Yoshiko Takahashi

Dietary fiber intake, dietary glycemic index and load, and body mass index: a cross-sectional study of 3931 Japanese women aged 18-20 years.

Objective:Few observational studies have investigated dietary fiber intake and dietary glycemic index (GI) and glycemic load (GL) simultaneously in relation to obesity, particularly in non-Western populations. We examined the associations between dietary fiber intake and dietary GI and GL, and body mass index (BMI) in young Japanese women.Design:Cross-sectional study.Subjects:A total of 3931 female Japanese dietetic students aged 18–20 years from 53 institutions in Japan.Methods:Dietary fiber intake and dietary GI and GL (GI for glucose=100) were assessed by a validated, self-administered, diet history questionnaire. BMI was calculated from self-reported body weight and height.Results:Mean values of BMI, dietary fiber intake, dietary GI and dietary GL were 21.0 kg/m2, 6.5 g/4186 kJ, 65.1 and 82.1/4186 kJ, respectively. White rice (GI=77) was the major contributor to dietary GI and GL (45.8%). After controlling for potential dietary and nondietary confounding factors, dietary fiber intake was negatively correlated with BMI (adjusted mean=21.1 kg/m2 in the lowest and 20.7 kg/m2 in the highest quintiles; P for trend=0.0007). Conversely, dietary GI and GL were independently positively correlated with BMI (20.8 and 21.2 kg/m2; P for trend=0.03, and 20.5 and 21.5 kg/m2; P for trend=0.0005, respectively).Conclusions:Dietary fiber intake showed an independent negative association with BMI, and dietary GI and GL showed an independent positive association with BMI among relatively lean young Japanese women.

Reproducibility and relative validity of dietary glycaemic index and load assessed with a self-administered diet-history questionnaire in Japanese adults

Although many epidemiological studies have examined the association of dietary glycaemic index (GI) and glycaemic load (GL) with health outcomes, information on the reproducibility and relative validity of these variables estimated from dietary questionnaires is extremely limited. We examined the reproducibility and relative validity of dietary GI and GL assessed with a self-administered diet-history questionnaire (DHQ) in adult Japanese. A total of ninety-two Japanese women and ninety-two Japanese men aged 31-76 years completed the DHQ (assessing diet during the preceding month) and 4 d dietary records (DR) in each season over a 1-year period (DHQ1-4 and DR1-4, respectively) and the DHQ at 1 year after completing DHQ1 (DHQ5). We used intraclass correlations between DHQ1 and DHQ5 to assess reproducibility, and Pearson correlations between the mean of DR1-4 and mean of DHQ1-4 and between the mean of DR1-4 and DHQ1 to assess relative validity. Reproducibility correlations for dietary GI and GL were 0.57 and 0.69 among women and 0.65 and 0.58 among men, respectively. Validity correlations for dietary GI and GL assessed by DHQ1-4 were 0.72 and 0.66 among women and 0.65 and 0.71 among men, respectively. Corresponding correlations for DHQ1 were 0.53 and 0.58 among women and 0.57 and 0.60 among men, respectively. White rice was the major contributor to GI and GL in both methods (49-64 %). These data indicate reasonable reproducibility and relative validity of dietary GI and GL assessed by a DHQ for Japanese adults, whose dietary GI and GL are primarily determined by the GI of white rice.

Association between dietary acid-base load and cardiometabolic risk factors in young Japanese women.

Mild metabolic acidosis, which can be caused by diet, may adversely affect cardiometabolic risk factors, possibly by increasing cortisol production. Methodologies for estimating diet-induced acid-base load using dietary-intake information have been established. To our knowledge, however, the possible association between dietary acid-base load and cardiometabolic risk factors has not been investigated. We cross-sectionally examined associations between dietary acid-base load and cardiometabolic risk factors in a free-living population. The subjects were 1136 female Japanese dietetic students aged 18-22 years. Dietary acid-base load was characterized as the potential renal acid load (PRAL), which was determined using an algorithm including dietary protein, P, K, Ca and Mg, as well as the ratio of dietary protein to K (Pro:K). Estimates of each nutrient were obtained from a validated comprehensive self-administered diet history questionnaire. Body height and weight, waist circumference and blood pressure were measured. Fasting blood samples were collected. After adjustment for potential confounding factors, higher PRAL and Pro:K (more acidic dietary acid-base loads) were associated with higher systolic and diastolic blood pressure (P for trend = 0.028 and 0.035 for PRAL and 0.012 and 0.009 for Pro:K, respectively). PRAL was also independently positively associated with total and LDL-cholesterol (n 1121; P for trend = 0.042 and 0.021, respectively). Additionally, Pro:K showed an independent positive association with BMI and waist circumference (P for trend = 0.024 and 0.012, respectively). In conclusion, more acidic dietary acid-base load was independently associated with adverse profile of several cardiometabolic risk factors in free-living young Japanese women.

