Development and reproducibility of a brief food frequency questionnaire for assessing the fat, fiber, and fruit and vegetable intakes of rural adolescents.

OBJECTIVE: To describe the systematic development and reproducibility of a food frequency questionnaire (FFQ) designed to meet the specific research requirements of the Goals for Health cancer prevention intervention program for rural middle school children. DESIGN: A 4-step process was used to develop a brief FFQ for scoring intakes of total fat, fiber, and fruits and vegetables. The resulting questionnaire consisted of 25 food frequency items and 10 supplemental questions. Reproducibility of the questionnaire was determined by comparing responses at the beginning and end of a 4-month interval. SUBJECTS: Study subjects were sixth- and seventh-grade students attending middle schools in rural areas of Virginia and upstate New York. Seventh-grade students participated in the pilot study, and sixth-grade students participated in the reproducibility study. The final version of the FFQ was completed twice by 539 sixth graders. After exclusions for missing and unreliable data, the usable sample size was 415. Boys were somewhat more likely than girls to be excluded for missing data. African-American students comprised 32% of the population. STATISTICAL ANALYSES PERFORMED: Each food frequency item was associated with 3 scores--a fat score, a fiber score, and a combined score for the number of servings of fruits and vegetables. Means and standard deviations were determined for nutrient variables, differences between repeat administrations were tested for significance by paired t test, and Pearson correlation coefficients were calculated for nutrients and for individual food items. RESULTS: Correlation coefficients for nutrient scores were 0.58 for fat, 0.49 for fiber, and 0.51 for fruits and vegetables. For individual food items, correlations ranged from 0.24 to 0.59 (mean=0.41). APPLICATIONS/CONCLUSIONS: Using a systematic approach to developing a study-specific FFQ for rural adolescents is feasible. Further, the reproducibility of the Goals for Health questionnaire was demonstrated for the 3 nutrient scores it was designed to measure. This developmental approach may be readily adapted to other populations, study designs, and nutrients of interest. The validity of the questionnaire remains to be tested.

Methods of dietary and nutritional assessment and intervention and other methods in the Multiple Risk Factor Intervention Trial.

Various dietary assessment instruments were used in the Multiple Risk Factor Intervention Trial (MRFIT), either to assist with the special intervention program or to assess trial outcomes. For the latter purpose, the 24-h recall was the main method and was selected with the understanding that the single recall collected at baseline and at most annual visits--considered by itself--would be useful mainly for assessing groups rather than individuals. Major components of the data collection and analysis system developed for the 24-h recall included central training and certification of nutritionists, a central nutrient coding system, and a food grouping system to assist interventionists in using recall data for counseling. Several additional nutritional assessment methods were used for men in the special intervention group only to assist them in attaining the dietary goals. These goals consisted chiefly of reduced intake of saturated fat and cholesterol and a modest increase in intake of polyunsaturated fat; total fat intake was also decreased, primarily for control of energy intake. Short-term success at attainment of these nutritional goals was evaluated by means of 3-d food records collected before the intervention and after the initial 10-wk intensive intervention period. The MRFIT nutrient goals, which became more vigorous at certain points in the trial, were translated into food patterns. Adherence to these food patterns was also assessed by scoring of 3-d records and by subjective evaluation by nutritionists throughout the trial. Methods of collecting other trial data are also described in this chapter.

Monitoring dietary change in a low-fat diet intervention study: advantages of using 24-hour dietary recalls vs food records.

OBJECTIVE: The purpose of the study was to evaluate two methods of dietary assessment for monitoring change in fat intake in a low-fat diet intervention study. DESIGN: The two dietary assessment methods were a 4-day food record (4DFR) and an unannounced 24-hour dietary recall conducted by telephone interview (referred to as a telephone recall [TR]). Subjects were assigned randomly to either a low-fat diet intervention group or a control group that received no counseling about fat intake. Dietary data were collected at baseline, 6 months, and 12 months. SUBJECTS: Two hundred ninety postmenopausal women with localized breast cancer were recruited at seven clinical centers in the United States. STATISTICAL ANALYSIS: Analysis of variance was used to test for significant differences in mean fat and energy intakes. RESULTS: Three sources of error were identified: (a) an instrument effect, suggesting underreporting at baseline of approximately 8% in mean energy intake and 11% in mean fat intake in the TR group compared with the 4DFR group (P = .0001); (b) a repeated measures effect observed for the 4DFR, suggesting underreporting of approximately 7% for energy intake and 14% for fat intake in the control group at 6 and 12 months compared with baseline values (P < .001); and (c) an adherence effect (or compliance bias), suggesting greater compliance to the low-fat intervention diet when subjects were keeping food records than when estimates were based on the unannounced TR. Compared with the TR, the 4DFR overestimated the extent of fat reduction in the low-fat diet intervention group by 41% (P = .08) and 25% (P = .62) at 6 and 12 months, respectively. APPLICATION: Multiple days of unannounced 24-hour recalls may be preferable to multiple-day food records for monitoring dietary change in diet intervention studies.

