Biomedical subjects

James R Hebert

Publications and source records attributed to James R Hebert.

33 records · Page 2Linked to original sources

PubMed2004

Algae -- a poor man's HAART?

Drawing inferences from epidemiologic studies of HIV/AIDS and in vivo and in vitro HIV inhibition by algae, we propose algal consumption as one unifying characteristic of countries with anomalously low rates. HIV/AIDS incidence and prevalence in Eastern Asia ( approximately 1/10000 adults in Japan and Korea), compared to Africa ( approximately 1/10 adults), strongly suggest that differences in IV drug use and sexual behavior are insufficient to explain the 1000-fold variation. Even in Africa, AIDS/HIV rates vary. Chad has consistently reported low rates of HIV/AIDS (2-4/100). Possibly not coincidentally, most people in Japan and Korea eat seaweed daily and the Kanemba, one of the major tribal groups in Chad, eat a blue green alga (Spirulina) daily. Average daily algae consumption in Asia and Africa ranges between 1 and 2 tablespoons (3-13 g). Regular consumption of dietary algae might help prevent HIV infection and suppress viral load among those infected.

Acquired Immunodeficiency Syndrome↗

PubMed2004

Physical activity, body size, and estrogen metabolism in women.

OBJECTIVES: Physical activity has demonstrable effects on estrogen levels in pre- and postmenopausal women. Increased oxidation of estrone to 2-hydroxyestrone (2HE) relative to 16alpha-hydroxyestrone (16HE) has been hypothesized to reduce breast cancer risk, but little is known about the effect of physical activity and body size in relation to the ratio of 2HE and 16HE in women. We examined these relationships in cross-sectional analyses of 157 North American and Chinese women. METHODS: Physical activity was assessed using validated questionnaires. Adiposity was assessed as body mass index (BMI, kg/m2) and by anthropometric methods (% body fat). Estrone metabolites, 2HE and 16HE, were determined from urine via ELISA. RESULTS: Regression analyses on the 2HE/16HE ratio revealed an interaction between leisure-time physical activities and adiposity in both North American and Chinese women (p < or = 0.05). Women reporting low levels of leisure-time physical activity who had higher BMI levels had 2HE/16HE ratios that were lower than their lean counterparts. In contrast, women with higher BMI levels that were physically active maintained higher 2HE/16HE ratios. CONCLUSION: These findings suggest that physical activity participation has the potential to modify the adverse effect of increased adiposity on estrogen metabolism in North American and Chinese women.

Adipose Tissue↗

PubMed2004

Folate intake, MTHFR C677T polymorphism, alcohol consumption, and risk for sporadic colorectal adenoma (United States).

OBJECTIVE: The purpose of this study was to investigate whether folate intake is associated with risk for incident sporadic colorectal adenoma, and whether the association differs according to methylenetetrahydrofolate reductase (MTHFR) genotypes or is modified by intakes of alcohol or other micronutrients in the folate metabolism pathway. METHODS: The authors analyzed data from a colonoscopy-based case-control study (n = 177 cases, 228 controls) conducted in North Carolina between 1995 and 1997. RESULTS: The multivariate-adjusted odds ratio (OR) comparing the highest to lowest tertile of total folate intake was 0.61 (95% confidence interval [CI] 0.35-1.05); for MTHFR C677T polymorphism CT and TT genotypes relative to the CC genotype they were, respectively, 1.09 (CI: 0.71-1.66) and 0.68 (CI: 0.29-1.61); and for heavy drinkers (> 3 drinks/week) compared to non-drinkers it was 1.67 (CI: 1.00-2.81). The multivariate-adjusted ORs comparing the highest to lowest tertile of total folate intake according to those with the MTHFR CC, CT, and TT genotypes, were, respectively, 0.65 (CI: 0.30-1.39), 0.57 (CI: 0.23-1.44), and 0.22 (CI: 0.02-3.19). For those in the lowest tertile of folate intake who drank more than three drinks a week compared to those who were in the highest tertile of folate intake and did not drink alcohol the OR was 6.54 (CI: 1.96-21.80). There was no substantial evidence for interactions of folate with intakes of methionine, vitamins B2, B6, or B12. CONCLUSIONS: These data are consistent with hypotheses and previous findings that higher folate intake may reduce risk for colorectal neoplasms, perhaps especially among those who consume more alcohol.

