Introduction to Nutrition: Food for Health
This lecture is divided into three sections:
1) How healthy is the Canadian diet?
2) Nutrients – overview
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3) Important nutrition concepts
Section 1: How healthy is the Canadian diet?
What is the science that studies of the interaction between human health, food, and nutrients?
HUMAN NUTRITION
Nutrition and the Canadian Diet: How healthy is the Canadian diet?
u Canadian Community Health Survey (CCHS)
u Survey of health information including food intake
u 2007-Canada’s Food Guide:
u Recommends food from four groups: u Grain products
u Milk and alternatives u Vegetables & Fruit
u Meat and alternatives
u Canadian Healthy Eating Index (CHEI): u Measures adherence to 2007-CFG
Two nutrition-focused surveys: 2004-CCHS-Nutrition 2015-CCHS-Nutrition
How are Canadians doing with respect to diet quality?
u CHEI: Perfect adherence to 2007-CFG = 100
Taller the bar the poorer the diet
Nutrition and Health:
u Good nutrition can reduce your risk of chronic disease
u Diabetes
u Heart disease u Hypertension u Obesity
u Osteoporosis
u Neurodegenerative disease
Section 2: Nutrients: An Overview
Food provides nutrients
ESSENTIAL NUTRIENTS
Essential to human life
Must be provided by the diet
Cannot be biosynthesized
in the body in sufficient quantities
Deficiency symptoms /illness
Add nutrient to diet
If absent from diet
Deficiency symptoms disappear
Food provides nutrients
MACRONUTRIENTS
u Carbohydrates
u Lipids (Dietary fat/fat) u Protein
Food provides nutrients
Carbohydrates and Lipids:
Provide energy:
u To support basal metabolism* and physical activity
u When present in excess in the diet, protein is also a source of energy .
*Basal metabolism: metabolic activity needed to maintain life at rest such as maintaining the function of internal organs
u Units of energy:
u Energy required by the human body
and energy content of foods:
u Kcalories
u Calories or calories u Kilojoules
Food provides nutrients
4 kcal/g carbohydrates 9 kcal/g fat or lipids
4 kcal/g protein
7 kcal/g alcohol
Know these numbers
Food provides nutrients Lipids or Dietary Fats:
Triglycerides:
u The major chemical form of lipids in food
u An ester of glycerol and three fatty acids
Condensation reaction
Food provides nutrients Lipids or Dietary Fats:
u Unsaturated fatty acids:
u Fatty acids that contain double bonds
u Considered to be beneficial to health- reducing the risk of cardiovascular disease
u Common in plant oils such as u canola oil
u soybean oil u olive oil
u Monounsaturated fatty acids (MUFA)
u Contain one double bond
u e.g. fatty acid: oleic acid found in olive oil
u Polyunsaturated fatty acids u (PUFA)
u Contain at least two double bonds
u e.g. found in canola oil & soybean oil
Food provides nutrients Lipids or Dietary Fats:
u Two PUFAs, found in oils like canola oil and soybean oil, are essential fatty acids:
uLinoleic acid u(omega-6 fatty acid)
uAlpha-linolenic acid u(omega-3 fatty acid)
uMust be obtained from the diet
Food provides nutrients Lipids or Dietary Fats:
u Other important omega-3 fatty acids u EPA-eicosapentaenoic acid
u DHA-docosahexaenoic acid
ualso known as long-chain (LC) omega-3 fatty acids
u EPA and DHA are omega-3 fatty acids synthesized in the body from alpha-
linolenic acid
u Also obtained from the consumption of fatty fish or fish oil supplements u Also linked to health benefits especially cardiovascular disease
Food provides nutrients Lipids or Dietary Fats:
u Saturated fatty acids
u found in high amounts in fats from animal sources
u Trans fatty acids
u found in partially hydrogenated vegetable oils, margarines, and shortening u These fats were banned from the Canadian food supply in 2018
u These fatty acids are associated with increased risk of disease
u Dietary recommendations are that foods high in saturated fats should be replaced with foods high in unsaturated fats
Food provides nutrients Carbohydrates:
u Indigestible
u Dietary fibre
u Whole grains, legumes, beans, peas, lentils
u Vegetables and fruit.
u High-fibre diets may reduce risk of CVD and colon cancer
u Digestible
u Starch –from rice, wheat, corn, potatoes,
cassava, etc.
