Week 5: LEC 8&9 Flashcards

(10 cards)

1
Q

Assessing the intakes of groups using the DRIs
LEC 8

** NOTE on slide 5 **

WHY would you want to know about the diet of a group? ->

Adjusting the intake distribution
-> Typically, group intake data is collected thru…
-> Usually, the nutrient intakes of a group from a normal distribution (bell-shaped) = AKA =
-> Variability within the intake distribution has…
-
-
* see visual graph slide 9 *
-> removing within-person variability (‘adjusting’) you get:

A

-> To create guidelines/ to understand if population is vulnerable or at risk / to create intervention or know how to target an intervention or education

-> … thru 24 recalls or food records
ie. in the CCHS

= intake distribution
…has 2 sources:
- within-person (intra-individual) variability
- between person (inter-individual) variability

: you get less variation affecting the curve / not adjusted = wide variation - may over or under assume intakes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Adjusting the intake distribution
> Day-to-day variation gets in the way of examining usual intake
> Adjusting the intake distribution by removing within-person variability does not change the mean but it decreases the SD
> If the intake distribution is not adjusted to reflect usual intakes, the prevalence of inadequate intakes may be overestimated

HOW is the intake distribution adjusted?
-> To remove within-person variability (to more closely reflect usual intakes) you need…
- this tells you how much:

A

-> multiple days of data from at least a representative subsample of the group
: day-to-day variation there is in your population (how much needs to be adjusted for)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Assessing prevalence of inadequacy
-> To assess the prevalence of inadequacy in groups, we need to use:
-
-

-> 2 methods can be used to determine the prevalence of inadequacy:
1
2

The EAR cut-point method
-> Simply calculate…
-> The percentage of intakes below the EAR is…

EXAMPLE - slide 18
[How does it work] - slide 18

A
  • The adjusted intake distribution that reflects usual intake of groups
  • The requirement distribution used to set the EAR

1 The EAR cut-point method
- this is commonly used shortcut
2 The full probability method
- just like what we did with individuals last class

-> … the proportion (or %) of the group with intakes less than the EAR

-> … a good estimate of the percentage of the group with intakes below their requirements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Points to keep in mind:
-> Assumptions of the EAR cut-point method
-
-
-
> When using the EAR cut-point method, we can’t determine the specific individuals whose intakes are inadequate… WHY?
1
2
[these 2 groups are expected to cancel eachother out]
- the prevalence of inadequacy in the group can thus be approximated by the proportion with usual intakes below the EAR

A
  • Intakes and requirements must be independent (not be correlated)
    • this is not true for energy
  • The distribution of requirements must be symmetrical
    • this is not true of iron
  • The distribution of intakes must be more variable than the distribution of requirements
    • thought to be true among groups of free-living indiv
    • this may not be true for groups who have very similar diets (ie. residents in LTC, prison inmates)

? 1 some ppl with intakes below the EAR have lower than avg requirements
2 some people with intakes above the EAR have higher than avg requirements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The Full Probability Method for groups
1
2

The Full Probability Approach method depends on 2 key assumptions:
->
->

EXAMPLE - slide 24 ***

READ ** What about Iron - SLIDES 26-27 & 30 **

EXAMPLE slide 28/29 ***

A

1 - Calculate the probability of inadequacy of the usual intake level for each person in the group
- if you have 200 participants, that means 200 z-score calculations

-> Intakes and requirements are independent, and thus no correlation exists between usual intakes and requirements
- this is thought to be true for most nutrients, although it is not known to be true for energy

-> The distribution of requirements for the nutrient in questions is known
[this method uses statistical eqns to estimate the prevalence of inadequacy]

2 - Calculate the avg of these individual probabilities across the group
- this avg is a good estimate of the % of people who would have inadequate intakes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Do not use the RDA for groups
-> It is not appropriate to use…
-> Comparing the mean intake of the group…

What about nutrients with an AI?
-> If a nutrient has an AI…
-> You can…
interpretations [ ]

NOTE: in this case you don’t need to adjust the distribution of intakes for day-to-day variability
- removing variability doesn’t alter the mean but decreases the standard deviation

A

-> … use the RDA as a cut-point for groups b/c it overestimates the requirements of 97-98% of the population
- many indiv have requirements below the RDA and therefore cannot be assumed to be deficient if intake is below the RDA

-> … to the RDA is also inappropriate

-> AI … you cannot estimate prevalence of inadequacy b/c the distribution of requirements is not known
- do not use the AI as a cut-point like the EAR
-> you can… compare the mean intake of the group to the AI and make a qualitative interpretation
[ mean intake < AI = nothing can be concluded about inadequacy /// mean intake >/= AI = prevalence of inadequacy is likely low]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What about nutrients with a UL?
-> Calculate the…
-> Remember that the UL for some nutrients doesn’t apply to intake from all food sources: __, ___, ___, __

EXAMPLE - slide 35 ***

What about nutrients with an AMDR?
> You can calculate the proportions of the group that fall below, within and above the AMDR
> If lg proportion of the population has usual intakes outside the AMDR range, there is increased concern about possible adverse health effects - chronic diseases

A

-> … proportion (or %) of the group with intakes above the UL
- the proportion of the group with usual intakes exceeding the UL may be at risk for adverse health effects

-> Mg, Vit E, Niacin, Folate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Assessing energy adequacy
-> The EAR cut-point method and full probability approach cannot be used to assess energy intakes
- Reason:
-> BMI is preferred for assessing the adequacy of energy of a group
- calc proportions of the group with BMIs below, within and above the desirable range

General Reminder…
[DRIs and nutrient intake estimates have limitations]
- Findings of inadequacy or excess need to be confirmed with other measures or nutrition status (ie. anthropometrics, biochemical tests)

Planning nutrient intakes for groups
> Menu planning for groups is important in many settings: Prisons / Hospitals / LTC / Child nutr and food assistance programs

Planning Menus
> Simply comparing mean intake of the group to the RDA is inappropriate
- The GOAL is to…

A
  • : energy intakes and energy requirements are correlated (not independent)
  • … is to have low prevalence of inadequate or excessive intakes
  • usually aim for 2-3% of intakes < EAR and 2-3% of intakes > UL
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Step 1: Determining the current intake distribution
-> This may mean:
-> If you cannot do a dietary assessment - you can -

-> Look at the intake distribution and determine how many people have intakes below the EAR : ex on graph - slide 42

Step 2: Setting a target distribution
->
- EX
(GRAPH slides 44-45 explaining)

A

-> : doing a dietary assessment to determine what your population is currently eating
EX: in LTC - record intake of residents for # of days and analyse intakes

  • you can use population data for your age group of interest (CCHS, NHANES)

-> Determine how much you would have to move the distribution so that only 2-3% of your population would have intakes below the EAR
- EX - if we increased everyone’s intake by 5mg only, 2-3% of the pop would have intakes below the EAR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Step 3: Planning your menu
> You can use the new median of the target distribution as a goal when planning menus
- continuing the ex above, if the new target median was 20mg - you would plan a menu where avg portion sizes would result in…

EXAMPLE - slide 47

What if intakes are too high?
-> If there is a high prevalence of intakes above the UL, use the…

Other criteria for menu planning
-> For nutrients with an AI…
-> For energy intake…
-> Aim for group to stay within the…

Menu planning is an ongoing process…
Set goals for usual intake / implement the plan / evaluate whether goals were achieved / modify the plan

A
  • … in an intake of 20mg per day

-> … same approach to create a target distribution with only 2-3 % of the group having intakes above the UL

-> AI… set a goal for median intake to equal the AI
-> … set a goal to provide the mean EER for the group
-> AMDRs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly