Week 4: LEC 6&7 Flashcards
(26 cards)
Introduction to the DRIs
LEC 6
** Overall read these notes from google docs - going to filter info **
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The Solution:
- Did not consider levels needed for prevention of chronic diseases
- Unknown nutrient needs for older adults
- No guidance on safe and effective use of supplements
- Nutrient interactions were not considered
: Dietary Reference Intakes (DRIs)
Underlying principles of DRIs
-> Are always set for…
- Adjustment in…
> Refer to the avg daily needs over a reasonable period of time (avg intake over several weeks or more)
-> Refer to levels of intake needed to maintain health in…
(intended for use with generally healthy people) - assume that requirements for energy and all other nutrients are met
->
-> for a particular group of individuals with specified characteristics, consuming a specified diet (ie. gender, life-stage group)
- in DRI values under certain circumstances - ie. Iron recommendations for individuals on vegetarian diets, or Vitamin C recommendations for smokers
-> in already healthy individuals
-> unless otherwise specified, they apply to all sources of a nutrient (including supplements) / generally ignore possible interactions of nutrients with other dietary components - these interactions not easy to quantify
Use in Clinical Practice
-> Not all nutrient requirements are affected by…
-> Use clinical practice guidelines regarding…
ex
-> the disease process - can use the DRIs for these nutrients
-> regarding nutrients influenced by the disease or that could influence the disease process
ex, PRO intakes and renal disease
[The nutrient requirements are defined in relation to a frequency distribution of individual requirements]
Normal Distribution of Requirements:
** SLIDE 13 for visual **
What do these terms mean?
- Z-score =
- Percentile rank =
- Median value =
- Mean value =
** Slide 15 for table of z-scores and probability of adequacy **
-> CANNOT have ____
Z = is the number of standard deviations a given data point lies from the mean
P = is the percent of cases that are at or below a score
Medi = middle number of a set of numbers
Mean = avg value of a set of numbers
-> Have a z-score if distribution is not normal
EX a skewed distribution = Iron needs of reproductive women, differs dramatically per woman
Determining Nutrient Requirements
-> Different for different nutrients
- For IRON, you need to measure iron balance: (measure total iron losses from the body - sweat, urine, blood etc) & measure efficiency of iron absorption
- For CALCIUM - it is the amt needed to promote bone health
-> For some nutrients, this type of data cannot be collected:
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: fibre - DRIs (AIs) are based on the intake level observed to protect against (CVD) based on epidemiological, clinical and mechanistic data
- Extrapolation of data from animal studies
- The intakes associated with chronic diseases based on epidemiological studies
- The observed nutrient intakes in healthy populations
- The intake of a nutrient:
- needed to maintain nutrient balance / needed to maintain a given tissue saturation or an adequacy of molecular function / needed to cure clinical signs of deficiency / which induces low or deficient levels of a nutrient (depletion/repletion studies) / associated with optimal physiological, psychological or immune function and performance
EAR =
- is actually the…
- if you don’t know an individual’s nutrient requirement - best estimate of their requirement is…
Defined as:
NOTE:
= Estimated Average Requirement
… the median (which is same as avg if normal distribution (symmetrical) which is true for most nutrients)
… is the EAR
: the amount of nutrient that is estimated to meet the nutrient requirement of half the healthy individuals in a life-stage and sex group
NOTE: intake at the EAR level is associated with a 50% risk of inadequacy
RDA =
-> Should be considered the goal intake for…
Defined as:
A usual intake at the RDA level is associated with…
- Recommended Daily Allowance
… for an individual
: Intake level that meets the daily nutrient requirements of almost all (97-98%) of the individuals in a specific life-stage and sex group
… with a 2-3% risk of inadequacy to an individual, and is used as a recommended intake when planning diets for individuals
RDA calculations from EAR
-> IF the variation in requirement is well defined and symmetrically distributed:
this eqn is used: (1)
-> When SD is unknown & if a coefficient of variation (CV) for the EAR of 10% is assumed (CV is equal to the SD/EAR), then: (2)
Alternatively, if the CV is 15% then: (3)
(1) RDA = EAR + 2 SD (standard deviation)
(2) RDA = 1.2 X EAR
(3) RDA = 1.3 x EAR
Skewed Distributions
-> If the requirement distribution is skewed - like Iron intake for W (= variability in blood loses)
- RDA is set at the 97th - 98th percentile of the requirement distribution
AI =
Defined as:
AKA…
The AI is NOT…
-> AI would be at or above the:
-> The AI should be considered the goal intake for…
= Adequate Intake
: Recommended avg daily nutrient intake level based on observed or experimentally derived approximations or estimates of the nutrient intake by a group (or groups) or apparently healthy people
… not enough was known about the requirement distribution to set an EAR
is NOT… equivalent to an RDA
: the RDA if it were possible to determine the requirement distribution and set an RDA
… goal intake for an individual
