Search

BackgroundSelenium (Se) is a nutritionally essential trace element and health may be improved by increased Se intake. Previous kinetic studies have shown differences in metabolism of organic vs. inorganic forms of Se [e.g., higher absorption of selenomethionine (SeMet) than selenite (Sel), and more recycling of Se from SeMet than Sel]. However, the effects on Se metabolism after prolonged Se supplementation are not known.ObjectiveTo determine how the metabolism and transport of Se changes in the whole-body in response to Se-supplementation by measuring Se kinetics before and after 2 years of Se supplementation with SeMet.MethodsWe compared Se kinetics in humans [n = 31, aged 40 ± 3 y (mean ± SEM)] studied twice after oral tracer administration; initially (PK1), then after supplementation for 2 y with 200 µg/d of Se as selenomethionine (SeMet) (PK2). On each occasion, we administered two stable isotope tracers of Se orally: SeMet, the predominant food form, and selenite (Na276SeO3, or Sel), an inorganic form. Plasma and RBC were sampled for 4 mo; urine and feces were collected for the initial 12 d of each period. Samples were analyzed for tracers and total Se by isotope dilution GC-MS. Data were analyzed using a compartmental model, we published previously, to estimate fractional transfer between pools and pool masses in PK2.ResultsWe report that fractional absorption of SeMet or Sel do not change with SeMet supplementation and the amount of Se absorbed increased. The amount of Se excreted in urine increases but does not account for all the Se absorbed. As a result, there is a net incorporation of SeMet into various body pools. Nine of the 11 plasma pools doubled in PK2; two did not change. Differences in metabolism were observed for SeMet and Sel; RBC uptake increased 247% for SeMet, urinary excretion increased from two plasma pools for Sel and from two different pools for SeMet, and recycling to liver/tissues increased from one plasma pool for Sel and from two others for SeMet. One plasma pool increased more in males than females in PK2.ConclusionsOf 11 Se pools identified kinetically in human plasma, two did not increase in size after SeMet supplementation. These pools may be regulated and important during low Se intake.

Selenium (Se) metabolism is affected by its chemical form in foods and by its incorporation (specific vs. nonspecific) into multiple proteins. Modeling Se kinetics may clarify the impact of form on metabolism. Although the kinetics of Se forms have been compared in different participants, or the same participants at different times, direct comparisons of their respective metabolism in the same participants have not been made. The aim of this study was to simultaneously compare kinetics of absorbed Se from inorganic selenite (Sel) and organic selenomethionine (SeMet) in healthy participants (n = 31). After oral administration of stable isotopic tracers of each form, urine and feces were collected for 12 d and blood was sampled over 4 mo. Tracer enrichment was determined by isotope-dilution-GC-MS. Using WinSAAM, a compartmental model was fitted to the data. Within 30 min of ingestion, Se from both forms entered a common pool, and metabolism was similar for several days before diverging. Slowly turning-over pools were required in tissues and plasma for Se derived from SeMet to account for its 3-times-higher incorporation into RBC compared with Se from Sel; these presumably represent nonspecific incorporation of SeMet into proteins. Pool sizes and transport rates were determined and compared by form and gender. The final model consisted of 11 plasma pools, 2 pools and a delay in RBC, and extravascular pools for recycling of Se back into plasma. This model will be used to evaluate changes in Se metabolism following long-term (2 y) Se supplementation.

