Development and Validation of the Meiji Nutritional Profiling System (Meiji NPS) to Address Dietary Needs of Adults and Older Adults in Japan

This study introduces the Meiji Nutritional Profiling System (Meiji NPS), which was specifically designed to respond to age-related shifts in nutrient requirements among Japanese adults (<65 years old) and older adults (≥65 years old). Japan has one of the most aged societies in the world. The health issues of interest are malnutrition and lifestyle-related diseases among adults and frailty among older adults. Two versions of the NPS were developed based on nutrients to encourage (protein, dietary fibers, calcium, iron, and vitamin D), food groups to encourage (fruits, vegetables, nuts, legumes, and dairy), and nutrients to limit (energy, saturated fatty acids, sugars, and salt equivalents). The Meiji NPS for older adults did not include iron or saturated fatty acids. The algorithms were based on the Nutrient-Rich Foods Index (NRF). The convergent validity between the Meiji NPS and the existing NPSs for the same foods was confirmed using Spearman's correlation coefficients (NRF: r = 0.67 for adults and r = 0.60 for older adults; Health Star Rating: r = 0.64 for adults and r = 0.61 for older adults). The Meiji NPS may be useful for nutritional evaluation and reformulation of food products, tailored to adults and older adults to ameliorate health issues in Japan.

Traditional japanese diet score and the sustainable development goals by a global comparative ecological study

BACKGROUND

Reducing the environmental impact of the food supply is important for achieving Sustainable Development Goals (SDGs) worldwide. Previously, we developed the Traditional Japanese Diet Score (TJDS) and reported in a global ecological study that the Japanese diet is associated with reducing obesity and extending healthy life expectancy etc. We then examined the relationship between the TJDS and environmental indicators.

METHODS

The average food (g/day/capita) and energy supplies (kcal/day/capita) by country were obtained from the Food and Agriculture Organization of the United Nations Statistics Division database. The TJDS was calculated from eight food groups (beneficial food components in the Japanese diet: rice, fish, soybeans, vegetables, and eggs; food components that are relatively unused in the traditional Japanese diet: wheat, milk, and red meat) by country using tertiles, and calculated the total score from - 8 to 8, with higher scores meaning greater adherence to the TJDS. We used Land Use (m2), Greenhouse gas (GHG) emissions 2007/2013 (kg CO2eq), Acidifying emissions (g SO2eq), Eutrophying emissions (g PO43- eq), Freshwater (L), and water use (L) per food weight by Poore et al. as the environmental indicators and multiplied these indicators by each country's average food supply. We evaluated the cross-sectional and longitudinal associations between the TJDS and environmental indicators from 2010 to 2020. This study included 151 countries with populations ≥ 1 million.

RESULTS

Land use (β ± standard error; -0.623 ± 0.161, p < 0.001), GHG 2007 (-0.149 ± 0.057, p < 0.05), GHG 2013 (-0.183 ± 0.066, p < 0.01), Acidifying (-1.111 ± 0.369, p < 0.01), and Water use (-405.903 ± 101.416, p < 0.001) were negatively associated with TJDS, and Freshwater (45.116 ± 7.866, p < 0.001) was positively associated with TJDS after controlling for energy supply and latitude in 2010. In the longitudinal analysis, Land Use (β ± standard error; -0.116 ± 0.027, p < 0.001), GHG 2007 (-0.040 ± 0.010, p < 0.001), GHG 2013 (-0.048 ± 0.011, p < 0.001), Acidifying (-0.280 ± 0.064, p < 0.001), Eutrophying (-0.132 ± 0.062, p < 0.05), and Water use (-118.246 ± 22.826, p < 0.001) were negatively associated with TJDS after controlling for confounders.

CONCLUSIONS

This ecological study suggests that the traditional Japanese dietary pattern might improve SDGs except Fresh water.

Development of a Machine Learning Model for Classifying Cooking Recipes According to Dietary Styles

To complement classical methods for identifying Japanese, Chinese, and Western dietary styles, this study aimed to develop a machine learning model. This study utilized 604 features from 8183 cooking recipes based on a Japanese recipe site. The data were randomly divided into training, validation, and test sets for each dietary style at a 60:20:20 ratio. Six machine learning models were developed in this study to effectively classify cooking recipes according to dietary styles. The evaluation indicators were above 0.8 for all models in each dietary style. The top ten features were extracted from each model, and the features common to three or more models were employed as the best predictive features. Five well-predicted features were indicated for the following seasonings: soy sauce, miso (fermented soy beans), and mirin (sweet cooking rice wine) in the Japanese diet; oyster sauce and doubanjiang (chili bean sauce) in the Chinese diet; and olive oil in the Western diet. Predictions by broth were indicated in each diet, such as dashi in the Japanese diet, chicken soup in the Chinese diet, and consommé in the Western diet. The prediction model suggested that seasonings and broths could be used to predict dietary styles.

Investigation of Amino Acid and Fatty Acid Profiles of Japanese Diets Using the Food Exchange Lists for Diabetes Diet

Dietary Reference Intakes for Japanese provide target values for proteins, fats, and carbohydrates. However, they do not provide information on reference values for amino acids (AAs) and fatty acids (FAs), which determine the quality of foods in detail. Therefore, we evaluated AAs and FAs using the Food Exchange Lists-Dietary Guidance for Persons with Diabetes (in Japanese) Utilization, Second Edition Sample Menus and Practice (FELD) as an ideal Japanese diet. Based on FELD, 15 different daily meal patterns were employed with combinations of three levels of carbohydrates %energy (high carbohydrate [HC], 60%; middle carbohydrate [MC], 55%; and low carbohydrate [LC], 50%) and five levels of energy (1,200-2,000 kcal). Using the Japanese Food Composition Table 2020 adjusted for 1,000 kcal, 18 AAs, 49 FAs, and calorie densities (CDs, kcal/g) were calculated and compared among the three groups. Dietary AA was rich in glutamic acid, aspartic acid, and leucine; in order, no significant differences were observed among HC, MC, and LC for 18 AAs. Dietary FA was higher for 18:1 total, 16:0, and 18:2 n-6. Moreover, 16:0, 20:0, and 18:1 total in LC and 22:0 and 18:3 n-3 in MC were significantly higher than those in HC. The HC, MC, and LC CD was low at 0.82, 0.84, and 0.93 kcal/g, respectively. No significant differences in 18 AAs and CD were noted among HC, MC, and LC in FELD; however, significant differences were observed in the FA profiles. This study suggests the importance of evaluating diet using AA and FA units.

Global Association between Traditional Japanese Diet Score and All-Cause, Cardiovascular Disease, and Total Cancer Mortality: A Cross-Sectional and Longitudinal Ecological Study

OBJECTIVE

Studies conducted on Japanese people have suggested that a traditional Japanese diet contributes to good health, longevity, and protection against several non-communicable diseases. However, it is unknown whether traditional Japanese dietary patterns are associated with all-cause mortality, cardiovascular disease, and cancer mortality globally. The purpose of this cross-sectional and longitudinal ecological study is to clarify the global association between the traditional Japanese diet score (TJDS) and all-cause, cardiovascular disease, and total cancer mortality.

METHODS

Data on food supply and all-cause mortality, cardiovascular disease mortality, total cancer mortality, and covariables by country were obtained from a relevant internationally available database. TJDS by country was calculated from eight food groups and the total score ranged from -8 to 8, with higher scores indicating greater adherence to a traditional Japanese diet. We evaluated the cross-sectional and 10-year longitudinal association between TJDS and all-cause, cardiovascular disease, and total cancer mortality using 2009 as the baseline in 142 countries with populations of more than one million. A cross-sectional analysis and a longitudinal analysis were performed using three general linear models or three linear mixed models with different covariables.

RESULTS

In cross-sectional models controlled for fully-adjusted covariables, TJDS was negatively associated with all-cause mortality (β ± standard error; -43.819 ± 11.741, p < 0.001), cardiovascular disease mortality (-22.395 ± 4.638, p < 0.001), and total cancer mortality (-3.893 ± 1.048, p < 0.001). In 10-year longitudinal models controlled for fully-adjusted covariables, TJDS was significantly negatively associated with all-cause mortality (-31.563 ± 7.695, p < 0.001), cardiovascular disease mortality (-16.249 ± 4.054, p < 0.001), and total cancer mortality (-3.499 ± 0.867, p < 0.001).