Adenoma↗

PubMed2003

Association between eating patterns and obesity in a free-living US adult population.

Some studies have suggested that eating patterns, which describe eating frequency, the temporal distribution of eating events across the day, breakfast skipping, and the frequency of eating meals away from home, may be related to obesity. Data from the Seasonal Variation of Blood Cholesterol Study (1994-1998) were used to evaluate the relation between eating patterns and obesity. Three 24-hour dietary recalls and a body weight measurement were collected at five equally spaced time points over a 1-year period from 499 participants. Data were averaged for five time periods, and a cross-sectional analysis was conducted. Odds ratios were adjusted for other obesity risk factors including age, sex, physical activity, and total energy intake. Results indicate that a greater number of eating episodes each day was associated with a lower risk of obesity (odds ratio for four or more eating episodes vs. three or fewer = 0.55, 95% confidence interval: 0.33, 0.91). In contrast, skipping breakfast was associated with increased prevalence of obesity (odds ratio = 4.5, 95% confidence interval: 1.57, 12.90), as was greater frequency of eating breakfast or dinner away from home. Further investigation of these associations in prospective studies is warranted.

Adult↗

PubMed2003

Personality characteristics as predictors of underreporting of energy intake on 24-hour dietary recall interviews.

OBJECTIVE: To identify characteristics associated with misreporting of energy intake during 24-hour dietary recalls (24 HR). DESIGN: Ninety-eight subjects were administered two 24 HRs. Energy expenditure was determined by doubly labeled water (44 subjects) or intake balance (54 subjects). Data on subjects' physical, lifestyle, and psychosocial characteristics were also collected. Subjects/setting At the Beltsville Human Nutrition Research Center 52 women and 46 men were administered 24HR and completed lifestyle and personality questionnaires and a memory test. Physical characteristics such as weight, percent body fat, and total energy expenditure were measured. Statistical analysis The influences of subject parameters on energy misreporting were assessed by linear regression and Pearson product-moment correlation analysis for continuous variables and by ANOVA for discrete variables. Stepwise regression was used to identify key factors in underreporting. RESULTS: Factors particularly important in predicting underreporting of energy intake include factors indicating dissatisfaction with body image; for example, a 398 kcal/day underreport in subjects attempting weight loss during the past year with a nearly 500 kcal/day underreport in women. Overall, women underreported by 393 kcal/day relative to men and women evinced a social desirability bias amounting to a 26 kcal underreport for each point on the social desirability scale. Gender differences also were evident in the effect of percent body fat (with men underreporting about 16 kcal/day/percent body fat) and in departure from self-reported ideal body weight (with women underreporting about 21 kcal/day/kg). APPLICATIONS/CONCLUSIONS: Body image and fatness are key factors on which health professionals should focus when seeking predictors of underreporting of dietary intake. Dietary interviews must be conducted to minimize bias related to subjects' tendencies to win approval and avoid censure by the interviewer. In addition, dissatisfaction with body image may lead to underestimation of food intake, therefore reducing likelihood of success in weight loss. Thus, health care professionals involved in weight loss counseling may achieve better success if treatment includes generating a more positive body image.

Adipose Tissue↗

PubMed2003

Differences between estimated caloric requirements and self-reported caloric intake in the women's health initiative.

