Biomedical subjects

L Beth Dixon

Publications and source records attributed to L Beth Dixon.

13 recordsLinked to original sources

PubMed2006

Supplemental and dietary vitamin E, beta-carotene, and vitamin C intakes and prostate cancer risk.

BACKGROUND: Vitamin E, beta-carotene, and vitamin C are micronutrient antioxidants that protect cells from oxidative damage involved in prostate carcinogenesis. In separate trials, supplemental vitamin E was associated with a decreased risk of prostate cancer among smokers and supplemental beta-carotene was associated with a decreased risk of prostate cancer among men with low baseline plasma beta-carotene levels. METHODS: We evaluated the association between intake of these micronutrient antioxidants from foods and supplements and the risk of prostate cancer among men in the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. At baseline, trial participants completed a 137-item food frequency questionnaire that included detailed questions on 12 individual supplements. Cox proportional hazards models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs). All statistical tests were two-sided. RESULTS: We identified 1338 cases of prostate cancer among 29 361 men during up to 8 years of follow-up. Overall, there was no association between prostate cancer risk and dietary or supplemental intake of vitamin E, beta-carotene, or vitamin C. However, among current and recent (i.e., within the previous 10 years) smokers, decreasing risks of advanced prostate cancer (i.e., Gleason score > or = 7 or stage III or IV) were associated with increasing dose (RR for > 400 IU/day versus none = 0.29, 95% CI = 0.12 to 0.68; Ptrend = .01) and duration (RR for > or = 10 years of use versus none = 0.30, 95% CI = 0.09 to 0.96; Ptrend = .01) of supplemental vitamin E use. Supplemental beta-carotene intake at a dose level of at least 2000 microg/day was associated with decreased prostate cancer risk in men with low (below the median of 4129 microg/day) dietary beta-carotene intake (RR = 0.52, 95% CI = 0.33 to 0.81). Among smokers, the age-adjusted rate of advanced prostate cancer was 492 per 100,000 person-years in those who did not take supplemental vitamin E, 153 per 100,000 person-years in those who took more than 400 IU/day of supplemental vitamin E, and 157 per 100,000 person-years in those who took supplemental vitamin E for 10 or more years. Among men with low dietary beta-carotene intake, the age-adjusted rate of prostate cancer was 1122 per 100,000 person-years in those who did not take supplemental beta-carotene, and 623 per 100,000 person-years in those who took at least 2000 microg/day of supplemental beta-carotene. CONCLUSIONS: Our results do not provide strong support for population-wide implementation of high-dose antioxidant supplementation for the prevention of prostate cancer. However, vitamin E supplementation in male smokers and beta-carotene supplementation in men with low dietary beta-carotene intakes were associated with reduced risk of this disease.

Adult↗

PubMed2006

Bone health of immigrant Chinese women living in New York City.

Osteoporosis is a serious national and global public health problem, but data on bone health are limited for Asian women living in the U.S., the majority of whom are Chinese. For this study, we measured bone mineral density (BMD) by dual energy X-ray densitometry (DXA) at the lumbar spine and hip region in 300 immigrant Chinese women, ages 40-90 y, living in New York City. We also collected demographic and health data, information about knowledge and care for osteoporosis, and anthropometric measures, and estimated calcium intake from the women. In our sample, 55% had osteoporosis and 38% had low bone mass (osteopenia). Older age, lower body mass index (BMI), and shorter height were associated with lower BMD at all sites. Years lived in the U.S. and number of children were also associated with lower BMD of the lumbar spine. Chinese women who emigrated from Mainland China had lower BMD at the lumbar spine and femoral neck than Chinese women who emigrated from Hong Kong, after adjusting for potential confounders. Both groups of immigrant women had lower BMD at all sites than a national sample of U.S. Caucasian women. Although the women in our study had generally poor knowledge about osteoporosis, most could identify at least one food rich in calcium. The large number of immigrant Chinese women in New York City with osteoporosis calls for major efforts to increase awareness, prevention, diagnosis, and treatment of this condition in this susceptible population.

Absorptiometry, Photon↗

PubMed2006

Predictors for research involvement among registered dietitians.

