WHO recommendations of EPA/DHA intake.

This cross-sectional study evaluated the dietary characteristics of snacks, the contribution of snacks to daily nutrient intake and the association of energy intake (EI) from snacks with the prevalence of nutritional inadequacy in Japanese nursery school children.

Foods and nutrients consumed in each eating occasion were assessed by 3-d dietary records. The prevalence of inadequate intake of twenty nutrients assessed by the age- and sex-specific reference values in the Japanese Dietary Reference Intakes was compared according to tertile categories of EI from snacks.

A multi-regional dietary survey based on nursery schools in Japan.

A total of 187 boys and 191 girls aged 3–6 years.

EI from snacks accounted for 19·5 % (sd 6·9) of total daily EI. Confectionaries accounted for the largest part of EI from snacks (35·3 %), followed by milk (19·5 %). Relative to their energy contribution, snacks accounted for a small proportion for all nutrients examined, except for free sugar, calcium, SFA and riboflavin. Although a higher EI from snacks was associated with favourable profiles for intakes of calcium, iron, thiamine and riboflavin, excessive intakes of free sugar and Na were more prevalent among children with a higher EI from snacks.

Although snacks are effective in meeting the requirement of some nutrients among Japanese nursery school children, snacks are generally not nutrient-dense and have an impact on excessive intake of some nutrients. There is hence room for improvement in food choices at snack time.

To develop a greenhouse gas emissions (GHGE) database for Japanese foods using three different approaches, compare the results of estimated diet-related GHGE and determine major food contributors among Japanese adults.

Cross-sectional. Three GHGE databases were developed: (1) a literature-based method including a literature review of life cycle assessment studies of Japanese foods and (2) production- and (3) consumption-based input–output tables (IOT)-applied methods using the Japanese IOT. All databases were linked to the Japanese food composition table and food consumption data. Diet-related GHGE was estimated based on each database and the 4-d dietary record data. Diet-related GHGE were compared in both total and food group level between the databases.

Japan.

392 healthy adults aged 20–69 years.

The mean diet-related GHGE significantly differed according to the calculation methods: 4145 g CO2-equivalent (CO2-eq)/d by the literature-based method, 4031 g CO2-eq/d by the production-based method and 7392 g CO2-eq/d by the consumption-based IOT-applied methods. It significantly differed in food group level as well. Spearman’s correlation coefficients between three methods ranged from 0·82 to 0·86. Irrespective of the methods, the top contributor to GHGE was meat (19·7–28·8 %) followed by fish and seafood (13·8–18·3 %).

Although the identified major food contributors to GHGE were comparable between the three methods, the estimated GHGE values significantly differed by calculation methods. This finding suggested that caution must be taken when interpreting the estimated diet-related GHGE values obtained using the different calculation methods of GHGE.

Although a high intake of fat, particularly SFA, is a well-known risk factor for CVD, fat intake in Japan has attracted relatively little attention from health professionals to date due to the low intake in the Japanese population. However, recent surveys have shown an increase in fat intake in younger Japanese populations. Here, we described the fat intake and dietary sources of SFA in Japanese schoolchildren. Also, we experimentally exchanged a high-SFA food with a low-SFA substitute in the data, and calculated the resulting changes in nutrient intakes.

The study was conducted nationwide under a cross-sectional design. A non-consecutive, three-day diet record was performed on two school days and a non-school day.

Fourteen elementary and thirteen junior high schools.

Elementary-school children (n 629) and junior high-school children (n 281).

Prevalence of excess fat intake was 35·4 % in boys and 45·0 % in girls. Excess SFA intake was suspected in 97·7 % of boys and 99·4 % of girls when the dietary reference intake values for adults were applied. Major dietary sources of SFA were meat (26·4 % of total SFA intake), dairy products (25·7 %) and confectioneries (11·3 %).

Since one-third to nearly one-half of our Japanese schoolchildren consumed excess fat, careful monitoring of fat intake in the Japanese population should be continued. Adoption of low-fat milk and/or lean meat in daily meals might be a suitable means of reducing fat, particularly SFA intake, in schoolchildren.

The role of school lunches in diet quality has not been well studied. Here, we aimed to determine the contribution of school lunches to overall nutrient intake in Japanese schoolchildren.

The study was conducted nationwide under a cross-sectional design. A non-consecutive, three-day diet record was performed on two school days and a non-school day separately. The prevalence of inadequate nutrient intake was estimated for intakes on one of the school days and the non-school day, and for daily habitual intake estimated by the best-power method. The relationship between food intake and nutrient intake adequacy was examined.

Fourteen elementary and thirteen junior high schools in Japan.