PURPOSE: To compare energy intake derived from a food frequency questionnaire (FFQ) with estimated energy expenditure in postmenopausal women participating in a large clinical study. METHODS: A total of 161,856 women aged 50 to 79 years enrolled in the Women's Health Initiative (WHI) Observational Study (OS) or Clinical Trial (CT) [including the Diet Modification (DM) component] completed the WHI FFQ, from which energy intake (FFQEI) was derived. Population-adjusted total energy expenditure (PATEE) was calculated according to the Harris-Benedict equation weighted by caloric intakes derived from the National Health and Nutrition Examination Survey. Stepwise regression was used to examine the influence of independent variables (e.g., demographic, anthropometric) on FFQEI-PATEE. Race, region, and education were forced into the model; other variables were retained if they increased model explanatory ability by more than 1%. RESULTS: On average, FFQEI was approximately 25% lower than PATEE. Regression results (intercept=-799 kcal/d) indicated that body mass index (b=-23 kcal/day/kg.m(-2)); age (b=15 kcal/day/year of age); and study arm (relative to women in the OS, for DM women b=169 kcal/d, indicating better agreement with PATEE) increased model partial R(2)>.01. Results for CT women not eligible for DM were similar to those of women in the OS (b=14 kcal/d). There also were apparent differences by race (b=-152 kcal/d in Blacks) and education (b=-67 kcal/d in women with<high school). CONCLUSION: This large, carefully studied population confirms previous observations regarding underestimates in self-reported caloric intake relative to estimates of metabolic need in younger women, and those with higher weight, with less education, and in Blacks. These differences, along with effects related to intervention assignment, underline the need for additional research to enhance understanding of errors in dietary measurement.

Aged↗

PubMed2003

Urinary phytoestrogen excretion and breast cancer risk: evaluating potential effect modifiers endogenous estrogens and anthropometrics.

Steroid sex hormones play a central role in breast carcinogenesis. Evidence from in vitro and animal studies suggests that phytoestrogens may inhibit the development of mammary tumors through their role in regulating the synthesis, metabolism, and signal transduction of steroid hormones. In a study of 117 case-control pairs of postmenopausal women in Shanghai, we investigated whether the association between urinary phytoestrogen excretion and breast cancer risk may differ by levels of endogenous steroid sex hormones, sex hormone binding globulin (SHBG), body mass index (BMI), and waist:hip ratio (WHR). Fasting morning blood and urine samples were collected for the analysis of urinary isoflavonoids and mammalian lignans, as well as blood levels of SHBG and selected steroid hormones. For cancer patients, samples were collected before any cancer therapy. Conditional logistic regression models were used to estimate odds ratios and 95% confidence intervals after adjusting for potential confounding factors. The inverse associations between urinary phytoestrogens and breast cancer risk were found to be more evident among women with a high BMI or WHR than those with a low level of these anthropometric measurements. Although a reduced risk of breast cancer was observed among women with a high excretion rate of urinary isoflavonoids in all of the strata defined by blood SHBG and steroid hormones, the inverse association was more pronounced among women with a high blood concentration of estradiol, a low level of estrone sulfate, or a low level of SHBG. The risks of breast cancer were also reduced with increasing excretion rate of mammalian lignans, although no test for a linear association was statistically significant in stratified analyses. Findings from this study suggest that the potential protective association of phytoestrogens may be modified by BMI, WHR, and blood levels of SHBG, and steroid hormones.

Adult↗

PubMed2003

Calcium, vitamin D, and risk for colorectal adenoma: dependency on vitamin D receptor BsmI polymorphism and nonsteroidal anti-inflammatory drug use?

Previous epidemiological studies have been inconclusive in demonstrating an inverse association among calcium, vitamin D, and risk for colorectal adenoma. The purpose of this analysis was to evaluate the associations among calcium and vitamin D and risk for incident, sporadic colorectal adenoma according to the vitamin D receptor BsmI polymorphism and nonsteroidal anti-inflammatory drug (NSAID) use. We analyzed data from a colonoscopy-based case-control study (n = 177 cases, 228 controls) conducted in North Carolina between 1995 and 1997. Adjusted odds ratios (ORs) comparing participants in the highest to those in the lowest tertiles of total calcium and vitamin D intakes were 0.64 [95% confidence interval (CI), 0.35-1.15], P(trend) = 0.14 and 0.69 (95% CI, 0.41-1.18), and P(trend) = 0.19, respectively. Adjusted ORs for those in the upper tertile of total calcium intake relative to those in the lower were 0.25 (95% CI, 0.08-0.80) among those who had a Bb genotype, 0.57 (95% CI, 0.18-1.82) among those who had a bb genotype, and 0.36 (95% CI, 0.15-0.85) among those who did not take NSAIDs. The ORs for the highest tertile of calcium intake was 0.05 (95% CI, 0.01-0.41), P(trend) < 0.01 among those who were Bb and did not take NSAIDs, and 0.16 (95% CI, 0.02-1.36), P(trend) = 0.47 among those who were bb and did not take NSAIDs. These data support the hypotheses that higher calcium intakes may decrease risk for colorectal neoplasms, and that such a relationship is more readily detectable among those who do not take NSAIDs, and may be strongest among those who have at least one vitamin D receptor BsmI b allele.

