We aimed to validate a method for assessing trans-fatty acid (TFA) intake in the Japanese population using the FFQ developed in the 1990s from a prospective study that was based on the Japan Public Health Center-based Prospective Cohort Study. For FFQ validation, we included 565 participants (Cohort I: n 215, Cohort II: n 350) aged 40–69 years. We used a 28-d dietary record (DR) over 1 year and two FFQ administered before and after DR assessment. We calculated total TFA intake, TFA from industrial oils (i-TFA) and TFA from ruminants (r-TFA) considering a database of measurements obtained mainly from Japan. Spearman’s rank correlation coefficients (CC) were computed for validity and reproducibility. Energy adjustments were applied using two methods considering the TFA measurement: density method for TFA % of total energy and residual method for TFA g/d. The total TFA intake (% of the total energy intake) was 0·08–0·76 % (median, 0·27–0·37 %) in DR of both cohorts and was 0·00–1·13 % (median, 0·30–0·40 %) in FFQ. The i-TFA accounted for approximately 50 % of the total TFA intake in DR and approximately 40 % in FFQ. For total TFA (% of the total energy intake), CC were 0·54–0·69, and weighted κ coefficients were 0·88–0·92 for both cohorts. The de-attenuated CC was 0·46–0·62 for i-TFA (g/d) and 0·57–0·68 for r-TFA (g/d). Our study showed that the validity and reproducibility of TFA intake estimation using the FFQ were reasonable, suggesting its suitability among the Japanese population with low-TFA intake.

Reducing Na intake is an urgent global challenge, especially in East Asia and high-income Asia-Pacific regions. However, the sources of Na and their effects on urinary Na excretion have not been fully studied. We sought to clarify these sources and their association with urinary Na excretion. We examined four 3-d weighed food records and five 24-h urinary collections from each of 253 participants in Japan, aged 35–80 years, between 2012 and 2013. We compared the levels of Na according to four categories: foods contributing to discretionary or non-discretionary Na intake, the situation in which dishes were cooked and consumed, food groups and types of cuisine. We also conducted regression analysis in which 24-h urinary Na excretion was a dependent variable and the amounts of food intake in the four categories were independent variables. Levels of Na were the highest in discretionary intake (60·6 %) and in home-prepared dishes (84·0 %). Of the food groups, miso soup showed the highest percentage contribution to Na intake (13·3 %) after seasonings such as soya sauce. In the regression analysis, the standardised coefficient for foods of non-discretionary Na sources was larger than that for discretionary sources, whereas that for home-prepared dishes was consistent with the levels of Na in those foods. Pickled products, followed by fresh fish and shellfish, miso soup and rice, were associated with high urinary Na excretion. Thus, discretionary foods (such as miso soup) contribute the most to Na consumption, although non-discretionary intake (such as pickled vegetables) may influence urinary Na excretion.

The association between the intake of non-alcoholic beverages and CVD in Asians is uncertain. The intake of non-alcoholic beverages was estimated in 77 407 participants of the Japan Public Health Centre-based cohort study aged 45–74 years. The Cox regression calculated the hazard ratios (HR) and 95 % CI for incident CVD according to sex-specific quintiles of intake of non-alcoholic beverages. A total of 4578 incident CVD (3751 strokes and 827 CHD) were diagnosed during a 13·6-year median follow-up. The risks of stroke and total CVD were lower for the highest v. lowest intake quintiles of non-alcoholic beverages in men and women: the multivariable HRs (95 % CIs) were 0·82 (0·71, 0·93, Ptrend = 0·005) and 0·86 (0·76, 0·97, Ptrend = 0·02), respectively, in men and were 0·73 (0·63, 0·86, Ptrend = 0·003) and 0·75 (0·65, 0·87, Ptrend = 0·005), respectively, in women. The reduced risk was evident for both ischaemic and haemorrhagic strokes and was mainly attributable to green tea consumption. The intake of non-alcoholic beverages from coffee and other beverages was not associated with the risk of CVD in both men and women. Also, there was no association between the intake of non-alcoholic beverages and the risk of CHD in either sex. In conclusion, the risks of stroke and total CVD were lower with a higher intake of non-alcoholic beverages in Japanese men and women.

