NS 210 – Unit 3 Seminar

Measuring Diets and Interview Techniques

Jennifer Neily, MS, RD, CSSD, LDRegistered/Licensed DietitianKaplan University

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 trends in food and nutrient consumption

• Estimating exposure to food additives and contaminants

Figure 1

Source: Journal of the American Dietetic Association 2010; 110:1638-1645 (DOI:10.1016/j.jada.2010.08.018 )

Copyright © 2010 American Dietetic

Figure 3

Source: Journal of the American Dietetic Association 2010; 110:1638-1645 (DOI:10.1016/j.jada.2010.08.018 )

Formulating and Evaluating Government Health & 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 (FFQs)• 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 Food Diary

• An extensive record of log including brands and portions of all foods eaten over the course of several days or weeks.

• A diary may include more information like when, where, and with whom.

One month “Billy C” client food record

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.

– Must know portions and be able to estimate

Food Frequency Questionnaires (FFQ)

• Assess energy and/or nutrient intake by determining frequency of intake

• Usually 150 foods or less. What food and how often

• May take 7 – 60 minutes depending on complexity of FFQ

• May provide visual pictures/graphics to help assess portion

Food Frequency Questionniares

• Strengths– Usually self

administered– Computer read– Modest demand on

respondents– Relatively inexpensive

for large sample sizes– May be more

representative of usual intake than food diary

– 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

– Intake data can be compromised when multiple foods are grouped within single listings

– Depend on ability of subject to describe diet

Block Questionnaires

• Very popular in research setting

• Solid history of validatoin• Evidence based results

used in hundreds of research studies.

• Multiple versions: long, short, fruits/veggies, meat, soy, nutrients, adults, children, physical activity

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

p. 294

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

Estimating Portion Sizes…

Portion Distortion!

FRENCH FRIES 20 Years Ago

Today

210 Calories

2.4 ounces

How many calories are intoday’s portion of fries?

National Heart Lung and Blood Institute

FRENCH FRIES 20 Years Ago

Today

210 Calories

2.4 ounces

National Heart Lung and Blood Institute

610 Calories6.9 ounces

How long will you have to walk leisurely in order to burn those extra 400 calories?*

*Based on 160-pound person

Maintaining a Healthy Weight is a Balancing ActCalories In = Calories Out

National Heart Lung and Blood Institute

*Based on 160-pound person

If you walk leisurely for 1 hour and 10 minutes you will burn approximately 400 calories.*

Calories In = Calories Out

National Heart Lung and Blood Institute

320 calories

How many calories are in today’s turkey sandwich?

TURKEY SANDWICH 20 Years Ago

Today

National Heart Lung and Blood Institute

320 calories

TURKEY SANDWICH 20 Years Ago

Today

National Heart Lung and Blood Institute

820 calories

*Based on 160-pound person

If you ride a bike for 1 hour and 25 minutes,you will burn approximately 500 calories.*

Calories In = Calories Out

National Heart Lung and Blood Institute

CHICKEN CAESAR SALAD

20 Years Ago Today

390 calories 1 ½ cups

How many calories are in today’s chicken

Caesar salad?

National Heart Lung and Blood Institute

CHICKEN CAESAR SALAD

20 Years Ago Today

390 calories 1 ½ cups

National Heart Lung and Blood Institute

790 calories

3 ½ cups

Calorie Difference: 400 calories

Bagel

Calorie difference: 210

• 25 years ago:– 140 calories– 2 inch diameter

• Today:– 350 - 400 calories– 6 inch diameter

Blueberry Muffin

Calorie difference: 290

• 25 years ago:– 210 calories– 1.5 ounces

• Today:– 500 calories– 4 ounces

Chocolate Chip Cookie

Calorie difference: 220+++

• 25 years ago:– 55 calories– 1.5 inch diameter

• Today:– 275 - 600 calories– 3.5 - 4 inch diameter

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

Stuff you need to know!

• Always check announcements and your email.

• Unit 5 midterm coming up. Information posted in Doc Sharing. It’s worth 140 points – 14% of your grade!

• New sections in Doc Sharing: – APA info, samples and formatting– Turnitin.com and plagiarism