Adenoma↗

PubMed2002

Systematic errors in middle-aged women's estimates of energy intake: comparing three self-report measures to total energy expenditure from doubly labeled water.

PURPOSE: To evaluate energy intake (EI) derived from a food frequency questionnaire (FFQ), seven-day dietary recall (7DDR), and seven 24-hour dietary recall interviews (24HR) for reporting errors associated with social desirability and social approval. METHODS: The FFQ and 7DDR were administered once before and once after a 14-day metabolic period during which total energy expenditure was determined using the doubly labeled water method (TEE(dlw)). Seven 24HR were conducted over the 14-day period. Data obtained from 80 healthy women (mean age = 49.1 years) were fit to linear regression models in which the EI estimates were the dependent variables and estimates of social desirability and social approval traits, body mass index [weight (kg)/ height (m)(2)], and TEE(dlw) were fit as independent variables. RESULTS: indicated that in college-educated women there was an underestimate associated with social desirability on the FFQ (-42.24 kcal/day/point on the social desirability scale; 95% CI:-75.48, -9.00). For college-educated women with an average social desirability score ( approximately 17 points) this would equal an underestimate of 507 kcal/day compared to women with the minimum score (4 points). The 7DDR was associated with a differential effect of social approval when comparing by education; i.e., there was a difference of 36.35 kcal/day/point between the two groups (-14.69 in women with >/=college and 21.66 in women with <college) (95% CI: 10.25, 62.45). CONCLUSIONS: Social desirability and social approval distort energy intake estimates from structured questionnaires, in a manner that appears to vary by educational status. Results observed have important implications for subject recruitment, data collection, and for methods of detection and control of biases in epidemiologic studies.

Adult↗

PubMed2002

Dietary exposures and oral precancerous lesions in Srikakulam District, Andhra Pradesh, India.

OBJECTIVE: To test the effect of dietary nutrients on oral precancerous lesions in a reverse-smoking (i.e. smoking with the glowing end inside the mouth) population in South India. DESIGN: Case-control. Cases with precancerous lesions were matched to an equal number of lesion-free controls matched on age (+/- 5 years), sex and village. All subjects used tobacco in some form. Dietary data were obtained using an interviewer-administered food-frequency questionnaire, designed for use in this population. All interviews were conducted blinded to the disease status of the subject. Data were analysed using logistic regression. SETTING: Nineteen rural villages in Srikakulam District, Andhra Pradesh. SUBJECTS: From a survey of 6007 tobacco users, 485 (79% women) were found to have precancerous, mostly palatal, lesions (cases), and 487 lesion-free subjects were selected as controls. RESULTS: All eligible subjects consented to participate and nearly all (> 99%) had complete data for analyses. Reverse smoking was the most common form of tobacco use among cases (81.9%) and controls (73.5%), and reverse smokers were 5.19 times more likely than chewers to have these lesions (95% confidence interval = 1.35, 19.9). After controlling for relevant covariates, including the type of tobacco use, protective linear effects were observed for zinc (70% reduction across the interquartile range, P < 0.002), calcium (34% reduction, P < 0.002), fibre (30% reduction, P < 0.009), riboflavin (22% reduction, P < 0.03) and iron (17% reduction, P < 0.05). CONCLUSIONS: Several dietary nutrients appear to protect against oral precancerous lesions that are strongly associated with reverse smoking. The results of this study indicate scope for targeting dietary factors in preventing oral cancer, which should be coupled with aggressive anti-tobacco use efforts.