CONCLUSIONS

This cross-sectional and longitudinal ecological study suggests that the traditional Japanese diet is associated with lower all-cause mortality, cardiovascular disease mortality, and total cancer mortality, worldwide.

Elevated arsenic level in fasting serum via ingestion of fish meat increased the risk of hypertension in humans and mice

Aims

There has been a shortage of human studies to elucidate the association between serum arsenic levels and the prevalence of hypertension. This study multidirectionally investigated associations among arsenic exposure, dietary ingestion, and the risk of hypertension by combined human epidemiological and mouse experimental studies.

Methods and results

This study focused on the total arsenic level in fasting serum, a biomarker of arsenic exposure. Associations among ingestion frequencies of 54 diet items of Japanese food separated into six categories, total arsenic level in fasting serum, and the prevalence of hypertension were investigated in 2709 general people in Japan. Logistic regression analysis demonstrated a dose-dependent association between serum arsenic level and hypertension and a positive association between the ingestion of fish meat and hypertension. Further analysis showed that the latter association was fully mediated by increased fasting serum arsenic levels in humans. Similarly, oral exposure to the putative human-equivalent dose of arsenic species mixture with the same ratios in a common fish meat in Japan increased systolic blood pressure and arsenic levels in fasting serum in mice.

Conclusion

This interdisciplinary approach suggests that fish-meat ingestion is a potential risk factor for arsenic-mediated hypertension. Because the increased consumption of fish meat is a recent global trend, health risks of the increased ingestion of arsenic via fish meat should be further investigated.

Development of the Scores for Traditional and Modified Japanese Diets

Increasing attention is being paid to the role of diet quality in the prevention and management of non-communicable diseases. We developed a scoring system for the traditional Japanese diet and its modified version considering the dietary culture in Japan, dietary guidelines for the Japanese, and updated evidence for disease prevention. The traditional Japanese diet comprises white rice, miso soup, soybean products, vegetables, mushrooms, seaweeds, fish and shellfish, high-sodium foods, and green tea. In the modified Japanese diet, unprocessed or minimally refined rice and raw vegetables, milk and dairy products, and fruits were additionally considered, while salty food was reverse-scored. The cutoff for the intake frequency of each food/food group was determined with reference to a health survey of >12,000 workers. Among the participants in the validation study, we confirmed the nutritional gradient with increasing scores in the expected direction. The scores were closely correlated with the respondents' backgrounds, including occupational factors. This simple scoring system can be used for diet quality assessments and epidemiological research.

Association between the Japanese Diet and Coronary Artery Disease in Patients Undergoing Coronary Angiography

Several cohort studies have reported that the Japanese diet is associated with reduced cardiovascular disease mortality. However, the results were not always consistent, and most of those studies conducted dietary surveys around 1990. We investigated the association between the Japanese diet and coronary artery disease (CAD) in 802 patients undergoing coronary angiography. The Japanese diet score was defined as the sum of scores of the intakes of fish, soy products, vegetables, seaweed, fruits, and green tea. CAD was found in 511 patients, of whom 173 had myocardial infarction (MI). Intakes of fish, soy products, vegetables, seaweed, fruits, and green tea were lower in patients with CAD, especially in those with MI, than in those without CAD. As a result, the Japanese diet score was significantly lower in patients with CAD than in those without CAD (p < 0.001). To clarify the association between the Japanese diet and CAD, the 802 study patients were divided into three tertiles by the Japanese diet score. The proportion of CAD decreased with the Japanese diet score, reaching 72% in patients at T1 (lowest score), 63% at T2, and 55% at T3 (highest) (p < 0.05). The proportion of MI also decreased with the Japanese diet score, reaching 25% at T1, 24% at T2, and 15% at T3 (p < 0.05). In a multivariate analysis, compared with T1, the adjusted odds ratios for CAD and MI were 0.41 (95% confidence interval [CI]: 0.26-0.63) and 0.61 (95% CI: 0.38-0.99) for T3, respectively. Thus, the Japanese diet was found to be inversely associated with CAD in Japanese patients undergoing coronary angiography.

Severity of Liver Fibrosis Is Associated with the Japanese Diet Pattern and Skeletal Muscle Mass in Patients with Nonalcoholic Fatty Liver Disease

It is not fully clear as to which dietary patterns are associated with the pathogenesis of nonalcoholic fatty liver disease (NAFLD) in Asia. We conducted a cross-sectional study of 136 consecutively recruited patients with NAFLD (49% female, median age 60 years). Severity of liver fibrosis was assessed using the Agile 3+ score, a recently proposed system based on vibration-controlled transient elastography. Dietary status was assessed using the 12-component modified Japanese diet pattern index (mJDI12). Skeletal muscle mass was assessed by bioelectrical impedance. Factors associated with intermediate-high-risk Agile 3+ scores and skeletal muscle mass (75th percentile or higher) were analyzed by multivariable logistic regression. After adjustment for confounders, such as age and sex, the mJDI12 (OR: 0.77; 95% CI: 0.61, 0.99) and skeletal muscle mass (75th percentile or higher) (OR: 0.23; 95% CI: 0.07, 0.77) were significantly associated with intermediate-high-risk Agile 3+ scores. Soybeans and soybean foods were significantly associated with skeletal muscle mass (75th percentile or higher) (OR: 1.02; 95% CI: 1.00, 1.04). In conclusion, the Japanese diet pattern was associated with the severity of liver fibrosis in Japanese patients with NAFLD. Skeletal muscle mass was also associated with the severity of liver fibrosis, and intake of soybeans and soybean foods.

Twenty-year prospective cohort study of the association between a Japanese dietary pattern and incident dementia: the NILS-LSA project

PURPOSE

Evidence has suggested that adherence to a Japanese diet may be beneficial for health. However, its association with incident dementia remains unclear. The aim was to explore this association in older Japanese community-dwellers, taking apoprotein E genotype into consideration.

METHODS

A 20-year follow-up cohort study involving 1504 dementia-free older Japanese community-dwellers (aged 65-82 years) living in Aichi Prefecture, Japan, was conducted. Based on a previous study, a 9-component-weighted Japanese Diet Index (wJDI9) score (range - 1 to 12) was calculated using 3-day dietary record data and used as an indicator of adherence to a Japanese diet. Incident dementia was confirmed by the Long-term Care Insurance System certificate, and dementia events occurring within the first 5 years of follow-up were excluded. A multivariate-adjusted Cox proportional hazards model was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for incident dementia, and Laplace regression was used to estimate percentile differences (PDs) and 95% CIs (expressed in months) in age at incident dementia (i.e., dementia-free duration differences), according to tertiles (T1-T3) of wJDI9 scores.

RESULTS

The median (IQR) follow-up duration was 11.4 (7.8-15.1) years. During the follow-up period, 225 (15.0%) cases of incident dementia were identified. Because the smallest prevalence of incident dementia was 10.7% for the T3 group of wJDI9 scores, to avoid inaccurately estimating the dementia-free duration of participants in the T3 group, the 11th PDs in age at incident dementia between the T1 and T3 groups of wJDI9 scores were estimated. A higher wJDI9 score was associated with a lower risk of incident dementia and a longer dementia-free duration difference. The multivariate-adjusted HR (95% CI) and 11th PDs (95% CI) in age at incident dementia for participants in the T1 vs. T3 group were 1.00 (reference) vs. 0.58 (0.40, 0.86), and 0 (reference) vs. 36.7 (9.9, 63.4) months, respectively. Each 1-point increase of the wJDI9 score was associated with a 5% lower risk of incident dementia (P value = 0.033) and 3.9 (0.3, 7.6) additional months of dementia-free duration (P value = 0.035). No differences were seen in sex or smoking status (current smoker vs. non-current smoker) at baseline.

CONCLUSION

These findings suggest that adherence to a Japanese diet defined by wJDI9 is associated with a lower risk of incident dementia in older Japanese community-dwellers, suggesting the benefit of the Japanese diet for dementia prevention.