Diet reportedly alters serum sex hormone concentrations in adults, but little is known about the influence of diet during puberty on these hormones.We aimed to determine whether an intervention to lower fat intake during adolescence alters serum sex hormone concentrations and progression through puberty.In 1990-1997, we conducted an ancillary study to the Dietary Intervention Study in Children, a multicenter, randomized, controlled clinical trial to test the safety and efficacy of a cholesterol-lowering dietary intervention in children.Healthy, prepubertal, 8 to 10 yr olds with elevated low-density lipoprotein cholesterol were randomized to usual care or a behavioral intervention. Of 362 randomized Dietary Intervention Study in Children boys, 354 participated in the ancillary study. Eighty-four percent of boys attended last visits when their median time on trial was 7.1 yr.The behavioral intervention continued throughout the duration of the trial and promoted a diet with 28% energy from total fat, less than 8% from saturated fat, 9% or less from polyunsaturated fat, and less than 75 mg cholesterol per 1000 kcal.The main outcome measure for boys formulated before study initiation was non-SHBG bound testosterone concentration. Secondary outcomes included serum total testosterone, dihydrotestosterone, androstenedione, estradiol, estrone, SHBG, and Tanner stage.There were no significant treatment group differences in boys' serum hormone levels, SHBG, or Tanner stages at any individual visit or over the course of the trial when evaluated by longitudinal models.Modest reductions in total fat, saturated fat, and possibly energy intake do not alter progression through puberty or serum sex hormone concentrations in adolescent boys.

High fruit and vegetable intake is associated with decreased cancer risk. However, dietary recall data from national surveys suggest that, on any given day, intake falls below the recommended minima of three daily servings of vegetables and two daily servings of fruit. There is no single widely accepted measure of “usual” intake. One approach is to regard the distribution of intake as a mixture of “regular” (relatively frequent) and “nonregular” (relatively infrequent) consumers, using an indicator of whether an individual consumed the food of interest on the recall day. We use a new approach to summarizing dietary data, latent class analysis (LCA), to estimate “usual” intake of vegetables. The data consist of four 24-hour dietary recalls from the 1985 Continuing Survey of Intakes by Individuals collected from 1,028 women. Traditional LCA based on simple random sampling was extended to complex survey data by introducing sample weights into the latent class estimation algorithm and by accounting for the co...

Objective The purpose of this study is to assess population-based changes in vegetable and fruit consumption and psychosocial correlates. Design Two nationally representative random digit dial surveys conducted in 1991 and 1997; respondents were queried regarding consumption of and attitudes and knowledge about vegetables and fruit. Subjects/Setting Respondents were 2,755 and 2,544 adults (in 1991 and 1997, respectively) older than 18 years. Statistical Analysis Performed Vegetable and fruit consumption and message awareness were measured using weighted-only and regression model-adjusted analyses to assess changes. Results Mean vegetable and fruit consumption was significantly ( P =.007) higher in 1997 than in 1991 using weighted-only analyses, but remained significant only for Hispanic ( P =.03) and nonsmoker ( P =.004) subgroups when adjusted for demographic shifts. Significantly higher percentages were found in the model-adjusted analyses for those consuming 5 or more daily servings (23.4% to 25.8%), message awareness (7.7% to 19.2%), and knowledge of the 5 A Day Program (2.0% to 17.8%). Applications/Conclusions A significantly positive change in vegetable and fruit consumption occurred between 1991 and 1997 according to traditional methods of survey data analysis, but null findings resulted when the data were adjusted for demographic shifts. Nutrition professionals should continue targeting specific demographic subgroups with tailored interventions to move all Americans toward achievement of dietary guidelines for vegetable and fruit consumption. J Am Diet Assoc. 2002;102:809–817.

Objective: To explore the relationship between serum selenium and cervical cancer. Methods: We conducted a case–control study of cervical cancer in five areas around Birmingham, AL; Chicago, IL; Denver, CO; Miami, FL; and Philadelphia, PA. Community controls were selected by random-digit dialing and were matched to invasive cervical cancer cases by age, race/ethnicity, and telephone exchange. Serum selenium was determined by neutron activation analysis. Logistic regression analysis controlling for known risk factors of cervical cancer, including human papillomavirus (HPV) type-16 measured serologically, was performed on 227 invasive cases, 127 in-situ cases, and 526 controls. Results: Values of serum selenium ranged from 67.5 to 185.0 ng/ml. Adjusted odds ratios for invasive cervical cancer by quintile were: 1.0 (highest selenium), 1.1, 1.0, 0.8, and 1.0 (lowest selenium), p for trend = 0.82. Similar patterns were observed for Stage I invasive, and Stages II–IV invasive cases, suggesting severity of disease did not influence the null results. Although no associations were seen among current or never smokers, a protective effect of selenium was suggested among former smokers. Effect modification was not evident for other variables examined. Conclusions: This study does not support a relationship between serum selenium and invasive cervical cancer at typical serum selenium levels in the US.