Calcium, Dietary↗

PubMed2002

Urinary excretion of dithiocarbamates and self-reported Cruciferous vegetable intake: application of the 'method of triads' to a food-specific biomarker.

OBJECTIVE: Greater intake of Cruciferous vegetables (e.g. broccoli) may prevent cancer at several sites. Urinary excretion of isothiocyanate conjugates (dithiocarbamates, DTC) provides a specific biomarker of Cruciferous vegetable consumption suitable for epidemiological investigations. However, no gold-standard referent is available for evaluating urinary DTC levels as an estimator of Cruciferous vegetable consumption. We compared urinary DTC levels to intake as measured by two self-reported dietary assessment techniques. DESIGN: Cruciferous vegetable consumption was measured before and after a behavioural dietary intervention using multiple 24-hour recalls (24HR), a food-counting questionnaire (VFQ) and urinary DTC excretion levels. Analysis included a structural equation approach (Method of Triads) combining these three assessment techniques to estimate the relationship between DTC level and the study population's 'true' Cruciferous vegetable intake. SETTING: The intervention curriculum assisted participants in consuming about 2 servings per day for a 6-week period. Participants attended four classes emphasising problem-solving skills, dietary counselling and vegetable preparation skills. There were no dietary restrictions. SUBJECTS: Thirty-three healthy, free-living, post-menopausal women. RESULTS: Although few participants reported Cruciferae consumption prior to the intervention, 30 participants reported Cruciferae consumption after the intervention (Post-intervention). Urinary DTC levels were correlated with estimated intake derived from either the 24HR (r = 0.57; 95% confidence interval (95% CI) 0.28, 0.76) or VFQ (r =0.49; 95% CI 0.17, 0.71). The validity coefficient (Method of Triads) between urinary DTC excretion and an index of true Cruciferous intake was stronger than the Pearson correlation (r(v) = 0.65; 95% CI 0.35, 0.90), and comparable to estimates derived from the 24HR (r(v) = 0.82; 95% CI 0.65, 1.00) or VFQ (r(v) = 0.76; 95% CI 0.47, 0.92) method. These associations were not affected by adjustment for body mass index, energy intake, or social approval or desirability response sets. CONCLUSIONS: Food-frequency questionnaires (FFQ) suitable for large epidemiological studies may not be designed to measure all Cruciferae, and cannot capture exposure to phytochemicals derived from those vegetables. Urinary DTC measurement was significantly correlated with Cruciferae intake derived from two dietary assessment approaches, and urinary DTC levels could supplement traditional FFQ data by providing an index of recent Cruciferous vegetable intake not susceptible to reporting biases.

Aged↗

PubMed2002

Moderate to vigorous physical activity and risk of upper-respiratory tract infection.

PURPOSE: A "J"-shaped model has been proposed to describe the relationship between physical activity and risk of upper-respiratory tract infection (URTI). However, little epidemiologic evidence is available to support the contention that moderately active individuals are at lowest risk of URTI. This investigation examined differences in URTI risk between physically inactive and moderately active adults. METHODS: Observational study of 547 healthy adults (49% women) aged 20-70 yr reported URTI events at 90-d intervals over 12-month of follow-up (5 evaluations). Three 24-h physical activity recalls per evaluation were obtained and averaged to quantify total moderate-vigorous activity (> or =3.0 metabolic equivalents [MET]). Associations between URTI and physical activity levels were estimated using incidence rate ratios (IRR) derived using Poisson regression while adjusting for a number of potential confounders including age, education, anxiety, cynicism, and selected dietary factors. RESULTS: Men and women reported 1.2 (1.4) and 1.2 (1.2) URTI events per year, respectively (mean [(SD]). Adjusting for gender and potential confounders, the IRR for less than 3.93, 3.94-7.15, 7.16-11.95, and > or = 11.96 MET-h.d(-1) among men, and less than 2.38, 2.39-4.09, 4.10-6.24, and > or = 6.25 MET-h.d(-1) among women, were 1.00 (referent), 0.87 (95% confidence interval [CI], 0.70-1.07), 0.88 (95% CI, 0.71-1.09), and 0.77 (95% CI, 0.62-0.95), respectively (P(trend) = 0.03). This effect was stronger in men (P(trend) = 0.03) than women (P(trend) = 0.17), although at similar expenditure levels (6-7 MET-h.d-1), risk was reduced by about 20% in men and women. Risk reduction was most pronounced in the fall of the year (P(trend) = 0.02). CONCLUSIONS: These data support the hypothesis that moderate levels of physical activity are associated with a reduced risk for URTI.

