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Lecture 3

NFS284 Lecture 3 - verbatim

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Nutritional Science
Debbie Gurfinkel

NFS284 Lecture 3 Chapter 2: Nutrition: Guidelines: Applying the Science of Nutrition • 2.1 Nutrition Recommendation for the Canadian Diet o Nutrient-based approach  How much of a nutrient is required to maintain health? o Food-based approach  Dietary pattern • Types and amounts of foods to maintain health o Recommendations are regularly updated o Nutrient-based approach  History • First recommendations in Canada 1939, 1943 • Recommended Nutrient Intakes (RNI)  Today • Dietary Reference Intake (DRIs) • Determined by the Institute of Medicine (IOM) by Canadian and American scientists beginning in the 1990’s and continuing today o Canada’s Official Food Rules 1942: Fig 2.2 – Food-based approach • 2.2 Dietary Reference Intakes (DRIs) o For planning and assessing diets of healthy individuals o Values for different life stages/males or females  Infants  Children  Teens  Young, middle, older adults  Pregnancy/lactation o Energy  Estimated Energy Requirement (EER) o Macronutrients  Acceptable Macronutrient Distribution Range (AMDR) o Other Nutrients  Estimated Average Requirement (EAR)  Recommended Dietary Allowance (RDA)  Adequate Intake (AI)  Tolerable Upper Intake Level (UL) o Know terms and abbreviations o Statistics  Distribution curve  Median = 50% above, 50% below  Measure of range or variance -> diff. from lowest level to highest level  Median is the same, standard deviation (or variance) is different  Frequency: # of individuals  Look at areas under curve -> look at probability  Shaded area under the curve -> probability of adequate or inadequate nutrient intake  50% of the curve is shaded -> 50% probability of adequate or inadequate nutrient intake  Estimated Average Requirement (EAR) • Definition: nutrient intake that meets the requirement of 50% of individuals in a group (ie. Sex; age) • How is it used o To estimate the probability that an individual’s usual intake is meeting his/her requirement o To estimate what proportion of a group is meeting their requirements o Used by individual and population • How is it determined? o Determine a biochemical criterion that allows you to determine the intake at which an individual’s requirement is being met o Determine the requirement distribution from a sample of the population o Nutrient basis o Can measure criterion; using this, can measure requirement for each individual  Establishing EARs • CONSIDER: Hypothetical Vitamin X o Physiological criteria:  Vitamin X requirement is met when the level of Vitamin H in serum reaches saturation  IMPORTANT: not universal criterion for all nutrients • Conduct a depletion-repletion experiment on a population of healthy adults • Know when someone has reached nutrient requirement when reached saturation • Depletion o Fed a vitamin X-free diet o Levels of vitamin X in blood are tracked o Eventually levels decline until no vitamin X is detected (ie. The individual is deficient) • Then repletion • Repletion o Begin refeeding vitamin X o What happens?  Blood levels of vitamin X begin to rise  Eventually each individual reaches an intake at which there is no corresponding rise in blood levels, ie. Blood is saturated with vitamin X  That vitamin X intake is the individual’s vitamin X requirement o Start w/ low levels, eventually reach plateau o Intake of Vit X to saturation level is requirement of Vit X o Will the requirement be the same for each individual? At end, would know each individual requirement • Requirement Distribution for Vit X (39 subjects) o Start w/ 39 subjects; get 39 different requirements, get normal distribution o Middle line corresponds w/ intake of 100 so EAR = 100 mg; if someone intakes 100 mg, 50% making requirement o EAR = middle point of distribution o To understand how requirement distributions are used, it is important to distinguish between REQUIREMENT and INTAKE  Nutrition Requirement • Experimentally determined requirement for a nutrient • Amount required to maintain health  Nutrient Intake • Amount of nutrient consumed • Determined by the composition of the diet o EAR (Estimated Average Requirement)  From the Vit X requirement distribution the EAR can be determined  EAR represents the average daily nutrient intake that meets the requirements of half the healthy individuals in a given grp  If an individual’s nutrient intake is equal to the EAR then there is a 50:50 chance the individual is meeting his/her requirement  EAR = median line  May or may not be meeting requirement; 50% chance o Determining the probability of meeting requirements from the requirement distribution of a nutrient  What is the probability that A is meeting his requirement?  Gray area represents 12% of the total area under the curve  Individual A has 12% of meeting requirement  Consuming less than EAR  What is the probability that B is meeting his requirement?  Gray area represents 80% of the total area under the curve  Intake greater than EAR  Higher the intake the higher the probability of meeting requirement  Recommendations depend on probabilities • 2.2 Dietary Reference Intakes: o How is the RDA used? o As a goal for an individual’s usual intake, because it is almost certainly adequate o RDA = EAR + 2 Standard Deviations  If go out 2 SDs out from median on normal distribution, cover 98% of curve  Theoretically curve goes on forever so can’t have 100%  Recommended dietary allowance (RDA) • Target intake that increase probability of meeting requirement  If consume nutrient @ level of RDA  If consume nutrient @ level of RDA, have 98% chance of meeting requirement  Assess intake based on how close to RDA o Recommended Dietary Allowance  RDA: meets the requirements of 98% of individuals: 140mg  1 person outside o Using the EAR to Determine the Prevalence of Adequate Intake within a Group  To estimate what proportion of a group is meeting their requirements  EAR cut point method  intake distribution (results of a survey of nutrient intakes)  EAR represents median; 50% probability  RDA = target; increase probability o EAR Cutpoint Method  Intake distribution  90%  has intake less than EAR, not meeting requirement; bad  EAR cutpoint method  proportion of the population whose intake is less than the EAR = Proportion of the population that is NOT meeting its requirement • Can’t identify which individuals, but can calculate how well GROUP doing  Before answer Q, intake distribution or requirement  Plot intakes based on dietary survey  Shape of curve not normal; have tail @ high intake; @ low end, almost never have 0 mg b/c nutrients so widespread  78% not meeting requirement; median intake low (top graph)  Median intake high (bottom graph) • 10% of population not meeting requirement  2 intake distributions when median intakes o QUESTION: If the median intake is equal to the RDA does that mean that 98% of the population is meeting it
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