Free radicals and oxidation are involved in several aspects of blood pressure physiology. We investigated the relationship between blood pressure and antioxidants, including plasma ascorbic acid (AscA), in a 17-week controlled-diet study. Study subjects included 68 men aged 30 to 59 years who had a mean diastolic blood pressure of 73.4 mm Hg and a mean systolic blood pressure of 122.2 mm Hg. One month of vitamin C depletion was followed by 1-month repletion with 117 mg/d, repeated twice. All food and drink were provided in the study. Subjects did not smoke or drink alcohol, all consumed fruits and vegetables, and body weight was maintained. Plasma was assayed periodically for AscA, α-tocopherol, carotenoids, and lipids. Plasma AscA was inversely related to diastolic blood pressure 1 month later (correlation −0.48, P 7 mm Hg higher diastolic blood pressure than did those in the top fourth of the plasma AscA distribution. Multivariate analysis with control for age, body mass index, other plasma antioxidants, and dietary energy, calcium, fiber, sodium, and potassium did not reduce the plasma AscA effect. One fourth of the variance in diastolic blood pressure was accounted for by plasma AscA alone. Plasma AscA was also significantly associated with systolic blood pressure in logistic regression. Vitamin C may be an important component of the effectiveness of fruits and vegetables in the reduction in blood pressure, and tissue AscA levels may be important in the maintenance of low blood pressure. Long-term intervention studies are warranted.

Epidemiological evidence suggests that intake of vitamin C and of fruit and vegetables rich in vitamin C may reduce the risk of certain cancers. Most epidemiological studies have relied on estimates of vitamin C based on questionnaires because serum ascorbic acid (AA) can be very unstable. The objective of this study was to investigate the effect of extended storage at −70°C and of multiple free-thaws on AA concentration in stabilized human serum from a large multi-center cervical cancer case-control study; the serum samples had been stabilized by acidification with meta-phosphoric acid and stored at −70°C. The results showed that under these conditions human serum samples are stable for periods of at least 2 years. There were indications that sample preparation in the field and freezing and thawing the stabilized serum samples could affect reproducibility and validity. Overall, our results indicate that with this stabilization method, biological material collected in large-scale, multicenter studies remains useful for AA analysis for at least 2 years after collection.

Purpose.The purpose of the Five A Day Baseline Survey was to assess fruit and vegetable intake and associated factors among US adults.Design.Questionnaires querying frequency of intake of 33 fruits and vegetables, as well as demographics, attitudes, and knowledge related to fruits and vegetables were administered by telephone.Setting.The study was a nationally representative random digit dial survey conducted by telephone in the summer of 1991; response rate was 42.8%.Subjects.Respondents were 2811 US adults (including an oversample of African-Americans and Hispanics).Measures.Mean and median self-reported intakes of fruits and vegetables were calculated. Estimated servings per week were adjusted on the basis of responses to summary questions regarding overall fruit and vegetable intakes.Results.Median intake of fruits and vegetables was 3.4 servings per day. Linear regressions (accounting for no more than 10% of the variation) showed that education, income, and smoking status were predictors of fruit and vegetable intake and that intake increased with education, income, and nonsmoking status. Women had higher intakes than men at all ages; these differences between men and women increased with age. Fruit and vegetable intakes increased with age for whites and Hispanics, but not for African-Americans.Conclusions.Fruit and vegetable intake among adults in the United States is lower than the recommended minimum of five daily servings. These data will be useful in targeting campaign efforts and in assessing progress of the Five A Day for Better Health Program.

