Estimating energy contributed by fiber using a general factor of 2 vs 4 kcal/g.
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Adolescent↗
Biomedical subjects
P M Guenther
Publications and source records attributed to P M Guenther.
Validity of portion-size measurement aids: a review.
A review of research studies that focus on the validity of portion-size measurement aids (PSMAs) was undertaken because guidelines for the use of PSMAs in studies of food intake have not been developed. Also, the accuracy of food quantity estimates may greatly influence the quality of dietary intake data. Generally, the review indicated that differences between the food quantity estimates obtained from different PSMAs were not statistically significant. Research on PSMA accuracy was lacking in several areas. Additional information is needed on the validity of PSMAs, particularly as it relates to PSMA use by different socio-demographic groups. Little research has focused on the specific effects that PSMAs have on quantity estimates or on subject perceptions of PSMA use. Improved reporting of PSMAs in the literature is also needed. Future research should be directed toward these issues so that PSMA guidelines can be developed. Until there is a more complete research base, it is not possible at this time to establish guidelines for use of PSMAs in clinical practice or in research settings.
Diet↗
Development of an approach for estimating usual nutrient intake distributions at the population level.
Assessment of the dietary intake of a population must consider the large within-person variation in daily intakes. A 1986 report by the National Academy of Sciences (NAS), commissioned by the U.S. Department of Agriculture (USDA), marked an important milestone in the history of this issue. Since that time, USDA has been working cooperatively with statisticians at Iowa State University (ISU), who have further developed the measurement error model approach proposed by NAS. The method developed by the ISU statisticians can be used to estimate usual dietary intake distributions for a population but not for specific individuals. It is based on the assumption that an individual can more accurately recall and describe the foods eaten yesterday than foods eaten at an earlier time. The method requires as few as two independent days of nutrient intake information or three consecutive days for at least a subsample of the individuals. It removes biases of subsequent reporting days compared with the first day, and temporal effects such as day-of-the-week and seasonal effects can be easily removed. The method developed at ISU is described conceptually and applied to data collected in the 1989-91 USDA Continuing Survey of Food intakes by individuals to estimate the proportion of men and women age 20 y and older having "usual" (long-run average) intakes below 30% of energy from fat, below the 1989 Recommended Dietary Allowances for vitamin A and folate, and above 1000 micrograms for folate. These results were compared with the results from the distributions of 1-d intakes and of 3-d mean intakes to demonstrate the effect of within-person variation and asymmetry on usual nutrient intakes in a population.
Adult↗
Separating fact from artifact in changes in nutrient intake over time.
OBJECTIVE: To determine whether the differences between the procedures and nutrient databases used in the 1977-1978 Nationwide Food Consumption Survey (1977-78 NFCS) and those used in the 1987-88 NFCS could notably affect the estimated mean nutrient intakes. DESIGN: This was a split-sample field experiment. Seventy-two area segments were randomly selected; 10 housing units were selected in each segment and randomly assigned to one of two experimental groups. SETTING: The study took place in the Philadelphia, Pa, metropolitan area. SUBJECTS: The subjects were 697 women aged 20 to 49 years. TREATMENT: Group A was interviewed using 1987-88 NFCS 24-hour recall procedures and their nutrient intakes were calculated using the 1987-88 NFCS food codes, weight conversion factors, and nutrient database. Group B was interviewed using 1977-78 NFCS 24-hour recall procedures and nutrient intakes were calculated four ways using various combinations of 1987-88 and 1977-78 NFCS food codes, weight conversions, and nutrient database. MAIN OUTCOME MEASURE: Mean intakes of food energy and 14 nutrients were calculated. STATISTICAL ANALYSIS: We used two-sample, multivariate t tests; univariate t tests; univariate repeated measures analysis of variance; and univariate paired t tests. RESULTS: Changes in the nutrient database caused by improved analytic techniques and increased number of foods sampled were great enough to warrant revising the 1977-78 NFCS estimated intakes for iron, magnesium, and vitamins B-6 and B-12. Changes in intake of fat, vitamin A, and thiamin, however, were caused by real changes in foods so no revisions were necessary for these nutrients. Other nutrients were unaffected. CONCLUSION: When considering changes in nutrient intake over time, it is important to correct the earlier food composition estimates so that they accurately reflect the composition of foods at the time they were consumed. This requires preserving the real differences in the composition of foods while correcting for artifactual differences attributable to improvements in the quality of nutrient data.
Adult↗
Research needs for dietary assessment and monitoring in the United States.
The 10-y Plan for the National Nutrition Monitoring and Related Research Program calls for research related to dietary data collection and interpretation and for improved data dissemination. The United States Department of Agriculture Human Nutrition Information Service has released data from the 1989 Continuing Survey of Food Intakes by Individuals and is planning for the next one. Respondent burden will be reduced. The sample is designed for improved estimates of dietary intakes for children and elderly individuals. An automated coding system will contribute to improved data management. Current research projects include developing data collection strategies in a cognitive research laboratory, exploring alternative interview structures for children, and developing methods to estimate the distributors of usual intakes of nutrients and foods. Priorities for further research and development are applying cognitive psychology research techniques to improve accuracy of responses, ensuring the temporal validity of food-composition databases, and developing the probability approach for assessing dietary adequacy.
Aged↗
Mean proportion and population proportion: two answers to the same question?
Two different, but equally correct, answers can be given to a question such as "What proportion of the cholesterol that is consumed comes from eggs?" This is because the question can have two different meanings, depending on whether one is referring to the mean proportion of cholesterol from eggs or the population proportion. The mean proportion of cholesterol from eggs for a group of persons is determined by first calculating the proportion of cholesterol from eggs for each person and then taking an arithmetic mean of all the proportions. The population proportion is calculated by summing the amount of cholesterol from eggs for all persons and then dividing that by the sum of the cholesterol from all foods for all persons. These two different formulas often yield similar results. Sometimes, however, the results can be quite different because of variation in the ratio, variation in the denominator, and/or the correlation between the ratio and the denominator. Each of these formulas is designed to answer a specific question: the mean proportion addresses the question about the average per person and the population proportion addresses the question of population intakes. But because either may be used to answer the same general question, confusion may result. This article discusses the factors influencing differences between the two formulas and the implications of those differences for reporting and interpreting dietary intake data.
Data Interpretation, Statistical↗
Beverages in the diets of American teenagers.
The purpose of this study was to investigate the role of beverages, particularly soft drinks, in the diets of American teenagers by analyzing data collected in the Nationwide Food Consumption Survey, 1977-78. Interviewers obtained 24-hour recalls of dietary intake, and respondents completed diet records for the following 2 days. Variation in beverage intake was examined by eating occasion, season, day of the week, region, urbanization, race, age, sex, and household income. Soft drink and milk intakes were negatively correlated (r = -.22). Soft drinks were just as likely to be drunk at lunch or supper as for snacks. Those results suggest that teenagers may have substituted soft drinks for milk at meals. The nutritional impact of soft drink consumption was assessed by determining the part correlations of soft drink intake with intakes of energy and 14 nutrients, while controlling for 19 variables related to time, location, and personal and household characteristics. The negative part correlations of soft drink intake with intakes of calcium (-0.11), magnesium (-0.06), riboflavin (-0.09), vitamin A (-0.08), and ascorbic acid (-0.06) indicate that soft drinks may contribute to low intakes of those nutrients by some teenagers.
Adolescent↗