Serum retinol and risk of prostate cancer.

Greater exposure to retinol (vitamin A) may prevent prostate cancer, although under some conditions it could promote cell growth and de-differentiation. The authors prospectively examined prostate cancer risk and serum retinol levels, measured by using high-performance liquid chromatography, at baseline (n = 29,104) and after 3 years (n = 22,843) in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort. Cox proportional hazards models were used to estimate the relative risk of total (n = 2,041) and aggressive (n = 461) prostate cancer by quintiles of baseline and 3-year serum retinol concentrations and by change in serum retinol levels from baseline to 3 years. Men with higher retinol concentrations at baseline were more likely to develop prostate cancer (quintile 5 vs. quintile 1 hazard ratio = 1.19, 95% confidence interval: 1.03, 1.36; P(trend) = 0.009). The results were similar for aggressive disease. Joint categorization based on baseline and 3-year retinol levels showed that men who were in the highest quintile at both time points had the greatest increased risk (baseline/3-year quintile 5/quintile 5 vs. quintile 1/quintile 1 hazard ratio = 1.31, 95% confidence interval: 1.08, 1.59). In this largest study to date of vitamin A status and subsequent risk of prostate cancer, higher serum retinol was associated with elevated risk, with sustained high exposure conferring the greatest risk. Future studies may clarify the underlying biologic mechanisms of the retinol-prostate cancer association.

Patterns of meat intake and risk of prostate cancer among African-Americans in a large prospective study.

OBJECTIVE: Given the large racial differences in prostate cancer risk, further investigation of diet and prostate cancer is warranted among high-risk groups. The purpose of this study was to examine the association between type of meat intake and prostate cancer risk among African-American men. METHODS: In the large, prospective NIH-AARP Diet and Health Study, we analyzed baseline (1995-1996) data from African-American participants, aged 50-71 years. Incident prostate cancer cases (n = 1,089) were identified through 2006. Dietary and risk factor data were ascertained by questionnaires administered at baseline. Cox models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) within intake quantiles. RESULTS: Neither white nor processed meat intake was associated with prostate cancer, regardless of meat-cooking method. Red meats cooked at high temperatures were associated with an increased risk of prostate cancer (HR = 1.18, 95% CI = 1.00-1.38 and HR = 1.22, 95% CI = 1.03-1.44, for the upper two intake tertiles). Intake of the heterocyclic amine (HCA), 2-amino-3,4,8-trimethylimidazo[4,5-f] quinoxaline (DiMeIQx) was positively associated with prostate cancer (HR = 1.30; 95% CI = 1.05-1.61, p = 0.02). No associations were observed for intake of other HCAs. CONCLUSION: Red meats cooked at high temperatures were positively associated with prostate cancer risk among African-American men. Further studies are needed to replicate these findings.

Alcoholic beverages and prostate cancer in a prospective US cohort study.

Despite numerous investigations, the correlation between alcohol consumption and prostate cancer risk remains uncertain. This report investigated the association between alcohol use and prostate cancer risk in a prospective cohort study of 294,707 US men aged 50-71 years in 1995-1996. Cox proportional hazards regression models with hazard ratios and 95% confidence intervals were adjusted for characteristics including age, race, body mass index, physical activity, and family history of prostate cancer, as well as testing for prostate-specific antigen and a digital rectal examination. There were 15,327 nonadvanced and 1,900 advanced prostate cancers identified through 2003 and 514 fatal cases through 2005. Risk of nonadvanced prostate cancer was 25% higher for men consuming ≥6 drinks daily (hazard ratio = 1.25, 95% confidence interval: 1.13, 1.37), 19% higher for men consuming 3-<6 drinks daily, and 6% higher for men consuming up to 3 drinks daily, compared with nondrinkers. The association between alcohol consumption and nonadvanced prostate cancer risk did not differ appreciably by age, family history of prostate cancer, smoking status, body mass index, or self-reported prostate-specific antigen testing and digital rectal examination (the latter available for >60% of respondents). The authors observed no association between alcohol intake and advanced prostate cancer and an inverse association with fatal prostate cancer among heavy drinkers. These findings suggest that higher alcohol consumption modestly increases nonadvanced prostate cancer risk.