u Major sources of kcalories that feed humanity
u Digestion à breakdown to glucose
u Glucose-main carbohydrate that circulates in
u Source of energy for cells, especially the brain
u Sucrose – disaccharide of glucose &
u High fructose corn syrup- mixture of glucose & fructose (1:1)
u Sweeteners for sugar-sweetened beverages (SSB)
u Linked to obesity
This Photo by Unknown Author is licensed under CC BY-NC
Food provides nutrients Proteins:
u amino acids, joined by peptide bonds
u Some amino acids are essential/
indispensable and some are non-essential/ dispensable
u essential amino acids must be obtained from the diet
Micronutrients: Vitamins and Minerals
u Vitamins
u Organic compounds
uFat-soluble vitamins
uWater-soluble vitamins
u Minerals
u Inorganic compounds
u Iron-prevents iron deficiency anemia
u Iodine-prevents goitre
u Calcium-maintains bone health
u Fat-Soluble Vitamins:
u Vitamin A, D, E & K
u Can be stored in the liver and adipose tissue
u are NOT rapidly depleted from the body
u If intake is extremely high can have toxic effects
u Water-Soluble Vitamins
u B vitamins and vitamin C u Not stored in the body
u Are rapidly depleted so need to be consumed regularly
u except vitamin B12 which is efficiently conserved
u When consumed in excess excreted in the urine
Required Reading: Focus on Phytochemicals (after chapter 9) pg 443-449.
u Substances not made by the body u Phytochemicals-sources: plants
u Not essential but may be beneficial to health
u Many phytochemicals are antioxidants that may reduce the risk of diseases such as
cardiovascular disease and cancer
u See the next slide for information on what you need to know about phytochemicals.
Questions: Required Reading: Focus on Phytochemicals
u Make sure after reading about phytochemicals you are able to: u Define:
u functional food
u antioxidant u Identify:
u The two carotenoids that may reduce the risk of macular degeneration
u The carotenoid that gives tomatoes their red colour.
u The family of vegetables that include broccoli, cauliflower, bok choy and cabbage, two phytochemicals they contain, and how these phytochemicals are beneficial.
u The sulfur compounds found in garlic and onions and their health benefits u The phytochemicals found in green tea and their health benefits
u The polyphenolic compound associated with longevity
u Explain briefly how phytoestrogens reduce the risk of disease.
u Explain briefly how dark chocolate and white chocolate differ with respect to phytochemical content.
u Explain briefly why bread made with whole grain flour contains more phytochemicals than grain made from white flour 24
Section 3: Important Nutrition Concepts
Food provides nutrients: Nutrition and Health
Malnutrition
Food Provides Nutrients: Diet-
u Nutritional genomics or nutrigenomics
u Study of the interaction between genetic variation and diet
u Personalized nutrition
Food Choices for a Healthy Diet: Choosing a Healthy Diet
u Adequacy
u Enough of a nutrient to maintain
u Choose foods high in nutrient
u High nutrient levels/kcalorie
Food Choices for a Healthy Diet:
Table 1.3 Choices to Boost Nutrient Density
Food Choices for a Healthy Diet: Choosing a healthy diet
u Eat a variety of foods
u Eat a balanced diet
u Avoid excess kcalorie intake u Everything in moderation
u These principles are applied in Canada’s Food Guide (Ch 2)
Food Choices for a Healthy Diet: Choosing a Healthy Diet
Portion Distortion
Typical portion sizes have increased, over the last forty years, and with it an increase in the consumption of
kcalories.
http://www.nhlbi.nih.gov/health/educational/wecan/eat-right/portion-distortion.htm
Subpackaging
-packaging in 100 kcal portions
Chapter 2: Nutrition Guidelines:
Section 1:Dietary reference intakes: EAR & RDA, EAR cutpoint method, AI, UL Section 2:Dietary reference intakes: Energy and Macronutrients
Dietary reference intakes:
EAR & RDA, EAR cutpoint, AI, UL
Nutrition Recommendations for the Canadian Diet
Nutrient-based approach
Food-based approach
u How much of a nutrient is required u Dietary pattern
to maintain health?
u Combination of types and amounts of foods that impact health
Recommendations are regularly updated.
Nutrition Recommendations for the Canadian Diet
History Today
u First recommendations in Canada 1939, 1943
u Recommended Nutrient Intakes (RNI)
u Dietary Reference Intake (DRIs)
u Determined by the Institute of Medicine (IOM) by Canadian and American scientists beginning in the 1990’s and continuing today
Nutrient-based approach
Canada’s Official Food Rules 1942: Fig 2.2
Food-based approach
Dietary Reference Intakes (DRIs)
u For planning and assessing diets of healthy individuals u Values for different life stages/ males or females
u Children
u Young, middle, older adults u Pregnancy/lactation
2.2 DIETARY REFERENCE INTAKES (DRI)
ENERGY MACRONUTRIENTS
OTHER NUTRIENTS
Estimated Energy requirement (EER)
Acceptable Macronutrient Distribution Range
Adequate intake (AI)
Tolerable Upper Intake Level (UL)
Chronic Disease Risk Reduction Intake (CDRR)
Estimated Average requirement (EAR) Recommended Dietary Allowance (RDA)
Know what abbreviations stand for
Statistics
Median intake
Normal distribution
Frequency: Number of individuals
Standard deviation Variance
Nutrient intake (mg)
Statistics
What is the same ? What is different?
