Simplified information about dietery assessment methods when conducting epidemiological research

1. Presented By:
Mona Mohammed Ali

2.  Diet is a major lifestyle-related risk
factor of various chronic diseases.
 Dietary intake can be assessed by
subjective report and objective
observation.
 Subjective assessment is possible
using open-ended surveys such as
dietary recalls or records, or using
closed-ended surveys including food
frequency questionnaires.
 Each method has inherent strengths
and limitations

3. 1. Duplicate diet approach by a trained
research staff.
2. Food consumption record.
3. Nutritional biomarkers
No information on how foods were
consumed by each individual within
household or about foods consumed outside
the home were collected !
DIETARY ASSESSMENT BY OBJECTIVE
OBSERVATION :

4. 1. The 24-hour dietary recall
(24HR).
2. Dietary record (DR).
3. Dietary history.
4. FFQ
DIETARY ASSESSMENT BY
SUBJECTIVE REPORT:

5.  Is a dietary assessment tool that consists
of a structured interview in which
participants are asked to recall all food
and drink they have consumed in the
previous 24 hours.
 It may be self-administered
 Typically requires 20 to 30 minutes to
complete a single day recall.
24-hour Diet Recall:

6.  Detailed data about food preparation
methods, ingredients used in mixed
dishes, and the brand name of
commercial products may be required
 The amounts of each food consumed are
estimated in reference to a common size
container (e.g., bowls, cups, and
glasses), standard measuring cups and
spoons, a three-dimensional food model,
or two-dimensional aids such as
photographs
24-hour Diet Recall:

7. ADVANTAGES :
1. A relatively minimal burden is
imposed on respondents
2. Measure intake with less bias
than food frequency
questionnaire.
24-hour Diet Recall:

8. LIMITTATIONS:
1. All information depends on the respondents’ memory
and the skills of a well-trained interviewer to
minimize recall bias
2. Affected by reactivity.
3. A poor method for measuring intake for food or
drink with a high day-to-day variability.
4. Unsuitable for large scale studies due to its time,
literacy, and economic constraints.
5. Used less frequently in pregnant women[
24-hour Diet Recall:

9.  A food record (also called a food diary)
is a self-reported account of all foods
and beverages (and possibly, dietary
supplements) consumed by a respondent
over one or more days (i.e., an n-day
food record).
 It is a prospective open end survey.
Dietary Record:

10.  A new generation of records
that takes advantage of recent
technological advances is being
developed. These include
applications for smartphones
and Internet users, and
wearable photography devices

11. ADVATAGES:
 collects data by subjects’ self-record at the time the
food are eaten, thus minimizes reliance on a subjects’
memory.
 they are used as a reference instrument to validate or
calibrate estimates from other less-detailed assessment
instruments, such as a FFQ.
 used to examine relationships between some factor and
diet in which diet is the dependent variable
 Used to examine relationships between diet and health
or other variables, in which diet is the independent
variable
Dietary Record:

12. LIMITATIONS :
 Focused on short-term intake.
 Reactivity is known to affect estimates
 The open-ended format that requires considerable
efforts in the course of data collection, entry, and
analyses
 The requirements of completing a food record may
limit participation in some groups, leading to potential
selection bias.
 Quality of data may decline with increased number of
days reported.
Dietary Record :

13.  The FFQ is an advanced form of the
checklist in dietary history method, and
asks respondents how often and how
much food they ate over a specific
period
 Presenting about 100 to 150 foods,
this questionnaire takes 20-30 minutes
to complete and can self-administered
or collected via interview.
F00d Frequency Questionnaire:

14.  Should be developed specifically for each study
group and research purposes because diet may
be influenced by ethnicity, culture, an
individual’s preference, economic status, etc.
 The utility of questions in FFQs about
portion size has been controversial.
 Should be evaluated for their accuracy before
being used as a dietary assessment tool in
studies.
 Data can be linked to a database to yield
information about total dietary intake.
FFQ (cont.):

15. 1. Enables the assessment of long-term
dietary intakes in a relatively simple,
cost-effective, and time-efficient
manners .
2. May be better than short-term
instruments [24HR] at assessing intake
of episodically consumed foods because
they attempt to directly capture usual
intake over a period of time.
FFQ :
ADVATAGES:

16. 3. Are commonly used as the
main dietary assessment
instrument in large prospective
studies.
4. Are the only practical methods
for capturing diet in
retrospective case-control studies.
FFQ :
ADVATAGES

17. 1. Contains systematic error .
2. Detailed information about food preparation,
and contextual information about intake is
lacking.
3. Because an FFQ is composed of a pre-specified
food list, any single FFQ may not reflect the
eating patterns of a given population. Thus,
the performance of a particular FFQ in a
particular population may not reflect its
performance in a different population.
FFQs:
LIMITATIONS:

18.  Because of known systematic error in an
FFQ, a less biased short-term instrument
(e.g., 24HR) may be administered in an
internal calibration sub-study to improve
estimates of intake from an FFQ through
regression calibration , allowing for a
more accurate estimate of the
association between diet and another
variable. Alternatively, data from an
external source (called an external
calibration study) can be used .

19. 24HR DR FFQ
Required
technology
Software,
internet,
etc.
Software, internet,
, mobile phone,
application, etc.
S kip algorithms,
questions that ask
for multiple details,
pictures of foods,
etc.
Strengths Standardized data
collection possible
(reducing interviewer
bias); likely reduce
time and cost;
improve feasibility
Standardized, real-
time data collection
possible; likely reduce
time and cost;
improve feasibility
Able to collect
complex
information and
highly accurate
data
Limitations Inherent bias
related to
self-report
Inherent bias related
to self-report;
requires participant
training on how to use
the technology
Measurement
errors related to
methodology
remain

20.  Used to obtain basic information about a limited
number of foods and beverages consumed or dietary
practices over a period of time, typically the past
month or year.
 2 types:
1.A short food frequency questionnaire, usually without
portion size questions.
2.A behavioral questionnaire that asks about general
dietary practices (for example, "Do you generally butter
your bread?").
 For both approaches, the questionnaire is usually self-
administered, but can be interviewer-administered.
 Completing a screener usually requires less than 15
minutes
Screener:

21.  Data can be used to assess particular
aspects of diet but not total dietary
intake.
 Resulting estimates may be quantitative
or qualitative, depending on the
instrument.
 If data are linked to a nutrient
composition database, nutrient intakes
can be determined
Screener:

22.  Screeners can be used in retrospective
case-control studies when interest is
limited to a small number of dietary
components rather than the total diet.
 Because of their limited scope, screeners
are seldom used as the main instrument
in prospective studies describing
associations between diet and another
factor.
Screener:

23.  Systematic error.
 The performance of a particular
screener in a particular population may
not reflect its performance in a
different population.
 Use of procedures to score various
dimensions of behavior developed in one
population may not be appropriate in
other populations.
Screener:

24. THANKS