Comparison of three oxidative stress biomarkers in a sample of healthy adults.

Oxidative stress is a potentially important aetiological factor for many chronic diseases, including cardiovascular disease, neurodegenerative disease and cancer, yet studies often find inconsistent results. The associations between three of the most widely used biomarkers of oxidative stress, i.e. F(2)-isoprostanes for lipid peroxidation and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) and the comet assay with FPG for oxidative DNA damage, were compared in a sample of 135 healthy African-American and white adults. Modest associations were observed between F(2)-isoprostanes and the comet assay (r = 0.22, p = 0.01), but there were no significant correlations between 8-oxo-dG and the comet assay (r = -0.09) or F(2)-IsoP (r = -0.04). These results are informative for researchers seeking to compare results pertaining to oxidative stress across studies and/or assessment methods in healthy disease-free populations. The development and use of oxidative stress biomarkers is a promising field; however, additional validation studies are necessary to establish accuracy and comparability across oxidative stress biomarkers.

Psychosocial correlates of dietary fat intake in African-American adults: a cross-sectional study.

BACKGROUND: Current dietary guidelines recommend that dietary fat should comprise 20-35% percent of total energy intake, with less than 10% of energy from saturated fat. However, many Americans exceed these goals and data suggest that African Americans tend to consume a higher percentage of energy from dietary fat than Whites. Because diets low in dietary fat, particularly saturated fat, are associated with lower risk for many chronic illnesses, it is important to identify strategies to reduce high fat intakes. This study examined associations of psychosocial factors with dietary fat intake in African American adults 18 to 70 years. METHODS: Data are self-reported from a cross-sectional survey of African Americans (n = 658) using an 11-page questionnaire, collected from June to October 2003. Associations of psychosocial (predisposing, reinforcing, and enabling) factors based on the PRECEDE framework, dietary fat-related behaviors, and participant characteristics (e.g., age, sex, education, BMI) with total and saturated fat consumption are described using linear regression and analysis of variance. RESULTS: The mean age of participants was 43.9 years, 57% were female, 37% were college graduates, and 76% were overweight/obese. Respondents with lower fat intakes were female, older, had high education and very good/excellent perceived health. Among the psychosocial factors, the strongest (inverse) associations with fat intake were with two predisposing factors: belief in the importance of a low-fat diet (both genders) and high self-efficacy (women only). Fat intake was also significantly lower among participants who could count on those close for encouragement to eat healthy foods (a reinforcing factor) and among men who needed more information about preparing healthy foods (an enabling factor). CONCLUSION: Dietary interventions to decrease fat intake in African American adults may benefit from incorporating predisposing factors, such as personal beliefs and self-efficacy, in their design and implementation.

Associations of antioxidant nutrients and oxidative DNA damage in healthy African-American and White adults.

High antioxidant intake has been shown to reduce cancer risk and may also mitigate the effects of oxidative DNA damage, which is hypothesized to be causally linked to carcinogenesis. This study examined potential racial differences in (a) dietary intakes and plasma concentrations of vitamin C, vitamin E, and carotenoids and oxidative DNA damage and (b) associations between plasma antioxidants and oxidative DNA damage. Data were from a cross-sectional study of 164 generally healthy nonsmoking African-Americans and Whites in North Carolina, ages 20 to 45 years, equally distributed by race and sex. Participants completed a demographic and health questionnaire, four 24-h dietary recalls, and a dietary supplement inventory; had height and weight measured; and provided a semifasting blood sample. African-Americans had statistically significantly lower plasma concentrations of vitamin E, alpha-carotene, beta-carotene, and lutein + zeaxanthin than Whites, as well as lower self-reported intake of most antioxidants. Levels of oxidative DNA damage, measured using the alkaline comet assay, were lower in African-Americans than Whites. An inverse association between lycopene and oxidative DNA damage (r = -0.20; P = 0.03) was found in the combined study population after adjusting for sex, age, body mass index, passive smoke exposure, physical activity, education, income, and alcohol intake. There was also a positive association of vitamin E with oxidative DNA damage in the total population (r = 0.21; P = 0.02) and in African-American men (r = 0.63; P = 0.01) after adjusting for covariates. This study is among the first to examine these associations in a sample of healthy adults with an adequate representation of African-Americans.

