Dietary assessment Methods (1C) Flashcards
Dietary assessment approach? input:
24h dietary recall(s)
Food Frequency
Questionnaire
Diet Record(s)–>
Quantitative
Assessment
of total/part
of diet–>
Coding of Dietary intake
Dietary assessment approach? Processing:
Coding of dietary intake–>
food composition databases and daily nutrient intake–>
Dietary assessment approach? output:
food composition databases and daily nutrient intake–>
dietary reference values and dietary evaluation
Measurement error: Aim of a dietary assessment
• To estimate habitual (long term) intake
Measurement error: Consequences of Measurement Error
- Underreporting will overestimate nutrient inadequacy
* May limit usefulness of associations with other markers and diseases.
Measurement error: Sources of Measurement Error
• Non-response bias
• Respondent bias (Participant misunderstanding)
– Socially desirable responses (to avoid criticism)
– Socially acceptable responses (to seek praise)
- Interviewer bias
- Coding errors
- Limited food composition databases
- Respondent memory
- Incorrect portion size
- Day-to-day variation
- Impact of assessment method
Dietary assessment methods: why?
• To measure usual intake
Dietary assessment methods: Day to Day variation?
- Nutrient specific
* Seasonal/Weekday v wkd
Dietary assessment methods: Methodology
• Dietary assessment methods have advantages & disadvantages
Dietary assessment methods: Which is best?
- Situation specific
* Be aware of limitations
24h Dietary Recall: advantages:
- Provide very detailed information on eating patterns
- Method cannot affect food choice
- Quick & Easy
- Minimal participant effort
24h Dietary Recall: disadvantages:
- Requires multiple days to
estimate intake - Relies on participants memory and ability to estimate portion size
24h Dietary Recall: error:
- Systematic underreporting
2. Multiple days can still be poor estimates of usual intake
24h Dietary Recall: application:
- Individual Intake (multiple days)
2. Group Intake
Food Frequency Questionnaire: advantages:
- Method cannot affect food choice
- Quick & Easy
- May be more representative of
usual intakes
Food Frequency Questionnaire: disadvantages:
- Less precise estimate than other methods
2. Appropriate foods / frequencies
Food Frequency Questionnaire: error:
- Systematic underreporting
Food Frequency Questionnaire: application:
- To identify food consumption
patterns - Relationships between diets & disease state in large scale studies
Food Records: advantages:
- Provide very detailed
information on eating patterns - Weighed/measured/household
- Not dependent on memory
Food Records: disadvantages:
- Requires motivated participant
- Time commitment - Experimenter
- Requires multiple days to
estimate intake - Recording affects food choices
Food Records: error:
- Systematic underreporting
2. Multiple days can still be poor estimates of usual intake
Food Records: application:
- Individual Intake (multiple
days) - Group Intake
- Relationship between nutrient intake and other variables
Limitations of food tables: Analytical techniques:
• Fibre
– McCance & Widdowson Food Table
– Calculated non-starch polysaccharide
– Food Label – Enzymatic method (includes lignin) resulting in higher values
• Vitamins
– Dependent on terminology (micrograms, international units, equivalents)
Limitations of food tables: Conversion Factors:
- Energy
* Protein – Nitrogen content x 6.25
Limitations of food tables: Sampling Procedure
• UK specific or brand of product
Limitations of food tables: Date of Testing
• Altered manufacturing process / Farming / Cooking/ seasons / storage
Limitations of food tables: Bioavailability
• The proportion of a nutrient that can be absorbed/is available
Limitations of food tables: Coding
- Missing nutrient values / Inappropriate food chosen / Incorrect entry / Portion size
- Your skills will be developed in workshops