The purpose of this study was to determine how estimates of fruit and vegetable intake, as determined from food frequency questionnaires, may be affected by the number of foods included. Three different national surveys of adults were used. Each of the surveys employed a food frequency questionnaire, but each included a different number of questions related to fruits and vegetables. Compared across surveys, values for median frequency of intake of individual fruits and vegetables were generally similar. However, values for median frequency of total fruit and vegetable intake, determined by summing across all fruits and vegetables included in the respective questionnaires, were very different and were associated with the number of questions asked: the 1987 National Health Interview Survey included 20 questions regarding fruits and vegetables, and the median frequency of intake was 23.8 times per week; the baseline survey for the national 5 A Day for Better Health Program included 33 questions, and the median intake was 34.6; and the 1982–1984 NHANES I Epidemiologic Follow-up Survey included 40 questions, and the median intake was 38.8. These findings suggest that summing across frequencies for individual foods may not be a valid way to assess intakes of total fruits and vegetables. Summary questions and/or adjustment factors may need to be employed to increase precision of the estimates.

Dietary guidelines posit an association between diet and cancer. Different cancer mortality rates among whites, blacks, and Hispanics may be related to differences in diet. Food frequency data from the 1987 National Health Interview Survey on 20,143 adults were used to estimate the percentage of adults, by gender and race/ethnicity, who consume some 59 foods six or more times per year, median number of servings for consumers, and frequency of consumption of skin on poultry and fat on red meat. On the basis of percent consumption of these foods, women appear to have a more diverse diet than men. Women eat more fruits and vegetables, less meat, and fewer high-fat foods and drink fewer alcoholic beverages. Whites eat a more varied diet than blacks and Hispanics; blacks eat more fried and high-fat food; consumption of high-fat foods is lowest among Hispanics. Public health messages, especially those aimed at cancer prevention, should be targeted at increasing the overall consumption of fruits and vegetables, decreasing consumption of high-fat foods, especially among white and black men, and increasing consumption of those healthful foods already consumed by particular race/ethnicity groups.

OBJECTIVES. The results of an evaluation of "Eat for Health," a supermarket nutrition intervention, are presented. The study tested whether such a program could be successfully carried out and whether it could effect changes in knowledge, attitudes, and food purchasing behavior in line with nutrition and cancer risk reduction guidelines. METHODS. The evaluation consisted of an in-store monitoring element, an in-store and telephone consumer survey, and an analysis of sales data on selected foods. A matched-pair design, using a total of 40 stores in the intervention and comparison groups, was used. RESULTS. The intervention was successfully implemented and had limited success in changing some food purchasing behaviors. There appeared to be no effect on knowledge and attitudes except for increased awareness of a link between diet and cancer and of the program itself. CONCLUSIONS. Despite the intervention's success, limitations of the consumer survey and sales data analyses and the continuing diffusion of nutrition messages throughout society make it difficult to specify the impact of this program on consumer nutrition knowledge and behaviors.

Selenium (Se) metabolism is affected by its chemical form in foods and by its incorporation (specific vs. nonspecific) into multiple proteins. Modeling Se kinetics may clarify the impact of form on metabolism. Although the kinetics of Se forms have been compared in different participants, or the same participants at different times, direct comparisons of their respective metabolism in the same participants have not been made. The aim of this study was to simultaneously compare kinetics of absorbed Se from inorganic selenite (Sel) and organic selenomethionine (SeMet) in healthy participants (n = 31). After oral administration of stable isotopic tracers of each form, urine and feces were collected for 12 d and blood was sampled over 4 mo. Tracer enrichment was determined by isotope-dilution-GC-MS. Using WinSAAM, a compartmental model was fitted to the data. Within 30 min of ingestion, Se from both forms entered a common pool, and metabolism was similar for several days before diverging. Slowly turning-over pools were required in tissues and plasma for Se derived from SeMet to account for its 3-times–higher incorporation into RBC compared with Se from Sel; these presumably represent nonspecific incorporation of SeMet into proteins. Pool sizes and transport rates were determined and compared by form and gender. The final model consisted of 11 plasma pools, 2 pools and a delay in RBC, and extravascular pools for recycling of Se back into plasma. This model will be used to evaluate changes in Se metabolism following long-term (2 y) Se supplementation.

