Lecture 12 - How Good is this Groups Nutrient Intake Flashcards
why is information on group intake important
- monitor population intakes
- identify problem nutrients for a population
- plan programmes to address problem nutrients
- need to know appropriate methods to decide whether to believe (and use) papers you read
what is the use of EAR in groups
use to estimate the prevalence of inadequate intakes within a group
use of RDI in groups
DO NOT USE
use of AI in groups
mean usual intake > this level implies low prevalence of inadequate intakes
use of UL in groups
use to estimate %age of population at potential risk of adverse effects
what are the steps to assessing nutritional adequacy in groups
step 1 : collect multiple days dietary data
step 2 : adjust intake distribution
step 3 : use EAR to determine adequacy
what is the first step to assessing nutritional adequacy in groups
collect multiple days dietary data
- diet record : collect 2+ independent days (or 3+ consecutive days)
- 24hr recall : collect 2nd independent day in >50%
what is step 2 to assessing nutritional adequacy in groups
adjust distribution of observed intakes to remove day to day variability in intakes
what are the two methods for step three of assessing nutritional adequacy in groups
use EAR to determine adequacy
- cut point methods
- probability approach
what is the EAR cut point method
prevalence of inadequacy ~ proportion of group with intakes < EAR
what does the EAR cut point method assume
- no correlation between intakes and requirements
- distribution of requirements is symmetrical
- variance of intakes > variance in requirements
- prevalence of inadequate intakes is neither very high nor very low (ideally 10-90%)
in the EAR cut point method, if your values are higher than the EAR but your intake is lower than your requirement then
you are part of the group that are missed by the EAR cut point method
in the EAR cut point method, if your values are above what you need but below the EAR you are considered a
false positive
in the EAR cut point method the number of false positives and negatives should
be the same and cancel each other out
what is the probability approach
the prevalence of inadequacy = weighted average of risks at each intake level
the probability approach assumes
no correlation between intakes and requirements
the probability approach must be used if
- Fe in premenopausal women
- if prevalence inadequate intakes very high or low in population
what are the steps to the probability approach
- construct a risk curve (gives probability for each intake level that intake is inadequate)
- determine % of intakes in each risk category
- determine prevalence of inadequacy
the AI can not be used to
determine the prevalence of inadequate intake in a group
when using the AI for a group, mean intake of group is > AI then
prevalence inadequate intakes probably low
when using the AI for a group, mean intake of group is < AI then
can not determine adequacy
when using the Ai for a group it assumes
variance of intake similar to that of population AI based on
AI based on mean intake of healthy population
when using the UL for groups , it uses
similar approach to the EAR cut point method
when using the UL for groups it uses appropriate
intake distribution
e.g
- some nutrients need intakes from all sources (like Vitamin C)
- some nutrients need intakes from supplements only (like Vitamin E)
what are the limitations for determining group nutrient adequacy
- cant use EAR cut point method or probability methods to identify specific people with inadequate intake
- full probability approach time consuming
- don’t have EAR for all nutrients
group nutritional adequacy methods can only be used for
groups not individuals because there are some false positives and negatives with the cut off method and issues with the probability method
things not to do when assessing nutrition groups
- compare group mean intakes to EAR or RDI
- use EAR cut point method to assess Fe intake in premenopausal women
- use EAR cut point method for small groups (<30)
- use the proportion of the groups < RDI
- forget to adjust for day-to-day variation in intakes