OBJECTIVE: The primary aim of this study was to measure registered dietitians' (RDs') research involvement (by creating a research score) and to determine whether their perceptions, attitudes, and knowledge of evidence-based practice and key antecedent factors (eg, sociodemographic characteristics, education and training, professional experiences, and employment setting) predicted their research involvement. DESIGN: This cross-sectional, descriptive study used the Dietitian Research Involvement Survey and followed the Tailored Design Method. SUBJECTS/SETTING: This study surveyed 258 randomly selected RDs from seven dietetic practice groups of the American Dietetic Association. STATISTICAL ANALYSES PERFORMED: Descriptive statistics, bivariate relationships, and multiple linear regression analyses were conducted to test whether perceptions, attitudes, and knowledge of evidence-based practice score and antecedent factors predicted the research score of dietitians. RESULTS: Perceptions, attitudes, and knowledge of evidence-based practice score (r = 0.59, P < 0.0005), level of education (r = 0.53, P < 0.0005), taking a research course (r = 0.40, P < 0.0005), last time read research (r = 0.35, P < 0.0005), frequency of professional reading (r = 0.32, P < 0.0005), primary area of practice (r = 0.14, P = 0.02), association memberships (r = 0.14, P = 0.02), and dietetic practice group affiliation (r = 0.14, P = 0.02) were significantly correlated with research score. Using multivariate linear regression, the perceptions, attitudes, and knowledge of evidence-based practice score (beta = 0.48, P < 0.0005) and level of education (beta = 0.39, P < 0.0005) were identified as the strongest predictors of research score. CONCLUSIONS: Involvement in research by RDs is largely determined by their perceptions, attitudes, and knowledge of evidence-based practice and their level of education. Additional education and training related to research methodology and design, and evidence-based practice, is essential for greater participation in research activities by RDs.

Adult↗

PubMed2006

Carotenoid and tocopherol estimates from the NCI diet history questionnaire are valid compared with multiple recalls and serum biomarkers.

To improve the measurement of usual dietary intake, the National Cancer Institute developed a cognitively based Diet History Questionnaire (DHQ), which has been validated against four 24-h dietary recalls (4 24-HR) for energy, macronutrients, and several vitamins and minerals. This analysis used data from The Eating at America's Table Study (EATS) to determine the validity of estimates for carotenoids and tocopherols from the DHQ. Over the course of a year, 163 participants provided 1 or 2 blood samples and completed the DHQ and 4 24-HR. For both the DHQ and the 4 24-HR, crude correlations between serum and diet were modest to strong for the provitamin A carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin), low to modest for lycopene, and very low for lutein. The individual dietary tocopherols were weakly correlated with the serum tocopherols, but vitamin E from food and dietary supplements was strongly and positively correlated with serum alpha-tocopherol and strongly and inversely correlated with serum gamma-tocopherol for both instruments. Adjustment for energy, BMI, smoking status, serum total cholesterol, and serum triacylglycerol did not appreciably change the correlations. Using the method of triads, validity coefficients for the DHQ were comparable to the 4 24-HR and were especially strong for alpha-carotene, beta-cryptoxanthin, lutein + zeaxanthin, and total vitamin E in men and gamma-tocopherol and total vitamin E in women. In this study, there was no advantage of 2 blood samples over 1, suggesting reasonably stable ranking of individuals for these biomarkers, which is important for large epidemiologic studies that typically obtain only 1 blood sample for biomarker status.

Adult↗

PubMed2006

Dietary intake and risk of coronary heart disease differ among ethnic subgroups of black Americans.

Coronary heart disease (CHD) morbidity and mortality are more prevalent in Blacks than Whites in the United States. Most studies evaluate the dietary intake and health of Black Americans as one group and do not consider possible differences among ethnic subgroups within the U.S. Black population. We used data from NHANES III to assess whether dietary intake, CHD risk factors, and predicted 10-y risk of CHD differed between non-Hispanic Black adults born in the United States (NHB-US), and non-Hispanic and Hispanic Black adults born outside of the United States (NHB-non US, HB-non US). Data were provided from single 24-h dietary recalls, biochemical measures, the medical examination, and self-reported responses to survey questions. NHB-US had higher intakes of energy, fat, protein, meat, added sugars, and sodium, and lower intakes of fruits, fiber, and most micronutrients. NHB-US also had higher predicted 10-y risk of developing CHD (5.8%) than NHB-non US (3.7%, P<0.001) or HB-non US (4.7%, P=0.017). Both immigrant groups had better CHD risk profiles and lower proportions of persons with metabolic syndrome and other CHD-related conditions. Our findings show differences in dietary intake and risk of CHD and related health conditions among ethnic subgroups of Blacks living in the United States. Future studies of diet and health should consider cultural differences within the Black population to better understand and reduce overall health disparities in the United States.

Adult↗

PubMed2006

A prospective study of lycopene and tomato product intake and risk of prostate cancer.

