Masayuki Akabane

Single measurement of serum phospholipid fatty acid as a biomarker of specific fatty acid intake in middle-aged Japanese men

Objective: To assess the utility of serum phospholipid fatty acid (FA) levels as a biochemical indicator of habitual dietary fatty acid intake in Japanese, whose diet is characterized by low fat intake and high intake of n-3 polyunsaturated fatty acids (PUFA) of marine origin.Subjects and methods: Eighty-seven male volunteers from four public health center districts that were part of the Japan Public Health Center based Prospective Study (JPHC Study) cohort I, were included in this study. Habitual intake of fatty acid was obtained by 7 day weighed dietary records four times (in one area only twice) in 1994–1995. Blood was collected twice, in February and August of the same year, and the composition of FA in serum phospholipid was analyzed by gas chromatography. The correlation coefficient between serum phospholipid FA levels and fatty acid intake was calculated.Results: High correlations were observed for eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA), which are marine origin n-3 PUFA (r=0.75, 0.49, 0.50, respectively). No significant correlation was observed for saturated fatty acid (SFA), although the monounsaturated fatty acid (MUFA), palmitoleic acid and oleic acid intake were moderately correlated (r=0.22, 0.35, respectively). The correlations for EPA, DPA and DHA were similar in both samples collected in February and August.Conclusions: These data suggest that in populations with a high and stable over time intake of n-3 PUFA of marine origin, a single measurement of serum phospholipids reflects the ranking of habitual intake of marine origin n-3 PUFA.European Journal of Clinical Nutrition (2001) 55, 643–650

Urinary salt excretion and stomach cancer mortality among four Japanese populations.

A relationship between salt intake and the occurrence of stomach cancer has been suggested by both epidemiologic and experimental data. To test this hypothesis, urinary excretion of salt in 24 hours and dietary intake of salt were measured in four male populations with different levels of stomach cancer mortality. Age-adjusted mortality rate of stomach cancer showed a high correlation (r2=0.995) with the average amount of salt excretion in 24-hour urine. This strong correlation, however, was not shown (r2=0.265) with dietary salt intake calculated from the standard food-composition table. The results confirmed the important role of salt in the development of stomach cancer in Japan, and raised the problem of evaluating the level of salt intake by using the uniform composition table.

Food Composition and Empirical Weight Methods in Predicting Nutrient Intakes from Food Frequency Questionnaire

PURPOSE Although the empirical weight (regression-based) method has theoretical advantages over the traditional food composition method in predicting nutrient levels from food frequency questionnaires (FFQs), the empirical assessments have been limited. METHODS We compared the validity of the two approaches for a 44-item questionnaire used in a population-based prospective study in Japan. Based on four 7-day diet records and questionnaire responses collected from a subsample of the prospective study (94 men and 107 women), we developed a food composition table and stepwise regression models to predict intakes of energy and 14 nutrients from the questionnaire. RESULTS When we applied the two methods to an independent population (207 men and 166 women) providing a 3-day diet record and responding to a 36-item dietary questionnaire, energy-adjusted and deattenuated correlation coefficients between the questionnaire and the diet records were not higher for the empirical weight method than for the food composition method; the median (range) was 0.22 (0.07-0.57) for men and 0.23 (-0.09-0.62) for women in the former method, and 0.26 (-0.04-0.58) for men and 0.38 (0.18-0.67) for women in the latter method. CONCLUSIONS We did not find the improved validity of FFQ by empirical weight method in predicting nutrient intakes.