Qualitative study to explore Prospect Theory and message framing and diet and cancer prevention-related issues among African American adolescents.

BACKGROUND: There is a dearth of knowledge regarding factors that may motivate African American adolescents to consume healthier diets. OBJECTIVE: To develop and test cancer prevention messages based on Prospect Theory on motivation to improve dietary intake in African American adolescents and to explore other salient factors that may inform dietary intervention design and implementation in this population. METHODS: Semistructured in-person qualitative interviews were conducted with 13 African American male and female adolescents, aged 12 to 16 years, in North Carolina. Prospect Theory and message framing were used to guide the design of the 4 sets of diet-related messages related to cancer prevention: short-term, gain-framed; long-term, gain-framed; short-term, loss-framed; and long-term, loss-framed messages. Data were also collected on demographic, behavioral, and psychological factors; usual health behaviors; and preferences for intervention delivery. RESULTS: Most respondents found the gain-framed, short-term messages most salient for both fruits/vegetables (8 [61.5%]) and fat consumption (7 [53.8%]). For fat consumption only, 2 (15.4%) found the loss-framed, short-term messages pertinent; none found the loss-framed, long-term messages relevant for either dietary variable. All indicated interest in participating in a dietary intervention/education program; most preferred the Internet as a channel for intervention delivery. Participants expressed diverse views regarding knowledge, attitudes, and beliefs regarding healthy eating. CONCLUSION: The gain-framed, short-term messages were most salient for motivating the majority of respondents to consume a healthy diet and most expressed a strong interest in participating in programs about diet and nutrition, with the Internet as the preferred communication channel. IMPLICATIONS FOR PRACTICE: Researchers conducting dietary interventions and education initiatives and medical professionals who counsel African American adolescents should consider using Prospect Theory as a theoretical framework, should focus on gain-framed, short-term messages regarding cancer prevention, and should use the Internet for data collection and intervention and information delivery.

Analysis of 8-oxo-7,8-dihydro-2'-deoxyguanosine by ultra high pressure liquid chromatography-heat assisted electrospray ionization-tandem mass spectrometry.

Increased amounts of reactive oxygen species (ROS), generally termed oxidative stress, are frequently hypothesized to be causally associated with many diseases. Analyses of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) in DNA and urine are widely used biomarkers for oxidative stress. Over the years it became clear that analysis of 8-oxo-dG in DNA is challenging due to artifactual formation during sample work up. The present study demonstrates that 8-oxo-dG can be measured reliably and accurately when appropriate precautions are taken. First, the presence of an antioxidant, metal chelator, or free radical trapping agent during sample preparation improves reproducibility. Second, sample enrichment by HPLC fraction collection was used to optimize sensitivity. Third, heat assisted electrospray ionization (HESI) eliminated potential interferences and improved assay performance and sensitivity. Subsequently, the UPLC-HESI-MS/MS method was applied to show the biphasic dose response of 8-oxo-dG in H(2)O(2)-treated HeLa cells. Application of this method to human lymphocyte DNA (n=156) gave a mean+/-SD endogenous amount of 1.57+/-0.88 adducts per 10(6) dG, a value that is in agreement with the suggested amount previously estimated by European Standard Committee on Oxidative DNA Damage (ESCODD) and others. These results suggest that the present method is well suited for application to molecular toxicology and epidemiology studies investigating the role of oxidative stress.

Validation of an antioxidant nutrient questionnaire in whites and African Americans.

