NUTR 337- 1

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NUTR 337- 1
2013-02-17 11:45:43

DRI, first 2 lectures
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  1. Why were dietary reference intakes developed?
    To expand upon and replace the former Recommended Dietary Allowances (RDAs) in US (since 1941) and the Recommended Nutrient (RNAs) in Canada (since 1938)
  2. Who oversees the 5 year process of establishing DRIs?
    Standing Committee
  3. Who develops the series of DRI reports, based on a review of the scientific literature?
    Nutrient Expert Panels, in conjunction with two subcommittees 
  4. Who derives the tolerable upper intake levels and how do they do it?
    The Upper Reference Levels of Nutrients Subcommittee, using a risk assessment model
  5. What does the UL committee do?
    Derives the tolerable upper intake levels for all nutrients since supplementation and food fortification are now a major source of nutrition in addition to food itself
  6. What does the Uses of DRIs sub-committee do?
    Deals with appropriate applications for reference intakes (assessment of intakes, planning for intakes of groups/individuals and nutrition education)
  7. What are the 4 sub-sets of nutrient-based references that make up the DRIs?
    EAR, RDA, AI, UL
  8. What is EAR?
    Estimated Average Requirement, from which the RDA is determined
  9. What is RDA?
    Recommended Daily Allowance, which replaces the formed RDA and RNI
  10. What is AI?
    Adequate Intake (used as an alternative reference when EAR and consequently RDA are not available)
  11. What is UL?
    Tolerable Upper Intake Level
  12. What is the trend established to focus on chronic disease prevention (4 steps)?
    • 1- Look at the RDA values for micronutrients as research suggests that micronutrients have importance in chronic disease prevention
    • 2- Requirement standards will therefore examine recommendations for deficiency disease prevention AND chronic disease prevention
    • 3- Common use of food and nutritional supplements- upper levels of intake need to be established
    • 4- Also include looking at non-essential food components such as phytochemicals for chronic disease prevention
  13. What is RDA?
    Average daily intake level that is sufficient to meet the needs for nearly all (97-98%) of the individuals in a particular life stage and gender group
  14. Does RDA refer to nutrient intake for individuals or groups?
    RDA refers to level of nutrient intake to meet the nutrient requirement of individuals not NOT groups
  15. How is RDA determined?
    Determined by experimentation in a healthy popultion
  16. What is RDA based upon?
    Based upon estimation of a minimal requirement to achieve some measurable outcome
  17. What is the basis for setting RDA?
    • First define the intake of the nutrient that provides adequate intake for 50% of individuals in a life stage and gender group
    • The index od adequacy will differ for each nutrient and each life stage there may be different indices of adequacy for the same nutrient
    • Safety factor is added to allow for optimal tissue stores
    • Factor that accounts for the additional needs for growth such as pregnancy and lactation is also needed
  18. How is variability in nutrients accounted for in RDA?
    To account for variability in nutrient needs 2SD are added to get the final RDA value
  19. How is RDA determined when there are no studies for a specific group?
    Data obtained experimentally through balance studies, epidemiological studies or extrapolated from data other for other age groups
  20. What are deficiency and balance studies?
    Show a quantitative relationship between intake below a certain level and deleterious changes in biochemical and physiological responses
  21. What must the RDA account for?
    • Individual variability in a population (coefficient of variability of population)
    • Bioavailability
    • Gender and age differences
    • Physiological state (pregnancy, lactation)
  22. What are the scientific approaches used to derive RDA?
    • The individual variability in requirements must be considered
    • Differences in bioavailability of the nutrient depending on the composition in the national diet
    • Differences in gender and age in requirements
    • Difference in physiological states pertaining to growth such as pregnancy and lactation
  23. What is EAR?
    The usual intake level that is estimated to meet the requirement of half the healthy individuals in a life stage and gender group
  24. How is the EAR derived, and what is it used for?
    • Typically derived from balance studies and serves as the foundation for setting the RDA
    • It is suitable as a method to assess the prevalence of inadequate intakes for groups
  25. What is EAR based on?
    • Has to be based on the intake distribution of the group and not on the average intake of the group
    • Based on a specific criterion of adequacy
  26. How is the RDA set based on the EAR?
    RDA is set for each nutrient at 2 standard deviations above the EAR
  27. What is the major difference between the former RDAs and RNIs and the modern RDAs?
    RDA is now determined quantitatively through EAR, rather than through judgement-based safety factors
  28. How is the EAR determined graphically?
    Midpoint of the normal distribution: the average requirement for individuals (only in a Gaussian distribution)