A food frequency questionnaire can detect pregnancy-related changes in diet.

OBJECTIVE: To determine whether a food frequency questionnaire (FFQ) can detect changes in dietary intake before pregnancy to mid-pregnancy relative to a 4-day food record. DESIGN: FFQs and 4-day, weighed food records (4DRs) were completed during similar time intervals before pregnancy and again near mid-pregnancy by women served by a large health maintenance organization in the Minneapolis-St Paul, Minn, area. The outcome of interest was change in the intake of energy and 16 nutrients. Participants were members of the Diana Project, a prospective study of relationships among prepregnancy and pregnancy nutritional and other exposures and reproductive outcomes. Fifty-six (51%) of the eligible women completed the study. SUBJECTS: Well-educated, healthy, white women. STATISTICAL ANALYSES PERFORMED: Spearman rank order correlations. RESULTS: Mean energy and nutrient intake levels estimated using the 4DR were generally higher than those estimated using the FFQ. Correlations between change in energy and nutrient intakes measured by the 4DR and FFQ ranged from .75 for vitamin C to .02 for cholesterol and averaged .48. APPLICATIONS: Comparisons with 4DRs indicate that the FFQ used in this study is appropriate for obtaining reliable estimates of prepregnancy to mid-pregnancy changes in intake of energy and a number of nutrients in similar groups of women.

Reproducibility of a comprehensive diet history in the Diabetes Control and Complications Trial. The DCCT Research Group.

OBJECTIVE: To evaluate the reproducibility of a modified Burke-type diet history within the context of a long-term, randomized, 29-center clinical diabetes study. DESIGN: Diet histories were collected by trained interviewers at the end of years 1 and 2 after subjects were randomly assigned to the intensive treatment group or the conventional treatment group. Mean daily intakes of energy, protein, carbohydrate, total fat, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, cholesterol, and dietary fiber were calculated for each treatment group at each time period. SUBJECTS: The study population consisted of 139 subjects in the intensive treatment group and 128 subjects in the conventional treatment group. Ages ranged from 13 to 39 years; groups included men and women. Distribution by age, sex, race, proportion of smokers, weight reported as percent ideal body weight, and duration of IDDM were similar in both groups. STATISTICAL METHODS: Differences in nutrient intake between the conventional and intensive treatment groups at each time period were tested for significance using the Wilcoxon rank-sum test. The Wilcoxon paired differences test was used to assess changes between time periods within treatment groups. Linear agreement between repeated administrations of the diet history was evaluated using Pearson's correlation coefficient, and the extent of within-subject reproducibility was assessed by intraclass correlation. RESULTS: No statistically significant differences in energy and nutrient intakes were observed between the two groups at either year 1 or year 2. Within each treatment group, energy and nutrient intake differences between times were not statistically significant. Correlation coefficients between years 1 and 2 ranged from .51 for dietary fiber to .72 for dietary cholesterol; within-subject reproducibility was slightly higher. APPLICATIONS: These results demonstrate long-term reproducibility for the meal-based diet history in the DCCT population.

Rationale for an international conference series on dietary assessment methods.

The rationale for establishing an international conference series on dietary assessment methods is based on the needs expressed by numerous national and international organizations for better methods of collecting and analyzing dietary data. Dietary assessment is essential for investigating diet-health relationships, formulating policies to reduce health risks, predicting the adequacy of the food supply, and monitoring trends in food use, exposure to contaminants, and compliance with dietary guidelines. The conference rationale is discussed with respect to 1) the need for improved methods to enhance our understanding of diet-health relationships, 2) the need for better methods to facilitate development and monitoring of nutrition-related health objectives, and 3) the importance of international participation. Improved methods for assessing food intakes will enhance our understanding of the role of diet in the etiology and prevention of disease and will facilitate the development of nutrition policy and programs leading to improved health worldwide.