BACKGROUND: Dietary lycopene and tomato products may reduce risk of prostate cancer; however, uncertainty remains about this possible association. METHODS: We evaluated the association between intake of lycopene and specific tomato products and prostate cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a multicenter study designed to investigate cancer early detection methods and etiologic determinants. Participants completed both a general risk factor and a 137-item food frequency questionnaire at baseline. A total of 1,338 cases of prostate cancer were identified among 29,361 men during an average of 4.2 years of follow-up. RESULTS: Lycopene intake was not associated with prostate cancer risk. Reduced risks were also not found for total tomato servings or for most tomato-based foods. Statistically nonsignificant inverse associations were noted for pizza [all prostate cancer: relative risk (RR), 0.83; 95% confidence interval (95% CI), 0.67-1.03 for >or=1 serving/wk versus < 0.5 serving/mo; P(trend)=0.06 and advanced prostate cancer: RR, 0.79; 95% CI, 0.56-1.10; P(trend)=0.12] and spaghetti/tomato sauce consumption (advanced prostate cancer: RR=0.81, 95% CI, 0.57-1.16 for >or=2 servings/wk versus<1 serving/mo; P(trend)=0.31). Among men with a family history of prostate cancer, risks were decreased in relation to increased consumption of lycopene (P(trend)=0.04) and specific tomato-based foods commonly eaten with fat (spaghetti, P(trend)=0.12; pizza, P(trend)=0.15; lasagna, P(trend)=0.02). CONCLUSIONS: This large study does not support the hypothesis that greater lycopene/tomato product consumption protects from prostate cancer. Evidence for protective associations in subjects with a family history of prostate cancer requires further corroboration.

Aged↗

PubMed2005

Socioeconomic influences on bone health in postmenopausal women: findings from NHANES III, 1988-1994.

Our objectives were (1) to examine the associations of education and income with bone health in non-Hispanic White, non-Hispanic Black and Mexican-American postmenopausal women, (2) to determine if any observed associations can be explained by behavioral factors such as calcium intake and physical activity and (3) to determine if government food assistance and education are associated with increased calcium intake among low-income women. Cross-sectional data were gathered by the Third National Health and Nutrition Examination Survey, 1988-1994 (NHANES III) using a stratified multistage probability design. Bone health was indicated by total hip bone mineral density (BMD, g/cm2). Multiple linear regression was used to evaluate the associations of education, income and behavioral factors with BMD. There were 2,905 postmenopausal women with acceptable DXA scans and complete relevant data selected from a nationally representative sample of the civilian non-institutionalized population aged 2 months and older. Education and income were positively associated with BMD in Black and White women, respectively, but not in Mexican-American women. When behavioral factors were included in the analyses, associations with education and income were eliminated. Instead, positive associations with estrogen use, calcium intake and physical activity, and a negative association with smoking, were noted in White women. Among low-income women, education was associated with increased calcium intake, while participation in the Food Stamp Program was associated with increased calcium intake in Black women. We conclude that education and/or income are positively associated with BMD among Black and White postmenopausal women, and that efforts to promote bone health among low-income women are warranted.

Black or African American↗

PubMed2005

Importance of generational status in examining access to and utilization of health care services by Mexican American children.

OBJECTIVES: To describe the sociodemographic differences among Mexican American children (first, second, and third generation), non-Hispanic black children, and non-Hispanic white children; to compare the health status and health care needs of Mexican American children (first, second, and third generation) with those of non-Hispanic black children and non-Hispanic white children; and to determine whether first-generation Mexican American children have poorer health care access and utilization than do non-Hispanic white children, after controlling for health insurance status and socioeconomic status. METHODS: The Third National Health and Nutrition Examination Survey was used to create a sample of 4372 Mexican American children (divided into 3 generational groups), 4138 non-Hispanic black children, and 4594 non-Hispanic white children, 2 months to 16 years of age. We compared parent/caregiver reports of health status and needs (perceived health of the child and reported illnesses), health care access (usual source of health care and specific provider), and health care utilization (contact with a physician within the past year, use of prescription medications, physician visit because of earache/infection, and hearing and vision screenings) for different subgroups within the sample. RESULTS: More than two thirds of first-generation Mexican American children were poor and uninsured and had parents with low educational attainment. More than one fourth of first-generation children were perceived as having poor or fair health, despite experiencing similar or better rates of illnesses, compared with other children. Almost one half of first-generation Mexican American children had not seen a doctor in the past year, compared with one fourth or less for other groups. Health care needs among first-generation Mexican American children were lower, on the basis of reported illnesses, but perceived health status was worse than for all other groups. After controlling for health insurance coverage and socioeconomic status, first-generation Mexican American children and non-Hispanic black children were less likely than non-Hispanic white children to have a usual source of care, to have a specific provider, or to have seen or talked with a physician in the past year. CONCLUSIONS: Of the 3 groups of children, Mexican American children had the least health care access and utilization, even after controlling for socioeconomic status and health insurance status. Our findings showed that Mexican American children had much lower levels of access and utilization than previously reported for Hispanic children on the whole. As a subgroup, first-generation Mexican American children fared substantially worse than second- or third-generation children. The discrepancy between poor perceived health status and lower rates of reported illnesses in the first-generation group leads to questions regarding generalized application of the "epidemiologic paradox." Given the overall growth of the Hispanic population in the United States and the relative growth of individual immigrant subgroups, the identification of subgroups in need is essential for the development of effective research and policy. Furthermore, taking generational status into account is likely to be revealing with respect to disparities in access to and utilization of pediatric services.

