NR228 Nutrition
rebcca 1
Chapter_006.pptxChapter 6
Protein
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Define the composition of protein.
Describe how the composition of protein differs from that of carbohydrate and lipids.
Define essential and nonessential amino acids.
Distinguish between complete proteins and incomplete proteins.
Learning Objectives (1 of 2)
Discuss how protein is digested, is absorbed as amino acids, and becomes available to cells.
List functions of protein.
Learning Objectives (2 of 2)
Food protein is the only source of amino acids.
Amino acids are absolutely necessary to make the thousands of proteins that form every aspect of the human body.
Role in Wellness
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Proteins: organic compounds formed from chains of amino acids
Amino acids: compounds containing carbon, hydrogen, oxygen, and nitrogen
All the proteins required by plants and animals: made from 20 amino acids
Essential amino acids (EAAs)
Nonessential amino acids (NEAAs)
Amino acid pool
Structure of Protein (1 of 3)
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Protein composition
Primary, secondary, tertiary, and quaternary structures
Peptide bonds
Denatured proteins: proteins whose structures’ shapes are changed by heat, light, acids, alcohol, or mechanical actions
Structure of Protein (2 of 3)
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Structure of Protein (3 of 3)
Fig. 6.2 Peptide bonds.
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Mouth
Site of only mechanical digestion of protein
Stomach
Stomach mucosa secretes pepsinogen (inactive form of pepsin, gastric protease) and hydrochloric acid (HCL)
Polypeptides result and pass to small intestine
Renin: important for protein digestion during infancy and early childhood
Protein as a Nutrient in the Body: Digestion and Absorption (1 of 3)
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Small intestine
Small intestine and pancreas produce trypsin, chymotrypsin, and carboxypeptidase.
Intestinal amino peptidase and dipeptidase result in hydrolysis to amino acids.
Absorption through intestinal wall by active transport requires vitamin B6.
Protein as a Nutrient in the Body: Digestion and Absorption (2 of 3)
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Summary of Protein Digestion and Absorption
Fig. 6.3 Summary of protein digestion and absorption. HCL, hydrochloric acid. (From Rolin Graphics.)
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Anabolism and catabolism
Most protein functions are the result of anabolism (synthesis) in cells.
Catabolism (breakdown) begins in liver cells through deamination.
Hormonal effects occur.
Deamination
Liver conversion of ammonia to urea; excreted in urine
Metabolism (1 of 3)
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Metabolism (2 of 3)
Fig. 6.4 The body’s equilibrium depends on a balance between the rates of protein breakdown (catabolism) and protein synthesis (anabolism). (Modified from Williams SR: Essentials of nutrition and diet therapy, ed 7, St Louis, 1999, Mosby.)
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Protein excess
Increased deamination
Health effects: increased risk of coronary artery disease, some cancers, and osteoporosis
Metabolism (3 of 3)
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Nitrogen-balance studies: amount of nitrogen entering body in comparison with amount excreted
Nitrogen equilibrium or zero nitrogen balance
Positive and negative nitrogen balance
Nitrogen Balance
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Growth and maintenance
Amino acids for muscle, tissue, bone formation, and cells
Collagen; hair, nails, and skin composed of similar protein substances
Creation of communicators and catalysts
Communicators: hormones
Catalysts: enzymes
Blood clotting: fibrogen
Functions (1 of 3)
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Immune system response
Antibodies
Fluid and electrolyte regulation
Balance among intravascular, intracellular, and interstitial fluids
Acid–base balance
Buffering effect: maintains proper pH level
Functions (2 of 3)
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Transportation
Protein helps transport nutrients and other vital substances.
Protein pumps nutrients in and out of cells.
Lipoproteins carry nutrients in blood.
Protein enables transport of hemoglobin and myoglobin.
Functions (3 of 3)
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Quality of protein foods
Complete versus incomplete proteins
High-quality proteins
Incomplete protein; limiting amino acids
Complementary proteins
Food Sources (1 of 4)
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High-quality protein contains best balance and assortment of EAAs and NEAAs for protein synthesis.
Two highest quality protein foods: eggs and human milk
Incomplete protein lacks one or more EAAs.
Better sources: grains and legumes
Food Sources (2 of 4)
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Measures of food protein quality
Biologic value: determines quality of food protein by measuring amount of nitrogen kept in body after digestion, absorption, and excretion
Amino acid score: measure of amino acid composition of food in comparison with reference protein; based on limiting amino acid
Protein efficiency ratio (PER): measure of quality of food protein by comparing weight gain to protein intake
Food Sources (3 of 4)
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Protein Recommended Dietary Allowance (RDA)
Provides sufficient EAAs and amino groups for NEAA synthesis
Other factors include age, gender, physiologic state, and protein sources
Protein RDA: 0.8 g/kg for adults
(male: 56 g to 63 g; female: 46 g to 50 g)
Acceptable Macronutrient Distribution Range (AMDR): 10% to 35% of energy intake as protein
Food Sources (4 of 4)
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Vegan dietary pattern
No animal-derived foods are consumed.
Lactovegetarian dietary pattern
The only animal-derived foods consumed are dairy products.
Ovo-lacto vegetarian dietary pattern
The only animal-derived foods eaten are dairy products and eggs.
Vegetarianism (1 of 4)
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Benefits of vegetarianism
Health:
Lower intake of total fat, saturated fat, and cholesterol
High amounts of fiber
Reduced risk of obesity, cardiovascular disease, type 2 diabetes mellitus, hypertension, gastrointestinal disorders, and certain cancers
Spiritual: nonharmful to animals; animal rights
Economic/environmental: animal-derived protein involves high production costs and loss of natural resources
Vegetarianism (2 of 4)
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Drawbacks of vegetarianism
Vegan: potential deficiencies
Adequate nutrients except for vitamins D and B12
Potential deficiencies of iron, zinc, and calcium
Effects on social health
MyPlate food patterns for vegetarians
Vegetarianism (3 of 4)
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Contemporary vegetarianism
Semivegetarian patterns evolving to decrease risk of chronic diet-related diseases
Pescetarian pattern: vegetarian food consumption with small amounts of fish
Flexitarian pattern: vegetarian food consumption with occasional meat, chicken
Vegetarianism (4 of 4)
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Restructuring the dinner plate
Deemphasizing protein foods
Deck of cards: size of animal protein portion
Dietary Patterns of Protein
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Malnutrition: imbalanced nutrient intake, energy intake, or both
Protein energy malnutrition
Marasmus
Kwashiorkor
Malnutrition factors
Biologic; social; economic; environmental
Protein and Malnutrition (1 of 2)
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Populations at risk in North America
Homeless individuals living in shelters or other temporary sites
Older adults
Hospitalized patients: iatrogenic malnutrition
Chronic hunger: working poor, whose incomes barely cover basic expenses of housing, utilities, and health care and leave little for food purchases
Protein and Malnutrition (2 of 2)
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Chaining: linking together two behaviors
If two actions consistently occur together, they often become linked or tied to each other, becoming one behavior or habit.
Chaining has applications in improving nutrition and wellness.
Toward a Positive Nutrition Lifestyle: Chaining
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