Sex and seasonal variations of plasma retinol, alpha-tocopherol, and carotenoid concentrations in Japanese dietitians.

AIM: To clarify sex and seasonal variations of plasma antioxidant concentrations among middle-aged Japanese. SUBJECTS AND METHODS: We investigated sex and seasonal variations of plasma antioxidant concentrations, including retinol, alpha-tocopherol, and carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein and lycopene), in 55 middle-aged dietitians (46 women and 9 men) in Aichi Prefecture, Central Japan, who took no supplements from autumn 1996 to summer 1997. Reversed-phase high performance liquid chromatography was used to measure plasma antioxidant concentrations in overnight-fasting blood samples. RESULTS: Plasma levels of alpha-tocopherol, alpha-/beta-carotene, b-cryptoxanthin and lutein were significantly influenced by sex, being significantly higher for women than men in each corresponding season; retinol and lycopene, however, showed no such difference. For women, winter values of alpha-tocopherol, alpha-/beta-carotene, lutein and lycopene were significantly lower than corresponding summer values, and had reached their annual lowest. Retinol failed to show any significant seasonal variation, whereas the winter value of beta-cryptoxanthin had reached its annual highest. For men, beta-cryptoxanthin exhibited significant seasonal changes and was also highest in winter. Winter values of alpha-tocopherol, alpha-/beta-carotene and lycopene were lower compared with other seasons, but not statistically significant, probably due to the small sample size. CONCLUSIONS: The findings indicate that sex and seasonal variations of plasma antioxidant concentrations should be taken into account in nutritional epidemiologic studies.

Development of a data-based short food frequency questionnaire for assessing nutrient intake by middle-aged Japanese.

OBJECTIVE: Development of a data-based short food frequency questionnaire (FFQ) for evaluating intake of nutrients by middle-aged Japanese. METHODS: Of 102 foods listed in the formerly developed semi-quantitative FFQ, foods having similar nutrient contents were combined into 72 foods/food groups by research dietitians. Nutrient contents were computed by multiplying the weight of foods consumed and its nutrient contents. Next, a cumulative multiple regression coefficient up to 0.85 was applied, and 47 foods/food groups were chosen for a brief FFQ for assessing intake of 21 nutrients including energy, protein, fat, carbohydrate, vitamins, minerals, and dietary fibers. RESULTS: The 47 foods/food groups comprised rice, bread and noodles (3), margarine/butter (2), eggs (1), milk and dairy products (2), soybean and soybean products (3), miso-soup (1), meat including beef, pork and chicken (4), fish (3), other fish, shellfish and fish products (4), green-yellow vegetables (5), other vegetables and mushrooms (3), edible roots (4), seaweeds (1), mayonnaise (1), fried dishes (2), seeds (1), fruit (2), beverages, including alcohol (3), and confectioneries (2). CONCLUSIONS: The evidence-based short FFQ efficiently covered the intake of 21 nutrients, and may be competent to rank the middle-aged general public Japanese according to intake of nutrients.

Plasma concentrations of (n-3) highly unsaturated fatty acids are good biomarkers of relative dietary fatty acid intakes: a cross-sectional study.

A cross-sectional study was conducted to clarify the associations of lifestyle factors (habitual exercise, alcohol intake and smoking habit) and plasma fatty acid (FA) concentrations as biomarkers of dietary FA intakes. We collected 7-d weighed diet records, lifestyle information and blood samples from 15 male and 79 female Japanese dietitians, and estimated dietary FA intakes and analyzed plasma FA concentrations. Plasma concentrations of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and (n-3) highly unsaturated FA (HUFA) derived from marine foods, but not linoleic and alpha-linolenic acid from plant origins, demonstrated positive correlations with dietary intakes (r = 0.303-0.602, P < 0.05) in both genders. Multiple linear regression analyses adjusted for age, BMI, total energy intake, fat (or respective FA) consumption and lifestyle factors showed that dietary intakes of EPA, DHA and (n-3) HUFA were positively associated with age in men (P < 0.05) and negatively associated with BMI in women [P < 0.01 for DHA and (n-3) HUFA]. The plasma concentrations of EPA, DHA and (n-3) HUFA in women were found to be positively associated with age and marine oil (or respective FA) intake (P < 0.01), and negatively associated with total energy intake [P < 0.05 for EPA and (n-3) HUFA]. Lifestyle factors were not associated with dietary FA intakes and plasma FA concentrations. These findings suggest that the plasma concentrations of EPA, DHA and (n-3) HUFA might be useful biomarkers for the assessment of relative FA intakes without considering associations with habitual exercise, alcohol intake and smoking habit.

Seasonal variation in consumption and plasma concentrations of fatty acids in Japanese female dietitians.

