NUTRITION

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NUTRITION

• Learning Objectives
• To be familiar with different dietary reference
  standards of the intake of nutrients.
• To study the use of energy generated by the
  metabolism of the macronutrients.
• To study the types of dietary fats and their
  effect on our health.
• To study the classification of dietary
  carbohydrates and the importance of dietary
  fiber.
• To study the nitrogen balance, the requirement
  for protein in our body and protein-calorie
  malnutrition.

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I- OVERVIEW Nutrients -
Macronutrients - provide
the body with Energy
carbohydrates, fats, proteins
- the intake is more. -
Micronutrients Needed in small
amounts
vitamins minerals


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DRIs Estimates of the amounts of nutrients
required to 1- prevent deficiencies 2-
maintain optimal health and growth
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• 1- Estimated Average Requirement (EAR)
• is the average daily nutrient intake level
  estimated to meet the requirement of 50 the
  healthy individuals in a particular life stage
  and gender group
• It is useful for actual requirements in
  individuals and groups

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• 2-The Recommended Dietary Allowance (RDA)
• the average daily dietary intake level
  sufficient to meet the nutrient requirements of ?
  97 98 of individuals in a life stage and
  gender group .
• RDA is not the minimal requirement for healthy
  individuals.
• RDA is set to provide a margin of safety for most
  individuals.
• RDA EAR 2 SDEAR

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• 3- Adequate Intake (AI)
• is set instead of RDA if there is no sufficient
  
• evidence to calculate EAR or RDA.
• is based on estimates of adequate nutrient
  intake
• by a group of healthy people.
• Ex.AI for young infants(4-6 months)is based on
  the estimated daily nutrient intake supplied by
  human milk.

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• 4- Tolerable Upper Intake Level (UL)
• UL is the highest average daily nutrient intake
  level with no adverse effect.
• ? Intake (? UL) ? ? risk of adverse effects.
• UL is not considered as a recommended level of
  nutrient intake.
• ULs are useful because of the ? fortified foods
  and the ? use of dietary supplements.
• UL applies to chronic daily use.

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Using the DRIs

• Most nutrients have a set of DRIs .
• Usually a nutrient has an EAR and a
  corresponding RDA.
• Most are set by age, gender influenced by
  pregnancy and lactation in women.
• AI is judged by experts to meet the needs of all
  individuals in a group as it is based on less
  data than EAR RDA .

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Figure 27.3 Dietary Reference Intakes for
vitamins and minerals in individuals one year and
older EAR Estimated Average Requirement RDA
Recommended Dietary Allowance AI Adequate
Intake UL
Tolerable Upper Intake Level ? no value
established
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Intakes below the EAR ? to be improved Intakes
between the EAR RDA ? to be improved Intakes at
or above the RDA ? Adequate. Intakes above the AI
? Adequate. Intakes between the RDA UL ? No
risk for adverse effects.
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• III. ENERGY REQUIREMENTS IN HUMANS
• The Estimated Energy Requirement is
• The average dietary energy intake predicted to
  maintain an energy balance in a healthy adult
  with defined age, gender, height, weight and
  level of physical activity
• Recommended energy intake for
• - Sedentary adults 30 kcal / kg / day.
• - Moderately active adults 35 kcal / kg /
  day.
• - Very active adults 40 kcal / kg / day .

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• A. Energy content of food
• The energy content of food is calculated from the
  heat released by the total combustion of food in
  a calorimeter.
• It is expressed in kilo- calories (kcal or
  Cal).
• b) Energy content of
• Fat gtgt CHO and proteins.
• Fat gt Ethanol gt CHO
• Many scientists use joules (J), rather than
  calories (I cal 4.128 J).
• The joule is a unit of energy widely used in many
  countries other than the USA.

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B. How energy is used in the body

• The total energy required by an individual is the
  sum of three energy - requiring processes that
  occur in the body
• Resting Metabolic Rate (RMR),
• Thermic Effect of Food
• Physical Activity.

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• 1. Resting Metabolic Rate (RMR) (60)
• Resting (formerly Basal) Metabolic Rate (RMR) is
  the energy expended by an individual in a
  resting, postabsorptive state).
• It represents the energy required to carry out
  the normal body functions, such as respiration,
  blood flow, ion transport and maintenance of
  cellular integrity.
• In an adult RMR is about
• 1800 kcal for men ( 70 kg ) and
• 1300 kcal for women ( 50 kg ).
• From 50 - 70 of the daily energy expenditure in
  sedentary individuals is attributable to the RMR

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RMR is the energy required for the normal body
functions e.g. respiration, blood flow, ion
transport, maintenance cellular integrity
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• 2. Thermic effect of food (diet-induced
  thermogenesis)
• The production of heat by the body increases as
  much as 30 above the basal level during the
  digestion and absorption of food.
• Over a 24- hour period, the thermic response to
  food intake may amount to 5 - 10 of the total
  energy expenditure.