We examine the validity and reproducibility of a food frequency questionnaire (FFQ) in a subsample of participants in the Japan Public Health Center-based Prospective Cohort Study using a database of polyphenol-containing foods commonly consumed in the Japanese population. Participants of the validation study were recruited from two different cohorts. In Cohort I, 215 participants completed a 28-d dietary record (DR) and the FFQ, and in Cohort II, 350 participants completed DRs and the FFQ. The total polyphenol intake estimated from the 28-d DR and FFQ were log-transformed and adjusted for energy intake by the residual method. Spearman correlation coefficients (CCs) between estimates from the FFQ and 28-d DR as well as two FFQs administered at a 1-year interval were computed. Median intakes of dietary polyphenols calculated from the DRs were 1172 mg/d for men and 1024 mg/d for women in Cohort I, and 1061 mg/d for men and 942 mg/d for women in Cohort II. The de-attenuated CCs for polyphenol intake between the DR and FFQ were 0⋅47 for men and 0⋅37 for women in Cohort I and 0⋅44 for men and 0⋅50 for women in Cohort II. Non-alcoholic beverages were the main contributor to total polyphenol intake in both men and women, accounting for 50 % of total polyphenol intake regardless of cohort and gender, followed by alcoholic beverages and seasoning and spices in men, and seasoning and spices, fruits and other vegetables in women. The present study showed that this FFQ had moderate validity and reproducibility and is suitable for use in future epidemiological studies.

We sought to examine the prospective associations of specific fruit consumption, in particular flavonoid-rich fruit (FRF) consumption, with the risk of stroke and subtypes of stroke in a Japanese population. A study followed a total of 39 843 men and 47 334 women aged 44–76 years, and free of CVD, diabetes and cancer at baseline since 1995 and 1998 to the end of 2009 and 2012, respectively. Data on total and specific FRF consumption for each participant were obtained using a self-administrated FFQ. The hazard ratios (HR) of stroke in relation to total and specific FRF consumption were estimated through Cox proportional hazards regression models. During a median follow-up of 13·1 years, 4091 incident stroke cases (2557 cerebral infarctions and 1516 haemorrhagic strokes) were documented. After adjustment for age, BMI, study area, lifestyles, dietary factors and other risk factors, it was found that total FRF consumption was associated with a significantly lower risk of stroke in women (HR = 0·70; 95 % CI 0·58, 0·84), while the association in men was not significant (HR = 0·93; 95 % CI 0·79, 1·09). As for specific FRF, consumptions of citrus fruits, strawberries and grapes were found associated with a lower stroke risk in women. Higher consumptions of FRF, in particular citrus fruits, strawberries and grapes, were associated with a lower risk of developing stroke in Japanese women.

Although the association between fruit consumption and CHD risk has been well studied, few studies have focused on flavonoid-rich fruits (FRF), in particular strawberries and grapes. We aimed to verify the association of total and specific FRF consumption with risk of CHD by a large prospective cohort study. A total of 87 177 men and women aged 44–75 years who were free of CVD and cancer at study baseline were eligible for the present analysis. FRF consumption was assessed using a FFQ. Cox proportional hazards regression models were used to estimate the hazard ratios (HR) of CHD in relation to FRF consumption with adjustment for potential risk factors and confounders. During a mean follow-up of 13·2 years, we identified 1156 incident CHD cases. After full adjustment for covariates including demographics, lifestyles and dietary factors, the HR were 0·93 (95 % CI 0·77, 1·11), 0·91 (95 % CI 0·75, 1·11), 0·84 (95 % CI 0·67, 1·04) and 0·78 (95 % CI 0·62, 0·99) for the second, third, fourth and fifth quintiles compared with the lowest quintile of FRF consumption. Regarding specific fruits, we observed a significant inverse association for citrus fruit consumption and a borderline inverse association for strawberry consumption, while no association was observed for apple/pear or grape consumption. Although the associations appeared to be stronger in women, they were not significantly modified by sex. Higher consumption of FRF, in particular, citrus fruits, may be associated with a lower risk of developing CHD.

