W6 - Dietary Assessments Flashcards
List the dietary assessment methods
Total energy (Calorie) intake
Macro +/or micronutrient intakes
Consumption of ind. foods or food groups
Dietary patterns
Dietary behaviour i.e timing of food consumption
List the dietary assessment tools
Dietary recall
Food Record
FFQ
Biomarkers
Name an advantage to dietary recall + food records
Can be easily applied to diverse groups w/ a wide range of eating habits.
What do dietary recall + food records provide?
Provides detailed info of food consumption over a specific period of time.
How are 24hr recalls conducted?
In-depth interview
OR
Open-ended questionnaire.
What is required from the interviewer in the 24hr recall?
For them to be trained + knowledgeable on how they ask the Qs to ensure they’re not effecting the answer.
Strengths to 24hr recalls
Minimal subject burden - i.e easy for subject to do.
Limitations to 24hr recall
Info depends on subjects memory
Risk of recall bias
Time consuming
Expensive to analyse + interpret
Strengths to weighted food record
Min reliance on subjects memory if food is recorded at time of consumption.
Provides weighed portion - no reliance on estimation.
Detailed descriptions of foods consumed + all occasions are provided.
Limitations to weighed food record
Subjects must be trained in order to provide accurate data.
Ind. must be numerate + literate.
Weighing + recording food eaten away from home can be difficult.
Ind. may alter diet to make it easier to record or conceal poor diet.
Recall + records limitations
Focused on ST intake - not useful for investigation of chronic diseases.
To measure an avg intake, need multiple 24hrs.
Req a lot of time
Repetition can influence their diet:
- Intentionally to avoid a burden i.e more basic meals so less ingredients to record.
- May chose to not report an intake.
Define a nutritional biomarker
Any biological specimen that is an indicator of nutritional status w/ respect to intake or metabolism of dietary constituents.
What do nutritional biomarkers provide?
Objective info on dietary intake - thus overcoming many limitations of self-reported dietary intake.
What are the types of nutritional biomarkers?
Biomarkers of dietary exposure
Biomarkers of nutritional status
Biomarkers of dietary exposure
Assess dietary intake of different nutrients, foods, food groups or diet patterns.
Biomarkers of nutritional status
Assesses intake + metabolism of. nutrients + pot effects from disease processes.
List the main classes of biomarkers
Recovery biomarkers
Concentration biomarkers
Predictive biomarkers
Replacement biomarkers
Recovery biomarkers
Based on the metabolic balance between intake + excretion during a fixed period of time.
What are recovery biomarkers used for?
To assess absolute intake
i.e urinary nitrogen + urinary potassium
Concentration biomarkers
Based on the conc of the marker + used for ranking of intake.
NOT used to determine absolute intake as they’re related to metabolism, personal characteristics + lifestyle factors.
i.e plasma vitamin c
Predictive biomarkers
For biomarkers with incomplete recovery but a stable + time-dependent high correlation w/ intake.
What can predictive biomarkers predict
Dietary intake i.e urinary sucrose + fructose.
Replacement biomarkers
Serve as a proxy for intake.
When it’s not possible to capture due to info in nutrient databases is unsatisfactory or unavailable.
i.e Sodium
Are biomarkers of nutritional status nutrients?
Not necessarily
When are methylmalonic acid levels elevated?
In a deficiency state of vitamin B12
= Methylmalonic acid is a biomarker of vitamin B12 status.
When are homocysteine levels elevated?
In the absence of enzymes to metabolise it to cysteine or methionine.
The enzymatic reactions req vitamins incl. vitamin B6, B12 + folic acid, thus elevated homocysteine is a biomarker for these nutrients.
What can enzymatic activity serve as?
Nutritional biomarkers.
Strengths to biochemical markers
Highly correlates to dietary intake levels
Free of bias
Independent of memory
Limitations to biochemical markers
Expensive
Difficult to assess intake of food groups
Sometimes affected by disease
What happens when combining subjective dietary assessment tools with biomarkers
Dietary intakes can be estimated
- These estimates are more valid as 1 method can account partly for the disadvantages of the other method.
i. e biomarkers account for dietary misreporting + self-reporting methods account for errors associated w/ the metabolism of nutrients.
What happens when combining subjective dietary assessment tools with biomarkers
Dietary intakes can be estimated
- These estimates are more valid as 1 method can account partly for the disadvantages of the other method.
i. e biomarkers account for dietary misreporting + self-reporting methods account for errors associated w/ the metabolism of nutrients.
List biological specimens used for biomarker testing
Serum + plasma
Erythrocytes
Adipose tissue
Urine
Hair + nails
Cheek cells - Buccal swab
Stool
Cond. that impact specimen result validity
Time of day
Seasonal variation
Physiological state
Storage
What does choosing the dietary assessment tool depend on?
Objective of study
Study design
Demographic characteristics of pop
Available resources