A 2-year supermarket intervention in 20 pair-matched stores tested whether a nutrition education program could produce changes in food purchasing behavior. Food sales data for 2 intervention years were compared with baseline year data. The evaluation presented challenges related to the quasi-experimental study design and to the high variability and auto- and cross-sectional correlations in the data. A complex time series model was used to take these factors into account and to test for intervention effects.

The process of building a kinetic model for the metabolism of selenite in humans is described. Plasma, urine and fecal data from a selenium pharmacokinetics study are compared with an a priori model hypothesized before the study was conducted. The reasons for the rejection of the model are given. The iterative process of observing the fit of the model, modifying the model and testing the modification is illustrated by using as examples an intermediate model and a current working model. Several specific problems encountered in trying to fit the a priori and the intermediate model are described along with the approaches taken to resolve them. Finally, some uses of the current model are given, including checking an assumption underlying the pharmacokinetics study, making predictions about the effect of supplementation on plasma levels and developing research leads.

Approximately 200 studies that examined the relationship between fruit and vegetable intake and cancers of the lung, colon, breast, cervix, esophagus, oral cavity, stomach, bladder, pancreas, and ovary are reviewed. A statistically significant protective effect of fruit and vegetable consumption was found in 128 of 156 dietary studies in which results were expressed in terms of relative risk. For most cancer sites, persons with low fruit and vegetable intake (at least the lower one-fourth of the population) experience about twice the risk of cancer compared with those with high intake, even after control for potentially confounding factors. For lung cancer, significant protection was found in 24 of 25 studies after control for smoking in most instances. Fruits, in particular, were significantly protective in cancers of the esophagus, oral cavity, and larynx, for which 28 of 29 studies were significant. Strong evidence of a protective effect of fruit and vegetable consumption was seen in cancers of the pancreas and stomach (26 of 30 studies), as well as in colorectal and bladder cancers (23 of 38 studies). For cancers of the cervix, ovary, and endometrium, a significant protective effect was shown in 11 of 13 studies, and for breast cancer a protective effect was found to be strong and consistent in a meta analysis. It would appear that major public health benefits could be achieved by substantially increasing consumption of these foods.

Background: Selenium, a potential cancer prevention agent currently being tested against prostate cancer in the Selenium and Vitamin E Cancer Prevention Trial (SELECT), plays an integral role in thyroid metabolism. The effects of long-term selenium supplementation on thyroid hormone concentrations are unknown. Objective: The objective was to investigate the effects of long-term selenium supplementation on thyroid hormone concentrations. Design: Twenty-eight healthy adults took 200 μg selenomethionine/d for 28 mo. The thyroid hormones triiodothyronine (T3), thyroxine (T4), and thyrotropin (TSH) were measured in plasma for 4 mo before supplementation and quarterly during supplementation. The assay methods were changed midstudy; the results of the 2 methods were not comparable. Therefore, one analysis was conducted based on the results of the first method, and a second analysis was based on all of the data, adjusted for the change. Serial data collection permitted a test for trends rather than simply a difference between initial and final values. Results: By 9 mo, mean (±SEM) plasma selenium concentrations had increased from 1.78 ± 0.07 μmol/L at baseline to 2.85 ± 0.11 μmol/L for men and from 1.64 ± 0.04 to 3.32 ± 0.1.2 μmol/L for women. T3 concentrations in men increased 5% per year (P = 0.01). T4 and TSH concentrations were unchanged. Conclusions: Selenium supplementation produced no clinically significant changes in thyroid hormone concentrations. A small but statistically significant increase in T3 concentrations was noted in men, with no corresponding decreases in TSH. A subset of SELECT subjects might be monitored periodically for changes during long-term selenium supplementation.