Favorable Dietary Patterns Associated with Lower Incidence of Metabolic Syndrome in Middle-Aged Japanese Men: A Prospective Cohort Study

Dietary patterns, such as selecting what food to regularly eat, may play role in reducing the incidence of metabolic syndrome (MetS). This study examined the causal relationships of Japanese dietary patterns and the relationship with the risk of MetS onset using a prospective cohort design. Data of annual health checks between 2008 and 2017 were analyzed, and middle-aged men and women (n=3,298 and 3,925, respectively) were followed up for 15,498 and 19,459 person-years, respectively. We investigated six dietary patterns using a questionnaire, and the participants were divided into low, middle, and high dietary score groups. During the follow-up period, cases of new-onset MetS were found in 698 men (21.2%) and 350 women (8.2%). Covariate-adjusted Cox proportional hazard models revealed that the risk of new-onset MetS was significantly lower in the male participants who responded that they "often eat vegetables" (HR: 0.77, 95% CI: 0.66-0.91). For dietary score, the male participants had significantly lower adjusted HRs of MetS onset in the middle-score group (HR: 0.80, 95% CI: 0.69-0.94) and high-score group (HR: 0.54, 95% CI: 0.41-0.72) compared to the low-score group. On the other hand, there was no association of each dietary pattern and dietary score with new-onset MetS among the female participants. This study found that favorable dietary patterns are associated with a lower risk of MetS; thus, education that aims to encourage a favorable diet may have an important role in reducing the incidence of MetS in middle-aged men.

Nutritional Adequacy Assessment of the Japanese Diet Using the Number of Dishes Compared to Existing Dietary Diversity Indices: A Cross-Sectional Analysis from the 2012 National Health and Nutrition Survey, Japan

The Japanese diet has attracted attention as a factor contributing to the Japanese population's longevity. A typical Japanese meal, traditionally called "ichiju-sansai," is composed of various dishes. This study assessed the nutritional adequacy of the Japanese diet using the number of dishes in all meals (NDAM) compared to existing dietary diversity indices (DDIs). This cross-sectional study used data from the 2012 National Health and Nutrition Survey. A total of 25,976 participants aged ≥20 y were included in this study. NDAM was calculated for whole dishes or single foods (except supplements and beverages) from one-day weighted dietary records. The food variety score (FVS), number of foods, dietary diversity score (DDS), and number of food groups are some of the existing DDIs. NDAM had relatively high positive correlation coefficients with potassium, magnesium, and dietary fiber. The partial correlation coefficients with an indicator of the overall nutrient adequacy of NDAM was 0.42 for men and 0.42 for women. It was almost the same as that of the FVS (men: 0.44, women: 0.42) and DDS (men: 0.44, women: 0.43). On the other hand, NDAM, similar to existing DDIs, was also positively correlated with nutrient restriction in both sexes. These findings indicate that the nutrient adequacy of NDAM is similar to that of the existing DDIs. Because of the higher sodium intake and cholesterol intake in higher NDAM and existing DDIs, the effect of higher NDAM on health outcomes must be investigated in future studies.

Association of eating habits and Firmicutes/Bacteroidetes ratio among Japanese female university students: A cross-sectional study

Background & Aims: University students are prone to changes in their health status and lifestyle due to changes in their living environment and associated stress and anxiety. These changes may affect them in later life. This study utilized a cross-sectional study among Japanese female university students to examine dietary factors affecting their fecal microbiota. Methods: Sixty-eight healthy female university students were evaluated using an eating behavior assessment and diet history questionnaire. The 12-component Japanese diet index (JDI-12) was then calculated. A quantitative real-time PCR method was used to analyze the predominant bacterial species in the gut, and the Firmicutes/Bacteroidetes ratio (F/B ratio) at the phylum level was calculated. The partial correlation between the fecal microbiota and eating behavior abnormality score was assessed, and dietary habits associated with the F/B ratio were analyzed. Results: A significant correlation was identified between F/B ratios and the eating behavior abnormality score (r = 0.26, FDR = 0.064). Additionally, multiple regression analysis identified a negative correlation trend between the F/B ratio and JDI-12 score (β = -0.22; p = 0.091), and exploratory analysis found a negative association between the F/B ratio and consumption of beef and pork, one of the less beneficial JDI-12 components (β = -0.33, FDR = 0.120). Conclusion: In healthy female university students, there was a positive correlation between eating behavior abnormality and the F/B ratio, indicating that adherence to the Japanese diet pattern may be associated with a lower F/B ratio.

Relationship of chronotype and social jetlag with adherence to the Japanese dietary guidelines among workers

While late chronotype and greater social jetlag have been associated with poor dietary behavior among the general population, these associations have not been investigated among workers, who struggle to align their sleep timings with work schedules. We aimed to explore the cross-sectional association of social jetlag and a late chronotype with adherence to a healthy diet among Japanese workers. Participants were 1,435 non-shift workers (18-78 years) who attended a nutritional survey. Social jetlag was defined as the difference in the midpoint of sleep times between weekdays and weekends, while chronotype was estimated using the mid-sleep time on weekends that was corrected with sleep debt on weekdays. We calculated the adherence score of the Japanese Food Guide Spinning Top (JFGST) - healthy diet guidelines for Japanese. Multivariable linear regression analyses were used to calculate the adjusted means and 95% confidence intervals (CI) for adherence scores of social jetlag and chronotype. We found that greater social jetlag was associated with a lower JFGST score. The multivariable-adjusted mean (95% CI) of JFGST scores were 39.7 (39.1-40.2), 38.7 (37.9-39.6), and 38.1 (36.6-39.7) for <1 hour, 1 to <2 hours, and ≥2 hours of social jetlag, respectively (P-trend = 0.02). Workers with late chronotypes had significantly lower adherence scores on JFGST [36.3 (34.7-37.8); P-trend = 0.002]. Results suggest that a late chronotype and social jetlag are inversely associated with adherence to a healthy diet among Japanese workers.

Rice-Based Diet and Cardiovascular Disease Mortality in Japan: From the Takayama Study

Rice is the staple food in Japan and many other Asian countries, but research on rice-based diets and cardiovascular disease is limited. We aimed to evaluate the association between rice consumption as grain dishes and cardiovascular disease mortality in comparison with bread and noodle consumption. The subjects were 13,355 men and 15,724 women aged ≥35 years who enrolled in the Takayama Study. Diet intake was assessed using a validated food-frequency questionnaire. Causes of death were identified from death certificates. Cardiovascular disease was defined according to the International Classification of Diseases and Health Related Problems, 10th Revision (code I00–I99). Hazard ratios in the second, third, and highest quartiles versus the lowest quartile of rice intake for cardiovascular disease mortality were 0.98, 0.80, and 0.78 for men, respectively (trend p = 0.013), but no significant association was observed among women. Rice intake was positively correlated with the intake of soy products and seaweed, and negatively correlated with the intake of meat and eggs. Neither bread nor noodles were associated with cardiovascular disease mortality. In Japan, choosing rice as a grain dish is likely to be accompanied by healthier foods as side dishes, which may have a potential role in the prevention of cardiovascular disease.

Japanese-Style Diet and Cardiovascular Disease Mortality: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

This systematic review and meta-analysis elucidate the effects of the Japanese-style diet and characteristic Japanese foods on the mortality risk of cardiovascular disease (CVD), cerebrovascular disease (stroke), and heart disease (HD). This review article followed the PRISMA guidelines. A systematic search in PubMed, The Cochrane Library, JDreamIII, and ICHUSHI Web identified prospective cohort studies on Japanese people published till July 2020. The meta-analysis used a random-effects model, and heterogeneity and publication bias were evaluated with I² statistic and Egger’s test, respectively. Based on inclusion criteria, we extracted 58 articles, including 9 on the Japanese-style diet (n = 469,190) and 49 (n = 2,668,238) on characteristic Japanese foods. With higher adherence to the Japanese-style diet, the pooled risk ratios (RRs) for CVD, stroke, heart disease/ischemic heart disease combined (HD/IHD) mortality were 0.83 (95% CI, 0.77–0.89, I² = 58%, Egger’s test: p = 0.625, n = 9 studies), 0.80 (95% CI, 0.69–0.93, I² = 66%, Egger’s test: p = 0.602, n = 6 studies), and 0.81 (95% CI, 0.75–0.88, I² = 0%, Egger’s test: p = 0.544, n = 6 studies), respectively. Increased consumption of vegetables, fruits, fish, green tea, and milk and dairy products decreased the RR for CVD, stroke, or HD mortality. Increased salt consumption elevated the RR for CVD and stroke mortality. Increased consumption of dietary fiber and plant-derived protein decreased the RR for CVD, stroke, and HD/IHD mortality. The Japanese-style diet and characteristic Japanese foods may reduce CVD mortality. Most studies conducted diet surveys between 1980 and the 1990s. This meta-analysis used articles that evaluated the same cohort study by a different method. A new large-scale cohort study matching the current Japanese dietary habits is needed to confirm these findings.