Little is known about predictors of decline in vitamin D status (vitamin D decline) over time. We aimed to determine demographic and lifestyle variables associated with vitamin D decline by sufficiently controlling for seasonal effects of vitamin D uptake in a middle-aged to elderly population. Using a longitudinal study design within the larger framework of the Murakami Cohort Study, we examined 1044 individuals aged between 40 and 74 years, who provided blood samples at baseline and at 5-year follow-up, the latter of which were taken on a date near the baseline examination (±14 d). Blood 25-hydroxyvitamin D (25(OH)D) concentrations were determined with the Liaison® 25OH Vitamin D Total Assay. A self-administered questionnaire collected demographic, body size and lifestyle information. Vitamin D decline was defined as the lowest tertile of 5-year changes in blood 25(OH)D (Δ25(OH)D) concentration (<6·7 nmol/l). Proportions of those with vitamin D decline were 182/438 (41·6 %) in men and 166/606 (27·4 %) in women (P < 0·0001). In men, risk of vitamin D decline was significantly lower in those with an outdoor occupation (P = 0·0099) and those with the highest quartile of metabolic equivalent score (OR 0·34; 95 % CI 0·14, 0·83), and higher in those with ‘university or higher’ levels of education (OR 2·92; 95 % CI 1·04, 8·19). In women, risk of vitamin D decline tended to be lower with higher levels of vitamin D intake (Pfor trend = 0·0651) and green tea consumption (Pfor trend = 0·0025). Predictors of vitamin D decline differ by sex, suggesting that a sex-dependent intervention may help to maintain long-term vitamin D levels.

Although dietary Ca, vitamin D and vitamin K are nutritional factors associated with osteoporosis, little is known about their effects on incident osteoporotic fractures in East Asian populations. This study aimed to determine whether intakes of these nutrients predict incident osteoporotic fractures. We adopted a cohort study design with a 5-year follow-up. Subjects were 12 794 community-dwelling individuals (6301 men and 6493 women) aged 40–74 years. Dietary intakes of Ca, vitamin D and vitamin K were assessed with a validated FFQ. Covariates were demographic and lifestyle factors. All incident cases of major osteoporotic limb fractures, including those of the distal forearm, neck of humerus, neck or trochanter of femur and lumbar or thoracic spine were collected. Hazard ratios (HR) for energy-adjusted Ca, vitamin D and vitamin K were calculated with the residual method. Mean age was 58·8 (sd 9·3) years. Lower energy-adjusted intakes of Ca and vitamin K in women were associated with higher adjusted HR of total fractures (Pfor trend = 0·005 and 0·08, respectively). When vertebral fracture was the outcome, Pfor trend values for Ca and vitamin K were 0·03 and 0·006, respectively, and HR of the lowest and highest (reference) intake groups were 2·03 (95 % CI 1·08, 3·82) and 2·26 (95 % CI 1·19, 4·26), respectively. In men, there were null associations between incident fractures and each of the three nutrient intakes. Lower intakes of dietary Ca and vitamin K were independent lifestyle-related risk factors for osteoporotic fracture in women but not men. These associations were robust for vertebral fractures, but not for limb fractures.

Evidence that diet is associated with breast cancer risk is inconsistent. Most of the studies have focused on risks associated with specific foods and nutrients, rather than overall diet. In this study, we aimed to evaluate the association between dietary patterns and breast cancer risk in Japanese women. A total of 49 552 Japanese women were followed-up from 1995 to 1998 (5-year follow-up survey) until the end of 2012 for an average of 14·6 years. During 725 534 person-years of follow-up, 718 cases of breast cancer were identified. We identified three dietary patterns (prudent, westernised and traditional Japanese). The westernised dietary pattern was associated with a 32 % increase in breast cancer risk (hazard ratios (HR) 1·32; 95 % CI 1·03, 1·70; Ptrend=0·04). In particular, subjects with extreme intake of the westernised diet (quintile (Q) Q5_5th) had an 83 % increase in risk of breast cancer in contrast to those in the lowest Q1 (HR 1·83; 95 % CI 1·25, 2·68; Ptrend=0·01). In analyses stratified by menopausal status, postmenopausal subjects in the highest quintile of the westernised dietary pattern had a 29 % increased risk of breast cancer (HR 1·29; 95 % CI 0·99, 1·76; Ptrend=0·04). With regard to hormone receptor status, the westernised dietary pattern was associated with an increased risk of oestrogen receptor-positive/progesterone receptor-positivetumours (HR 2·49; 95 % CI 1·40, 4·43; Ptrend<0·01). The other dietary patterns were not associated with the risk of breast cancer in Japanese women. A westernised dietary pattern is associated with an increased risk of breast cancer in Japanese women.