High antioxidant intakes are inversely related to risk for many diseases. However, there is no comprehensive instrument that captures consumption of antioxidant nutrients from both foods and dietary supplements. This report examines the validity of a newly developed questionnaire assessing self-reported dietary and supplemental intakes of antioxidant nutrients (carotenoids, vitamin C, and vitamin E). Between March and December 2005, participants (n=164), 20 to 45 years old, completed the new 92-item antioxidant nutrient questionnaire, a demographic/health questionnaire, four 24-hour dietary recalls, a dietary supplement inventory, and provided semi-fasting blood samples that were analyzed for plasma antioxidant levels. Data analyses included descriptive statistics, correlation coefficients, and linear regression. Mean age of participants was 31.9 years, 51% were African American, and 52% were female. Median antioxidant intakes from the questionnaire and mean of the four recalls were generally comparable. Adjusted Pearson's correlations of questionnaire- and recall-derived intakes ranged from r=0.06 to r=0.56; correlations for the questionnaire and biomarkers ranged from r=0.10 to r=0.33. Agreement rates for classification of intakes from the questionnaire and recalls into the same/adjacent quartiles were 65% to 89%; misclassification to the opposite quartile was rare (range=0 to 12%). For most nutrients, there were linear trends of increasing plasma concentrations with higher questionnaire-derived intakes (P<0.01). Correlations of supplement use between the questionnaire and a supplement inventory were r=0.33 to r=0.84. The new antioxidant nutrient questionnaire demonstrated good validity for collecting self-reported antioxidant nutrient intakes from foods and supplements in both whites and African Americans. The study also underscores the importance of examining the performance characteristics of dietary assessment instruments separately in different population subgroups.

Cigarette smoking and prostate cancer in a prospective US cohort study.

Smoking is an important risk factor for many cancers, yet the relationship between smoking and prostate cancer remains uncertain. We investigated whether smoking affected the risk of prostate cancers within a large prospective cohort study of dietary and environmental cancer risk factors among men ages 50 to 71 upon enrollment in 1995-1996 (n = 283,312). Cox proportional hazards regression models with hazard ratios (HR) and 95% confidence intervals (95% CI) were adjusted for age, race, education, height, body mass index, physical activity, family history of prostate cancer, diabetes, self-reported health status, prostate-specific antigen testing, digital rectal exam, total energy, alpha-tocopherol, calcium, alpha-linolenic acid, selenium, red meat, fish, and tomato intake. There were 14,810 nonadvanced and 1,830 advanced incident prostate cancers identified through 2003, and 394 men died of their disease through 2005. Current smokers had a decreased risk of nonadvanced prostate cancer (HR, 0.82; 95% CI, 0.77-0.88), but an increased risk of fatal prostate cancer (HR, 1.69; 95% CI, 1.25-2.27). Former smoking was also associated with decreased risk of nonadvanced prostate cancers (HR, 0.89; 95% CI, 0.86-0.92), but not fatal prostate cancers (HR, 1.03; 95% CI, 0.83-1.27). There was no apparent association between smoking and advanced prostate cancer. A number of biologically plausible mechanisms could explain these results, including the direct effects of carcinogens in tobacco smoke and the resulting changes in sex hormone or growth factor profiles. These findings suggest that current and former smokers may be at decreased risk of being diagnosed with prostate cancer and current smokers are at an increased risk of dying from prostate cancer.

Associations between alpha-tocopherol, beta-carotene, and retinol and prostate cancer survival.

Previous studies suggest that carotenoids and tocopherols (vitamin E compounds) may be inversely associated with prostate cancer risk, yet little is known about how they affect prostate cancer progression and survival. We investigated whether serum alpha-tocopherol, beta-carotene, and retinol concentrations, or the alpha-tocopherol and beta-carotene trial supplementation, affected survival of men diagnosed with prostate cancer during the alpha-Tocopherol, beta-Carotene Cancer Prevention Study, a randomized, double-blind, placebo-controlled primary prevention trial testing the effects of beta-carotene and alpha-tocopherol supplements on cancer incidence in adult male smokers in southwestern Finland (n = 29,133). Prostate cancer survival was examined using the Kaplan-Meier method with deaths from other causes treated as censoring, and using Cox proportional hazards regression models with hazard ratios (HR) and 95% confidence intervals (CI) adjusted for family history of prostate cancer, age at randomization, benign prostatic hyperplasia, age and stage at diagnosis, height, body mass index, and serum cholesterol. As of April 2005, 1,891 men were diagnosed with prostate cancer and 395 died of their disease. Higher serum alpha-tocopherol at baseline was associated with improved prostate cancer survival (HR, 0.67; 95% CI, 0.45-1.00), especially among cases who had received the alpha-tocopherol intervention of the trial and who were in the highest quintile of alpha-tocopherol at baseline (HR, 0.51; 95% CI, 0.20-0.90) or at the 3-year follow-up measurement (HR, 0.26; 95% CI, 0.09-0.71). Serum beta-carotene, serum retinol, and supplemental beta-carotene had no apparent effects on survival. These findings suggest that higher alpha-tocopherol (and not beta-carotene or retinol) status increases overall prostate cancer survival. Further investigations, possibly including randomized studies, are needed to confirm this observation.

