ProteinsPatty Maloney MSN/Ed

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Chapter 6

Proteins

• Proteins-organic compounds formed by linking many smaller molecules of amino acids.

• Amino acids-organic compounds made of carbon, hydrogen, and oxygen.

• Protein in food is our only source of amino acids, which are necessary for every aspect of human life.

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Amino Acids: Building Blocks

• Each protein is composed of hundreds of amino acids• When protein foods are eaten, proteins are broken down

into amino acids• Amino acids are reassembled in the body to form a

variety of proteins

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Functions of Proteins

• Growth & Maintenance ; replacement of cells.• Creation of Communicators and Catalysts;

hormones, blood clotting.• Immune System Response; defense system.• Fluid & Electrolyte Regulation• Acid-Base Balance.• Transportation of Nutrients

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• The protein in foods are categorized by the essential amino acids they contain.

• Complete protein-contains all nine essential amino acids to support growth and maintenance.

• Sources-animal-derived foods, including meat, poultry, fish, eggs, and dairy products.

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Protein Foods

Protein

• Incomplete Proteins-lack one or more of the nine essential amino acids.

• Does not supply sufficient amount of amino acids to support life.

• Plant foods are incomplete sources, grains and legumes are better sources.

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Classes of Amino Acids

• Essential amino acids – 9 (lycine)• Body cannot manufacture, must come from diet

• Conditionally essential amino acids – 5 (cysteine)• Body can synthesize from indispensable, do not have to come from

diet (may be lacking in disease process).

• Nonessential amino acids – 6 (alanine)• Normally synthesized but some health conditions may require

dietary intake (Table 5-2).7

A Healthy Balance• Protein balance

• Catabolism: breakdown of proteins • Anabolism: resynthesis of proteins

• Nitrogen balance (intake = excretion)• Nitrogen equilibrium (ideal)• Positive nitrogen balance: body stores more protein than

it excretes (ie, growth, preg, lact)• Negative nitrogen balance: body takes in less protein

than it excretes (ie, malnutrition, illness)

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Food Source of Proteins

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Food Sources of Protein• Complete proteins – contain all 9 essential amino acids

• Meat, fish, eggs, seafood (animal)• Soy (plant)

• Incomplete proteins (lack one or more essential amino acids).

• Plant-origin foods• Grains• Legumes (peas, beans, peanuts, lentils)• Nuts• Seeds• Fruits and vegetables

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Vegetarian Diets

• Approx. 3-5% of population• Reasons = religious beliefs (buddhism, hinduism,

7th day Adventist), animal cruelty concerns, environmental concerns, aversion to animal products

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Vegetarian Categories

• Vegan-includes all plant foods, grains, legumes, fruits, vegetables, seeds and nuts. Excludes all animal-derived foods.

• Lacto-vegetarian-includes all plant foods plus dairy products, (milk, cheese, yogurt, and butter). Excludes animal meat, (meat, fowl, fish, and eggs).

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Vegetarian Diets

• Ovo-lacto vegetarian-includes all plant foods, dairy products, and eggs. Excludes animal meat.

• Pescetarian-includes all plant foods, dairy products, eggs and fish. Excludes meat and fowl.

• Flexitarian-includes all plant foods, dairy, and eggs, with occasional consumption of meat, fowl, or fish. No exclusions, but minimal consumption of animal meat.

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Digestion of Proteins• Mouth – mechanical digestion, chewing• Stomach: enzymes to breakdown protein into amino acids

• Pepsin **• Hydrochloric acid

• Small intestine• Pancreatic secretions aid digestion

• Trypsin, chymotrypsin, carboxypeptidase

• Intestinal secretions• Aminopeptidase, dipeptidase

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Summary of Protein Digestion

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Body Needs for Protein

• Tissue growth* more protein needed during growth periods

* fetus, infant, children, adolescents

• Additional needs caused by illness* More protein needed during illness (fever, traumatic

injury, burns, surgery)

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Dietary Deficiency

• Kwashiorkor• Protein energy malnutrition• Occurs after child is weaned from breast feeding• Not enough protein to support growth• Clinically the child looks chubby, especially in

abdomen (fluid retention)• Endemic in areas where diet lacks protein

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Kwashiorkor

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Marasmus

• Protein Energy Malnutrition• Too few calories and insufficient protein• Person appears to be wasting away• Commonly seen in developing countries• Seen in debilitating diseases such as cancer or

AIDS

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Marasmus

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Dietary Guides

• Recommended Dietary Allowances (RDAs)• Relate to age, sex, weight• Highest at birth and slowly decline into adulthood• Men and women: 0.8 g/kg of desirable weight

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Dietary Guides

• First, convert lb. to kg.• 200 lb divided by 2.2 • 90.9 kg (round to 91 kg)

• Convert your body weight (lb.) to kg

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Calculating Protein Needs

• Calculation:• Recommended protein intake = 0.8 g/kg• 1 kg = 2.2 lb.

• Calculate: 220 lb. man• 220 divided by 2.2 = 100 kg• 100 kg multiplied by 0.8 g = 80 g protein

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Calculating Protein Needs

• Calculation:• Your body weight = _______ lb.

______ lb. divided by 2.2 = ______ kg

______ kg. multiplied by 0.8 = _______

** this equals # protein grams per day recommended for you

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Dietary Guides, cont’d

• Dietary Reference Intakes (DRIs) from National Academy of Sciences

• 10% to 35% of total caloric intake from protein (children and adults)

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Summary

• Protein provides the body with its primary tissue-building units, amino acids

• 20 common amino acids• Nine of the 20 amino acids are essential in the diet• Body can manufacture the remaining 11 amino acids• Complete proteins are foods that supply all the

indispensable amino acids

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Summary, cont’d

• Complete proteins are usually of animal origin• Plant foods are considered incomplete proteins because

they lack one or more of the indispensable amino acids (with the exception of soy)

• Vegetarian diets can be strict with only plant proteins (vegan), whereas other variations include dairy, egg, and sometimes fish

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Summary, cont’d

• Clinical influences on protein include fever, disease, surgery, or other trauma to the body

• Protein needs are calculated based on RDA standards related to age, sex, and weight, which for both men and women is set at 0.8 g of high quality protein per kilogram of body weight per day

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Summary, cont’d

• Adjustments for protein intake are required for infants and pregnant and breastfeeding women

• Adjustments also may be necessary for individuals following a vegan diet

• Adjustments are made for critical illness

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