Salt intake per dish in the Japanese diet: a clue to help establish dietary goals at home

The salt intake of Japanese at home remains high. To aid in salt reduction and encourage a balanced diet, we conducted a cross-sectional study using data from a previous clinical trial in community-dwelling individuals to evaluate major salt sources and relationships among the intake of different dishes in the Japanese diet at home. Dietary records and urinary salt excretion measurements were performed daily for 1 month in seventy-nine participants. The records were classified into six grain dish categories as staple dishes, seven side dish categories and a snack category. Regression analyses were used to estimate (1) salt intake per meal for each category of grain dish, (2) salt intake per dish from each dish category and its contribution to the total salt intake and (3) the influence of grain dish selection on the frequencies of other dishes. Salt intake per meal was approximately 3 g, regardless of grain dish selection. Fish and meat dishes showed the largest contribution to the total salt intake (35 %), followed by vegetable dishes (19 %). The intake of fish or meat and vegetables was promoted by plain rice and reduced by ramen noodles. The intake of dairy products was only promoted by bread, while that of fruits was not influenced by any grain dish category. These results suggest simple strategies to reduce salt intake while maintaining dietary balance, such as eating plain rice more often and using less salt to cook meat/fish and vegetable dishes.

Changes in the association between the traditional Japanese diet score and suicide rates over 26 years: A global comparative study

BACKGROUND

This study examined the global association between the Traditional Japanese Diet Score and suicide rate.

METHODS

Average food supply and energy supply by country were obtained from the Food and Agriculture Organization of the United Nations Statistics Division database (FAOSTAT). Traditional Japanese Diet Score (TJDS) was calculated from food group classifications. Age-standardized suicide rates per 100,000 people by country were obtained from the Global Burden of Disease 2017 database. The 26-year associations between TJDS and suicide rates were examined controlling for covariates using a mixed-effects model in 138 countries with populations of 1 million or greater.

RESULTS

A significant negative association was found in the analysis of the relationship between TJDS and the prevalence of suicide [β (se) = -0.126 (0.031), p < 0.001]. The interaction term between TJDS and year was also significant [β (se) = -0.011 (0.003), p < 0.001]. The change in the effect of TJDS on suicide rates by year was examined. The effect of TJDS was not significant from 1991 to 1999 but became significant after 2000; the slope of the TJDS to suicide rate in 2017 was -0.270 (95% confidence interval -0.382, -0.169, p < 0.001).

LIMITATIONS

This was a national ecological study and did not consider individual differences in sex, age, and lifestyle.

CONCLUSIONS

TJDS may be is a protective factor for depression, which may prevent suicide. The association between TJDS and suicide rates became stronger over time and was inversely associated with suicide rates after 2000.

Relationship between the Japanese-style diet, gut microbiota, and dementia: A cross-sectional study

OBJECTIVE

Previous studies have shown associations between the gut microbiota, microbial metabolites, and cognitive decline. However, the effect of the dietary composition on such associations has not been fully investigated. The aims of this study were to evaluate the relationships between adherence to a Japanese-style diet, the gut microbiota, and cognitive decline. Furthermore, we aimed to evaluate the three forms of the Japanese diet index (JDI; the conventional [JDI₉], updated [JDI₁₂], and a newly modified JDI) to determine which would show the closest relationships with cognition and the gut microbiota.

METHODS

We performed a cross-sectional subanalysis of data from a prospective hospital-based cohort study. We assessed the patients' demographic characteristics, dietary composition, risk factors, cognitive function, brain imaging, gut microbiome, and microbial metabolites. On the basis of previous studies, a nine-component traditional JDI (JDI₉), a 12-component modern JDI (JDI₁₂), and a 12-component revised JDI (rJDI₁₂), were defined. We evaluated the relationships between the JDI scores, cognitive function, and the gut microbiome and microbial metabolites using multivariable logistic regression analyses.

RESULTS

We analyzed data from 85 eligible participants (61% women; mean age: 74.6 ± 7.4 y). Compared with participants who had dementia, those without dementia were more likely to consume foods in the JDI₁₂, including fish and shellfish (64.5 versus 39.1%, P = 0.048), mushrooms (61.3 versus 30.4%, P = 0.015), soybeans and soybean-derived foods (62.9 versus 30.4%, P = 0.013), and coffee (71 versus 43.5%, P = 0.024). There were non-significant trends toward lower fecal concentrations of gut microbial metabolites in participants with a more traditional Japanese diet. Participants with dementia had lower JDI scores than those without dementia (dementia versus non-dementia, median JDI₉ score: 5 versus 7, P = 0.049; JDI₁₂: 7 versus 8, P = 0.017; and rJDI₁₂: 7 versus 9, P = 0.006, respectively).

CONCLUSIONS

Adherence to a traditional Japanese diet was found to be inversely associated with cognitive decline and tended to be associated with lower concentrations of gut microbial metabolites.

Dietary fatty acids and CHD: from specific recommendations to dietary patterns

Several countries have issued dietary recommendations about total and specific fatty acid (FA) intake for the prevention of CHD. For many years until today, controversies have existed especially about the deleterious effect or not of SFA, and the protective effect or not of n-3 PUFA, so that some authors have criticised these recommendations. There are many reasons for these controversies, including the different conclusions of prospective cohort studies compared with randomised clinical trials (RCT), and the contradictory conclusions of meta-analyses depending on the quality, number and type of studies included. The interrelationships between different FA in the diet make it difficult to analyse the specific effect of a particular class of FA on CHD. Furthermore, based on clinical practice and effectiveness of population-based prevention, it is very difficult at the individual level to assess in personal dietary intake the actual percentage and/or amount of SFA contained in each meal or consumed daily/weekly. In this critical narrative review, we try to answer the question of whether it would not be more relevant, in 2020, to promote dietary patterns, rather than FA intake recommendations. We critically analyse past and recent data on the association of FA with CHD, then propose that the Mediterranean diet and Japanese diet should be revitalised for Westerners and Asian populations, respectively. This does not exclude the usefulness of continuing research about effects of FA towards CHD, and accepting that what seems true today might be revised, at least partially tomorrow.

Changes in a specific dietary pattern and incident dementia: A prospective cohort study

BACKGROUND & AIMS

Previous studies have reported that the Japanese diet is associated with a lower risk of dementia; however, whether changes in adherence to the Japanese diet affects incident dementia remains unknown. We aimed to evaluate the association between long-term changes in adherence to the Japanese diet and risk of incident dementia among older Japanese individuals.

METHODS

We collected dietary information from community-dwelling older individuals living in Ohsaki city, Japan using a validated 39-item food frequency questionnaire in 1994 and 2006. Adherence to the Japanese diet was assessed using the 8-item Japanese Diet Index (JDI8) score (range: 0 to 8 points). Changes in adherence to the Japanese diet were defined as changes in the JDI8 score from 1994 to 2006. Next, the participants were classified into five groups: great decrease, moderate decrease, no changes [ref.], moderate increase, or great increase. Then, 3146 Japanese adults aged ≥65 years in 2006 were followed-up for 5.7 years. Incident dementia was retrieved from the long-term care insurance database. The Cox proportional hazards model was used to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for incident dementia.

RESULTS

During 14,336 person-years of follow up, 231 cases of dementia were ascertained. Compared with no changes in the JDI8 score, the multivariable-adjusted HRs (95%CIs) were 1.72 (1.13, 2.62) for great decrease, 1.10 (0.73, 1.66) for moderate decrease, 0.82 (0.54, 1.25) for moderate increase, and 0.62 (0.38, 1.02) for great increase (p-trend <0.0001).

CONCLUSIONS

An increase in adherence to the Japanese diet was associated with a reduced risk of incident dementia, whereas a decrease in adherence was associated with an elevated risk among older Japanese individuals.

What is the scientific definition of the Japanese diet from the viewpoint of nutrition and health?