Seasonal misclassification error and magnitude of true between-person variation in dietary nutrient intake: a random coefficients analysis and implications for the Japan Public Health Center (JPHC) Cohort Study

OBJECTIVE We examine (1) the extent to which seasonal diet assessments correctly classify individuals with respect to their usual nutrient intake, and (2) whether the magnitude of true variation in intake between individuals is seasonal. These effects could lead, respectively, to bias in estimates of relative risk for associations between usual nutrient exposure and disease, and to an increase in required sample size. SUBJECTS AND SETTING One hundred and twenty-seven families in four regions of the Japan Public Health Center (JPHC) Cohort Study. DESIGN On average, 48 weighed daily food records were collected per family over six seasons of 1994 and 1995. RESULTS A random slopes regression model was used to predict the correlation between seasonal and annual average intakes, and to estimate true between-person variation in intakes by season. Mean vitamin C intake was greatest in summer and autumn, and seasonal variation was attributable to the consumption of fruit and vegetables. Predicted correlations between seasonal and annual average vitamin C intake ranged from 0.62 to 0.87, with greatest correlations in summer and autumn. True between-person variation in vitamin C intake was also strongly seasonal, ranging from 45 to 78% of total variance, and was again greatest in summer and autumn. These effects were less seasonal among energy and 13 other nutrients. CONCLUSIONS It may be possible substantially to reduce both seasonal misclassification of individuals with respect to their usual vitamin C intake, and required sample size, by asking subjects to report high-season intake of fruit and vegetables in the JPHC Study.

Nutrient consumption and gastric cancer mortality in five regions of Japan

To explore the causes of the threefold variation in mortality rate from gastric cancer in Japan, we studied the geographic correlations between nutrient consumption and the disease in five Public Health Center districts including the regions with the highest and lowest mortality rates in the country. In the winters of 1989-1991, a three-day weighed food record was collected from 207 men and the wives of 165 of the men sampled from the five districts. The average daily consumption of selected nutrients was computed and correlated with the age-adjusted mortality rates from gastric cancer. Partial rank correlation coefficients adjusted for sex and other nutrients were 0.45, -0.80, -0.20, and -0.07 for sodium, carotene, ascorbic acid, and retinol, respectively. The results suggest that variation in gastric cancer mortality in Japan may be partly accounted for by the regional differences in consumption of sodium, carotene, and possibly ascorbic acid.

Validity and reproducibility of a self-administered questionnaire to determine dietary supplement users among Japanese.

Objective: To evaluate reproducibility and validity of a self-administered food frequency questionnaire (FFQ) to determine the dietary supplement use.Design: Questionnaire data were compared with dietary records (DR) in four 7 day periods for validity. FFQ1 and FFQ2 administered at an interval of approximately one year were compared for reproducibility.Setting and subjects: A total of 361 samples were selected for a validation study of a questionnaire from the subgroup of the Japan Public Health Center-based prospective Study on cancer and cardiovascular disease (JPHC Study) cohort II. Categories of dietary supplements in the FFQ were ‘multivitamins’, ‘β-carotene’, ‘vitamin C’, ‘vitamin E’, and ‘other supplements’. For each category, inquiries were made as to the brand name, frequency and duration of use. A dietary supplement user was defined as a subject who used a dietary supplement one or more times a week for a year or longer.Results: Prevalence of overall supplement use was 10.9%. Percentage agreement between FFQ1 and FFQ2 was 91.7%. Sensitivity and specificity of supplement use by FFQ were 80.6% and 89.2%, respectively. Sensitivity was high for ‘vitamin C’. When the self-reported categories were corrected, sensitivity for ‘multivitamins’ and ‘vitamin E’ improved.Conclusions: The FFQ on dietary supplements used for the JPHC 5 y follow-up survey was valid to determine overall use and well-defined dietary supplement use such as vitamin C. Categories must be corrected when determining multivitamin and ‘vitamin E’.Sponsorship: Grant-in-Aid from the Ministry of Health and Welfare of Japan.European Journal of Clinical Nutrition (2001) 55, 360–365

Interpopulation and intrapopulation variability of nutrient intake in five regions of Japan

