Introduction to Public Health Nutrition January 2011 Nutrition 531.
Introduction to Nutrition
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Transcript of Introduction to Nutrition
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Introduction to Nutrition
Lecture II
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Dietary Reference Intakes
Collective term which includes four values:
EAR Estimated average requirement
RDA Recommended dietary allowance
AI Adequate Intake
UL Upper Intake Level
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Estimated average requirement
• Average daily nutrient intake estimated to meet the requirement of half the healthy (& assume intake of other nutrients are adequate) individuals in a particular age (life stage) and gender group.
• Meet the requirement -maintain normal function and health
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How are requirements estimated
• Observation of population groups - intakes associated with absence of deficiency
signs.• Intakes needed to maintain balance (e.g.
nitrogen balance studies for protein).• Depletion-repletion studies - intakes needed to prevent deficiency (clinical
or biochemical changes)
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How are requirements estimated
• Intakes needed to maintain circulating levels of nutrient or tissue concentration (tissue saturation)
• Intakes associated with biological markers of adequacy - functional adequacy e.g enzyme activity
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Recommended Dietary Allowance
• Average daily nutrient intake that is enough (or more than enough) to meet the requirement of 97-98% of the healthy individuals in a particular age (life stage) and gender group
• To determine need EAR and variability (SD) of EAR (assume distribution of requirements is normal)
RDA = EAR + 2 SD
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Adequate Intake
• Used when insufficient information to determine RDA
• recommended average daily nutrient intake based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups ) of apparently healthy persons that are assumed to be adequate
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Tolerable Upper Intake Level
• highest average daily intake likely to pose no risk of adverse health effects to almost all individuals in the life stage and gender group.
• As intake exceeds UL potential risk of adverse effects increase
• Need for this value came from increased fortification of foods and use of supplements
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STAPLESCereals:Bread (from whole grain or
enriched flour), wheat flour, corn (maize), corn meal, dried cereals, macaroni, spaghetti, rice, cereal porridges.
Starchy fruits, roots, tubers/ground provisions: Banana, plantain, breadfruit, yam, potato, dasheen, coco/ eddoe, cassava.
6-11 servings
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LEGUMES
Kidney beans, gungo/pigeon peas, black-eye peas, cow peas, other dried peas and beans, peanuts, cashew nuts, sesame seeds, pumpkin seeds.
3-4 servings
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VEGETABLESDark green leafy and yellow
vegetables: Callaloo/spinach, dasheen leaves, cabbage bush, pak choy, string beans, pumpkin, carrot.
Other vegetables: Squash, cho-cho, (christophene,
chayote), cucumber, tomato, garden egg/aubergine.
3- 5 Servings
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FRUITSMango, guava, citrus (orange,
grapefruit, limes, tangerine), pineapple, West Indian cherry, pawpaw/papaya, golden apple/Jew/June plum, sugar apple/sweet sop.
2 -4 Servings
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The Food Guide Pyramid
The Key to a Balanced Diet!
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Exchange System Lists
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WHAT COUNTS AS A SERVING?Food Groups
Bread, Cereal, Rice, and Pasta
1 slice of bread 1 ounce of ready to-eat cereal
1/2 cup of cooked cereal, rice, or pasta
Vegetable
1 cup of raw leafy vegetables
1/2 cup of other vegetables, cooked or raw
3/4 cup of vegetable juice
Fruit
1 medium apple, banana, orange
1/2 cup of chopped, cooked, or canned fruit
3/4 cup of fruit juice
Milk, Yogurt, and Cheese
1 cup of milk or yogurt 1-1/2 ounces of natural cheese
2 ounces processed cheese
Meat, Poultry, Fish, Dry Beans, Eggs, and Nuts
2-3 ounces of cooked lean meat, poultry, fish
1/2 cup of cooked dry beans or ½ cup tofu counts as a serving. 2 tablespoons of peanut butter or 1/3 cup of nuts count as 1 ounce of “meat” according to the USDA.
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Exchange Lists Categories
• Starch (80 kcal) – 15 grams carbohydrate – 3 grams protein – 0-1 grams fat
• Vegetable (25 kcal) – 5 grams carbohydrate – 2 grams protein – 0 grams fat
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Exchange Lists Categories
• Fruit (60 kcal) – 15 grams carbohydrate – 0 grams protein – 0 grams fat
• Protein- legumes, meats, cheeses (55-100 kcal) – 0 grams carbohydrate – 7 grams protein – 1-8 grams fat (depending on whether food is very lean, lean, medium fat
or high fat)
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Exchange Lists Categories
• Milk (90-150 kcal) – 12 grams carbohydrate – 8 grams protein – 0-8 grams fat (depending on amount of fat in milk)
• Fat (45 kcal) – 0 grams carbohydrate – 0 grams protein – 5 grams fat
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SAMPLE DIETS FOR A DAY AT 3 CALORIE LEVELS
Low1,600
Mod2,200
High2,800
Grain Group Servings 6 9 11Vegetable Group Servings 3 4 5Fruit Group Servings 2 3 4Milk Group Servings 2-3 2-3 2-3Meat Group (ounces) 5 6 7
Total Fat (grams) 53 73 93Total Added Sugars (teaspoons) 6 12 18
Women who are pregnant or breastfeeding, teenagers, and young adults to age 24 need 3 servings of Dairy or other Calcium-rich foods. “Meat” group amounts are in total ounces.