Twenty-four hour dietary recall data from the Second National Health and Nutrition Examination Survey (1976-80) were used to estimate the numbers of servings of fruit and vegetables consumed by Black and White adults, to examine the types of servings (e.g., potatoes, garden vegetables, fruit, and juice), and to estimate the mean intake of calories, fat, dietary fiber, and vitamins A and C by number of servings. An estimated 45 percent of the population had no servings of fruit or juice and 22 percent had no servings of a vegetable on the recall day. Only 27 percent consumed the three or more servings of vegetables and 29 percent had the two or more servings of fruit recommended by the US Departments of Agriculture and of Health and Human Services; 9 percent had both. Consumption was lower among Blacks than Whites. The choice of vegetables lacked variety. Diets including at least three servings of vegetables and two servings of fruit contained about 17 grams of dietary fiber. Although caloric and fat intake increased with increasing servings of fruit and vegetables, the percent of calories from fat remained relatively constant. Although these data are 10 years old, more recent surveys have shown similar results. The discrepancy between dietary guidelines and the actual diet suggests a need for extensive public education.

Background The field of cancer biomarker development has been evolving rapidly. New developments both in the biologic and statistical realms are providing increasing opportunities for evaluation of markers for both early detection and diagnosis of cancer. Purpose To review the major conceptual and methodological issues in cancer biomarker evaluation, with an emphasis on recent developments in statistical methods together with practical recommendations. Methods We organized this review by type of study: preliminary performance, retrospective performance, prospective performance and cancer screening evaluation. Results For each type of study, we discuss methodologic issues, provide examples and discuss strengths and limitations. Conclusion Preliminary performance studies are useful for quickly winnowing down the number of candidate markers; however their results may not apply to the ultimate target population, asymptomatic subjects. If stored specimens from cohort studies with clinical cancer endpoints are available, retrospective studies provide a quick and valid way to evaluate performance of the markers or changes in the markers prior to the onset of clinical symptoms. Prospective studies have a restricted role because they require large sample sizes, and, if the endpoint is cancer on biopsy, there may be bias due to overdiagnosis. Cancer screening studies require very large sample sizes and long follow-up, but are necessary for evaluating the marker as a trigger of early intervention.

Background: Results of several studies have suggested that diet during adolescence may influence the risk of breast cancer in adulthood. We evaluated whether an intervention to lower fat intake among adolescent girls altered their serum concentrations of sex hormones that, in adults, are related to breast cancer development. Methods: We conducted an ancillary hormone study among 286 of the 301 girls who participated between 1988 and 1997 in the Dietary Intervention Study in Children, in which healthy, prepubertal, 8- to 10year-olds with elevated low-density lipoprotein cholesterol were randomly assigned to usual care or to a behavioral intervention that promoted a low-fat diet. Median time on the intervention was 7 years. Blood samples collected before randomization and at the year 1, year 3, year 5, and last visits were assayed to determine the girls’ serum levels of sex hormones. All P values are two-sided. Results: At the year 5 visit, girls in the intervention group had 29.8% (95% confidence interval [CI] = 5.4% to 47.9%; P = .02) lower estradiol, 30.2% (95% CI = 7.0% to 47.7%; P = .02) lower nonsex hormone binding globulin-bound estradiol, 20.7% (95% CI = 4.7% to 34.0%; P = .02) lower estrone, and 28.7% (95% CI = 5.1% to 46.5%; P = .02) lower estrone sulfate levels during the follicular phase of the menstrual cycle and 27.2% (95% CI = 5.7% to 53.1%; P = .01) higher testosterone levels during the luteal phase of the menstrual cycle than did girls in the usual care group. At the last visit, the luteal phase progesterone level was 52.9% (95% CI = 20.0% to 72.3%) lower for girls in the intervention group than for girls in the usual care group (P = .007). Conclusion: Modest reductions in fat intake during puberty are associated with changes in sex hormone concentrations that are consistent with alterations in the function of the hypothalamic–pituitary–ovarian axis. Whether these changes influence breast cancer risk is currently unknown. [J Natl Cancer Inst 2003;95:132–41]