The Japanese people have enjoyed longevity for several decades, and Japanese dietary habits are considered to contribute to this longevity. The scientific definition of the Japanese diet, however, is not yet fully established. The Working Group 1 of the Healthy Diet Research Committee of the International Life Sciences Institute Japan reviewed the literature to collect definitions of the Japanese diet appearing in articles in the fields of diet, nutrition, foods, and human health. This report addresses the definitions and the questions raised by these definitions. Among 283 relevant articles identified, 116 were carefully screened and included in the analysis. In most of the articles, the authors self-defined the Japanese diet; some studies used a government-proposed definition. This review revealed no systematic approach to define the Japanese diet from the viewpoints of nutrition and health. Before conducting studies to determine whether the Japanese diet is healthy, it is important to address the question of what the Japanese diet is from the viewpoint of human nutrition rather than culinary culture.

Association between adherence to the Japanese diet and all-cause and cause-specific mortality: the Japan Public Health Center-based Prospective Study

Purpose

The present study aimed to examine the association between adherence to the Japanese diet and the subsequent risk of all-cause and cause-specific mortality using a large-scale cohort from settings all over Japan.

Methods

We analyzed data from a cohort study of 92,969 Japanese adults aged 45–74 years, covering 11 public health center areas nationwide. We collected dietary information using a validated 147-item food frequency questionnaire. Adherence to the Japanese diet consisting of eight components (high intake of rice, miso soup, seaweeds, pickles, green and yellow vegetables, fish, and green tea; low intake of beef and pork) was assessed using 8-item Japanese Diet Index (JDI8) score, with scores ranging from 0 to 8. The Cox proportional hazards model was used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for all-cause and cause-specific mortality.

Results

During a median follow-up of 18.9 years, we documented 20,596 deaths. A higher JDI8 score was significantly associated with a lower risk for all-cause and cardiovascular disease (CVD) mortality. The multivariable-adjusted HR of all-cause and CVD mortality for the highest JDI8 score group (score of 6–8) versus the lowest JDI8 score group (score of 0–2) were 0.86 (95% CI 0.81–0.90, P trend < 0.001), and 0.89 (95% CI 0.80–0.99, P trend = 0.007), respectively.

Conclusions

Adhering to the Japanese diet, as assessed by the JDI8, was associated with a decreased risk of all-cause and CVD mortality among adults living in multiple areas across Japan.

Electronic supplementary material

The online version of this article (10.1007/s00394-020-02330-0) contains supplementary material, which is available to authorized users.

The 1975 type Japanese diet improves the gut microbial flora and inhibits visceral fat accumulation in mice

In this study, the 1975 type Japanese diet was prepared and its effects and related mechanism were examined in mice. Mice were assigned to three experimental groups, the CD group fed a control diet, the MD group fed a modern Japanese diet (MD), and the JD group fed the 1975 type Japanese diet (JD) for 4 weeks. MD and JD were low protein, high fat, and high carbohydrate diets compared to the CD. Total white adipose tissue weights were significantly increased in the MD group compared to those in the CD group and were decreased in the JD group compared to those in the MD group. In the JD group, adipocyte hypertrophy was inhibited and Hsl mRNA expression was enhanced in epididymal adipose tissue and the number of bacteria associated with the production of short chain fatty acids was increased. Therefore, the JD inhibits lipid accumulation in white adipose tissue.

ABBREVIATIONS

Actb: β-actin; ALT: alanine aminotransferase; ANOVA: analyses of variance; AST: aspartate aminotransferase; Fas: fatty acid synthase; G6pdx: glucose 6-phosphate dehydrogenase; HE: hematoxylin and eosin; HOMA-IR: Homeostatic model assessment for insulin resistance; Hsl: hormone-sensitive lipase; JD: 1975 type Japanese diet; Leptin: leptin; MD: modern Japanese diet; Me: malic enzyme; NEFA: non-esterified fatty acids; PL: phospholipids; Pparδ: peroxisome proliferator-activated receptor delta; Pparγ: peroxisome proliferator-activated receptor gamma; qRT-PCR: quantitative reverse transcriptase polymerase chain reaction; SAMP8: senescence-accelerated prone 8; SEM: standard error of the mean; Srebp1c: Sterol regulatory element binding protein 1c; TBARS: thiobarbituric acid reactive substance; TC: total cholesterol; TG: Triacylglycerol; V3: variable regions 3.

Proposal for an Empirical Japanese Diet Score and the Japanese Diet Pyramid

A traditional Japanese diet (JD) has been widely regarded as healthy, contributing to longevity. The modern Japanese lifestyle has become markedly westernized, and it is speculated that the number of people who eat JD is decreasing. A simple evaluation of people with low adherence to JD will help improve dietary life. We developed a simple assessment tool that can capture JD, and examined factors associated with low adherence to JD. A total of 1458 subjects aged 18 to 84 years completed a brief self-administered diet history questionnaire. We constructed an empirical Japanese diet score (eJDS) consisting of 12 items from the common characteristics of a JD. In our participants, 47.7% of subjects reported low adherence to JD and only 11.1% demonstrated high adherence. In multivariate logistic regression analysis, younger age persons, physically inactive persons, and heavy drinkers were associated with low adherence to JD. Based on the cutoff values of eJDS, we proposed to create a Japanese diet pyramid that is easy to use visually. In conclusion, the eJDS and the Japanese diet pyramid will be useful tools for nutrition education and dietary guidance.

Association between improved adherence to the Japanese diet and incident functional disability in older people: The Ohsaki Cohort 2006 Study

BACKGROUND & AIMS

Although it has been reported that the Japanese dietary pattern is associated with a lower risk of incident functional disability among older people, the potential benefits of improving adherence to the Japanese diet remain unclear. The aim of the present study was to evaluate the association between 12-year change in adherence to the Japanese diet and the subsequent risk of incident functional disability in older people in Japan.

METHODS

We analyzed 10-year follow-up data from a cohort study of 2923 Japanese older adults (age ≥65 years) in 2006. We collected dietary information using a validated 39-item food frequency questionnaire at two time points (1994 and 2006). Adherence to the Japanese diet (high intake of rice, miso soup, seaweeds, pickles, green and yellow vegetables, fish, green tea; low intake of beef and pork, and coffee) was assessed using the Japanese Diet Index (JDI), which ranges from 0 to 9. Participants were categorized into five groups according to changes in the JDI score at these two time points. Data on incident functional disability from December 2006 to November 2016 were retrieved from the public long-term care insurance database. The Cox proportional hazards model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for incident functional disability.

RESULTS

During 22,466 person-years of follow-up, 1093 cases of incident functional disability were documented. Compared with participants in the group with the largest decrease in the JDI score (≤-2), the multivariate-adjusted HR (95% CI) of incident functional disability was 0.77 (0.61-0.98) for those in the largest increase group (≥+2).

CONCLUSIONS

Improved adherence to the Japanese diet was associated with a significantly lower risk of incident functional disability in older people in Japan.

Ramen restaurant prevalence is associated with stroke mortality in Japan: an ecological study

Background

The association between stroke and nutrition has recently been investigated. However, the association between diet and stroke in Japan has not been clarified. We hypothesized that there may be an association between consumption of ramen and stroke mortality. Therefore, we investigated the association between the prevalence of ramen restaurants and stroke mortality in Japanese prefectures.

Methods

We used Pearson’s correlation coefficients to evaluate associations between the prevalence of each of four restaurant types (ramen, fast food, French or Italian, and udon or soba) and age- and sex-adjusted stroke mortality rates in each prefecture. We also investigated correlations between acute myocardial infarction and the prevalence of each type of restaurant as a control. We obtained age- and sex-adjusted stroke mortality rates and the acute myocardial infarction mortality rate in each prefecture from the 2017 Trends in National Health published in Japan. Data on the number of restaurants of each type in each prefecture were obtained from the database of the Nippon Telegraph and Telephone Corporation.

Results

The prevalence of ramen restaurants, but not of other restaurant types, positively correlated with stroke mortality in both men and women (r > 0.5). We found no correlation between ramen restaurant prevalence and mortality from acute myocardial infarction.

Conclusion

The prevalence of ramen restaurants in Japanese prefectures has a significant correlation with the stroke mortality rate.

Electronic supplementary material

The online version of this article (10.1186/s12937-019-0482-y) contains supplementary material, which is available to authorized users.

A cross-sectional study of the associations between the traditional Japanese diet and nutrient intakes: the NILS-LSA project

Background

Although our previous study using a food frequency questionnaire simulated nutritional characteristics of the traditional Japanese diet, this issue has not been sufficiently evaluated. This study was conducted to examine the relationship between the traditional Japanese diet and nutrient density (ND).