Elementary-school children (n 629) and junior high-school children (n 281).

Intakes between the school and non-school days were significantly different for ≥60 % of nutrients. Almost all inadequacies were more prevalent on the non-school day. Regarding habitual intake, a high prevalence of inadequacy was observed for fat (29·9–47·7 %), dietary fibre (18·1–76·1 %) and salt (97·0–100 %). Inadequate habitual intake of vitamins and minerals (except Na) was infrequent in elementary-school children, but was observed in junior high-school children, particularly boys.

School lunches appear to improve total diet quality, particularly intake of most vitamins and minerals in Japanese children. However, excess intakes of fat and salt and insufficient intake of dietary fibre were major problems in this population. The contribution of school lunches to improving the intakes of these three nutrients was considered insufficient.

To identify dietary patterns in the current Japanese diet and evaluate the associations between these patterns and Na and K intakes.

Dietary patterns were extracted by factor analysis from the intakes of food groups assessed with a validated self-administrated diet history questionnaire. Na and K intakes and urinary Na:K were assessed by repeated 24 h urine collection.

Healthy Japanese adults aged 20–69 years (353 men and 349 women).

Twenty study areas in twenty-three prefectures in Japan.

Four dietary patterns were identified in each sex. After adjustment for several confounding factors, the ‘Fish and vegetable’ pattern was associated with higher urinary Na excretion, but the association was not significant (P=0·37 in men and P=0·06 in women). This pattern was also associated with higher K excretion in both sexes. The ‘Noodle’ pattern tended to be associated with higher urinary Na excretion (P=0·17 in men and P=0·04 in women) and higher Na:K (P=0·02 in men). The ‘Meat, vegetable and oil’ (in men)/‘Meat and oil’ (in women) and ‘Bread and confectioneries’ patterns were not associated with urinary Na excretion (in men) or were negatively associated (in women).

Contrary to the case in Western countries, the ‘Fish and vegetable’ and ‘Noodle’ patterns contributed to higher Na intake in Japan. Target foods for salt reduction should be set based on careful consideration of the relationships between dietary patterns and Na and K intakes in the target population.

Globally, the Na consumption of most people exceeds the WHO recommendation. To be effective, salt reduction programmes require assessment of the dietary sources of Na. Due to methodological difficulties however, comprehensive assessments are rare. Here, we identified Na sources in the Japanese diet using a 4 d diet record that was specifically designed for Na source description.

A cross-sectional study.

Apparently healthy men (n 196) and women (n 196) aged 20–69 years.

The subjects were recruited from twenty-three of forty-seven prefectures in Japan.

The proportion of discretionary Na intake in total Na intake was 52·3 % in men and 57·1 % in women, and was significantly lower in younger subjects. The two major food groups contributing to Na intake were seasonings such as salt or soya sauce (61·7 % of total Na intake in men, 62·9 % in women) and fish and shellfish (6·7 % in men, 6·6 % in women). The third major contributor differed between men and women (noodles in men, 4·9 %; bread in women, 5·0 %). Further, the contribution of each food group to total Na intake differed among age groups.

While individual efforts to decrease Na intake remain important, population approaches to reducing Na content in processed foods are already equally important and will assume greater importance in the future even in Japan, an Asian country facing a rapid Westernization in dietary habits.

We evaluated the association of nutrient intake with Fe deficiency with regard to lifestyle factors and health condition in young Japanese women. Uniquely among developed countries, dietary habits render Japanese populations vulnerable to Fe deficiency, owing to their relatively low intake of Fe and high intake of Fe absorption inhibitors, such as green tea and soyabeans.

A cross-sectional study.

The subjects were 1019 female Japanese dietetic students aged 18–25 years. Dietary habits during the preceding month were assessed using a previously validated, self-administered, diet history questionnaire. Blood analysis was performed to assess body Fe status. Subjects were categorized with Fe deficiency when their serum ferritin levels were <12 ng/ml. Twenty-nine dietary variables, i.e. intakes of energy, sixteen nutrients including Fe and twelve food groups, were analysed using multivariate logistic regression models adjusted for possible confounders.

Of the subjects, 24·5 % were categorized with Fe deficiency. However, no dietary factors assessed were significantly associated with Fe deficiency. The risk of Fe deficiency was significantly lower in women with infrequent or no menstrual cycles than in those with regular cycles (OR = 0·58; 95 % CI 0·34, 1·00) and significantly higher in women with heavy menstrual flow than in women with average flow, albeit that these were self-reported (OR = 1·83; 95 % CI 1·35, 2·48).

These results suggest that dietary habits, including Fe intake, do not significantly correlate with Fe deficiency among young Japanese women.