To explore the relationship between serum selenium and cervical cancer.We conducted a case-control study of cervical cancer in five areas around Birmingham, AL; Chicago, IL; Denver, CO; Miami, FL; and Philadelphia, PA. Community controls were selected by random-digit dialing and were matched to invasive cervical cancer cases by age, race/ethnicity, and telephone exchange. Serum selenium was determined by neutron activation analysis. Logistic regression analysis controlling for known risk factors of cervical cancer, including human papillomavirus (HPV) type-16 measured serologically, was performed on 227 invasive cases, 127 in-situ cases, and 526 controls.Values of serum selenium ranged from 67.5 to 185.0 ng/ml. Adjusted odds ratios for invasive cervical cancer by quintile were: 1.0 (highest selenium), 1.1, 1.0, 0.8, and 1.0 (lowest selenium), p for trend = 0.82. Similar patterns were observed for Stage I invasive, and Stages II-IV invasive cases, suggesting severity of disease did not influence the null results. Although no associations were seen among current or never smokers, a protective effect of selenium was suggested among former smokers. Effect modification was not evident for other variables examined.This study does not support a relationship between serum selenium and invasive cervical cancer at typical serum selenium levels in the US.

Concern has been raised about the adequacy of radioimmunoassays to measure steroid sex hormones in population studies. We compared steroid sex hormone measurements in serum by radioimmunoassay with mass spectrometry. Four male and four female serum pools with known relative concentrations of steroid sex hormones were measured multiple times by both methods. Because measurements are expected to increase linearly with concentration for each sex, we examined whether the linear regressions of hormone measurements on concentration were the same for radioimmunoassay and mass spectrometry. Estradiol, estrone, androstenedione, testosterone, and dehydroepiandrosterone sulfate were measured in female pools; testosterone, dihydrotestosterone, androstenedione, and dehydroepiandrosterone sulfate were measured in male pools. Regression slopes for radioimmunoassay and mass spectrometry measurements were comparable for all hormones except androstenedione, which had a steeper slope when measured by mass spectrometry (Por = 0.02). Intercepts for radioimmunoassay and mass spectrometry were similar and close to zero for estradiol, androstenedione, dehydroepiandrosterone sulfate, and in male samples, testosterone. For testosterone in female samples, estrone, and dihydrotestosterone, radioimmunoassay and mass spectrometry intercepts differed significantly. Standard deviations of individual measurements by radioimmunoassay and mass spectrometry differed by hormone and serum concentration; neither method consistently measured hormone concentrations with less variability. Our findings suggest that although absolute concentrations may differ for some hormones, radioimmunoassay and mass spectrometry can yield similar estimates of between subject differences in serum concentrations of most steroid sex hormones commonly measured in population studies. Relative power of studies using radioimmunoassay and mass spectrometry will depend on the hormones measured and their serum concentrations.

To evaluate the role of factors that may affect the level of plasma ascorbic acid (AA), including age, body weight, physical activity, minor illness and the impact of prior depletion and repletion.After one month of stabilization on 60 mg vitamin C/day, subjects underwent two complete depletion-repletion cycles (one cycle=one month of vitamin C depletion with nine mg/day, followed by one month of repletion with 117 mg per day). Subjects (68 men, ages 30 to 59 years) did not smoke or drink alcohol during the study. All food was provided by the study.There was extreme individual variability in the plasma AA level achieved on an identical repletion dose: after four weeks at 117 mg/day of vitamin C, AA ranged from 26.8 micromol/L to 85.8 micromol/L. Body weight was inversely associated with plasma AA attained (p0.0001). Regression analysis indicated that, compared to a 130-lb man, a 200-lb man reached 10 micromol/L lower AA after the first repletion and 18 micromol/L lower AA after the second repletion. One-third of the subjects did not reach a plasma plateau after the first repletion. Prior depletion and apparent repletion also had a major impact, and only 10% of subjects reached the same plasma AA on the second repletion as on the first repletion.Plasma AA attained on a given dose depends on body weight (or dose per kg of body weight) and on whether or not any prior depletions had been repleted adequately. The results have implications for nutrition recommendations and research design.

