Western studies have suggested cultural differences in food and nutrient intake patterns associated with dietary glycaemic index (GI) and glycaemic load (GL). Here, we conducted a cross-sectional study to examine the GI and GL of Japanese diets in relation to food and nutrient intakes.

Dietary intake was assessed using a validated, self-administered, diet history questionnaire.

A total of thirty-five of forty-seven prefectures in Japan.

Young (age 18 years), middle-aged (mean age 48 years) and older (mean age 74 years) Japanese women (n 3961, 3800 and 2202, respectively).

Irrespective of age, a positive association with dietary GI was seen for white rice only, which contributed most (37–42 %) to the variation in dietary GI. Conversely, all other food groups (such as fruit and vegetable juice, dairy products, noodles and fruit) were negative predictors of dietary GI. For dietary GL, 95–96 % of variation was explained by carbohydrate-rich food groups, all of which were positive predictors of GL. After adjustment for potential confounding factors, only carbohydrate intake was positively associated with dietary GI and GL, irrespective of age. Conversely, dietary GI and GL were inversely associated with intakes of all other nutrients examined (including SFA and Na).

A low-GI and -GL diet, which was characterized principally by a low intake of white rice, was associated with both favourable (higher intakes of dietary fibre and key vitamins and minerals) and unfavourable (higher intakes of SFA and Na) aspects of dietary intake patterns in three generations of Japanese women.

To examine the relationships of monetary value of diets with sociodemographic and lifestyle characteristics and dietary intake among Japanese adults.

Cross-sectional study based on two nationally representative surveys: the Comprehensive Survey of Living Conditions and the National Health and Nutrition Survey, 2013. Dietary intake was assessed by a 1 d semi-weighed household dietary record with information on individual proportion of intakes. Diet cost was estimated by linking dietary data with retail food prices. A wide variety of sociodemographic and lifestyle variables were obtained from the two surveys.

A random sample of nationally representative households in Japan.

Japanese adults aged 20 years or older (n 4658).

Lower energy-adjusted diet cost (Japanese yen/4184 kJ) was significantly associated with being younger, having a lower education, less equivalent monthly household expenditure, large household size, less physical activity and living in rented houses. Lower diet cost was associated with a lower intake of pulses, vegetables, fruits, fish, meat and dairy products, and a higher intake of grain, eggs, and fats and oils. At the nutrient level, lower diet cost was associated with a lower intake of protein, alcohol, dietary fibre, cholesterol and all vitamins and minerals examined, and a higher intake of carbohydrate. Diet cost was inversely associated with dietary energy density.

These data suggest that certain low socio-economic subgroups in Japan consume diets of lower monetary value, resulting in a lower quality of food and nutrient intake pattern except for lower sodium, cholesterol and alcohol consumption.

A growing body of evidence from Western countries shows that infant feeding practices are associated with later childhood dietary habits, but little is known about these relationships in non-Western countries with different food cultures. We examined the association of breast-feeding duration and age at introduction of solid foods with later intake of fruit and vegetables among Japanese toddlers.

Information on breast-feeding duration, age at introduction of solid foods and child’s intake frequency of fruit and vegetables were collected with a self-administered questionnaire at 16–24 months postpartum. Logistic regression analysis was used to calculate odds ratios of low intake (<1 time/d) of fruit or vegetables for each infant feeding practice.

Japan.

Japanese mother–child pairs (n 763) from a prospective birth cohort study.

Neither breast-feeding duration nor age at introduction of solid foods was associated with fruit intake at 16–24 months of age. Breast-feeding duration, but not age at introduction of solid foods, was associated with later intake of vegetables. When breast-feeding duration was categorized into two groups with the cut-off at 6 months, children who were breast-fed for ≥6 months had a significantly decreased risk of low intake of vegetables (OR=0·53; 95 % CI 0·34, 0·84) than those breast-fed for <6 months. This association was independent of potential confounders including maternal education and maternal vegetable intake (OR=0·59; 95 % CI 0·36, 0·97).

This finding suggests that ≥6 months of breast-feeding may prevent low intake of vegetables in early childhood among Japanese toddlers.

To compare the relative validity of food group intakes derived from a comprehensive self-administered diet history questionnaire (DHQ) and a brief-type DHQ (BDHQ) developed for the assessment of Japanese diets during the previous month using semi-weighed dietary records (DR) as a reference method.

Between November 2002 and September 2003, a 4 d DR (covering four non-consecutive days), a DHQ (150-item semi-quantitative questionnaire) and a BDHQ (fifty-eight-item fixed-portion-type questionnaire) were completed four times (once per season) at 3-month intervals.

Three areas in Japan: Osaka, Nagano and Tottori.