The midpoint of sleep is associated with dietary intake and dietary behavior among young Japanese women

OBJECTIVES How human chronotype is correlated to nutrient and food-group intakes and dietary behavior remains to be elucidated. We cross-sectionally examined the association between the midpoint of sleep and these dietary variables in young Japanese women. A calculated halfway point between bedtime and rise time was used as midpoint of sleep. METHODS The subjects were 3304 female Japanese dietetics students aged 18-20years from 53 institutions in Japan. Dietary intake during the previous month was assessed by a validated, self-administered diet history questionnaire. The midpoint of sleep was calculated using self-reported bedtimes and rise times. RESULTS Late midpoint of sleep was significantly negatively associated with the percentage of energy from protein and carbohydrates, and the energy-adjusted intake of cholesterol, potassium, calcium, magnesium, iron, zinc, vitamin A, vitamin D, thiamin, riboflavin, vitamin B(6), folate, rice, vegetables, pulses, eggs, and milk and milk products. It was also significantly positively associated with the percentage of energy from alcohol and fat, and the energy-adjusted intake of noodles, confections, fat and oil, and meat. Furthermore, subjects with a later midpoint of sleep tended to begin meals later, eat for a longer time, skip meals more frequently, and watch TV at meals, not only at breakfast but also at lunch and dinner. CONCLUSIONS The midpoint of sleep is significantly associated with dietary intake of certain nutrients and foods and other dietary behaviors in young Japanese women. This finding may contribute to consider the relationships between chronotype and dietary intakes and behaviors.

Monetary costs of dietary energy reported by young Japanese women: association with food and nutrient intake and body mass index.

OBJECTIVE 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. DESIGN 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. SUBJECTS A total of 3931 female Japanese dietetic students aged 18-20 years. RESULTS 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). CONCLUSIONS 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.

Blood pressure change in a free-living population-based dietary modification study in Japan.

Objective To assess whether dietary intervention in free-living healthy subjects is effective in improving blood pressure levels. Design Open randomised, controlled trial. Setting Free-living healthy subjects in two rural villages in north-eastern Japan. Participants Five hundred and fifty healthy volunteers aged 40–69 years. Interventions Tailored dietary education to encourage a decrease in sodium intake and an increase in the intake of vitamin C and carotene, and of fruit and vegetables. Main outcome measures Blood pressure, dietary intake and urinary excretion of sodium, dietary carotene and vitamin C, and fruit and vegetable intake data were collected at 1 year after the start of the intervention. Results During the first year, changes differed significantly between the intervention and control groups for dietary (P = 0.002) and urinary excretion (P < 0.001) of sodium and dietary vitamin C and carotene (P = 0.003). Systolic blood pressure decreased from 127.9 to 125.2 mmHg (2.7 mmHg decrease; 95% confidence interval, −4.6 to −0.8) in the intervention group, whereas it increased from 128.0 to 128.5 mmHg (0.5 increase; −1.3 to 2.3) in the control group. This change was statistically significant (P = 0.007). In contrast, the change in diastolic blood pressure did not significantly differ between the groups. In hypertensive subjects, a significant difference in systolic blood pressure reduction was seen between the groups (P = 0.032). Conclusion Moderate-intensity dietary counseling in free-living healthy subjects achieved significant dietary changes, which resulted in a significant decrease in systolic blood pressure.

Total n-3 polyunsaturated fatty acid intake is inversely associated with serum C-reactive protein in young Japanese women.

Little is known about the relation of dietary factors to circulating C-reactive protein (CRP) concentrations in young adults and non-Western populations. We cross-sectionally examined associations between dietary intake and serum CRP concentrations in young Japanese women. The subjects were 443 female Japanese dietetic students aged 18 to 22 years. Dietary intake was assessed with a validated, self-administered, comprehensive, diet history questionnaire. Serum CRP concentrations were measured by highly sensitive nephelometry. The prevalence of elevated CRP (> or = 1 mg/L) was 5.6%. After adjustment for possible confounding factors including body mass index, a significant inverse association was seen between total n-3 polyunsaturated fatty acid intake and elevated CRP. The multivariate adjusted odds ratios of elevated CRP for women with intake below and above the median (1.1% of energy) were 1.00 and 0.33 (95% confidence interval, 0.13-0.82; P = .02), respectively. Intake of eicosapentaenoic acid + docosahexaenoic acid and alpha-linolenic acid was not associated with elevated CRP concentrations (P = .62 and P = .27, respectively). Vitamin C intake was independently inversely associated with elevated CRP, although the association was nonsignificant (P = .10). No clear associations were observed for other dietary factors examined including total fat, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, total dietary fiber, soluble dietary fiber, insoluble dietary fiber, and magnesium; fruits, vegetables, and fish and shellfish; and dietary glycemic load (P = .27 to P = .99). In conclusion, total n-3 polyunsaturated fatty acid intake showed an independent inverse association with elevated serum CRP concentration in a group of young Japanese women.