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• 3. Physical activity
• Muscular activity provides the greatest variation
  in energy expenditure.
• The amount of energy consumed depends on the
  duration and intensity of the exercise
• A sedentary person requires about 30 50 more
  than the basal caloric requirement for energy
  balance.
• A highly active individual may require 100 or
  more calories above the RMR.

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IV. Acceptable Macronutrient Distribution
Ranges(AMDR)

• Definition
• " a range of intakes for a particular
  macronutrient to reduce the risk of chronic
  diseases while providing adequate amounts of
  essential nutrients".
• The AMDR for adults is
• 45 - 65 of their total calories from
  carbohydrates
• 20 - 35 from fat
• 10 - 35 from protein

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• Chronic diseases are significantly influenced by
  the kinds and amounts of nutrients consumed.

• ?? risk of CHD in
• Dyslipidemias
• Smoking
• Obesity
• Sedentary lifestyle.

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V. DIATARY FAT

• Dietary fats most strongly influence the
  incidence of coronary heart disease (CHD).
• In the past dietary recommendations emphasized
  decreasing the total amount of fat in the diet.
• Research now indicates that the type of fat is
  more important than the total amount of fat
  consumed.

• A. Plasma lipids and CHD
• Plasma cholesterol may arise from the diet or
  from endogenous biosynthesis. In either case,
  cholesterol is transported between the tissues in
  combination with protein and phospholipids as
  lipoproteins.

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• LDL and HDL
• Plasma cholesterol level varies in response to
  the diet.
• ?? total plasma cholesterol levels ? ? risk for
  cardiovascular diseases (CHD).
• High levels of LDL cholesterol ? ? risk for CHD.
• High levels of HDL cholesterol ? ? risk for CHD.

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• 2. Beneficial effect of lowering plasma
  cholesterol
• Dietary or drug treatment of hypercholesterolemia
  ? ? decreasing LDL ? HDL? ? the risk for
  cardiovascular events.
• Dietary treatment ? 10 - 20 reduction in plasma
  lipoprotein concentrations.
• Treatment with statin drugs ? 30 - 40
  reduction in plasma cholesterol.

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Statins ? 30 - 40 reduction in plasma
cholesterol level
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• B. Dietary fats and plasma lipids
• Triacylglycerols are quantitatively the most
  important class of dietary fats.
• The influence of triacylglycerols on blood lipids
  is determined by
• The chemical nature of the constituent fatty
  acids.
• The presence or absence of double bonds
  (saturated vs. mono- and polyunsaturated).
• The number and location of the double bonds (n-6
  vs n-3).
• The cis vs trans configuration of the unsaturated
  fatty acids.

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• 1. Saturated fat
• Saturated fats are triacylglycerols containing
  fatty acids with no double bonds in its side
  chains.

Sources

• Dairy and meat products.
• Vegetable oils, such as coconut palm oils

Effects

• ? levels of total plasma cholesterol
• ? LDL cholesterol
• ? Risk of CHD.

Limitation of saturated fats intake ? ? risk of
CHD.
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• Saturated fatty acids with carbon chain lengths
  of 14 (myristic) and 16 (palmitic) are most
  potent in increasing the serum cholesterol.
• Stearic acid (18 carbonsfound in many foods
  including chocolate) ? modest ? in blood
  cholesterol.

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• 2. Monounsaturated fats
• Monounsaturated fats are triacylglycerols
  containing primarily fatty acids with one double
  bond.
• Unsaturated fatty acids are generally derived
  from vegetables and fish.
• When substituted for saturated fatty acids in the
  diet, monounsaturated fats ? ? total plasma
  cholesterol LDL cholesterol and ? HDLs.
• Mediterranean cultures, with diets rich in olive
  oil (high in monounsaturated oleic acid), show a
  low incidence of coronary heart disease.

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• The Mediterranean diet
• rich in - monounsaturated fatty acids (from
  olive oil)
• - n-3 fatty acids (from fish oils
  and some nuts)
• low in - saturated fat.
• The Mediterranean diet ? ? serum total
  cholesterol and LDL - but little change in HDL.
• Plasma triacylglycerols are unchanged.

• Seasonally fresh food
• Abundance of plant material
• Low amounts of red meat
• Olive oil as the principal source of fat.