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Standards For Food Labeling
• RDA not used on food label since it is gender and age specific
• FDA developed the Daily Values – Reference Daily Intake (RDI) for vitamins and
minerals – Daily Reference Value (DRV) for nutrients
without RDAs – Only used on food labels
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Reading Food Labels
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Nutritional Assessment Why?
• The purpose of nutritional assessment is to:
• Identify individuals or population groupsat risk of becoming malnourished
• Identify individuals or population groups who are malnourished
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Nutritional Assessment Why? 2
• To develop health care programs that meet the community needs which are defined by the assessment
• To measure the effectiveness of the nutritional programs & intervention once initiated
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Direct Methods of Nutritional Assessment
These are summarized as ABCD
• Anthropometric methods• Biochemical, laboratory methods• Clinical methods• Dietary evaluation methods
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Anthropometric Methods• Anthropometry is the measurement of body height,
weight & proportions.
• It is an essential component of clinical examination of infants, children & pregnant women.
• It is used to evaluate both under & over nutrition.
• The measured values reflects the current nutritional status & don’t differentiate between acute & chronic changes .
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Other anthropometric Measurements
• Mid-arm circumference
• Skin fold thickness
• Head circumference
• Head/chest ratio• Hip/waist ratio
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Anthropometry for children
• Accurate measurement of height and weight is essential. The results can then be used to evaluate the physical growth of the child.
• For growth monitoring the data are plotted on growth charts over a period of time that is enough to calculate growth velocity, which can then be compared to international standards
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Measurements for adults
• Height:– The subject stands erect & bare footed on a
stadiometer with a movable head piece. The head piece is leveled with skull vault & height is recorded to the nearest 0.5 cm.
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WEIGHT MEASUREMENT
• Use a regularly calibrated electronic or
balanced-beam scale. Spring scales are less
reliable.
• Weigh in light clothes, no shoes
• Read to the nearest 100 gm (0.1kg)
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Nutritional Indices in Adults
• The international standard for assessing body size in
adults is the body mass index (BMI).
• BMI is computed using the following formula: BMI =
Weight (kg)/ Height (m²)
• Evidence shows that high BMI (obesity level) is associated
with type 2 diabetes & high risk of cardiovascular
morbidity & mortality
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BMI (WHO - Classification)
BMI < 18.5 = Under WeightBMI 18.5-24.5= Healthy weight rangeBMI 25-30 = Overweight (grade 1 obesity)BMI >30-40 = Obese (grade 2 obesity)BMI >40 =Very obese (morbid or grade 3 obesity)
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Waist/Hip Ratio
• Waist circumference is measured at the level of the umbilicus to the nearest 0.5 cm.
• The subject stands erect with relaxed abdominal muscles, arms at the side, and feet together.
• The measurement should be taken at the end of a normal expiration.
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Waist circumference• Waist circumference predicts mortality better than any
other anthropometric measurement.
• It has been proposed that waist measurement alone can be used to assess obesity, and two levels of risk have been identified
MALES FEMALELEVEL 1 > 94cm > 80cmLEVEL2 > 102cm > 88cm
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Waist circumference/2
• Level 1 is the maximum acceptable waist circumference irrespective of the adult age and there should be no further weight gain.
• Level 2 denotes obesity and requires weight management to reduce the risk of type 2 diabetes & CVS complications.
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ADVANTAGES OF ANTHROPOMETRY
• Objective with high specificity & sensitivity• Measures many variables of nutritional
significance (Ht, Wt, MAC, HC, skin fold thickness, waist & hip ratio & BMI).
• Readings are numerical & gradable on standard growth charts
• Readings are reproducible. • Non-expensive & need minimal training
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Limitations of Anthropometry• Inter-observers errors in measurement
• Limited nutritional diagnosis
• Problems with reference standards, i.e. local versus international standards.
• Arbitrary statistical cut-off levels for what considered as abnormal values.
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DIETARY ASSESSMENT
• Nutritional intake of humans is assessed by five different methods. These are:
– 24 hours dietary recall– Food frequency questionnaire– Dietary history since early life– Food dairy technique– Observed food consumption
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24 Hours Dietary Recall
• A trained interviewer asks the subject to recall all food & drink taken in the previous 24 hours.
• It is quick, easy, & depends on short-term memory, but may not be truly representative of the person’s usual intake
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Food Frequency Questionnaire
• In this method the subject is given a list of
around 100 food items to indicate his or her
intake (frequency & quantity) per day, per week
& per month.
• inexpensive, more representative & easy to use.
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Food Frequency Questionnaire/2
Limitations: long Questionnaire
Errors with estimating serving size.
Needs updating with new commercial food products to
keep pace with changing dietary habits.
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DIETARY HISTORY
• It is an accurate method for assessing the nutritional status.
• The information should be collected by a trained interviewer.
• Details about usual intake, types, amount, frequency & timing needs to be obtained.
• Cross-checking to verify data is important.
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FOOD DAIRY
• Food intake (types & amounts) should be
recorded by the subject at the time of
consumption.
• The length of the collection period range
between 1-7 days.
• Reliable but difficult to maintain.
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Observed Food Consumption
• The most unused method in clinical practice, but it is
recommended for research purposes.
• The meal eaten by the individual is weighed and contents
are exactly calculated.
• The method is characterized by having a high degree of
accuracy but expensive & needs time & efforts.
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Initial Laboratory Assessment
• Hemoglobin estimation is the most important test, & useful index of the overall state of nutrition. Beside anemia it also tells about protein & trace element nutrition.
• Stool examination for the presence of ova and/or intestinal parasites
• Urine dipstick & microscopy for albumin, sugar and blood
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