Objectives: To determine the extent to which interpopulation (between-population) variance, relative to intrapopulation (within-population) variance, contribute to the total variability in nutrient intakes.Design: Cross-sectional study.Setting: Five Public Health Center districts in Japan.Subjects: Two hundred and seven men and 183 spouses.Interventions: A three-day weighed food record.Main outcome measures: The total variance in the consumption of 17 nutrient variables was partitioned by analysis of variance into its inter- and intrapopulation components separately for men and women.Results: The percentage contribution of the interpopulation to total variance differed according to the nutrient; it was notable (8–17%) for total energy, carbohydrates, phosphorus, and sodium in both men and women, but was negligible (less than 4%) for micronutrients such as retinol, carotene, thiamin, riboflavin, niacin and ascorbic acid. The ratio of intra- to interpopulation variance was estimated for 31 nutrients (17 in men and 14 in women). The point estimates of the ratio were larger than unity in all nutrients, and the lower limit of the 95% confidence intervals exceeded unity for all but 5 nutrients. Of the two sources of intrapopulation variation, intraindividual variance was larger than interindividual variance in most of the nutrient.Conclusions: The relative magnitude of interpopulation variation in dietary data can be used to quantify the range of exposure in ecological studies and to examine the heterogeneity of populations pooled for individual-based analysis.Sponsorship: This study was supported in part by Grants-in-Aid for Cancer Research from the Ministry of Health and Welfare, and for Scientific Research from the Ministry of Education, Science and Culture of Japan.

Four Food-Frequency Categories of Fruit Intake as a Predictor of Plasma Ascorbic Acid Level in Middle-Aged Japanese Men

PURPOSE Plasma levels of ascorbic acid are assumed to be determined not only by dietary amount of ingested vitamin C, but also by other dietary and nondietary factors. To assess the predictability of plasma ascorbic acid level in Japanese men, we examined its association with dietary sources of vitamin C and other lifestyle factors. METHODS In a cross-sectional study of 621 healthy men aged 40-49 years who were sampled randomly from five areas in Japan, the weekly intake frequency of foods rich in vitamin C (< 1, 1-2, 3-4, > or = 5 days/week), alcohol consumption per week, use of vitamin C supplements, and smoking were assessed by use of a food-frequency questionnaire (FFQ) (all subjects) and a 3-day weighed dietary record (DR) from 203 volunteers. RESULTS In univariate analyses of FFQ data, the intake frequency of fruit (R2 = 0.12), pickled vegetables (R2 = 0.03), potatoes (R2 = 0.01), and alcohol consumption (R2 = 0.02) were significant determinants of plasma ascorbic acid in addition to supplement use and study area. In a multivariate analysis, four FFQ categories of fruit intake accounted for 19% of the variation in plasma ascorbic acid among nonsupplement users after adjustment for study area and alcohol intake. The association between plasma ascorbic acid level and quartile of dietary vitamin C intake (mg/day) measured by DR was weaker (R2 = 0.04) than the association between plasma ascorbic acid level and dietary intake of fresh fruit (g/day) (R2 = 0.09). CONCLUSION The predictability of plasma ascorbic acid by a four-category FFQ assessment of fruit intake was superior to calculated vitamin C or fruit intake assessed by detailed DR.

Effects of human diets of two different Japanese populations on cancer incidence in rat hepatic drug-metabolizing and antioxidant enzyme systems

Hepatic enzyme systems of drug metabolism and antioxidation were investigated in rats fed the complete human diets consumed in the two Japanese prefectures, Akita and Okinawa, where the incidence of cancers was quite different: Okinawa had the lowest and Akita the highest age-adjusted mortality rate. In rats fed the human diet consumed in Okinawa, hepatic glutathione S-transferase activity was higher and lipid peroxide content was lower than in rats fed the diet consumed in Akita. These data might indicate that the number and/or quantity of the dietary components attributed to the detoxification of carcinogens and the scavenging reactive carcinogen species was much higher in the foods consumed in the population having lower cancer mortality rate.