Cruciferae interact with the UGT1A1*28 polymorphism to determine serum bilirubin levels in humans.

UDP-glucuronosyltransferase (UGT) 1A1 is a conjugating biotransformation enzyme that plays a role in maintaining levels of endogenous compounds (e.g., bilirubin) and handling exogenous compounds, including carcinogens. The UGT1A1*28 polymorphism results in decreased UGT1A1 promoter activity due to 7 thymine-adenine (TA) repeats instead of the commonly found 6 repeats. Studies indicate that foods from the botanical families Cruciferae (e.g., broccoli), Rutaceae (citrus), Liliaceae (e.g., onions), and Leguminosae (legumes) may increase UGT activity. We investigated, in an observational study, whether foods from these botanical groups were associated with increased UGT1A1 activity as indicated by serum bilirubin concentrations and whether the effect varied by UGT1A1*28 genotype, comparing those homozygous for the [TA](7)-repeat allele (7/7) to homozygous wild-types (6/6) and heterozygotes (6/7) combined. Healthy volunteers completed 3-d food records. Blood samples were drawn for genomic DNA collection and bilirubin measures. For total, direct, and indirect bilirubin measures, there was no significant association with any botanical group independently. There was a significant inverse association between all 3 bilirubin measures and interaction of UGT1A1*28 genotype with Cruciferae intake (P < 0.02 for each measure); individuals with the 7/7 genotype had reduced bilirubin concentrations with increased intake of cruciferous vegetables, whereas individuals with the 6/6 or 6/7 genotype did not. With regard to UGT1A1-conjugated carcinogens (e.g., heterocyclic amines, polycyclic aromatic hydrocarbons), individuals with decreased UGT1A1 activity due to the 7/7 genotype may be at greater risk for carcinogenesis, but our results imply that they also may have greater opportunity to decrease that risk through dietary intervention.

A case-control study of risk factors for fibrocystic breast conditions: Shanghai Nutrition and Breast Disease Study, China, 1995-2000.

This study was conducted to identify reproductive and dietary factors associated with benign proliferative mammary epithelial cell changes. Subjects were women enrolled in a randomized trial of breast self-examination in Shanghai, China. Women who developed fibrocystic breast conditions classified as nonproliferative (175 women), proliferative (181 women), or proliferative with atypia (33 women) between 1995 and 2000 and 1,070 unaffected trial participants were administered general risk factor and food frequency questionnaires. Conditional logistic regression was used to estimate adjusted odds ratios and 95% confidence intervals. High parity and consumption of fresh fruits and vegetables were more strongly associated with a reduced risk of proliferative and atypical lesions than with nonproliferative conditions. For the fourth quartile of consumption versus the first, odds ratios for lesions diagnosed as nonproliferative, proliferative, and proliferative with atypia were 0.4 (95% confidence interval (CI): 0.2, 0.7), 0.2 (95% CI: 0.1, 0.4), and 0.1 (95% CI: 0.03, 0.5), respectively, for fruit intake and 0.6 (95% CI: 0.3, 1.1), 0.4 (95% CI: 0.2, 0.7), and 0.1 (95% CI: 0.1, 0.9), respectively, for vegetable intake. Reduced but nonsignificant risks in relation to soy products were observed for proliferative and atypical lesions. No single nutrient or botanical family was appreciably more strongly associated with proliferative conditions than with nonproliferative conditions, after results were controlled for total fruit and vegetable consumption. A diet rich in fruits and vegetables may reduce cellular proliferation in the mammary epithelium; this is one mechanism by which such a diet could reduce risk of breast cancer.

Selected nutritional biomarkers predict diet quality.

OBJECTIVE: To examine associations of biomarkers of nutrient intake with overall diet quality. SUBJECTS: A convenience sample of 102 healthy postmenopausal women in Seattle, Washington (USA). DESIGN AND METHOD: Participants attended a study centre where they provided fasting blood specimens and completed a 122-item validated food-frequency questionnaire (FFQ). Data from the FFQ were used to calculate Diet Quality Index (DQI) scores and categorise women as having diets of excellent, good, fair or poor quality. The blood specimens were analysed for nine phospholipid fatty acids (as percentage of total) and serum concentrations of vitamin C, alpha-tocopherol, gamma-tocopherol, vitamin B12, folate and six carotenoids. Multivariate linear regression was used to model associations of the nutrient biomarkers with DQI scores. RESULTS: Compared with women with poor-quality diets, women with excellent diets, as measured by the DQI, had higher plasma concentrations of vitamin C (P for trend=0.01), alpha-tocopherol (P for trend=0.02) and beta-cryptoxanthin (P for trend=0.03). Women with excellent diets also had lower proportions of plasma phospholipid fatty acids of two potentially atherogenic fatty acids: stearic acid (P for trend=0.01) and behenic acid (P for trend=0.03). A group of six biomarkers explained a moderate proportion of the total variability in DQI scores (36%). CONCLUSIONS: These objective measures of dietary intake support the use of the DQI as a useful tool to measure dietary patterns.