Adolescent↗

PubMed2005

Dietary patterns and breast cancer risk: results from three cohort studies in the DIETSCAN project.

OBJECTIVE: Only a few consistent findings on individual foods or nutrients that influence breast cancer risk have emerged thus far. Since people do not consume individual foods but certain combinations of them, the analysis of dietary patterns may offer an additional aspect for assessing associations between diet and diseases such as breast cancer. It is also important to examine whether the relationships between dietary patterns and breast cancer risk are consistent across populations. METHODS: We examined the risk of breast cancer with two dietary patterns, identified as "Vegetables" (VEG) and "Pork, Processed Meat, Potatoes" (PPP), common to all cohorts of the DIETSCAN project. During 7 to 13 years of follow-up, three of the cohorts--the Netherlands Cohort Study on diet and cancer (NLCS), the Swedish Mammography Cohort (SMC), and the Ormoni e Dieta nella Eziologia dei Tumori (Italy-ORDET)--provided data on 3271 breast cancer cases with complete information on their baseline diet measured by a validated food frequency questionnaire. RESULTS: After adjustment for potential confounders, VEG was not associated with the risk of breast cancer across all cohorts. PPP was also not associated with the risk of breast cancer in SMC and ORDET, but a high PPP score tended to be inversely associated with breast cancer in the NLCS study (RR = 0.69; 95% CI, 0.52-0.92, highest versus lowest quartile). PPP differed in one aspect between the cohorts: butter loaded positively on the pattern in all cohorts except NLCS, in which butter loaded negatively and appeared to be substituted by low-fat margarine loading positively. CONCLUSION: In general, the dietary patterns showed consistent results across the three cohorts except for the possible protective effect of PPP in the NLCS cohort, which could be explained by a difference in that pattern for NLCS. The results supported the suggestion derived from traditional epidemiology that relatively recent diet may not have an important role in the etiology of breast cancer.

Adult↗

PubMed2005

Evidence-based practice: what are dietitians' perceptions, attitudes, and knowledge?

OBJECTIVE: The objective of this study was to measure dietitians' perceptions, attitudes, and knowledge of evidence-based practice (PAK score), and to determine whether antecedent factors (eg, sociodemographic characteristics, education and training, professional experiences, and employment setting) predicted PAK score. DESIGN: This cross-sectional, descriptive study used the Dietitian Research Involvement Survey following the Tailored Design Method. SUBJECTS/SETTING: This study surveyed 500 randomly selected registered dietitians from seven dietetic practice groups of the American Dietetic Association. STATISTICAL ANALYSES PERFORMED: Bivariate relationships were examined between antecedent factors and PAK score. Multiple linear regression analyses were conducted to test whether these factors predicted PAK score. RESULTS: Higher PAK scores were associated with registered dietitians who completed more years of education (r=0.28, P<.0005), had taken a research course (r=0.28, P<.0005), frequently read research articles (r=0.41, P<.0005), earned an advanced-level board certification (r=0.18, P=.004), worked full-time (r=0.26, P<.0005), or belonged to professional organizations (r=0.18, P=.003). The strongest predictors for PAK score were "last time read research" (beta=.33, P<.0005), work status (beta=.20, P<.0005), level of education (beta=.19, P=.001), and association memberships (beta=.14, P=.01). CONCLUSIONS: Results indicated that dietitians' ability to incorporate an evidence-based approach is largely determined by their education and training, work experience, and professional association involvement. This study identified a need to integrate concepts and principles of evidence-based practice into dietetics curriculums so that practitioners are able to routinely apply research findings to clinical practice.

Adult↗

PubMed2005

Calcium and dairy intake and measures of obesity in hyper- and normocholesterolemic children.