Ninety-two Japanese women aged 31–69 years and ninety-two Japanese men aged 32–76 years.

Median food group intakes were estimated well for approximately half of the food groups. No statistically significant differences were noted between a 16 d DR and the first DHQ (DHQ1) or between the DR and the first BDHQ (BDHQ1) in fifteen (44 %) and fifteen (52 %) food items for women and in fourteen (41 %) and sixteen (55 %) food items for men, respectively, indicating that both questionnaires estimated median values reasonably well. Median Spearman's correlation coefficients with the DR were 0·43 (range: −0·09 to 0·77) for DHQ1 and 0·44 (range: 0·14 to 0·82) for BDHQ1 in women, with respective values of 0·44 (range: 0·08 to 0·87) and 0·48 (range: 0·22 to 0·83) in men, indicating reasonable ranking ability. Similar results were observed for mean values of the four DHQ and BDHQ.

In terms of food intake estimates, both the DHQ and the BDHQ showed reasonable validity.

To examine the adequacy and inadequacy of dietary patterns in pregnant women for which information is absolutely lacking.

Diet was assessed by a validated, self-administered diet history questionnaire (DHQ). Dietary patterns were extracted from the intake of thirty-three food groups (g/4184 kJ (1000 kcal)), which were summarized from 147 foods assessed with the DHQ, by cluster analysis. Nutritional inadequacy for selected twenty nutrients in each dietary pattern was examined using the reference values given in the Dietary Reference Intakes (DRI) for Japanese as the temporal gold standard.

Japan.

Nine hundred and ninety-seven pregnant Japanese women aged 18–43 years.

The three dietary patterns identified were labelled as ‘meat and eggs’ (n 423), ‘wheat products’ (n 371) and ‘rice, fish and vegetables’ (n 203). The ‘rice, fish and vegetables’ pattern characterized by high intake of rice, vegetables, potatoes, pulses, fruits, seaweed, fish and miso soup showed significantly the lowest prevalence of inadequate intake for fifteen nutrients and significantly the highest prevalence of inadequate sodium intake. In contrast, the ‘wheat products’ pattern characterized by high intake of bread, noodles, confectioneries and soft drinks showed the highest prevalence of inadequate intake for fourteen nutrients. The median number of nutrients not meeting the DRI as a marker of overall nutritional inadequacy was eight in the ‘rice, fish and vegetables’ pattern. It was significantly lower at ten in the ‘meat and eggs’ and eleven in the ‘wheat products’ patterns (P < 0·001).

In pregnant Japanese women, the dietary pattern high in rice, fish, vegetables, fruit and some others showed a better profile of nutritional adequacy except for sodium.

Although dietary pattern approaches derived from dietary assessment questionnaires are widely used, only a few studies in Western countries have reported the validity of this approach. We examined the relative validity of dietary patterns derived from a self-administered diet history questionnaire (DHQ) among Japanese adults.

The DHQ, assessing diet during the preceding month, and 4 d dietary records (DR) were collected in each season over one year. To derive dietary patterns, 145 food items in the DHQ and 1259 in the DR were classified into thirty-three predefined food groups, and entered into a factor analysis.

Three areas in Japan; Osaka (urban), Nagano (rural inland) and Tottori (rural coastal).

A total of ninety-two Japanese women and ninety-two Japanese men aged 31–76 years.

We identified three dietary patterns (‘healthy’, ‘Western’ and ‘Japanese traditional’) in women and two (‘healthy’ and ‘Western’) in men, which showed a relatively similar direction and magnitude of factor loadings of food groups across the first and mean of four DHQ (DHQ1 and mDHQ, respectively) and 16 d DR. The Pearson correlation coefficients between DHQ1 and 16 d DR for the healthy, Western and Japanese traditional patterns in women were 0·57, 0·36 and 0·44, and for the healthy and Western patterns in men were 0·62 and 0·56, respectively. When mDHQ was examined, the correlation coefficients improved for women (0·45–0·69).

Dietary patterns derived from the DHQ could be used for epidemiological studies as surrogates of those derived from DR.

Previous studies in Western populations have linked caffeine intake with health status. While detailed dietary assessment studies in these populations have shown that the main contributors to caffeine intake are coffee and tea, the wide consumption of Japanese and Chinese teas in Japan suggests that sources of intake in Japan may differ from those in Western populations. Among these teas, moreover, caffeine content varies widely among the different forms consumed (brewed, canned or bottled), suggesting the need for detailed dietary assessment in estimating intake in Japanese populations. Here, because a caffeine composition database or data obtained from detailed dietary assessment have not been available, we developed a database for caffeine content in Japanese foods and beverages, and then used it to estimate intake in a Japanese population.