Research priorities and recommendations for dietary assessment methodology. First International Conference on Dietary Assessment Methods.

A list of research priorities related to dietary assessment methodology is presented. The priorities are based on a consensus of opinion by a multidisciplinary international group of experts who participated in the First International Conference on Dietary Assessment Methods. These experts included researchers in dietary assessment methodology, major users of dietary assessment methods, and policymakers involved in setting food and nutrition policies. The list of priorities may be used as a guide for planning future research in dietary assessment methods, for prioritizing the allocation of available research resources, and for planning subsequent conferences. A list of recommendations related to dietary assessment methodology is also presented. Procedures used by the conference planners to select the experts are described, and the need for developing objective criteria for ranking priorities is discussed. An ongoing function of the conference series will be to continue the process of revising the priorities and recommendations to reflect progress made and newly identified needs in dietary assessment methodology.

Adherence to a dietary fat intake reduction program in postmenopausal women receiving therapy for early breast cancer. The Women's Intervention Nutrition Study.

PURPOSE: To evaluate the feasibility of integrating a program based on dietary fat intake reduction into adjuvant treatment strategies for postmenopausal women receiving therapy for early breast cancer. PATIENTS AND METHODS: Two hundred ninety postmenopausal women with localized (stage I to IIIa) breast cancer receiving conventional systemic therapy provided informed consent and were randomized in a multicenter trial to either a dietary intervention group receiving a program of individualized instruction for reducing total fat intake or a dietary control group with minimal dietary counseling. RESULTS: Significantly reduced (P < .001) fat intake (in terms of percent calories derived from fat) was observed in the intervention group versus the control group at 3 months (20.3% +/- 2.4% v 31.5% +/- 2.6%, mean +/- SD, respectively) and maintained throughout 24 months of observation. The 50% reduction in daily fat-gram intake (from 66 +/- 23 to 33 +/- 14 g, P < .001) seen at 6 months was associated with reduced saturated fat, monounsaturated fat, polyunsaturated fat, and linoleic acid (P < .001). Significantly lower body weight was also seen in intervention compared with control patients at all observation periods, resulting in a 3.3-kg weight difference 18 months after randomization (P < .001). CONCLUSION: Substantial and sustained dietary fat reduction with associated weight change can be achieved at relatively low cost within the context of conventional multimodality clinical management of postmenopausal women with localized breast cancer. This result supports the feasibility of conducting a full-scale evaluation of the influence of dietary fat intake reduction on the clinical outcome of breast cancer patients.

The effects of a low-fat dietary intervention and tamoxifen adjuvant therapy on the serum estrogen and sex hormone-binding globulin concentrations of postmenopausal breast cancer patients.

The purpose of the study was to determine the effect of a low-fat dietary intervention, with or without concomitant tamoxifen adjuvant therapy, on serum estrogen and sex hormone-binding globulin (SHBG) levels in postmenopausal patients with resected breast cancer. Ninety-three patients were randomized to either reduce their fat intake to 15-20% of total calories, or to a dietary control group. Serum estradiol, estrone, estrone sulfate, and SHBG concentrations were assayed at baseline, and at 6, 12, and 18 months thereafter. In 19% of patients, the preintervention serum estradiol levels were below the sensitivity of the assay (5 pg/ml). Tamoxifen had no significant effect on serum estrogen levels, but produced an elevation in SHBG. Patients with reliably quantifiable preintervention estradiol concentrations (> or = 10 pg/ml) showed a significant reduction in serum estradiol after 6 months on the low-fat diet (average, 20%; p < 0.005); this was sustained over the 18 month study period. Serum SHBG levels were increased by tamoxifen therapy, but were reduced significantly (p = 0.01) after 12 months on the low-fat diet in patients not receiving tamoxifen. No changes in serum estrone or estrone sulfate resulted from the dietary intervention. While the low-fat diet produced significant weight loss, patients treated with tamoxifen without dietary intervention showed a gain in body weight. These weight changes produced disruptions in the normal positive correlation between body weight and serum estrone sulfate, and the negative correlation with SHBG concentration.

Adjuvant dietary fat intake reduction in postmenopausal breast cancer patient management. The Women's Intervention Nutrition Study (WINS).