Methods

A cross-sectional study employing the dietary record method was conducted among 2221 community-dwelling Japanese adults (40–88 years) living in Aichi Prefecture, Japan, in 2006–2008. Based on previous studies, a 9-component Japanese Diet Index (JDI) and a 12-component modified JDI (mJDI₁₂) were defined. To develop a new weighted index, a multiple linear regression model was used to select food components which were significantly associated with an ND score (integrated by 11 nutrient components) from the mJDI₁₂ and weight them. Correlation analyses were performed between JDI, mJDI₁₂, the new weighted JDI score and the ND score and its 11 nutrient components. The findings were validated with data from 2008 to 2010 by assessing the associations between the JDIs scores and the ND score.

Results

Scores of the JDI and mJDI₁₂ were positively correlated with the ND score (corresponding Spearman’s ρ [95% confidence interval; CI], 0.34 [0.31, 0.38] and 0.44 [0.41, 0.48], respectively; P < 0.05 for both). Among the mJDI₁₂, 9 food components (rice, fish and shellfish, green and yellow vegetables, seaweed, green tea, beef and pork, soybeans and soybean foods, fruit, and mushrooms) significantly associated with the ND score. All of these 9 components were weighted and a new weighted JDI (wJDI₉) was developed. The wJDI₉ score was also positively correlated with the ND score (Spearman’s ρ [95% CI] = 0.61 [0.58, 0.64]; P < 0.05). However, scores for all 3 indices were positively correlated with sodium intake. The wJDI₉ score obtained using dietary record data from 2008 to 2010 was also positively correlated with the ND score (Spearman’s ρ [95% CI] = 0.61 [0.58, 0.64]; P < 0.05).

Conclusions-

Adhering to a traditional Japanese diet as defined by the JDI was associated with good ND. Furthermore, the modified indices (mJDI₁₂ and wJDI₉) had a higher performance for ND. However, all of the indices were correlated with high sodium intake.

Electronic supplementary material

The online version of this article (10.1186/s12937-019-0468-9) contains supplementary material, which is available to authorized users.

Japanese diet and survival time: The Ohsaki Cohort 1994 study

BACKGROUND & AIMS

Although it has been suggested that the Japanese diet contributes to the longevity of the Japanese population, no study has examined the association between the Japanese diet and survival time. The present study investigated the association between the Japanese diet and survival time.

METHODS

We analyzed 20-year follow-up data from a cohort study of 14,764 Japanese men and women aged 40-79 years. At the baseline survey in 1994, we collected dietary information using a validated 40-item food frequency questionnaire. Adherence to a Japanese diet consisting of nine components (rice, miso soup, seaweeds, pickles, green and yellow vegetables, fish, green tea, beef and pork, and coffee) was assessed in terms of a Japanese dietary index (JDI) score, the total score ranging from 0 to 9. Cox proportional hazards model and Laplace regression analysis were used to estimate the hazard ratios (HRs) and differences in median age at death (50th percentile differences - PDs in age at death) with 95% confidence intervals (CIs) according to the quartiles of the JDI score.

RESULTS

During the follow-up period, we documented 4,619 deaths. We observed that a higher JDI score was associated with a lower risk of mortality and longer survival time: In comparison to participants in the lowest JDI score quartile (0-4), the multivariate-adjusted HR (95% CI) of all-cause mortality was 0.91 (0.83-0.99) and the multivariate-adjusted 50th PD in age at death (95% CI) was 10.2 (3.2-17.2) months longer for those in the highest quartile (7-9).

CONCLUSIONS

Adherence to a Japanese diet is associated with a longer survival time.

Dietary Inflammatory Index Positively Associated With High-Sensitivity C-Reactive Protein Level in Japanese From NIPPON DATA2010

Background

It has been reported that chronic inflammation may play an important role in the pathogenesis of several serious diseases and could be modulated by diet. Recently, the Dietary Inflammatory Index (DII^®) was developed to assess the inflammatory potential of the overall diet. The DII has been reported as relevant to various diseases but has not been validated in Japanese. Thus, in the present study, we analyzed the relationship between DII scores and high-sensitivity C-reactive protein (hs-CRP) levels in a Japanese population.

Methods

Data of the National Integrated Project for Prospective Observation of Non-communicable Disease and its Trends in the Aged 2010 (NIPPON DATA2010), which contained 2,898 participants aged 20 years or older from the National Health and Nutrition Survey of Japan (NHNS2010), were analyzed. Nutrient intakes derived from 1-day semi-weighing dietary records were used to calculate DII scores. Energy was adjusted using the residual method. Levels of hs-CRP were evaluated using nephelometric immunoassay. Multiple linear regression analyses were performed.

Results

After adjusting for age, sex, smoking status, BMI, and physical activity, a significant association was observed between DII scores and log(CRP+1) (standard regression coefficient = 0.05, P < 0.01). Although it was not statistically significant, the positive association was consistently observed in almost all age-sex subgroups and the non-smoker subgroup.

Conclusions

The current study confirmed that DII score was positively associated with hs-CRP in Japanese.

Reduction in Gastroesophageal Reflux Disease Symptoms Is Associated with Miso Soup Intake in a Population-Based Cross-Sectional Study: The Nagahama Study

Dietary habits and lifestyles are considered to affect the frequency of epigastric symptoms. In our previous study, we found that three amino acids in Japanese broth promoted gastric emptying. We hypothesized that a higher consumption of miso soup which was mainly composed of Japanese broth and miso paste would be associated with a lower frequency of epigastric symptoms. We conducted a cross-sectional study of the association between frequency of miso soup intake and reflux or dyspepsia symptoms in a general Japanese population. Sixteen items of dietary habits were assessed using a self-reported questionnaire, and epigastric symptoms were evaluated using the Frequency Scale for Symptoms of Gastroesophageal Reflux Disease (FSSG). We fitted generalized linear models to analyze the association between miso soup intake and FSSG, reflux, or dyspepsia scores adjusted by age, sex, body mass index (BMI), another 15 dietary habits, smoking, drinking alcohol, and unfavorable dietary behaviors. A total of 9,364 subjects were included in the analysis. Trend analysis revealed that higher frequency of miso soup intake was associated with lower FSSG scores (p<0.001). In a generalized linear model, daily intake of miso soup was associated with lower FSSG, reflux, and dyspepsia scores independent of age, sex, BMI, other 15 dietary habits, smoking, drinking alcohol, and unfavorable dietary behaviors (estimate=-0.46, -0.22, and -0.27, respectively; 95% CI=-0.83, -0.12; -0.38, -0.07; and -0.47, and -0.08, respectively). Dairy intake of miso soup was associated with lower epigastric symptoms.

Frequency of Balanced-Meal Consumption and Frailty in Community-Dwelling Older Japanese: A Cross-Sectional Study

BACKGROUND

Although meals that combine a staple food, main dish, and side dish (balanced meals) are recommended in Japan, the health effects of such meals are unclear. We investigated the association of frequency of eating balanced meals with frailty among community-dwelling older Japanese.

METHODS

We analyzed data from 912 persons aged 65 years or older who participated in the Hatoyama Cohort Study or Kusatsu Longitudinal Study. The frequency of eating two or more balanced meals daily was self-reported as ≤1 day/week, 2 or 3 days/week, 4 or 5 days/week, and daily. Frailty was defined as the presence of at least three, and pre-frailty as the presence of one or two, of the following criteria: weight loss, muscle weakness, exhaustion, slowness, and low physical activity. Adjusted logistic regression was used to study associations of frequency of balanced-meal consumption with frailty (prefrailty and frailty combined) and frailty criteria.

RESULTS

Participants reporting a frequency of balanced-meal consumption of ≤2 or 3 days/week had a higher prevalence of frailty (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.21-2.64) than did those reporting a frequency of daily. Lower frequency of balanced-meal consumption was also associated with higher prevalences of weight loss (OR, 4.10; 95% CI, 1.90-8.85), exhaustion (OR, 6.35; 95% CI, 2.49-16.17), and low physical activity (OR, 1.92; 95% CI, 1.22-3.01).

CONCLUSIONS

Our findings suggest that more frequent twice daily consumption of meals with a staple food, main dish, and side dish decreases the risks of prefrailty and frailty.