Statistics
Shaded area under the curve àprobabilityor proportion of adequate or inadequate nutrient intake
50% of the curve is shadedà 50% probability or proportion of adequate or inadequate nutrient intake
Dietary Reference Intakes
Estimated Average Requirement (EAR)
Definition
u Nutrient intake that meets the requirement of 50% of individuals in a group (i.e. sex; age)
How is it used
u To estimate the probability that an individual’s usual intake is meeting his/her requirement
u To estimate what proportion of a group is meeting their requirements
Dietary Reference Intakes:
Estimated average requirement (EAR)
How is it determined?
u Determine a biochemical criterion that allows you to determine the intake at which an individual’s requirement is being met
u Determine the requirement distribution from a sample of the population
Dietary Reference Intakes: Establishing EARs
u CONSIDER: Hypothetical Vitamin X u Physiological criterion:
u Vitamin X requirement is met when the level of Vitamin X in serum reaches saturation
u IMPORTANT: not universal criterion for all nutrients
u Conduct a depletion-repletion experiment on a population of healthy adults
Dietary Reference Intakes: Establishing EARs: Hypothetical vitamin X
u Fed a vitamin X-free diet
u Levels of vitamin X in blood are tracked
u Eventually levels decline until no vitamin X is detected (i.e. the individual is deficient)
Next step?
Dietary Reference Intakes: Hypothetical vitamin X: Next step?
u Begin refeeding vitamin X
u What happens?
u Blood levels of vitamin X begin to
u Eventually each individual reaches an intake at which there is no corresponding rise in blood levels i.e. blood is saturated with vitamin X
u That Vitamin X intake is the individual’s vitamin X requirement
Will the requirement be
the same for each
individual?
Dietary Reference Intakes: Requirement Distribution for Vitamin X (39 subjects)
Normal distribution EAR = 100 mg
50% of subjects meet their requirements
Number of individuals
60 70 80 90100 110 120130 140
Vitamin X Intake (mg)
Dietary Reference Intakes:
To understand how requirement distributions are used, it is important to distinguish between REQUIREMENT and INTAKE
Nutrient Requirement Nutrient Intake
u Experimentally- determined requirement for a nutrient
u Amount required to maintain health
u Amount of nutrient consumed
u Determined by the composition of the diet
Dietary Reference Intakes EAR (Estimated average requirement)
EAR represents the average daily nutrient intake that meets the requirements of half the healthy individuals in a given group.
From the Vitamin X
requirement distribution the EAR can be determined
If an individual’s nutrient intake is equal to the EAR then there is a 50:50 chance the individual is meeting his/her
*that meets the requirements of Nutrient Intake* (mg) individuals in the experimental group
requirement
Dietary Reference Intakes:
Determining the probability of meeting requirements from the requirement distribution of a nutrient
Usual intake of nutrient
What is the probability that
A is meeting their requirement?
Assuming the grey area represents about 12% of the total area under the curve, than the probability that A is meeting their requirement is 12%..
Nutrient Intake (mg)
Determining the probability of meeting requirements from the requirement distribution of a nutrient
Nutrient Intake (mg)
What is the probability that
B is meeting their requirement?
Gray area represents 80% of the total area under the curve.
Dietary Reference Intakes:
How is the RDA used?
RDA = Recommended Dietary Allowance: intake that ensures a 98% probability of meeting your requirement
RDA = EAR + 2 Standard Deviations
As a goal for an individual’s usual intake, because it is almost certainly adequate
Dietary Reference Intakes Recommended Dietary Allowance
RDA: meets the requirements of 98% of individuals : 140 mg
EAR cut point methods
u Up to this point, we have looked at individuals and the probability that they are meeting their requirements based on the position of that intake on the requirement distribution
u Now we are going to look at populations and the proportion of a population meeting its requirements based on an intake distribution.
u This requires a new methodology à
Dietary Reference Intakes:
Using the EAR cut point method to Determine the Prevalence of Adequate Intake within a Group
u To estimate what proportion of a group is meeting their requirements
EAR cut point method Intake distribution
Results of a survey of nutrient intakes
Dietary Reference Intakes: EAR cut point method
Intake distribution
EAR cutpoint method
Median Intake
Proportion of the population whose intake is less than the EAR
Proportion of the population that is NOT meeting its requirement
Dietary Reference Intakes: EAR cut-point method
QUESTION: If two populations have the same the median intake, does that mean that the proportion of the population meeting its requirement is the same?
ANSWER: Not necessarily…
Consider these two intake distributions.
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
Dietary Reference Intakes:
How is the EAR cut point method used:
Health Canada:
u Considers a population to have an adequate intake if the proportion of the population whose intake is below the EAR is or less
Canadian Community Health Survey-Nutrition:
u Measured nutrient intake and used the EAR cut point method to determine the adequacy of nutrient intake
Remember this number
Dietary Reference Intakes: Adequate Intake
u Insufficient data to calculate an EAR u More research is needed
u Usually based on an estimate of average nutrient intake by a healthy population
u Example: Recommendations for calcium intake for young infants 0-6 months of age = 200mg
u Adequate intake of 200 mg
u the average calcium intakes of exclusively breast-fed infants
Dietary Reference Intakes Adequate Intake
u If your intake > AI, then intake OK u AI is good personal target
u If intake