Management of localized breast cancer now commonly involves a breast-sparing approach combined with systemic adjuvant therapy resulting in improved cosmetic results and patient survival. Reducing dietary fat intake represents a conceptually new approach to further improve outcome of patients with resected breast cancer. The rationale supporting evaluation of dietary fat reduction in the management of patients with localized breast cancer is based on: (1) epidemiologic observations (along with biochemical and hormonal correlates) of major differences in stage-by-stage survival of patients with localized breast cancer comparing outcome in countries with low fat (Japan) versus high fat (U.S.A.) dietary intakes; (2) relationships between dietary fat intake and factors prognostic of clinical outcome in patients with established breast cancer; (3) effects of weight gain (especially that associated with adjuvant chemotherapy) on breast cancer clinical outcome; (4) in vivo animal studies demonstrating adverse influence of increased dietary fat intake (especially linoleic acid) on growth and metastatic spread of mammary cancer; (5) direct adverse effects of increased linoleic acid on human breast cancer growth in vitro; (6) plausible mechanisms which could mediate the effects of dietary fat intake reduction on breast cancer growth and metastatic spread; (7) demonstration of adherence to dietary fat reduction regimens in ongoing clinical feasibility studies including those involving postmenopausal patients with resected breast cancer; and (8) favorable sample size requirements for definitive assessment of dietary fat intake reduction influence on breast cancer growth and metastases (using as endpoints relapse-free survival and overall survival) in postmenopausal breast cancer patients with localized disease.

Considerations for selecting nutrient-calculation software: evaluation of the nutrient database.

With the growing number of nutrient-calculation software packages on the market, potential users are faced with the increasingly difficult task of determining which system best meets their needs. Most published reviews of nutrient-calculation software focus on program features rather than on the quality of the nutrient database on which all calculations are based. This is unfortunate because program features are of little consequence if the nutrients calculated are not of acceptable quality. The purpose of this paper is to focus on the evaluation of the nutrient database as the foremost consideration in selecting nutrient-calculation software. Six questions that may be used as a guide for evaluating a nutrient database are presented and discussed.

Videotape dietary assessment: validity, reliability, and comparison of results with 24-hour dietary recalls from elderly women in a retirement home.

The validity and reliability of a videotape method for quantifying food intake were tested, and results of the method were compared with results obtained from 24-hour dietary recalls. Participants were 37 elderly Catholic nuns (aged 81.8 +/- 4.1 years) who were ambulatory and living in a retirement home. The videotape method of dietary assessment consisted of videotaping food trays of each participant for three meals during 1 day and the subsequent identification of food types and amounts from the videotapes. Estimates of food amounts obtained were used in the calculation of energy and nutrient intake. Correlation coefficients between values for energy and 14 nutrients obtained by direct measurement of food and estimates from the videotape method were high (r = 0.86 to 1.0). Compared with measured food amounts, the videotape method underestimated food quantities by an average of 6%. The reliability test indicated that mean nutrient values obtained from the videotape method by two research assistants differed by an average of 3.7% and were highly correlated (r = 0.84 to 0.98). Comparison of the videotape method with 24-hour dietary recalls revealed differences between mean values that were greater than 10% for energy and 6 of the 14 nutrients and correlations that ranged from 0.09 to 0.82. These results suggest that use of 24-hour dietary recalls among the elderly may result in a high percentage of error.

Diet intervention methods to reduce fat intake: nutrient and food group composition of self-selected low-fat diets.

A multicentered pilot study was conducted to test an intervention protocol designed to reduce fat intake to 15% of energy intake. Eligible subjects were postmenopausal women with stage II breast cancer whose baseline fat intake was more than 30% of energy intake. The low-fat diet intervention protocol consisted of bi-weekly individual counseling sessions with emphasis on substitution of lower-fat foods for high-fat foods and maintenance of nutritional adequacy. Nutrient intakes were calculated from 4-day food records collected at baseline and after 3 months of diet intervention. Mean daily fat intake for the 17 patients on the low-fat diet dropped significantly from 38.4 +/- 4.3% of energy intake at baseline to 22.8 +/- 7.8% at 3 months (p less than .001). A 25% reduction in mean energy intake, from 1,840 +/- 419 kcal at baseline to 1,365 +/- 291 kcal at 3 months, was accompanied by significant increases in protein and carbohydrate as percent of energy intake. A mean weight loss of 2.8 kg and a 7.7% reduction in serum cholesterol were observed; both changes were significant at the p less than .01 level. Absolute intakes of zinc and magnesium were significantly reduced. However, mean intake on the low-fat diet for 14 vitamins and minerals, including zinc and magnesium, exceeded two-thirds of the 1989 Recommended Dietary Allowances (RDAs). When expressed as nutrient density (i.e., amount of nutrient per 1,000 kcal), increases were observed for all micronutrients. These results support the hypothesis that a nutritionally adequate low-fat diet can be successfully implemented in a highly motivated, free-living population.