Effects of the 1975 Japanese diet on the gut microbiota in younger adults

Japan is known for its longevity worldwide; the Japanese diet is thought to contribute to this longevity. However, the Japanese diet has become westernized over the past years, with a parallel increase in the incidence of lifestyle diseases. Thus, whether the modern Japanese diet is still healthy requires investigation. A diet with characteristics of the 1975 Japanese diet (JD) was previously shown to have beneficial effects on mice and humans. In this study, we examined whether intestinal bacteria are involved in the health benefits of this diet by analyzing changes in the composition of the fecal microbiota between humans who ingested the JD and those consuming a modern Japanese diet (MD). We also examined correlations between intestinal bacteria and biological parameters. A randomized controlled trial was performed to determine the effects of the 1975 JD compared to those of the MD. Subjects aged 20-29 years were randomly assigned to the JD (n=11) and MD (n=10) groups. Each subject consumed their respective diet three times per day for 28 days, and changes in intestinal bacteria before to after this period were evaluated. Four genera (unclassified Lachnospiraceae, Parabacteroides, Sutterella and unclassified Rikenellaceae) were significantly changed upon intake of the JD. Based on correlation analysis, relationships were found between changes in these genera and decreases in fat%; fat mass; and levels of blood glutamic oxaloacetic transaminase, blood triacylglycerols and hemoglobin A1c. These results suggest that changes in intestinal bacteria are involved in the health benefits of the JD.

Characteristics of the Japanese Diet Described in Epidemiologic Publications: A Qualitative Systematic Review

CONTEXT

International interest in the Japanese diet has grown in recent years.

OBJECTIVE

The aim of this systematic review was to evaluate and organize the Japanese diet and dietary characteristics from an epidemiological perspective, mainly focusing on the nutritional and dietary elements.

DATA SOURCES

PubMed, Web of Science, Japan Medical Abstracts Society, JDream III, and CiNii databases were searched.

STUDY SELECTION

The eligibility criteria included research with an epidemiological study design that was either cross-sectional, cohort, or case-control-based that defined the dietary patterns of the Japanese diet using dietary pattern analysis. A total of 39 research articles that described the Japanese diet were included.

DATA EXTRACTION

The data that were extracted included the following: implementing country, location, study design, participant characteristics, key outcomes, methods used in the analysis of dietary patterns, and descriptions of the Japanese diet.

DATA SYNTHESIS

As a result of the systematic review analyzing the descriptions of the Japanese diet from 39 selected articles, we were able to aggregate the descriptions into 16 categories from 33 factors. After performing a content analysis using a further aggregation of categories, we found that the top three applicable categories were soybeans/soybean-derived products, seafood, and vegetables; these were followed by rice and miso soup.

CONCLUSION

The Japanese dietary content was found to be diverse based on an examination of epidemiological studies; however, we were able to aggregate the content into 16 categories. The Japanese diet is considered to be a dietary pattern that contains a combination of factors: the dietary staple, side dishes, and soup.

The Effect of White Rice and White Bread as Staple Foods on Gut Microbiota and Host Metabolism

The purpose of this study was to examine the influence of two kinds of major Japanese staple foods, white rice and white bread, on gut microbiota against the background in which participants eat common side dishes. Seven healthy subjects completed the dietary intervention with two 1-week test periods with a 1-week wash-out period in cross-over design (UMIN registration UMIN000023142). White bread or white rice and 21 frozen prepared side dishes were consumed during the test periods. At baseline and at the end of each period, fasting blood samples, breath samples, and fecal samples were collected. For fecal samples, 16S rRNA gene sequencing was used to analyze the gut microbiota. After the bread period, the abundance of fecal Bifidobacterium genus (19.2 ± 14.5 vs. 6.2 ± 6.6 (%), p = 0.03), fasting glucagon-like peptide 1 (GLP-1) (13.6 ± 2.0 vs. 10.5 ± 2.9 (pg/mL), p = 0.03), and breath hydrogen (23.4 ± 9.9 vs. 8.2 ± 5.5 (ppm), p = 0.02) were significantly higher than those of after the rice period. Plasma SCFAs also tended to be higher after the bread period. White bread contains more dietary fiber than refined short grain rice. These findings suggest that indigestible carbohydrate intake from short grain rice as a staple food may be smaller than that of white bread.

Effects of three major amino acids found in Japanese broth on glucose metabolism and gastric emptying

OBJECTIVES

To our knowledge, the effect of the broth of dried kelp and dried bonito, dashi, on glucose metabolism and digestion has rarely been studied. Based on the component analysis of three actual broths served in traditional restaurants, a chemically synthesized broth with three free amino acids (histidine, glutamate, aspartate) and salt was prepared to investigate their effect on glucose metabolism, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide 1 (GLP-1) secretion, and digestion.

METHODS

In study 1, seven healthy individuals were enrolled in a four-period crossover study. Participants drank or ate hot water, synthesized broth, hot water with rice, and synthesized broth with rice. Plasma glucose, serum insulin, plasma glucagon, plasma GIP, and plasma GLP-1 were measured at baseline and after ingestion. In study 2, 6 of the 7 individuals ingested rice steamed with 13C-labeled sodium acetate with hot water or synthesized broth to estimate gastric emptying by the 13C-labeled acetate breath test in a two-period crossover trial.

RESULTS

Ingesting water or synthesized broth alone elicited no change in plasma glucose or serum insulin levels. Ingesting synthesized broth with rice resulted in a rapid rise in plasma glucose and GLP-1 (P = 0.01 and 0.02, respectively) in an early postprandial phase compared with that by ingesting water with rice, but the area under the curve of those showed no significant differences. Ingesting synthesized broth with rice resulted in a significantly higher gastric emptying coefficient than that after rice with water (P = 0.03).

CONCLUSIONS

Three amino acids and sodium chloride corresponding to those found in actual broth promoted gastric emptying and led to a rapid response of plasma glucose. Our findings suggest that ingestion of the broth of dried kelp and dried bonito may improve gastric motility.

Dietary Patterns and Cardiovascular Disease Risk in People with Type 2 Diabetes

PURPOSE OF REVIEW

The primary objective of this review is to identify dietary patterns with beneficial effects on cardiovascular health of adults with type 2 diabetes.

RECENT FINDINGS

The prevalence of diabetes is increasing globally. People with diabetes have a greater risk for cardiovascular disease. Mediterranean diet, dietary approaches to stop hypertension diet, vegetarian diet, traditional Korean diet, Japanese diet, and low-glycemic-index diet can reduce cardiovascular disease risk in people with diabetes. Dietary intake is a key modifiable factor in the management of diabetes and plays a significant role in limiting the incidence of cardiovascular diseases.

Standardisation of the Japanese diet for use in animal experiments

The aim of this study was to develop a purified diet that mimics the characteristics of the Japanese diet using readily available materials with a simpler composition and a focus on quality, with the goal of facilitating performance of studies on the Japanese diet worldwide. The utility of the new diet was examined as a mimic of the standard Japanese diet for use in animal experiments. We examined whether a key characteristic of the Japanese diet of being less likely to cause obesity could be reproduced. The mimic diet had a balance of protein, fat and carbohydrate based on the 1975 Japanese diet, which is the least likely to cause obesity, and materials chosen with reference to the National Health and Nutrition Survey (NHNS). To examine similarities of the mimic diet with the model 1975 Japanese diet, we created a menu of the 1975 diet based on the NHNS and prepared the freeze-dried and powdered diet. The mimic diet, the 1975 Japanese diet, a control AIN-93G diet and a Western diet were fed to mice for 4 weeks. As a result, the mimic diet and the 1975 diet resulted in less accumulation of visceral fat and liver fat. Mice given these two diets showed similar effects. This indicates that the mimic diet used in this study has characteristics of the 1975 Japanese diet and could be used as a standard Japanese diet in animal experiments.

Identification of Characteristic Components and Foodstuffs in Healthy Japanese Diet and the Health Effects of a Diet with Increased Use Frequency of these Foodstuffs

SCOPE

Our recent study showed that the 1975 Japanese diet exhibited strong health benefits. In the current study, we aimed to develop a diet with even higher health benefits.

METHODS

First, to determine the characteristic components in the 1975 diet, we used mass spectrometry for analysis of Japanese diets from several years and performed principal component analysis. Next, a diet with an increased use frequency of foodstuffs contained characteristic components (the modified diet) was prepared and fed to mice.