Mediterranean diet contains
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• 3. Polyunsaturated fats
• Polyunsaturated fats are triacylglycerols
  containing primarily fatty acids with more than
  one double-bond.
• The effects of polyunsaturated fatty acids
  (PUFAs) on cardiovascular disease is influenced
  by the location of the double bonds within the
  molecule.

• n-6 Fatty acids
• long-chain, polyunsaturated fatty acids with the
  first double bond beginning at the sixth carbon
  atom (when counting from the methyl end of the
  fatty acid molecule).
• They are also called ?-6 (omega 6) fatty acids.

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a. n-6 Fatty acids contd

• Nuts
• Avocados
• Olives
• Soybeans
• Various oils (sesame, cottonseed corn oil).

Sources

• ? plasma cholesterol
• ? LDL
• ? HDL

Effects
The powerful benefits of ? LDL are only partially
offset because of the ? HDL
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• b. n- 3 Fatty acids
• Long-chain, polyunsaturated fatty acids, with the
  first double bond beginning at the third carbon
  atom (when counting from the methyl end of the
  fatty acid molecule)

• Plants (mainly a-linolenic acidan essential
  
• fatty acid).
• Fish oil containing docosahexaenoic acid
• (DHA) and eicosapentaenoic acid (EPA).

Sources

• suppress cardiac arrhythmias
• ? serum triacylglycerols
• ? tendency to thrombosis
• Lowers blood pressure
• ? risk of cardiovascular mortality
• little effect on LDL or HDL
• cholesterol levels.

Effects
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• The acceptable range for a -linolenic acid is 0.6
  - 1.2 of total calories.
• Two fish meals per week are recommended.
• The n-3 polyunsaturated fats are included in
  infant formulas.

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• Linoleic acid, along with linolenic acid (n-3
  fatty acid), are essential fatty acids ? fluidity
  of membrane structure and synthesis of
  eicosanoids .

Deficiency of essential fatty acids

• Scaly dermatitis.
• Hair loss.
• Poor wound healing

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• 4. Trans fatty acids
• Trans fatty acids are chemically classified as
  unsaturated fatty acids, behaving more
  like saturated fatty acids in the body, i.e. they
  ?? serum LDL (but not HDL) ?? the risk of CHD .
• Trans fatty acids do not occur naturally in
  plants and only occur in small amounts in
  animals.
• Trans fatty acids are formed during the
  hydrogenation of liquid vegetable oils, in the
  manufacture of margarine.
• Trans fatty acids are a major component of many
  commercial baked goods, such as cookies and
  cakes, and most deep-fried foods.

A key to the presence of trans fatty acids in a
food is the words partially hydrogenated on the
list of package ingredients.
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Effects of Dietary Fats
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5. Dietary Cholesterol
Sources Animal products milk, meat, eggs
The effect of dietary cholesterol on plasma
cholesterol is less important than the amount and
types of fatty acids consumed.
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C. Other dietary factors affecting coronary heart
disease

• 1. Soy protein
• Consumption of 25 - 50 g/day of soy protein ? 10
  ? in LDL cholesterol in patients with elevated
  plasma cholesterol.
• 2. Alcohol consumption .
• Moderate consumption of alcohol (??) ? ? risk of
  coronary heart disease, due to ? HDLs.
• Red wine contains phenolic compounds that inhibit
  lipoprotein oxidation.
• These antioxidants are also present in raisins
  and grape juice.

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VI. DIETARY CARBOHYDRATES

• The primary role of dietary carbohydrate is to
  provide energy.
• Although caloric intake in the United States has
  shown a modest increase since 1971 the incidence
  of obesity has dramatically increased

1. Classification of carbohydrates

• Monosaccharides
• Disaccharides
• Polysaccharides
• Fibers.

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• Monosaccharides
• Glucose and fructose
• The principal monosaccharides found in
  food.
• Glucose is abundant in
• fruits, sweet corn, corn syrup and honey.
• Free fructose together with free glucose and
  sucrose is found in honey and fruits.

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• 2. Disaccharides
• The most abundant disaccharides are
• Sucrose (glucose fructose),
• Lactose (glucose galactose)
• Maltose (glucose glucose).
• Sucrose table sugar is abundant in molasses
  and maple syrup.
• Lactose the principal sugar found in milk.
• Maltose a product of enzymic digestion of
  polysaccharides. It is also found in beer and
  malt liquors.

