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8 Minimizing Potential Errors in Assessing Group and Individual Intakes
Pages 147-161

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From page 147...
... to the specific group or incliviclual, ensuring that the intake ciata have the highest accuracy feasible, minimizing sampling errors when collecting intake ciata on groups, and determining stanciarci deviations of prevalence estimates. Dietary assessments involve comparing nutrient intakes of incliviciuals or groups with the DRIB.
From page 148...
... In most cases, adjustments are not likely to be required because the EAR already accounts for normal individual variability. However, adjustments may be warranted for individuals who have unusually high or low body weight, experience physiological changes at unusual ages, experience unusual physiological changes, or have unusually high energy requirements.
From page 149...
... Despite this lack of experimental ciata, the known biochemical functions of these nutrients suggest that adjustments for energy intake may be appropriate, particularly for individuals with very high intakes (such as those engaged in physically clemancling occupations or who spenci much time training for active sports)
From page 150...
... For thiamin, the coefficient of variation of the requirement is 10 percent, so the energy-adjusted RDA would be 20 percent higher than the energy-adjusted EAR, or 0.41 mg/1,000 kcal for men and 0.49 mg/1,000 kcal for women. MINIMIZING ERRORS IN MEASURING DIETARY INTAKES Factors influencing food and nutrient intakes are often the same as those influencing requirements, such as life stage, body size, lifestyle, genetic determinants, environment, etc.
From page 151...
... may appear to be attractive alternatives. Because of the ease of administration and entry of consumption data, semi-quantitative food-frequency questionnaires are widely available and often used in epiclemiological studies.
From page 152...
... Because they are quantitative and do not truncate information on frequency, amount, or the actual food items consumed, diet histories overcome many of the limitations of fooci-frequency questionnaires for assessment of the total nutrient intakes of inclivicluals (Kohlmeier and Bellach, 1995~. Diet histories have also been shown to capture total energy intake more accurately than other methods (Black et al., 1993~.
From page 153...
... In summary, intakes assessed by 24-hour recall, diet records, or quantitative diet histories remain the strongest bases for quantitative assessment of nutrient adequacy using the Dietary Reference Intakes (DRIsJ. Quantitative assessments require both accurate determination of the quantities of foods consumed by an individual and inclusion of all of the foods that contribute even modestly (more than 5 percents to the total nutrient intake.
From page 154...
... Determine Nutrient Supplement Use Supplement use needs to be determined, and quantified, to obtain accurate estimates of the prevalence of inacloquate nutrient intakes for a group. Otherwise, the prevalence of inadequacy will be overestimated, as will the probability of inadequacy for an individual.
From page 155...
... The extent of uncler- or overestimation will clepenci on the dosages and frequency of use, and for groups, on the percentage of the group using supplements. Currently, the only national surveys available which quantify supplement usage along with clietary nutrient intakes are the 1987 National Health Interview Survey and the Third National Health and Nutrition Examination Survey.
From page 156...
... Rapid Dietary Transition Inc;tuding Effects of Interventions Data may be biased by individuals whose dietary intakes are affected by rapidly changing life circumstances (such as migration or refugee status) or by successfully implemented nutrition intervention programs.
From page 157...
... Use Accurate Food Composition Data Deriving nutrient intake ciata from clietary intake ciata requires the use of a food composition database. Accuracy of the food composition ciata and the software to access it are critical for assessments of clietary acloquacy.
From page 158...
... Determining Standard Deviations of Prevalence Estimates Is the estimated prevalence of nutrient inadequacy in a population significantly di~fferentirom zero? Answering this question requires estimating the standard deviations associated with the prevalence estimates.
From page 159...
... Statistical techniques can be used to estimate the amount of sampling variability associated with prevalence estimates, although the computations are complex. When stanciarci deviations can be calculateci, it is appropriate to report not only the prevalence estimate but also its stanciarci deviation.
From page 160...
... Dietary intake ciata suffer from inaccuracies clue to unclerreporting of food, incorrect specification of portion sizes, incomplete or imprecise food composition tables, etc. These factors may have a compound effect on prevalence estimates.
From page 161...
... This chapter has focused on ways to increase the accuracy of both the requirement estimates (by considering the specific characteristics of the incliviclual or the population) and the intake estimates (by ensuring that clietary ciata are complete, portions are correctly specified, and food composition ciata are accurate)


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