Urinary level of 1,N6 ‐ethenodeoxyadenosine, a marker of oxidative stress, is associated with salt excretion and ω6‐polyunsaturated fatty acid intake in postmenopausal Japanese women

Excretion of 1,N6‐ethenodeoxyadenosine (ϵdA), a marker for lipid peroxidation (LPO)‐derived DNA damage was analyzed in urine of nonsmoking postmenopausal women participating in a dietary intervention trial in Northern Japan. Hereby the efficacy of dietary consultation in reducing salt and increasing vitamin C and carotenes during 1 year was estimated. Thirty postmenopausal women, 60–69 years of age, from the intervention group and 30 age‐matched women from the control group were randomly selected. The subjects completed a self‐administered diet history questionnaire and in the pre‐ and post‐intervention period 48 hr urine and fasting blood samples were collected. ϵdA in urine was analyzed by an immuno‐precipitation‐high performance liquid chromatography‐fluorescence detection method. ϵdA excretion (/48 hr) in the 59 postmenopausal Japanese women with complete urine collection ranged from 12–226 pmol at the pre‐intervention. At the pre‐intervention, ϵdA excretion was positively associated with urinary salt excretion (R = 0.33, p = 0.01) and ω‐6 polyunsaturated fatty acid intake (%energy value, R = 0.28, p = 0.03) in the 59 women. The average ϵdA excretion in the intervention group was 61 pmol at pre‐intervention and 44 pmol at post‐intervention (p = 0.14). In the control group, it was 58 pmol at pre‐intervention and 75 pmol at post‐intervention (p = 0.24). During the intervention period, 18/29 (62%) of the subjects in the intervention group exhibited the decreased excretion and 10/26 (38%) in the control group (p = 0.08). Results from this pilot study suggest urinary ϵdA as a potential biomarker of DNA damage possibly derived from salt‐induced inflammation and LPO; further exploration of ϵdA in human biomonitoring studies is warranted.

Soft Drink Intake Is Associated with Diet Quality Even among Young Japanese Women with Low Soft Drink Intake

BACKGROUND Unsweetened traditional Japanese tea has long been the main beverage consumed in Japan, with soft drinks only recently forming a part of peoples diets. Evidence suggests an association between soft drink intake and poor diet quality among youth in the United States. The association is not yet fully examined in the population with relatively low intake level of soft drinks such as the current Japanese population. OBJECTIVE To investigate the association of soft drink intake with dietary intake among young Japanese women. DESIGN A cross-sectional survey assessed dietary intake using a validated, self-administered, diet history questionnaire. SUBJECTS/SETTING Female dietetics students aged 18 to 20 years (n=3,931) in April 2005 in Japan. STATISTICAL ANALYSES Multivariate linear regression analyses examined the relationship of soft drink intake with that of foods, beverages, energy, and nutrients. RESULTS Mean+/-standard deviation soft drink intake was 70.6+/-93.0 g/1,000 kcal. Soft drink intake was significantly associated positively with intake of confection, fat and oil, noodles, 100% vegetable and fruit juices, diet soft drinks, energy, and carbohydrates and negatively with intake of vegetables, fruits, pulses, fish and shellfish, rice, eggs, potatoes, milk, coffee and black tea, traditional Japanese tea, protein, dietary fiber, cholesterol, and most of the micronutrients examined. CONCLUSIONS Not only among Western populations, but also among non-Western populations, soft drink intake may be an important factor to consider in evaluating overall dietary intake and diet quality.

Monetary cost of self-reported diet in relation to biomarker-based estimates of nutrient intake in young Japanese women.

OBJECTIVE All previous studies on monetary diet cost have examined the relationship of monetary cost of self-reported diet to self-reported, rather than biomarker-based, estimates of dietary intake. The present cross-sectional study examined the association between monetary costs of self-reported diet and biomarker-based estimates of nutrient intake. DESIGN Monetary diet cost (Japanese yen/1000 kJ) was calculated based on dietary intake information from a self-administered, comprehensive diet history questionnaire using retail food prices. Biomarker-based estimates of nutrient intake (percentage of energy for protein and mg/1000 kJ for K and Na) were estimated based on 24 h urinary excretion and estimated energy expenditure. SETTING A total of fifteen universities and colleges in Japan. SUBJECTS A total of 1046 female Japanese dietetic students aged 18-22 years. RESULTS Total monetary diet cost showed a significant positive association with biomarker-based estimates of protein, K and Na. Vegetables and fish were not only the main contributors to total monetary diet cost (16.4 % and 15.5 %, respectively) but also were relatively strongly correlated with total monetary diet cost (Pearsons correlation coefficient: 0.70 and 0.68, respectively). Monetary cost of vegetables was significantly positively associated with all three nutrients, while that of fish showed a significant and positive association only with protein. CONCLUSIONS Total monetary cost of self-reported diet was positively associated with biomarker-based estimates of protein, K and Na intake in young Japanese women, and appeared mainly to be explained by the monetary costs of vegetables and fish.