- when an RDA is not available for a nutrient
UL =
Defined as:
- as intake increases above the UL…
- applies to
- it is not depicted on the distribution of requirements graph
> ULs were not set for some nutrients with limited scientific data
- -> For some nutrients such as [Ca, P, Cu, Zn, Se and I, the UL refers to:
*-> For other nutrients such as Niacin, Folate and Mg, the UL applies only to:
= Tolerable Upper Intake Level
: The highest usual daily nutrient intake level likely to pose no risk of adverse health effects for almost all individuals in a life stage and sex group
… potential risk of adverse health effects increases
- Applies to chronic consumption (not just on one day) but many days in a row for a while
*: refers to the total intake from all sources including food, fortified food, water, supplements and medications, where relevant
*: to intake from supplements, fortificants and medications
[The UL is NOT a recommended level of intake]
-> Thresholds for adverse effects vary among individuals -
> based on dose-response data if available:
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-> UL may not apply to all sources of intake: ie.
-> If there is no UL set, apply caution:
- UL is set below the threshold of the most sensitive individuals
- No observed adverse effect level (NOAEL) - highest intake at which no adverse effects have been observed
- Lowest observed adverse effect level (LOAEL) - lowest intake at which adverse effects have been observed
: ie. only intake from folic acid, not food folate
: doesn’t necessarily mean all intake levels are safe; there just isn’t enough data to set the UL
Some notes on UL
Safe by a comfortable margin
- the UL is NOT…
- is NOT an
An intake somewhat exceeding the UL is not necessarily unsafe
- doesn’t apply to…
[The possible contribution of conventional foods and dietary supplements toward a UL level of intake varies greatly among nutrients
- the UL is intended to apply to total intakes from all sources of nutrients, unless specified otherwise; ie. folate and Mg]
-… NOT a threshold for adverse effects
- NOT an intake that if exceeded by any amount will likely cause harm
-… to temporarily elevated intakes or to persons who have greater needs and tolerances then the avg person (ie. deficiency states)
AMDR =
Defined as:
** Chart is on SLIDE 31 - should probably know **
[chronic disease prevention = AMDR]
> Based on the effect of macro distribution on risk of chronic diseases
Intake is considered appropriate if macronutrient intake expressed as a percentage of energy falls within the AMDRs [ any intake outside of range = red flag ]
-> Use…
= Acceptable Macronutrient Distribution Range
: a range of intake for a particular energy source (PRO, F, CHO), expressed as a percentage of total energy (kcal), that is associated with reduced risk of chronic disease while providing adequate intakes of essential nutrients
-> Use the AMDR rather than the RDA and AI for the macronutrients
- RDAs and AIs for macronutrients are based on overt deficiency, not chronic disease prevention
EER =
Defined as:
& in children or lactating women =
-> Calculations for different age and sex groups based on…
> Several DRI regression equations have been developed for estimating the energy requirements of different life-stage and sex groups
> - Several for normal weight (BMI: 18.5-24.9kg/m2) and overweight or obese (BMI >/= 25kg/m2)
= Estimated Energy Requirement
: the avg dietary energy intake that is predicted to maintain energy balance in healthy, normal weight individuals of a defined age, gender, weight, height and level of physical activity consistent with good health
= the EER includes the needs associated with growth or
secretion of milk at rates consistent with good health
-> … based on daily energy expenditure measured by doubly-labelled water technique
- Based on age, height, weight and PA level
— No RDA for energy
- Don’t want to exceed the requirements of all but 2-3% of the population - each body is different
Energy assessment in clinical practice
-> EER used freq to estimate energy needs
-> Non-DRI formulas may also be used (Har Bene)
-> For adequacy of intake, weight change is preferred
- considered…
** Individual dietary assessment: using qualitative approach ** SLIDE 38 - 45 REVIEW in notes
- … adequate if maintaining weight / weight loss or grain indicates imbalance
Assessing the intakes of individuals using the DRIs
LEC 7
** read these notes cause I am compressing **
Developing nutrient intake guidelines
For nutrients:
- Aiming for…
- Usual intake below the…
- Macronutrient intake should…
- Energy intake should be appropriate to maintain a…
- for… usual intake at or above the AI or RDA should ensure nutrient adequacy
- the… UL should reduce the risk of adverse effects of excessive intake
- should… fall within the AMDRs
- a… healthy body weight and support energy needs based on physical activity level
Using the DRIs in diseases
-> DRIs were developed for…
- they do not consider…
-> Not all nutrients & requirements are affected by the disease process
- For unaffected nutrients, it is appropriate…
- For nutrients that are either influenced by the disease or that can influence the disease process…
*** Dietary assessment involves some uncertainty
-> for generally healthy individuals
- don’t consider effects of disease process or drugs on nutrient requirements
- … to use the DRIs for dietary assessment and planning
- … clinical practice guidelines should be used
What is a standard Deviation?