RESULTS

Performed principal component analysis revealed that the 1975 diet contained 14 characteristic components that were found in fish, fruits, vegetables, seaweed, soybean foods, soup stock "dashi", and fermented seasoning. Based on these, the modified diet was prepared and fed to mice. The liver total cholesterol and serum LDL cholesterol decreased significantly in mice fed the modified diet and serum total cholesterol showed a downward trend, compared to mice fed the 1975 diet. There was no difference between the modified diet and the control groups. In addition, serum adiponectin level increased in mice fed the modified diet and serum TBARS and IL-6 levels decreased.

CONCLUSION

By modifying the 1975 diet, it was possible to make a diet with more benefit.

Fat Content Modulates Rapid Detection of Food: A Visual Search Study Using Fast Food and Japanese Diet

Rapid detection of food is crucial for the survival of organisms. However, previous visual search studies have reported discrepant results regarding the detection speeds for food vs. non-food items; some experiments showed faster detection of food than non-food, whereas others reported null findings concerning any speed advantage for the detection of food vs. non-food. Moreover, although some previous studies showed that fat content can affect visual attention for food, the effect of fat content on the detection of food remains unclear. To investigate these issues, we measured reaction times (RTs) during a visual search task in which participants with normal weight detected high-fat food (i.e., fast food), low-fat food (i.e., Japanese diet), and non-food (i.e., kitchen utensils) targets within crowds of non-food distractors (i.e., cars). Results showed that RTs for food targets were shorter than those for non-food targets. Moreover, the RTs for high-fat food were shorter than those for low-fat food. These results suggest that food is more rapidly detected than non-food within the environment and that a higher fat content in food facilitates rapid detection.

Dietary Patterns and Incident Dementia in Elderly Japanese: The Ohsaki Cohort 2006 Study

BACKGROUND

Although it has been speculated that the Japanese dietary pattern has a preventive effect against incident dementia, no reported study has yet investigated this issue. The present prospective cohort study investigated the association between dietary patterns and incident dementia in elderly Japanese subjects.

METHODS

We analyzed follow-up data covering a 5.7-year period for 14,402 older adults (≥65 years) participating in a community-based, prospective cohort study. Three dietary patterns (Japanese pattern, animal food pattern, and high-dairy pattern) were derived using principal component analysis of the consumption of 39 food and beverage items assessed using a food frequency questionnaire. Data on incident dementia were retrieved from the public Long-term Care Insurance database.

RESULTS

With 71,043 person-years of follow-up, incidence of dementia was 9.0%. The score for the Japanese dietary pattern was associated with a lower risk of incident dementia (hazard ratio of the highest quartile vs the lowest, 0.80; 95% confidence interval: 0.66-0.97; p-trend = .016). The animal food pattern and the high-dairy pattern showed no significant association with incident dementia.

CONCLUSIONS

In this population of elderly Japanese individuals, the Japanese dietary pattern was associated with a decreased risk of incident dementia.

Food sources of dietary sodium in the Japanese adult population: the international study of macro-/micronutrients and blood pressure (INTERMAP)

PURPOSE

It is often reported that Na intake levels are higher in Japan than in western countries. Detailed analysis of food intake and its association with Na intake are necessary for supporting further decreases in Na consumption in Japan. We investigated the association between Na and food intake by food group using data from the Japanese participants of the INTERMAP Study.

METHOD

Results from the Japanese participants of the INTERMAP Study who did not use antihypertensive medication and/or consume a reduced Na diet were used (531 men and 518 women, aged 40-59 years), obtained from four 24-h dietary recalls and two 24-h urine collections from each participant. We developed a classification system with 46 food group classifications; food consumption and Na intake from these groups were compared across quartiles of participants determined by 24-h urinary Na excretion per unit of body weight (UNa/BW).

RESULTS

Average daily Na intake from Japanese high-Na foods was 2552 mg/day. Participants with a higher UNa/BW consumed a significantly greater amount of high-Na Japanese foods, such as salted fish (P = 0.001) and miso soup (P < 0.001). They also had greater amount of rice (P = 0.001). Participants with lower UNa/BW consumed a significantly greater amount of western foods, such as bread (P < 0.001) and milk and dairy products (P < 0.001).

CONCLUSIONS

Detailed analyses of various Japanese and western food intakes in addition to Na intake were performed. These results can be used to help draw up effective programs for the reduction in Na intake and prevention of prehypertension/hypertension in the Japanese population.

The Difference in Nutrient Intakes between Chinese and Mediterranean, Japanese and American Diets

Across countries, the predominant diets are clearly different and highly related with human health. Therefore, it is necessary to evaluate dietary nutrients between them. This study aimed to evaluate dietary nutrients in China and compare those between Chinese and Mediterranean (Italian), Japanese and American diets. Dietary intakes of 2659 subjects in south-east China, Zhejiang province, from 2010 to 2012, were estimated by three consecutive 24-h dietary recalls. The contribution of carbohydrate to total energy in Chinese subjects was lower than that in Japanese and American subjects, but higher than that in Italian subjects. However, the energy contribution from fat in Chinese subjects was higher than that in Japanese and American subjects, and similar to that in Italian subjects. Moreover, the Chinese diet had lower daily intakes of fiber, calcium, phosphorus, potassium, selenium, vitamin A, vitamin B₁, vitamin B₂ and vitamin C, compared with the Japanese, American and Italian diets. Nevertheless, intakes of sodium, iron, copper and vitamin E were higher among Chinese people relative to the people of other three countries. The present study demonstrated that the structure of the Chinese diet has been shifting away from the traditional diet toward high-fat, low-carbohydrate and low-fiber diets, and nutrients intakes in Chinese people have been changing even worse than those in American people.

Japanese dietary pattern consistently relates to low depressive symptoms and it is modified by job strain and worksite supports

BACKGROUND

This study examined the association between traditional Japanese dietary pattern and depressive symptoms in Japanese workers, employing large-scale samples, considering socioeconomic status (SES) and job stress factors.

METHODS

A cross-sectional study of 2266 Japanese employees aged 21-65 years from all areas of Japan was conducted as part of the Japanese Study of Health, Occupation and Psychosocial factors related Equity (J-HOPE). Habitual diet was assessed by FFQ (BDHQ). The depression degree and job stress factors (job demand, job control, and worksite support) were measured by K6 and Job Content Questionnaire.

RESULTS

Participants with high scores for the balanced Japanese dietary pattern were significantly less likely to show probable mood/anxiety disorders (K6≥9) with multivariate adjustment including SES and job stress factors (odds ratio=0.66 [0.51-0.86], trend P=0.002). Other dietary patterns were not associated with depressive symptoms. Even after stratification by job stress factors, the Japanese dietary pattern was consistently protective against depressive symptoms. Furthermore, a highly significant difference between the first and third tertiles of the dietary pattern was observed in participants with active strain (high demand and high control) with low worksite supports (8.5 vs. 5.2, P=0.011).

LIMITATIONS

Female participant sample was relatively small.

CONCLUSIONS

Japanese dietary pattern consistently related to low depressive symptoms in this large-scale cohort of Japanese workers, even after adjusting for SES and job stress factors. The protective impact is especially strong for workers with active strain and low support. Making better use of traditional dietary patterns may facilitate reducing social disparities in mental health.

Effects of dietary fibre and tea catechin, ingredients of the Japanese diet, on equol production and bone mineral density in isoflavone-treated ovariectomised mice

Equol is a metabolite of the isoflavone daidzein (Dz) and is produced by the bacterial microflora in the distal intestine and colon. Some epidemiological studies have reported an association between increased equol production and intakes of green tea or dietary fibre, which are ingredients of the standard Japanese diet. We examined the effects of a diet supplemented with Dz and tea catechin or dietary fibre on equol production and bone mineral density in ovariectomised (OVX) mice. Female mice of the ddY strain were either sham operated or OVX. OVX mice were fed a control diet, a 0·1 % Dz-supplemented diet or a 0·1 % Dz diet supplemented with one of the food components commonly consumed in the Japanese diet. The mice were given 1 % tea catechin (w/w) as part of the diet in Expt 1 or 5 % polydextrose (PD) and 5 % raffinose (Raf) (w/w) as part of the diet in Expt 2. Catechin reduced serum equol levels and attenuated the beneficial effect of Dz on femoral bone loss. The soluble dietary fibres PD and Raf stimulated equol production, and enhanced the bone-protective effects of Dz on femoral bone. These results suggest that dietary fibre, in particular, PD, may alter the bioavailability of isoflavones and prevent osteopenia in OVX mice.