  29. How is RDA determined if standard deviation of EAR is unknown?
    CV is assumed to be 10%, and RDA=EAR+2*(EAR*0.1)
  30. How are energy requirements obtained?
    Energy requirements are estimated on an individual basis using gender, age, height, weight and physical activity level to estimate total energy expenditure.  Criterion of adequacy is maintenance of a healthy BMI with a healthy level of physical activity
  31. Can intake below RDA give certainty of nutritional deficiency?
  32. At what point on the RDA scale is a person likely to be deficient?
    Someone consuming a nutrient at 50% of RDA is likely to be deficient
  33. Does the RDA have to be met every day?
    No, it is to be achieved via average daily intakes over a period of days- not every day
  34. What is the RDA NOT designed to do?
    • It is developed to maintain good health and avoid deficiency
    • NOT designed to overcome nutrient deficiencies, recover from illness, prevent chronic diseases
  35. What does the period of time needed to compensate a deficient intake depend on?
    • Body pool size
    • Nutrient turn-over
  36. Why are babies more susceptible to deficiency diseases?
    Babies have not had time to accumulate stores of vitamins so they are more susceptible to deficiency diseases
  37. What must the new DRIs account for?
    • Individual variability in a population (coefficient of variability of population)
    • Bioavailability
    • Gender and age differences
    • Physiological state (pregnancy, lactation)
  38. If the mean intakes exceed the RDA does this guarantee a low prevalence of inadequacy?
    NO, If the group has a high variability, even-though the mean is above the RDA, there can still be many people who are deficient
  39. How is the target mean intake calculated using EAR values?
    • target mean intake for group= EAR/(1-[2xCVof intake])
    • Where CV=SD of intake/mean intake
  40. How do DRIs differ conceptually from the former RDAs and RNIs (4 points)?
    • Where specific data on safety and efficacy exist, reduction in the risk of chronic degenerative disease is included in the formulation of the recommendation rather than just the absence of signs of deficiency
    • The concepts of probability and risk explicitly underpin the determination of the DRIs and inform their application in assessment and planning
    • Upper levels of intake are established where data exists regarding risk of adverse health effects
    • Components of food that may not meet the traditional concept of a nutrient but are of possible benefit to health are reviewed, and if sufficient data exist, reference intakes are established
  41. When are AIs used?
    Adequate Intakes are used instead of RDAs when an EAR cannot be calculated
  42. What are ULs?
    Tolerable Upper Intake levels- Intake below the UL are unlikely to pose risks of adverse health effects in healthy people
  43. What is the criticism of RNIs?
    • Indicies of nutritional adequacy sometimes based upon insufficient information
    • Group mean intakes of the population used as the standard for nutritional adequacy (If they are not shown to be associated with frank nutritional deficiencies, then they can ne used as valid indicies for setting the RNI)
    • These mean values do not incorporate the 2SD from the mean safety factor
  44. How is AI determined?
    • Observed or experimentally determined
    • Estimates of nutrient intake by a group (or groups) of healthy people that are assumed to be adequate
    • Experimental and observational data used --> mean intake that sustains a desired indicator of health
  45. What happens if a persons intake falls below the AI?
    No quantitative (or qualitative) estimate can be made of the probability of nutrient adequacy because the point where risk increases cannot be determined
  46. What does it mean if there is not UL for a nutrient?
    does not mean that intake at any level is without risk, nut that safe level is undetermined
  47. Why is UL important?
    Important due to commonplace fortification and supplement use
  48. What does Canada's food guide do?
    • Describes a patter of eating that is sufficient to meet nutrient needs
    • Describes a pattern of eating that contributes to a reduced risk of nutrition-related health problems
    • Describes a patter of eating that supports the achievement and maintenance of a healthy body weight
    • Describes a pattern of eating that reflects the diversity of foods available to Canadians
    • Supports Canadians' awareness and understanding of what constitutes a pattern of healthy eating
    • Emphasizes that healthy eating and regular physical activity are important for health
  49. Where does the majority of energy in our diet come from?
    • Majority of energy as CHO
    • This can decrease heart disease and bowel cancer risk
  50. How much of our energy intake should come from alcohol?
    • No more than 5% of energy from alcohol (1-2 drinks daily)
    • If more- increase risk of cancers, heart disease and other (osteoporosis, dementia, liver diseases, hypertension, obesity, fetal alcohol syndrome, accidents, domestic violence)
  51. How much caffeine should we be consuming?
    • No more than in 4 cups of coffee
    • If above- increased risk of osteoporosis, hypertension, adverse pregnancy outcomes, CVD
  52. When should water be fluoridated and why?
    • Community water supplies containing fluoride at less than 2mg/L should be fluoridated
    • To prevent dental caries