Probability (What are the chances?)
1.0 probability = event will definitely happen
Determining probability of adequacy
- IF normal distribution…
- Z-scores tell us…
** ALL THE CALCULATIONS DO FROM SLIDE 11-12 (including examples) **
- … we can calculate z-score to determine the probability of adequacy
- tell us… how many standard deviations a value is from the mean
[smaller the z-score = less variable]
= tells us about how closely values of a data set are clustered around the mean
- ie. lower SD indicates that the values of the data set are spread over a relatively small range around the mean
… In a normal distribution - READ THIS SLIDE - 13
- by setting the RDA at a level 2SD above the mean, the requirements of ~97.5% of the group …
What is a z-score?
-> tell us
** eqn SLIDE 14 **
…. are met or exceeded
tell us how many SDs we are from the mean
*Practical probability approach
-> This is a…
[recom for RDs]
-> THIS APPROACH only determines…
** READ STEPS slide 17 **
-> … simplified approach for calculating the probability of adequacy of intake for nutrients with an EAR
-> only determines probability of adequacy for the days that intake was measured
- DOES NOT account for day-to-day variability of intake (only applies to day you took data - as it doesn’t account for variability)
What is the SD of the EAR?
-> Calculate the…
- most have CV of ____
SD =
(A higher CV is assumed for certain nutrients)
** EXAMPLE - slide 20-21 **
Points to keep in mind:
Advantages of practical probability approach…
Limitations of practical probability approach…
-> the SD of the EAR (SD of requirements for nutrients with an EAR) by multiplying the EAR by the Coefficient of Variation (CV) of requirements
-> Most nutrients have a CV of 10%
SD = CV x EAR ie. for folate, SD = 0.10 x 320 = 32 (ug/day)
… Adv - relatively quick and easy to calc
- results are relatively easy to communicate to clients
… Limi - conclusions abt nutr adequacy or excess should be limited to the days on which you collected data
- this method cannot be used for iron for women of childbearing age b/c requirement distribution is skewed
Full probability approach
> This is a more complex approach
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** READ STEPS slide 25 ***
-> It accounts for day-to-day (intra-individual) variability of intake
- more accurately reflects the probability of adequacy of usual intake
- the z-score calc uses the within-person standard deviation of intake from lg national survey
Where do I find the within - person SD of intake?
-> reference table linked SLIDE 26
** EXAMPLE - slide 27 with probability and chance of adequacy - DO THIS **
Points to keep in mind:
Advantages of full…
Limitations of full…
Adv… Accounts for day-to-day variability in intake
- it more closely reflects the probability of adequacy of usual intake
Limi… - it takes more time as it requires larger calculations
- may be more challenging to explain to clients
- this method cannot be used for iron for women…
- ALSO should not be used if CV of the within-subject variation in intake is larger than 60-70% (Vit A, E, C, B12 we can see this)
[if CV of intake is btw 60-70% - like folate or zinc) you can do full approach but findings interpreted with caution]
What about nutrients with an AI?
-> Usual intake at or above the AI has…
- if mean intake is above the AI…
- if mean intake is less than AI…
** READ STEPS -slide 32 + EXAMPLE slide 33 & prob table slide 34 ** REVIEW
-> … has a low probability of inadequacy
- is… above the AI, you can use statistical approach to determine probability (confidence) that usual intake is higher than the AI
- less than… probability of adequacy cannot be determined - use clinical judgement