Limited and inconsistent associations between cholesterol and egg consumption and type 2 diabetes risk have been observed in Western countries. In the present study, the association of dietary cholesterol and egg intakes with type 2 diabetes risk was examined prospectively. The study subjects comprised 27 248 men and 36 218 women aged 45–75 years who participated in the second survey of the Japan Public Health Center-based Prospective Study and had no histories of type 2 diabetes or other serious diseases. Dietary cholesterol and egg intakes were estimated using a validated 147-item FFQ. The OR of self-reported, physician-diagnosed type 2 diabetes over 5 years were estimated using multiple logistic regression. A total of 1165 newly diagnosed cases of type 2 diabetes were self-reported. Although dietary cholesterol intake was not associated with type 2 diabetes risk in men, it was found to be associated with a 23 % lower odds of type 2 diabetes risk in women in the highest quartile of intake, albeit not statistically significant, compared with those in the lowest quartile (Ptrend= 0·08). Such risk reduction was somewhat greater among postmenopausal women; the multivariable-adjusted OR for the highest quartile of cholesterol intake compared with the lowest quartile was 0·68 (95 % CI 0·49, 0·94; Ptrend= 0·04). No association between egg intake and type 2 diabetes risk was found in either men or women. In conclusion, higher intake of cholesterol or eggs may not be associated with an increased risk of type 2 diabetes in Japanese populations. The observed association between decreased type 2 diabetes risk and higher dietary cholesterol intake in postmenopausal women warrants further investigation.

The relationship between different types of meat intake and the risk of type 2 diabetes remains unclear. We prospectively examined the association between total meat, total red meat, unprocessed red meat, processed meat and poultry intake and the incidence of type 2 diabetes. Subjects were 27 425 men and 36 424 women aged 45–75 years who participated in the second survey of the Japan Public Health Center-based Prospective Study, and had no history of type 2 diabetes, cancer, stroke, IHD, chronic liver disease or kidney disease. Meat intake was estimated using a validated 147-item FFQ. OR of self-reported, physician-diagnosed type 2 diabetes over 5 years were estimated using a multiple logistic regression. A total of 1178 newly diagnosed cases of type 2 diabetes were self-reported. Intakes of total meat and total red meat were associated with the increased risk of type 2 diabetes in men but not in women. The multivariate-adjusted OR for the highest quartile compared with the lowest quartile of total meat and total red meat intake were 1·36 (95 % CI 1·07, 1·73; P for trend = 0·006) and 1·48 (95 % CI 1·15, 1·90; P for trend = 0·003) for men, respectively, and 0·82 (95 % CI 0·62, 1·09; P for trend = 0·14) and 0·77 (95 % CI 0·57, 1·02; P for trend = 0·08) for women, respectively. Intakes of processed red meat and poultry were not associated with the increased risk of diabetes in either men or women. In conclusion, elevated intake of red meat is associated with the increased risk of type 2 diabetes in Japanese men but not in women.

Evidence has shown that both C-reactive protein (CRP) and serum amyloid component A (SAA) are increased in individuals with gastritis and stomach cancer. Controlling the level of these biomarkers by inhibiting the gastric infection with high doses of ascorbic acid may reduce the risk of carcinogenesis. A population-based double-blind randomised controlled trial in a Japanese population with atrophic gastritis in an area of high stomach cancer incidence was conducted between 1995 and 2000. Daily doses of 50 or 500 mg vitamin C were given, and 120 and 124 participants completed the 5-year study, respectively. Although serum ascorbic acid was higher in the high-dosage group (1·73 (sd 0·46) μg/l) than in the low-dosage group (1·49 (sd 0·29) μg/l, P< 0·001), at the end of the study, no significant difference was observed for CRP between the low- and high-dosage groups (0·39 (95 % CI 0·04, 4·19) mg/l and 0·38 (95 % CI 0·03, 4·31) mg/l, respectively; P= 0·63) or for SAA between the low- and high-dosage groups (3·94 (95 % CI 1·04, 14·84) μg/ml and 3·85 (95 % CI 0·99, 14·92) μg/ml, respectively; P= 0·61). Vitamin C supplementation may not have a strong effect on reducing infections in individuals with atrophic gastritis.

