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Dietary Intake Methodology Chapter 10 NTRS 511 H. Singh Ph. D. Introduction To identify the relationship between diet and disease or health Unfortunately there is no single method suitable for all kind of studies Dietary methods are classified in to Group Individuals Group data
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Dietary Intake Methodology Chapter 10 NTRS 511 H. Singh Ph. D.
Introduction • To identify the relationship between diet and disease or health • Unfortunately there is no single method suitable for all kind of studies • Dietary methods are classified in to • Group • Individuals
Group data • Economic Research Services (ERS) and USDA compiles data for consumption – also called as food disappearance data • Does not include spoiled food, fed to pets, waste • To look for trends like income versus nutritional status • Food intakes are checked on weekly – RDA comparisons are made • Assumptions are made for sex and age differences • Used to develop family food plans
Individual Dietary methods • 24 hour recall method – easy to administer • Dietician help using visual aid to find how much they have eaten • Efficient method to compare groups of people differ in age, sex, race • Japanese in Hawaii - Show more intake of fat and less carb • National Health and Nutrition Examination Surveys (NHANES) use this method • Shortcoming – daily variations in diet – so calls are made on weekdays and weekends
Food Records • Subjects record food concurrent for three to seven days • Foods are weighed, measured or estimated • Need good instruction • After a few days subjects are tired and may skip • They do not rely on the memory- • Helpful in • developing diet history • Motivation of subject for food intervention study
Diet Histories • Measure for a long time – may be a year • Precision is compromised • Diet disease relationship • List may be provided from population's eating patterns - to choose what was eaten and how much
Potential Errors • Three kinds • Respondent and recorded error • People forget, do not know what is in food, may want to hide, underestimate or overestimate some foods – called as flat slope syndrome • Interviewer and reviewers error – • If not well trained • Need coding • guidelines • Nutrient based error • USDA primary resource • Food analysis data
Validity and reproducibility • Validity – ability of an instrument to measure what it is supposed to be • Difficult in these kinds of settings – like how much is eaten – should be weighed • Reproducibility ( repeatability or reliability) • Same person’s record of diet on different days • Similar to crop studies over the years