Blossom H. Patterson

Fruit, vegetables, and cancer prevention: A review of the epidemiological evidence

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.

Fruit and Vegetable Intake in the United States: The Baseline Survey of the Five a Day for Better Health Program:

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.

Fruit and vegetables in the American diet: data from the NHANES II survey.

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.

Changes in vegetable and fruit consumption and awareness among US adults: Results of the 1991 and 1997 5 A Day for Better Health Program surveys

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.

Using food frequency questionnaires to estimate fruit and vegetable intake: Association between the number of questions and total intakes

Abstract 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.

Measurement of steroid sex hormones in serum: a comparison of radioimmunoassay and mass spectrometry.

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 (P < or = 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.

Food choices of whites, blacks, and Hispanics : data from the 1987 National Health Interview Survey

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.

Ascorbic Acid Status and Subsequent Diastolic and Systolic Blood Pressure

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, &agr;-tocopherol, carotenoids, and lipids. Plasma AscA was inversely related to diastolic blood pressure 1 month later (correlation −0.48, P <0.0001). Persons in the bottom fourth of the plasma AscA distribution had >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.

Latent Class Analysis of Complex Sample Survey Data: Application to Dietary Data

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 complex sample design through the use of jackknife standard errors. A two-class model showed that 18%% do not regularly consume vegetables, compared to an unweighted estimate of 33%%. Simulations showed that ignoring sample weights resulted in biased parameter estimates and that jackknife variances were slightly conservative but provided satisfactory confidence interval coverage. Using a survey-wide estimate of the design effect for variance estimation is not accurate for LCA. The methods proposed in this article are readily implemented for the analysis of complex sample survey data.

Evaluating markers for the early detection of cancer: overview of study designs and methods.

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.