Validation of a soy food-frequency questionnaire and evaluation of correlates of plasma isoflavone concentrations in postmenopausal women.

BACKGROUND: Soy foods may have various health benefits, but little is known about the patterns and correlates of soy consumption among postmenopausal women in the United States. OBJECTIVE: We assessed the reliability and validity of a soy food-frequency questionnaire (FFQ) and examined demographic, lifestyle, and dietary correlates of plasma isoflavone concentrations in postmenopausal women. DESIGN: In this cross-sectional study, soy isoflavone intake and plasma isoflavone concentration were analyzed in 96 postmenopausal women aged 50-79 y; the data were obtained at 2 visits that were 1 wk apart. Intake was determined with a 20-item soy FFQ and a comprehensive FFQ that included questions about tofu and soymilk. Fasting plasma daidzein and genistein concentrations were determined with liquid chromatography-mass spectrometry. RESULTS: Intraclass correlations between week 1 and week 2 values were >0.98 for both the soy and comprehensive FFQs. Median reported isoflavone intake was <2 mg/d. Pearson's product-moment correlation coefficients relating isoflavone intakes with plasma isoflavone concentrations ranged from 0.35 to 0.43. Plasma isoflavone concentrations were positively associated with age, fiber consumption, servings of fruit and vegetables, and dietary supplement use and were inversely associated with caffeine consumption; no associations with body mass index, education, dietary beliefs, activity level, alcohol intake, or fat intake were observed. CONCLUSIONS: Within a population with low soy consumption, the soy FFQ and comprehensive FFQ showed good reliability and moderate validity. Associations of plasma isoflavone concentrations with other dietary behaviors suggest that these compounds may serve as biomarkers of health behaviors in populations with low soy consumption.

Participant characteristics associated with errors in self-reported energy intake from the Women's Health Initiative food-frequency questionnaire.

BACKGROUND: Errors in self-reported dietary intake threaten inferences from studies relying on instruments such as food-frequency questionnaires (FFQs), food records, and food recalls. OBJECTIVE: The objective was to quantify the magnitude, direction, and predictors of errors associated with energy intakes estimated from the Women's Health Initiative FFQ. DESIGN: Postmenopausal women (n = 102) provided data on sociodemographic and psychosocial characteristics that relate to errors in self-reported energy intake. Energy intake was objectively estimated as total energy expenditure, physical activity expenditure, and the thermic effect of food (10% addition to other components of total energy expenditure). RESULTS: Participants underreported energy intake on the FFQ by 20.8%; this error trended upward with younger age (P = 0.07) and social desirability (P = 0.09) but was not associated with body mass index (P = 0.95). The correlation coefficient between reported energy intake and total energy expenditure was 0.24; correlations were higher among women with less education, higher body mass index, and greater fat-free mass, social desirability, and dissatisfaction with perceived body size (all P < 0.10). CONCLUSIONS: Energy intake is generally underreported, and both the magnitude of the error and the association of the self-reporting with objectively estimated intake appear to vary by participant characteristics. Studies relying on self-reported intake should include objective measures of energy expenditure in a subset of participants to identify person-specific bias within the study population for the dietary self-reporting tool; these data should be used to calibrate the self-reported data as an integral aspect of diet and disease association studies.

Dietary determinants of plasma enterolactone.

Enterolactone is a lignan produced by fermentation of dietary precursors in the human gut. Because lignan precursors are uniquely found in plant foods, plasma enterolactone concentration may serve as a biological marker of plant food consumption. This cross-sectional study examined associations of dietary intake with plasma enterolactone concentration. Weight-stable, 20-40-year-old volunteers (115 women and 78 men in Seattle, Washington) reporting intake of < or =2.5 or > or =4.5 fruit and vegetable servings/day and no antibiotic use for > or =3 months completed a food frequency questionnaire and 3-day food record. Time-resolved fluoroimmunoassay was used to measure plasma enterolactone. Based on diet records, plasma enterolactone was positively correlated with daily vegetable servings (r = 0.17; P < 0.05), fiber (r = 0.36; P < 0.0001), alcohol (r = 0.24; P < 0.001), caffeine (r = 0.21; P < 0.001), and daily botanical group servings [Chenopodiaceae (r = 0.15; P < 0.05), Juglandaceae (r = 0.15; P < 0.05), Leguminosae (r = 0.20; P < 0.001), Pedaliaceae (r = 0.20; P < 0.001), and Vitaceae (r = 0.20; P < 0.001)]. Fat-related variables were not correlated with plasma enterolactone. Based on linear regression models, plasma enterolactone increased by 37.0% (SE = 2.3%) for each 10-g increase in fiber and by 6.6% (SE = 0.2%) for each 50-mg serving of caffeine. Participants consuming 0.5-1 alcoholic drink/day had plasma enterolactone concentrations that were 131.4% (SE = 37.6%) higher than those of nondrinkers. Although plasma enterolactone may be useful as a biological measure of exposure to lignan-containing foods, it may be of limited use as a specific biomarker of fruit and vegetable or plant food intake because coffee, tea, and alcoholic beverages also significantly increase its plasma concentration.