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 its requirement?

o ANSWER: It depends…

Consider these two intake distributions

This distribution is typically what is seen in real world data, i.e. when median intake = RDA more than 2% of population is not meeting its requirements

How well a population is doing with respect to nutrient intake depends on both the median intake and the standard deviation of the intake distribution, therefore use EAR cutpoint method for assessment

• Median intake same; in this case, = RDA but variance different

• EAR cutpoint produces diff results

• Diff proportion even though same median

• Can’t make assessments based on median intake; need EAR

cutpoint

• Depends on variance

• 2% and 12% not meeting requirement

o How is the EAR cutpoint method used:

Health Canada:

• Considers a population to have an adequate intake if the

proportion of the population whose intake is below the EAR is 10% or less (remember this number)

Canadian Community Health Survey:

• Measured nutrient intake and used the EAR cutpoint method to

determine the adequacy of nutrient intake

o Adequate Intake

Insufficient data to calculate an EAR

• More research is needed

Usually based on an estimate of average nutrient intake by a healthy population

Example: recommendations for calcium intake for young infants 0-6 months of age = 200mg

• Adequate intake of 200 mg

o The average calcium intakes of exclusively breast-fed

infants

If your intake > AI, then intake is OK

• AI is good personal target

If intake < AI your intake may or may not be OK

Don’t have requirement distribution

AI is personal; targeting

o Tolerable Upper Intake Level (UL)

The highest level of habitual nutrient intake that is unlikely to pose a risk of adverse effects

UL is not a recommended level of intake

• No additional benefit above RDA

Because of the popular use of supplements adverse effects are possible

• Some UL are based only on the amount of nutrient consumed in

supplement form

But it’s OK from natural food sources

• Main source of nutrients from food, but created UL for supplement

o DIETARY REFERENCE INTAKES (DRI)

Energy

• Estimated Energy Requirement (EER)

Macronutrients

• Acceptable Macronutrient Distribution Range (AMDR)

Other Nutrients

• Estimated Average Requirement (EAR)

• Recommended Dietary Allowance (RDA)

• Adequate Intake (AI)

• Tolerable Upper Intake Level (UL)

Know terms and abbreviations

o Energy Balance

Energy content (kcal) of food consumed = energy content expended for metabolism and physical activity weight is unchanged, i.e. energy balance

Energy content (kcal) of food consumed > energy content expended for metabolism and physical activity weight gain, i.e. positive energy balance

Energy content (kcal) of food consumed < energy content expended for metabolism and physical activity weight loss, i.e. negative energy balance

For us, try to maintain weight

o Estimated energy requirements (EER)

Equations (determined by experiment) are used to estimate the average energy needs of adults

• Men: EER = 662 – (9.53 X age [y]) + PA x (15.91 x weight [kg] +

539 x height [m])

• Women: EER = 354 – (6.91 X age [y]) + PA x (9.36 x weight [kg] +

726 x height [m])

• PA (physical activity term) = 1.00 (sedentary) 1.48 (very active)

• Don’t memorize equations, but know the variables involved

• See also section 7.3: Estimating Energy Needs pg 274

o Definitions of activity levels

Sedentary: Activities of daily living; less than 30 min of intentional exercise/day

Active: Walking 1 hour 45 minutes at 6.5 km per hour every day (+470 to 580 kcal)

Low Active: Walking 30 minutes at 6.5 km per hour every day (+135 to 165 kcal)

• Recommended; brisk pace; spend extra kcal

Very Active: Walking 4 hours 15 minutes at 6.5 km per hour every day (+1145 to 1405 kcal)

o EER (Estimated Energy Requirement) and Age

Female: 5’5”, 125 lb, 20 yrs, Sedentary, BMI 21, 1950 kcal

Female: 5’5”, 125 lb, 50 yrs, Sedentary, BMI 21, ? kcal = 1739

Female: 5’5”, 125 lb, 80 yrs, Sedentary, BMI 21, ? kcal = 1532

• Eat lot less to meet requirement

Estimates

This goes down b/c don’t eat much

Metabolism slows down; hormones stimulate

Use muscle mass; portion of muscle mass diff. in older and younger counterpart

o EER and Sex

Female: 5’5”, 125 lb, 20 yrs, Sedentary, BMI 21, 1950 kcal

• Typical female

Male: 5’5”, 125 lb, 20 yrs, Sedentary, BMI 21, ? kcal = 2266

• BMI higher b/c males have more muscle

Male: 5’10”, 150 lb, 20 yrs, Sedentary, BMI 21, ? kcal = 2516

• Typical

Men’s intake better than women; higher probability that will meet requirement

o EER and Body Size

Female: 5’5”, 125 lb, 20 yrs, Sedentary, BMI 21, 1950 kcal

Female: 5’5”, 150 lb, 20 yrs, Sedentary, BMI 25, ? kcal = 2053

• Higher energy requirement

o Weight change of individual in negative energy balance

Caloric requirement: 2000kcal dailty (typical)

Consumption: 1500kcal daily during time period shown

Low calorie diet; start in beginning

Trying to lose weight

Decrease consumption to 1500 kcal/day

Weight decrease and plateaus b/c 500 kcal deficit; body getting smaller as losing weight; energy requirement decreases so no longer 500 kcal deficit; deficit shrinks; manage to lose enough weight that energy is 1500 kcal, which balances intake, getting plateau, therefore weight loss difficult

• Smaller body, less energy requirement

• Now, can either start eating less food or increase PA to maintain

weight

• Requirement decrease as body size decrease

o DIETARY REFERENCE INTAKES (DRI)

Energy

• Estimated Energy Requirement (EER)

Macronutrients

• Acceptable Macronutrient Distribution Range (AMDR)

Other Nutrients

• Estimated Average Requirement (EAR)

• Recommended Dietary Allowance (RDA)

• Adequate Intake (AI)

• Tolerable Upper Intake Level (UL)

Know terms and abbreviations

o DRIs for Macronutrients = AMDR

Acceptable Macronutrient Distribution Ranges

• Expressed as % of total Calories

Carbohydrates: 45 – 65%

Fat: 20 – 35%

• Undesirable Fats:

o Saturated fat: as low as possible:

<10% kcal (Canada’s Food Guide)

<7% kcal (in scientific literature)

o Trans Fat: <1% kcal

Probably more in Canadian population

o Cholesterol: As low as possible: 300 mg

Protein: 10 – 35%

Where do these numbers come from?

• Balance b/w diff nutrients to build proteins in body

Cholesterol driven by LDL, determined by saturated fats in diet than direct cholesterol intake

Decrease intake

Vitamins and minerals usually expressed as weight

Want to consume carbs as 45 - 65% of calories

Don’t want too high or too low b/c won’t have enough of other macronutrients

Even vegetable fats have some saturated fats so can’t get down to 0

o Question: What percentage of total caloric intake for the individual described

below comes from each macronutrient?

An individual consumes a diet that contains:

• Carbohydrates: 300 gm

o [300gm x 4kcal/gm]/2100kcal x 100% = 57%

• Protein: 90 gm

o [90gm x 9kcal/gm]/2100kcal x 100% = 38.57%

• Fat: 60 gm

o [60gm x 4kcal/gm]/2100kcal x 100% = 11.4%

• Total kcalories: 2100 kcal (see Ch 1 Slides) (standard)

• Conform to AMDRs?

o Does conform