Vegetable and fruit intake has been associated with a reduced risk of cancer and CVD, but its relationship to the risk of type 2 diabetes remains unclear. We prospectively examined the association between vegetable and fruit intake and the incidence of type 2 diabetes. Subjects were 21 269 men and 27 168 women aged 45–75 years who participated in the second survey of the Japan Public Health Center-based Prospective Study and had no history of type 2 diabetes or other serious diseases. Intake of vegetables and fruit was estimated using a validated 147-item FFQ. The OR of self-reported, physician-diagnosed type 2 diabetes over 5 years was estimated using multiple logistic regression. A total of 896 newly diagnosed cases of type 2 diabetes were self-reported. Intake of vegetables and fruit combined or fruit only was not associated with a lower risk of type 2 diabetes. However, there was an approximately 20 %, albeit not statistically significant, risk reduction associated with vegetables (men only), green leafy vegetables (men and women) and cruciferous vegetables (men only). Such risk reduction was somewhat greater among obese or smoking men than non-obese or non-smoking men. In conclusion, although a small beneficial effect of vegetables, especially green leafy and cruciferous vegetables, cannot be excluded, vegetable and fruit intake may not be appreciably associated with the risk of type 2 diabetes for Japanese adults.

The objective of the present study was to evaluate the validity of a FFQ in the estimation of dietary amino acid intake. Amino acid intake was calculated using a composition database developed based on the Standard Tables of Food Composition for amino acids in Japan. Subjects were subsampled from two populations of the Japan Public Health Center-based Prospective Study who volunteered to participate in the validation study of the FFQ. The first group was from the population the FFQ was developed for (internal population; n 215) and the second was a separate population to confirm external validity (external population; n 350). The validity of the FFQ was evaluated using 28 d weighed dietary records (DR) as a reference method. Spearman's rank correlation coefficients (CC) between amino acid intake from the FFQ and DR were calculated. The dietary intake of amino acids was slightly underestimated by the FFQ. Deattenuated CC of energy-adjusted amino acid intake according to the FFQ and corresponding amino acid intake according to the DR ranged from 0·15 to 0·52. The median CC for twenty amino acids were 0·33 for men and 0·25 for women in the internal population, and 0·40 for men and 0·30 for women in the external population. In conclusion, the validity of the FFQ in estimating amino acid intake was low to moderate.

The purpose of this study was to evaluate the effect of low Ca intake on the 10-year incidence of vertebral fractures in cohorts I and II of the Japan Public Health Centre-based Prospective Study. The baseline studies were conducted in 1990–1994, with the follow-up studies conducted after 10 years. We analysed 33 970 subjects aged 40–59 years in cohort I and 41 664 subjects aged 40–69 years in cohort II. At baseline, the intake of Ca was assessed as a predictor, using validated FFQ. A meta-analysis was performed to estimate a summary relative risk (RR) for the two cohort studies. The 10-year cumulative incidences of self-reported vertebral fractures were 0·38 % for cohort I and 0·56 % for cohort II. In women, lower Ca intake was associated with a higher incidence of vertebral fractures (P for trend = 0·001), with the lowest quartile of Ca intake having a significantly higher incidence (0·89/1000 persons per year or RR 2·10 (95 % CI 1·25, 3·55)) than that (0·42/1000 persons per year) of the highest. In addition, the RR calculated using energy-adjusted Ca intake (by the residual method) as an outcome was 1·92 (95 % CI 1·28, 2·88). However, no such association was observed in men. An increase of Ca intake should be considered as a preventive strategy for vertebral fractures in peri- and post-menopausal women with a low Ca intake.