Correlates of antioxidant nutrients and oxidative DNA damage differ by race in a cross-sectional study of healthy African American and white adults.

Although antioxidant nutrients and oxidative DNA damage have been associated with carcinogenesis, few studies have investigated the factors that influence antioxidant intake and oxidative DNA damage in racially diverse populations. Demographic, behavioral, and diet-related psychosocial correlates of plasma antioxidant (carotenoids, vitamin C, and vitamin E) concentrations and oxidative DNA damage were examined using data from a cross-sectional study of 147 generally healthy, nonsmoking African American and white adults in North Carolina, aged 20 to 45 years. All participants completed self-administered demographic, diet, and health questionnaires and provided semifasting (> or = 6 hours) blood samples. Multivariate regression analyses were computed separately for each race to determine associations between the potential correlates with plasma antioxidant concentrations and oxidative DNA damage, separately. Our findings suggest appreciable differences by race. Only a few factors (age, supplement use, and several psychosocial factors) were associated with antioxidant concentrations in African Americans, whereas these and additional factors, including physical activity, waist circumference, and passive smoke exposure, were associated with antioxidant concentrations in whites. For oxidative DNA damage, passive smoke exposure was significantly associated with oxidative DNA damage in African Americans, and age and alcohol were significant in whites. In addition, the regression models generally explained more of the variance in plasma antioxidant concentrations and oxidative DNA damage in whites than in African Americans. Considering the salient correlates differed by race, this work has important implications for the design and implementation of future research studies investigating antioxidant nutrients and/or oxidative stress, especially those in racially diverse populations.

Associations of psychosocial factors with fruit and vegetable intake among African-Americans.

OBJECTIVE: To examine associations of various psychosocial factors with fruit and vegetable intake in African-American adults. METHODS: A cross-sectional survey of a population-based sample of 658 African-Americans, aged 18-70 years, in North Carolina. Information was collected on diet-related psychosocial (predisposing, reinforcing and enabling) factors based on the PRECEDE (Predisposing, Reinforcing, and Enabling Constructs in Educational Diagnosis and Evaluation) planning framework; demographic, lifestyle and behavioural characteristics, and fruit and vegetable intake. RESULTS: The mean participant age was 43.9 years (standard deviation 11.6), 57% were female and 76% were overweight/obese. Participants expressed healthy beliefs regarding many of, but not all, the psychosocial factors. For example, although half of the respondents believed it is important to eat a diet high in fruits/vegetables, only 26% knew that >or=5 daily servings are recommended. The strongest associations of the psychosocial factors with fruit/vegetable intake were for predisposing factors (e.g. belief in the importance of a high fruit/vegetable diet and knowledge of fruit/vegetable recommendations) and one reinforcing factor (social support), with differences between the healthiest and least healthy responses of 0.5-1.0 servings per day. There was evidence of effect modification by gender in associations between psychosocial factors and fruit/vegetable consumption (e.g. self-efficacy was only significant in women), with higher intakes and generally healthier responses to the psychosocial variables in women than men. CONCLUSIONS: Interventions to increase fruit/vegetable intake in African-Americans may be more effective if they focus primarily on predisposing factors, such as knowledge, self-efficacy and attitudes, but not to the exclusion of reinforcing and enabling factors. The psychosocial factors that are targeted may also need to be somewhat different for African-American men and women.