NS 210 – Unit 3 Seminar Interview Techniques Leslie Young MS RD LDN

Reasons for Measuring Diet “TO IMPROVE HUMAN HEALTH” 4 Major Uses Of Dietary Intake Data –Assessing and monitoring intake –Formulating and evaluating government and agricultural policy –Epidemiologic research –Commercial purposes

Assessing and Monitoring Food and Nutrient Intake Ensuring adequacy of the food supply Estimating the adequacy of dietary intakes of individuals and groups Monitoring rends in food and nutrient consumption Estimating exposure to food additives and contaminants

Formulating and Evaluating Government Health and Agricultural Policy Planning food production and distribution Establishing food production and distribution Establishing programs for nutrition education and disease risk reduction Evaluating the success and cost-effectiveness of nutrition education and disease risk reduction programs

Conducting Epidemiologic Research Studying the relationships between diet and health Identifying groups at risk of developing diseases because of their diet and/or nutrient intake

Commercial Purposes Data from national nutrition surveys are used by the food manufacturers to develop advertising campaigns or new food products

Measuring Diet Most widely used indirect indicator of nutritional status Estimating intake can be difficult –Weakness of data-gathering techniques –Human behavior –Natural tendency of intake –Limitations of nutrient composition tables and databases

Methods for Measuring Intake 24-hour recall Food Record or Diary Food Frequency Questionnaires Diet History Duplicate Food Collections Food Accounts Food Balance Sheets Photographic and Digital Video Methods

24-Hour Recall Strengths –Requires less than 20 minutes –Inexpensive –Easy to administer –Low respondent burden –Can provide detail info on types of food consumed –Probability sampling possible –More objective than dietary history –Does not alter usual diet Limitations –One recall is seldom representative of a person’s usually intake –Underreporting/ overrreporting occurs –Relies on memory –Omissions of dressings, sauces, and beverages can lead to low estimates of energy intake –May be a tendency to overreport intake at low levels and overreport intake at high levels of consumption –Data entry can be very labor intensive

Food Record or Diary Strengths –Does not depend on memory –Can provide detailed intake data –Can provide data about eating habits –Multiple-day data more representative of usually intake –Reasonably valid up to 5 days Limitations –Requires high degree of cooperation –Response burden can result in low response rates when used in large national surveys –Subject must be literate –Takes more time to obtain data –Act of recording may alter diet –Analysis is labor intensive and expensive.

Food Frequency Questionnaire Strengths –Can be self administered –Machine readable –Modest demand on respondents –Relatively inexpensive for large sample sizes –May be more representative of usual intake than a few days of diet records –Design can be based on large population data –Considered by some as the method of choice for research on diet-disease relationships Limitations –May not represent usual foods or portion sizes chosen by respondents –Intake data can be compromised when multiple foods are grouped within single listings –Depend on ability of subject to describe diet

Diet History Strengths –Assesses usually nutrient intake –Can detect seasonal changes –Data on all nutrients can be obtained –Can correlate well with biochemical means Limitations –Lengthy interview process –Requires highly trained interviewers –Difficult and expensive to code –May tend to overestimate nutrient intake –Requires cooperative respondent with ability to recall usual diet

Food Accounts Strengths –Suitable for use with large sample size –Can be used over relatively long periods –Gives data on dietary patterns and habits of families and other groups –Less likely to lead to alterations in diet than some other methods –Relatively economical Limitations –Does not account for food losses –Respondent literacy and cooperation necessary –Not appropriate for measuring individual food consumption

Food Balance Sheet Strengths –Can give a total view of a country’s food supplies –Indicates food habits and dietary trends –Sued to plan international nutrition policies and food programs –May be the only data available on a country’s food consumption practices Limitations –Accuracy of data may be questionable –Only represents food available for consumption –Does not represent food actually consumed –Does not indicate how food was distributed –Does not account for wasted food

Other Interview Techniques Duplicate Food Collection Method Photographic and Video Records Computerized Techniques

Issues in Dietary Measurement Validity –Ability of an instrument to measure what it is intended to measure Reproducibility –The ability of a method to produce the same estimate on two or more occasions How Many Days? –It is important to know how long a dietary intake must be measure before a sufficiently reliable estimate of usual intake is obtained

Estimating Portion Sizes Photographs of food Geometric Shapes Measuring Devices Lifelike plastic food models

Overview of Chapter 3 Research Design Considerations –Correlation Studies –Case Control Studies –Cohort studies Factors that influence selection of dietary methods Different Techniques in Measuring diet –Strengths and Limitations Validating Dietary Methods