OBJECTIVE: Calcium intake has been inversely associated with body weight and body fatness in adults and, to a lesser extent, in children. Dairy intake has been inversely associated with metabolic syndrome in overweight but not normal-weight adults. We assessed whether intakes of calcium and dairy foods were associated with measures of obesity in hypercholesterolemic (HC) and normocholesterolemic (non-HC) children at baseline and over 1 year. RESEARCH METHODS AND PROCEDURES: Non-obese 4- to 10-year-old HC and non-HC children (342) completed three 24-hour dietary recalls and provided measures of relative weight (BMI and BMI z scores) and adiposity (sum of skinfolds, trunk skinfolds) at baseline, 3, 6, and 12 months. Cross-sectional and longitudinal regression analyses, stratified by cholesterol risk status (HC vs. non-HC) and age (4 to 6 years and 7 to 10 years) and adjusted for potential confounders, were conducted. RESULTS: After adjusting for age, sex, energy intake, and percentage energy from fat, calcium intake was inversely associated with BMI, sum of skinfolds, and trunk skinfolds at baseline and over 1 year in the 7- to 10-year-old non-HC children. Results from the regression models also indicated an inverse relation between intake of dairy foods and measures of obesity at baseline in these children. Calcium or dairy intake was not associated with measures of obesity in HC children or in the 4- to 6-year-old non-HC children. DISCUSSION: These results suggest a complex relation among intake of calcium and dairy foods, measures of obesity, age, and serum cholesterol in children. Older children without risk of metabolic syndrome may benefit most from increased calcium intake.

Anthropometry↗

PubMed2004

Dietary patterns associated with colon and rectal cancer: results from the Dietary Patterns and Cancer (DIETSCAN) Project.

BACKGROUND: An analysis of dietary patterns or combinations of foods may provide insight regarding the influence of diet on the risk of colon and rectal cancer. OBJECTIVE: A primary aim of the Dietary Patterns and Cancer (DIETSCAN) Project was to develop and apply a common methodologic approach to study dietary patterns and cancer in 4 European cohorts: the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study (Finland-ATBC), the Netherlands Cohort Study (NLCS) on Diet and Cancer, the Swedish Mammography Cohort (SMC), and the Ormoni e Dieta nella Eziologia dei Tumori (Italy-ORDET). Three cohorts (ATBC, NLCS, and SMC) provided data on colon and rectal cancer for the present study. DESIGN: The cohorts were established between 1985 and 1992; follow-up data were obtained from national cancer registries. The participants completed validated semiquantitative food-frequency questionnaires at baseline. RESULTS: Exploratory factor analysis, conducted within each cohort, identified 3-5 stable dietary patterns. Two dietary patterns-Vegetables and Pork, Processed Meats, Potatoes (PPP)-were common across all cohorts. After adjustment for potential confounders, PPP was associated with an increased risk of colon cancer in the SMC women (quintile 4(multivariate) relative risk: 1.62; 95% CI: 1.12, 2.34; P for trend = 0.01). PPP was also associated with an increased risk of rectal cancer in the ATBC men (quintile 4(multivariate) relative risk: 2.21; 95% CI: 1.07, 4.57; P for trend = 0.05). Neither pattern was associated with the risk of colon or rectal cancer in the NLCS women and men. CONCLUSION: Although certain dietary patterns may be consistent across European countries, associations between these dietary patterns and the risk of colon and rectal cancer are not conclusive.

Adult↗

PubMed2003

Common and country-specific dietary patterns in four European cohort studies.

The association between diet and cancer, predominantly investigated univariately, has often been inconsistent, possibly because of the large number of candidate risk factors and their high intercorrelations. Analysis of dietary patterns is expected to give more insight than analysis of single nutrients or foods. This study aimed to develop and apply a common methodological approach to determine dietary patterns in four cohort studies originating in Finland, the Netherlands, Sweden and Italy. Food items on each of the food frequency questionnaires were aggregated into 51 food groups, defined on the basis of their position in the diet pattern and possible relevance to cancer etiology. Exploratory factor analysis was used to analyze dietary patterns. Using a standardized approach, 3-5 stable dietary patterns were identified, explaining 20-29% of total variance in consumption of the food groups. Two dietary patterns, which explained most of the variance, were consistent across the studies. The first pattern was characterized by high consumption of (salad) vegetables, the second by high consumption of pork, processed meat and potatoes. In addition, a few specifically national food patterns were identified. Sensitivity analyses showed that the identified patterns were robust for number of factors extracted, distribution of input variables and energy adjustment. Our findings suggest that some important eating patterns are shared by the four populations under study, whereas other eating patterns are population specific.

Adult↗