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• 3. Polysaccharides
• Complex carbohydrates are polysaccharides (most
  often polymers of glucose), which do not have a
  sweet taste.
• Starch a complex carbohydrate found in
  abundance in plants.
• Common sources
• wheat and other grains
• potatoes
• dried peas and beans
• vegetables

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Monosacch. Glucose Fructose Fruits, sweet corn, corn syrup, honey
Disaccharide Sucrose (GlcFrc) Lactose (GlcGal) Maltose (2 Glc) Table sugar, maple syrup Milk Malt drinks, digestion products of polysaccharides
Polysaccharides Starch Wheat, dried peas beans, vegetables, potatoes
Fibers Dietary Functional Plants
Simple sugars
Complex sugars
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• 4. Fiber
• Dietary fiber is defined as the
  nondigestible carbohydrates and lignin present in
  plats.
• Total fiber Dietary fiber Functional fiber.
• Dietary fiber provides little energy but has
  several beneficial effects.
• Functional fiber is the isolated, extracted, or
  synthetic fiber that has proven health benefits.

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• Soluble fibers
• Soluble fibers Form viscous gel when mixed with
  liquid .
• Functions of soluble fibers
• Soluble fiber delays gastric emptying ? sensation
  of fullness and ? peaks of postprandial blood
  glucose.
• Soluble fiber consumption ? ? LDL cholesterol
  levels by
• ?? fecal bile acid excretion and
• interfering with bile acid reabsorption
• . Diets rich in the soluble fiber oat bran (25 -
  50 g/day) ? ? risk for CHD by ?? total and LDL
  cholesterol levels

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Actions of Dietary Fibers
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• Insoluble fibers
• Pass through the digestive track intact
• Adds bulk to the diet .
  
• Absorbs 10-15 times its own weight in water ?
  drawing fluid into the intestine lumen ? ? bowel
  motility ? ? exposure of gut to carcinogens
• Fiber-rich diets ? ? risk for constipation,
  hemorrhoids, diverticulosis and colon cancer.
• The recommended daily fiber intake (AI)
• 25 g/day for women
• 38 g/day for men.

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• B. Dietary carbohydrate and blood glucose
• Some carbohydrate-containing foods ? rapid ?
  followed by a steep ? in blood glucose
  concentration.
• Other foods ? a gradual ? followed by a slow ?.
• Glycemic index proposed to quantitate these
  differences in the time course of postprandial
  glucose concentrations

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• Glycemic index is defined as
• the area under the blood glucose curves seen
  after ingestion of a meal with carbohydrate -
  rich food, compared with the area under the blood
  glucose curve observed after a meal consisting of
  the same amount of carbohydrate in the form of
  glucose or white bread .

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Food with a low glycemic index ? create a sense
of satiety over a longer period of time ?
limiting caloric intake.
Many experts feel that high nutrient and fiber
content, such as occurs in whole grains, fruits,
and vegetables, is a better guide than glycemic
index for selecting dietary carbohydrates.
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• C. Requirements for carbohydrate
• Carbohydrates are not essential nutrients because
  the carbon skeletons of amino acids can be
  converted into glucose .
• Carbohydrates are not inherently fattening. They
  yield 4 kcal/g (the same as protein and less than
  one half that of fat and result in fat synthesis
  only when consumed in excess of the body's energy
  needs
• Absence of dietary carbohydrate ? ketone body
  production and degradation of body protein whose
  constituent amino acids provide carbon skeletons
  for gluconeogenesis.
• The RDA for carbohydrate is set at 130 g / day
  for adults and children.
• Adults should consume 45 - 65 of their total
  calories from carbohydrates.
• Added sugar should represent no more than 25
  of total energy because ? sugar may displace
  nutrient-rich foods from the diet ? deficiencies
  of certain micronutrients.
• Excess sucrose consumption ? dental caries.

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VII. DIETARY PROTEIN

• the protein in food provides essential amino
  acids required for tissue maintenance.
• The essential amino acids cannot be synthesized
  by the body and must be obtained from diet for
  normal body synthesis.
• Essential amino acids are
• Methionine, Threonine, Valine, Isoleucine,
  Phenylalanine, Tryptophan, Leucine, Lysine-
  Histidine.

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• A. Quality of proteins
• The quality of a dietary protein is a measure of
  its ability to provide the essential amino acids
  required for tissue maintenance.
• The Protein Digestibility- Corrected Amino Acid
  Scoring (PDCAAS) is adopted to evaluate protein
  quality.
• PDCAAS is based on
• essential amino acids
• digestibility of the protein.

The highest possible score is 1.00.

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• 1. Proteins from animal sources
• Proteins from animal sources (meat. poultry,
  milk. fish) have a high quality (0.82 1.00)
  because they contain all the essential amino
  acids in proportions similar to those required
  for synthesis of human tissue proteins.
• Gelatin prepared from animal collagen has a low
  biologic value ( 0.08) as a result of
  deficiencies in several essential amino acids.