Maintenance of a nutrient database for clinical trials.

Maintenance of a nutrient database for use in dietary analysis for clinical trials and other medical research studies is described. The database, maintained at the University of Minnesota's Nutrition Coordinating Center (NCC), has been used to calculate dietary intake data for a wide range of diet-disease related investigations including studies on cardiovascular disease, hypertension, cancer, gastroenterology, and osteoporosis. Potential sources of error associated with nutrient databases are identified. Criteria are provided for the selection of a nutrient database to meet study objectives and to minimize the potential for errors and inconsistencies. NCC database maintenance procedures, designed to provide updated and verified nutrient calculations for clinical research, involve adherence to standardized procedures for all aspects of database maintenance including data selection, imputations, quality control, recipe calculations, and documentation. By maintaining multiple versions of the database, the NCC is able to update and expand a working version of the database while providing database stability for individual research studies.

Unpublished Data Summaries and the design and conduct of clinical trials. The Nutrition Adjuvant Study experience and commentary.

A trend in cancer clinical investigation has been the application of new analytic techniques and reporting forums to summarize developing trial results. Examples include: Consensus Conferences, Meta-Analyses, and most recently (in the breast cancer area), the "Clinical Alert." These Unpublished Data Summaries have been widely disseminated in lay and scientific communities and have frequently engendered debate conducted in the absence of primary information. We now report the impact of this process on a national, cooperative group effort (the Nutrition Adjuvant Study [NAS] ) designed to test a novel hypothesis involving dietary fat reduction as potential adjuvant breast cancer treatment. It is clear that these Unpublished Data Summaries in the breast cancer area directly resulted in changes in the NAS protocol design and may have influenced patient accrual. The challenge for clinical investigators and governmental agencies is to integrate the positive aspects of the new information forums with those of traditional "peer-review" publication into a system where the conduct of clinical investigation in a timely manner can be facilitated.

Computerized collection and analysis of dietary intake information.

A computer system has been developed which facilitates standardized and in-depth collection and analysis of dietary intake information required for nutritional research. The system uses a hierarchically arranged database of food descriptions. A user identifies a consumed food by traversing a hierarchy and reaching a leaf node food item via a succession of selections from menu displays. If a food contains ingredients or was cooked with additional fat or salt, multiple traversals of the food hierarchies are necessary. The system assigns one or more food codes and determines the gram weight of the food consumed using everyday measures such as cups, slices, ounces, etc. It then uses these food codes and gram weights to calculate nutrient content. Utilizing binary trees and physical pointers to expedite data retrieval from this nearly 10 Mbyte database permits the system's use in conducting real-time interactive interviews.

Comparison of a computerized and a manual method of food coding for nutrient intake studies.

The Dietary Data Collection (DDC) microcomputer system is currently being developed as a tool for the standardized and detailed collection of dietary intake data for human nutrition research studies. The system operates interactively, soliciting all necessary information on menu selection screens to ensure user entry of complete food descriptions and quantity information. The descriptive data are then automatically converted to food codes and gram weights for subsequent calculation of nutrient content. At the completion of the first phase of system development, a preliminary test was performed to compare the amount of time required to enter food intake data into the DDC system with the amount of time required to accomplish the same food coding task manually. Test subjects consisted of four experienced food coders and one coder trainee. Using a crossover design, each coder manually coded 16 1-day food records and entered another 16 records into the DDC system for automatic coding. Four of the five coders took significantly less time to code and enter descriptive dietary intake information using the DDC system than they took for manual coding and data entry. Time savings ranged between 9% and 44% among the test subjects.

Sources of data for developing and maintaining a nutrient database.

A nutrient database that contains current, reliable data is a prerequisite for accurate calculation of dietary intakes. Most nutrient databases are expanded from data supplied by the U.S. Department of Agriculture and may include additional foods or nutrients or data from more recent analyses, food manufacturers, or foreign food tables. Guidelines must be established for selection of reliable values from appropriate sources. A system for precise documentation of data sources provides a means for determining whether individual nutrient values were derived from chemical analyses, recipe calculations, or imputations. This article identifies data sources used by the Nutrition Coordinating Center at the University of Minnesota for its nutrient database and describes the procedures used to select and document nutrient values.