Adult↗

PubMed2002

Urinary excretion of phytoestrogens and risk of breast cancer among Chinese women in Shanghai.

Although the majority of ecological and experimental studies have suggested a potential role of phytoestrogens in breast cancer prevention, findings from epidemiological studies have been inconsistent. Part of the inconsistencies may be attributable to the difficulty in measuring intake levels of phytoestrogens. Overnight urine samples from 250 incident breast cancer cases and their individually matched controls were analyzed for urinary excretion rates of isoflavonoids, mammalian lignans, and citrus flavonoids. The study subjects were a subset of the participants in the Shanghai Breast Cancer Study, a large population-based case-control study conducted in Shanghai from 1996-1998. To minimize potential influence of treatment on the exposure of interest, urine samples from breast cancer cases were collected before cancer therapy. Urinary excretion of total isoflavonoids and mammalian lignans was substantially lower in breast cancer cases than in controls. The median excretion rate of total isoflavonoids was 13.97 nmol/mg creatinine in cases and 23.09 in controls (P = 0.01), and the median excretion rate of total lignans was 1.77 in cases and 4.16 in controls (P < 0.01). The risk of breast cancer was reduced with increasing excretion of total isoflavonoids (P for trend, 0.04) and total lignans (P for trend, <0.01), with adjusted odds ratios of 0.62 (95% confidence interval, 0.39-0.99) and 0.40 (95% confidence interval, 0.24-0.64) observed for the highest versus the lowest tertile of total isoflavonoid and lignan excretion, respectively. The adjusted odds ratio was 0.28 (95% confidence interval, 0.15-0.50) for women who had a high excretion rate of both total lignans and isoflavonoids compared with those with a low excretion of both groups of phytoestrogens. No association was observed with citrus flavonoids. The results from this study suggest that high intake of certain phytoestrogens may reduce the risk of breast cancer.

Adult↗

PubMedDate not supplied

Subject recruitment for cancer control studies in an adverse environment.

Subject recruitment in an adverse environment prompted researchers to identify a novel method to gain a different perspective on the problem. Lewin's Model of Change was used in a post hoc examination of recruitment strategies from 5 cancer control studies of breast or prostate cancer. Based on this evaluation, driving and restraining forces in recruitment were identified. Lessons learned and recommendations are discussed based on this evaluation. Five categories of restrainers were identified from this evaluation and include sociocultural, institutional, individuals, budget, and study design. Conversely, only 3 categories of drivers were elucidated by the examination: sociocultural, institutional, and individuals. Lessons and recommendations ranged from addressing institutional barriers to capitalizing on public relations. Researchers entering a new environment for recruitment would benefit from using Lewin's force field analysis before writing a proposal or implementing a project. This approach better directs energy and resources and enhances the ability of the investigator to maintain a broad, less biased perspective.

Breast Neoplasms↗

PubMedDate not supplied

Methodologic considerations in the study of diet as part of complementary and alternative medicine modalities.

Diet is an essential component of most comprehensive health systems. Food figures prominently in the consciousness of most individuals, and the sensations of taste and smell are fundamentally important in human emotion. Complex configurations of dietary sanctions and strictures exist in virtually every human society, providing additional force to the power of diet. A wide variety of epidemiologic and laboratory-based studies have implicated a number of specific dietary factors in health and disease, with the former producing much in the way of equivocal evidence on most diet-health relationships and the latter often focusing so narrowly as to call into question the relevance of findings to human health. Assessing the role of diet as an important component of complementary and alternative medical treatment and preventive strategies will require a broad understanding of methodologic issues. Careful consideration of what is required to answer substantive questions in this intriguing and important area also will serve to advance the study of complementary and alternative modalities more generally.

Attitude to Health↗