OBJECTIVE: To study seasonal variation in intake and plasma concentrations of fatty acids (FAs) in Japanese female dietitians. SUBJECTS AND METHODS: We assessed consumption of FAs based on four season 7 consecutive day weighed diet records from 71 Japanese female dietitians in 1996-1997. Using overnight fasting venous blood, plasma concentrations of FAs were analyzed by gas chromatography. Seasonal variation in consumption and plasma concentrations was examined by ANOVA for repeated values, followed by Tukey's multiple t-test. We calculated Spearman's partial rank correlation coefficients (CCs) between intake and plasma concentrations of FAs. Furthermore, we computed inter-seasonal Spearman's partial rank CCs for consumption and plasma concentrations of FAs. RESULTS: Statistically significant seasonal differences were observed in consumption for most FAs, except for myristic acid, monounsaturated FAs, oleic acid, n-6 polyunsaturated FAs (PUFAs), linoleic acid, gamma-linolenic acid, alpha-linolenic acid, PUFAs/saturated FAs, and n-6 PUFAs/n-3 PUFAs, and for most plasma concentrations, except for stearic acid, gamma-linolenic acid, n-3 PUFAs, alpha-linolenic acid, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and n-3 highly unsaturated FAs (HUFAs). However, statistically significant Spearman's partial rank CCs between intake and plasma concentrations were observed for EPA, DHA, n-3 HUFAs, n-6 PUFAs/n-3 PUFAs and n-6 PUFAs/n-3 HUFAs for almost all seasons. CONCLUSIONS: Seasonal variation exists in consumption and plasma concentrations of FAs, so that this should be taken into account in epidemiological analyses, including case-control and cohort studies.

Daily, weekly, seasonal, within- and between-individual variation in nutrient intake according to four season consecutive 7 day weighed diet records in Japanese female dietitians.

OBJECTIVE: To study daily, weekly, seasonal, within- and between-individual variance in intake of selected nutrients and minimal days necessary for assessing true intake with a specified degree of error based on four season consecutive 7 day weighed diet records (WDRs). SUBJECTS AND METHODS: We evaluated consumption of energy and 30 nutrients based on four season consecutive 7 day WDRs from 80 Japanese female dietitians in 1996-1997. We examined daily, weekly, seasonal, within- and between-individual variation in nutrient intake, relative contributions of their variances to total variance, and minimal days required to estimate a person's nutrient intake within 10% and 20% of their true mean with 95% confidence intervals. RESULTS: The relative contributions of variation for all nutrients by person were larger than those by day, week and season. Within-individual variances were greater than the between-individual variances. The ratios of within- vs. between-individual variances thus ranged from 1.3-26.9. Minimal days necessary for estimating nutrient consumption per person within 10% (20%) of the true mean with 95% confidence intervals ranged from 10-35 (3-9) days for energy and major nutrients and 15-640 (4-160) days for micro-nutrients. CONCLUSIONS: The relative contributions of variability by person were largest for all nutrients, followed by those due to sequence of days, season and day of week. Within-individual variation was greater than between-individual variation. Minimal days necessary for ascertaining major nutrients were in general fewer than micro-nutrients.

Reproducibility of a semi-quantitative food frequency questionnaire in Japanese female dietitians.

OBJECTIVE: To examine reproducibility of assessed intake of foods and nutrients according to a semi-quantitative food frequency questionnaire (SQFFQ) in Japanese female dietitians. SUBJECTS AND METHODS: An SQFFQ was self-administered to 106 (21 male and 85 female) Japanese dietitians in Aichi prefecture in autumn 1996 and the same questionnaire was repeated in autumn 1997. Reproducibility was evaluated in terms of consumption of 15 foods and energy and 30 macro- and micro-nutrients based on the SQFFQ from 84 Japanese female dietitians. RESULTS: For intake of foods, Pearson's correlation coefficients (CCs) with log-transformation and energy adjustment (minimum-median-maximum) ranged from 0.35 (beverages)-0.61-0.71 (dairy products). ANOVA intraclass correlation coefficients (ICCs) with log-transformation and energy adjustment ranged from 0.49 (beverages)-0.74-0.82 (dairy products). Spearman's rank CCs with energy adjustment ranged from 0.43 (confectionery)-0.57-0.76 (dairy products). Weighted kappa statistics with energy adjustment ranged from 0.34 (confectionery)-0.49-0.71 (dairy products). For consumption of nutrients, Pearson's CCs with log-transformation and energy adjustment ranged from 0.23 (zinc)-0.55-0.74 (insoluble dietary fiber). ANOVA ICCs with log-transformation and energy adjustment ranged from 0.37 (zinc)-0.70-0.84 (insoluble dietary fiber). Spearman's rank CCs with energy adjustment ranged from 0.25 (zinc)-0.56-0.74 (magnesium). Weighted kappa statistics with energy adjustment ranged from 0.25 (zinc)-0.50-0.68 (insoluble dietary fiber). CONCLUSIONS: Substantially high reproducibility of consumption of foods and nutrients was attained from an SOFFQ self-administered to Japanese female dietitians.

Folate intake and food sources in Japanese female dietitians.

OBJECTIVE: To assess intake of folate/folic acid and food sources in Japanese female dietitians. SUBJECTS AND METHODS: We evaluated folate consumption based on four season 7 consecutive day weighed diet records (WDRs) provided by 80 Japanese female dietitians and compared the results with data from a national survey. We then selected informative foods for folate intake on the basis of 2,240 WDRs according to contribution and multiple regression analyses. RESULTS: Daily folate consumption (mean±SD) among Japanese dietitians was 413±158 µg from raw foods and 343±128 µg from cooked foods. Average residual rate after cooking was 84±8%. Folate intake in summer was lower than that in other seasons by analysis of variance. According to contribution and multiple regression analyses, the major contributors were vegetables, fruit and green tea. CONCLUSIONS: Daily folate intake among Japanese female dietitians was far greater than the 200 µg recommended daily allowance for the Japanese. Irrespective of selection methods and raw/cooked foods, major folate sources were found to be green tea along with vegetables and fruit.