The caffeine food composition database was developed using analytic values from the literature, 16 d weighed diet records were collected, and caffeine intake was estimated from the 16 d weighed diet records.

Four areas in Japan, Osaka (Osaka City), Okinawa (Ginowan City), Nagano (Matsumoto City) and Tottori (Kurayoshi City), between November 2002 and September 2003.

Two hundred and thirty Japanese adults aged 30–69 years.

Mean caffeine intake was 256·2 mg/d for women and 268·3 mg/d for men. The major contributors to intake were Japanese and Chinese teas and coffee (47 % each). Caffeine intake above 400 mg/d, suggested in reviews to possibly have negative health effects, was seen in 11 % of women and 15 % of men.

In this Japanese population, caffeine intake was comparable to the estimated values reported in Western populations.

Little is known about the relationship of monetary diet costs to dietary intake and obesity, particularly in non-Western populations. This study examined monetary cost of dietary energy in relation to diet quality and body mass index (BMI) among young Japanese women.

Dietary intake was assessed by a validated, self-administered, diet history questionnaire. Diet costs were estimated using retail food prices. Monetary cost of dietary energy (Japanese yen 1000 kcal−1) was then calculated. BMI was computed from self-reported body weight and height.

A total of 3931 female Japanese dietetic students aged 18–20 years.

Monetary cost of dietary energy was positively associated with intakes of fruits, vegetables, fish and shellfish, and pulses; however, higher monetary cost of dietary energy was also associated with higher consumption of fat and oil, meat and energy-containing beverages, and lower consumption of cereals (rice, bread and noodles) (all P for trend <0.01). At the nutrient level, monetary cost of dietary energy was positively associated with intakes of dietary fibre and key vitamins and minerals, but also associated positively with intakes of fat, saturated fatty acids, cholesterol and sodium, and negatively with carbohydrate intake (all P for trend <0.0001). After adjustment for possible confounders, monetary cost of dietary energy was quite weakly but significantly negatively associated with BMI (P for trend = 0.0197).

Increasing monetary cost of dietary energy was associated with both favourable and unfavourable dietary intake patterns and a quite small decrease in BMI in young Japanese women.

To examine relationships between the ratio of energy intake to basal metabolic rate (EI/BMR) and age and body mass index (BMI) among Japanese adults.

Energy intake was assessed by 4-day semi-weighed diet records in each of four seasons (16 days in total). The EI/BMR ratio was calculated from reported energy intake and estimated basal metabolic rate as an indicator of reporting accuracy.

Residents in three areas in Japan, namely Osaka (urban), Nagano (rural inland) and Tottori (rural coastal).

One hundred and eighty-three healthy Japanese men and women aged ≥30 years.

The oldest age group (≥60 years) had higher EI/BMR values than the youngest age group (30–39 years) in both sexes (1.74 vs. 1.37 for men; 1.65 vs. 1.43 for women). In multiple regression analyses, age correlated positively (partial correlation coefficient, β = 0.012, P < 0.001 for men; β = 0.011, P < 0.001 for women) and BMI correlated negatively (β = −0.031, P < 0.001 for men; β = −0.025, P < 0.01 for women) with EI/BMR.

Age and BMI may influence the relative accuracy of energy intake among Japanese adults.

To evaluate the ratio of energy intake to basal metabolic rate (EI/BMR) among young female Japanese adults, and to compare the lifestyle and dietary characteristics between relatively low and high reporters.

Dietary intakes were assessed over a 1-month period with a validated, self-administered, diet history questionnaire, and lifestyle variables were assessed by a second questionnaire designed for this survey. The ratio of EI/BMR was calculated from reported energy intake and estimated basal metabolic rate.

In total, 1889 female Japanese university students aged 18–20 years who were enrolled in dietetics courses.

Ninety-five per cent of the subjects were classified into a non-obese group (body mass index (BMI) <25 kg m−2; mean±standard deviation (SD): 20.8±2.6 kg m−2). EI/BMR was 1.43±0.40 (mean±SD). Sixty-eight per cent of the subjects showed an EI/BMR level below the possibly balanced value of 1.56, 37% showed EI/BMR below the minimum survival value of 1.27 and 2% of the subjects showed EI/BMR exceeding the maximum value for a sustainable lifestyle of 2.4. BMI, body weight and BMR decreased significantly with the increase in EI/BMR (P<0.001). The percentage of energy from carbohydrate was significantly higher, whereas those from fat and protein were significantly lower, among the lower EI/BMR groups. As for food groups, a significantly declining trend from the lowest to the highest EI/BMR groups was observed for cereals.

Underreporting, rather than overreporting, of energy intake was predominant in this relatively lean Japanese female population. BMI was the most important factor affecting the reporting accuracy of energy intake.