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• 2. Proteins from plant sources
• Proteins from wheat, corn, rice, and beans have a
  lower quality ( 0.4 ) than animal proteins.
• Proteins from different plant sources may be
  combined in such a way that the result is
  equivalent in nutritional value to animal
  protein.

• Wheat (lysine-deficient but methionine-rich)
  combined with kidney beans (methionine-poor but
  lysine-rich) ? a complete protein of improved
  biologic value.

Eating foods with different limiting A.A. at the
same meal (or at least during the same day) can
result in a dietary combination with a higher
biologic value than either of the component
proteins.
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• B. Nitrogen balance Nitrogen balance
• Amount of nitrogen consumed nitrogen
  excreted in the urine, sweat, and feces.
• Most healthy adults are normally in nitrogen
  balance.

• 1. Positive nitrogen
• balance
• Nitrogen intake ? excretion
• Observed in situations of tissue
• growth
• - Children.
• - Pregnancy.
• - During recovery from an
• emaciating illness.

• 2. Negative nitrogen
• balance
• Nitrogen loss ? intake.
• Associated with inadequate
• dietary protein
• - lack of an essential AA.
• - during physiologic stresses
  
• ( trauma, burns, illness,
• surgery).

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C. Requirement for protein in humans

• The amount of dietary protein required in the
  diet varies with its biologic value
• The greater the proportion of animal protein
  included in the diet, the less protein is
  required.

Normally, RDA Adults 0.8 g/kg (56 g protein
for a 70 kg individual) Athletes 1 g/kg Pregnant
or lactating ? up to 30 g/kg 0.8 g/kg
Children 2 g/kg/day
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• 1. Consumption of excess protein
• No physiologic advantage to the consumption of
  more protein than the RDA.
• Protein consumed in excess of the bodys needs is
  deaminated ? metabolized ? energy or acetyl CoA
  for fatty acid synthesis.
• When excess protein is eliminated from the body
  as urinary nitrogen ? ? urinary calcium ? ? risk
  of nephrolithiasis and osteoporosis.

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• 2. The protein-sparing effect of carbohydrate
• Dietary protein requirement is influenced by the
  carbohydrate content of the diet.
• If carbohydrate intake is less than 130 g/day
  substantial amounts of protein are metabolized ?
  precursors for gluconeogenesis.
• Carbohydrate is considered to be
  protein-sparing because it allows amino acids
  to be used for repair and maintenance of tissue
  protein rather than for gluconeogenesis.

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• D. Protein-calorie malnutrition
• In developed countries, protein-calorie
  malnutrition is seen most frequently in
• Hospital patients with chronic illness,
• Individuals who suffer from major trauma,
• Severe infection,
• Effects of major surgery.
• Such highly catabolic patients frequently require
  intravenous administration of nutrients

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• In developing countries, an inadequate intake of
  protein and/or energy may be observed.
• Affected individuals show a variety of symptoms,
  including
• depressed immune system
• reduced ability to resist infection.
• Death from secondary infection is common.
• Two extreme forms of malnutrition are kwashiorkor
  and marasmus.

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Marasmus Kwashiorkor
Causes Inadequate calories in the presence of adequate protein intake Protein intake less than calories intake
Age under 1 year of age ( when mothers milk is supplemented with native cereals deficient In protein calories) after weaning (about one year of age),
Symptoms Arrested growth Extreme muscle wasting Weakness Anemia N0 edema or changes in plasma proteins Stunted growth Skin lesions depigmented hair Anorexia, Enlarged fatty liver ?? plasma albumin a deceptively plump belly as a result of Edema
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01 Dietary Reference Intakes (DRIs) incorporate more reference standards than Recommended Daily Allowance s (RDAs).
02 Recommended Daily Allowances is the upper tolerable intake level of nutrients.
03 As regards dietary carbohydrates, the AMDR for adults is 45-65 of their total calories intake.
04. Diet induced thermogensis is the energy required to carry out normal body function.
05. The total amount of fat in the diet is more important than the type of the fat.
06. In polyunsaturated fats, trans fatty acids are considered healthier as regards the incidence if coronary heart disease.
07. Consumption of n-3 fatty acids result in increase blood pressure.
08. Food with a high glycemic index tends to create a sense of satiety over a long period of time.
09. Nitrogen balance occurs when the amount of nitrogen consumed is more than the nitrogen excreted.
10. Marasmus occurs when protein deprivation is relatively greater than the reduction in total calories.
 
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End of Nutrition Lectures