To examine food intake trends in the US population, cross-sectional nationally representative food intake data were obtained from the 1987 and 1992 National Health Interview Survey Cancer Control Supplements. In each of these years, approximately 10,000 respondents completed methodologically consistent food frequency questionnaires containing the same 57 food items. Between 1987 and 1992, the proportion of Americans consuming high-fat foods, including fried fish, fried chicken, bacon, eggs, whole milk, and butter, decreased. The proportion of Americans drinking alcoholic beverages also decreased: fewer drank wine and hard liquor in 1992. The proportion of fruit and vegetable consumers remained stable over time. These results are similar to those obtained from more detailed national surveys. National guidelines urge Americans to avoid intake of high-fat foods, increase consumption of fruits and vegetables, and practice moderation when drinking alcoholic beverages to prevent cancer and other chronic diseases. The direction of Americans' apparent changes in food usage between 1987 and 1992, evaluated using limited data from food frequency questionnaires, suggests greater behavioral changes in the direction of guidelines recommending avoidance of foods that may increase the risk of cancer than in the direction of guidelines recommending increased consumption of foods that may confer protection.

Purpose.This study examined the relationship between various psychosocial factors and fruit and vegetable consumption.Design.The 5 A Day Baseline Survey, conducted in August 1991, just before the initiation of the 5 A Day for Better Health Program, obtained data on adults' intakes of, and their knowledge, perceptions, and attitudes regarding, fruits and vegetables.Setting.The survey was conducted by telephone.Subjects.Subjects were 2811 adults (response rate, 43%) aged 18 years and older in the 48 coterminous United States.Measures.Fruit and vegetable intake was measured as self-reported frequency of use; most of the psychosocial variables were measured using Likert scales.Results.This study estimates that only 8% of American adults thought that five or more servings of fruits and vegetables were needed for good health. Of the factors studied, the most important in determining someone's fruit and vegetable intake were the number of servings they thought they should have in a day, whether they liked the taste, and whether they had been in the habit of eating many fruits and vegetables since childhood. These few factors accounted for 15% more of the variation in fruit and vegetable consumption than did demographic variables alone (8%).Conclusions.Nutrition education should stress the need to eat five or more servings of fruits and vegetables per day because few adults are aware of this recommendation and such knowledge is strongly associated with increased intake. Furthermore, efforts to increase the palatability of fruits and vegetables, especially among children, should be promoted.

OBJECTIVES. This research used food frequency data to investigate dietary patterns associated with fat intake. METHODS. Data from the 1987 National Health Interview Survey of 20,143 adults were used to determine correlations between fat (adjusted for kilocalories) and both nutrient and food group intakes. Median food and nutrient intakes were determined within quartiles of percentage of kilocalories from fat. RESULTS. Intakes of vegetables, fruits, cereals, fish/chicken, low-fat milk, alcoholic beverages, vitamin C, percentage of kilocalories from carbohydrates, carotenoids, folate, dietary fiber, carbohydrates, and vitamin A decreased as percentage of kilocalories from fat increased. Intakes of salty snacks, peanuts, processed and red meats, whole milk and cheese, desserts, eggs, fried potatoes, table fats, cholesterol, vitamin E, sodium, protein, and energy increased with percentage of kilocalories from fat. Results by demographic subgroups showed few differences from those found in the total population. CONCLUSIONS. Fat intake is consistently associated with specific dietary patterns. Such patterns need to be evaluated concurrently in studies of diet and chronic disease.