Roles of Proteins Building material –Growth Collagen –E.g. bone or tooth »Collagen matrix »Calcium crystals are deposited –Ligaments and tendons –Glue holding cells together –Maintenance Proteins needed for new cells (skin cells replaced every 30 days) New proteins for growing hair and nails Muscle cells after exercise Copyright 2005 Wadsworth Group, a division of Thomson Learning

Roles of Proteins Enzymes –Catalysts –Allow a reaction to happen without being affected themselves Copyright 2005 Wadsworth Group, a division of Thomson Learning

Roles of Proteins Hormones –Signalling mechanism in the body Copyright 2005 Wadsworth Group, a division of Thomson Learning

Roles of Proteins Regulation of fluid balance –Edema –Proteins absorb water –If proteins accumulate in the area around cells, they attract water causing edema –Edema may be caused by Copyright 2005 Wadsworth Group, a division of Thomson Learning

Roles of Proteins Acid-base regulation –Proteins act as buffers A buffer is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. An acid is any molecule that can provide a H+ ion and a base is any molecule that can receive a H+ ion Proteins act as buffers because they tend to have both capabilities –Acidosis, Alkalosis Rare Extreme cases of too much acid or base in the blood Can cause coma or death Copyright 2005 Wadsworth Group, a division of Thomson Learning

Transport Proteins

Roles of Proteins Immunity –Antigens Proteins, carbohydrates etc on the surface of invading organisms like bacteria and viruses –Antibodies Proteins generated by the white blood cells that can specifically recognize each and every antigen Helps in killing the pathogen Basis of effectiveness of vaccines Copyright 2005 Wadsworth Group, a division of Thomson Learning

Roles of Proteins Source of energy –If there is no other source of glucose, proteins will be broken down to provide glucose to the brain –This is why fat and carbohydrate in the diet protect the protein from your body being used up Other roles –Structural function –Blood clotting –Vision –Wound healing Copyright 2005 Wadsworth Group, a division of Thomson Learning

Protein Metabolism Nitrogen balance –Positive nitrogen balance More protein synthesized than degraded Pregnant women, infants etc –Negative nitrogen balance More protein degraded than produced Burn victims, starving people etc Copyright 2005 Wadsworth Group, a division of Thomson Learning

Protein Metabolism Protein turnover –Amino acid pool The pool of amino acids in the body –Using amino acids to make proteins –Using amino acids to make nonessential amino acids If there is shortage of nonessential amino acids, proteins will be broken down to obtain essential amino acids –Using amino acids to make other compounds Neurotransmitters –Using amino acids for energy and glucose Deamination –Removing Nitrogen –Generates ammonia ---  Urea which is excreted by the kidneys –Using amino acids to make fat When there is excess protein – so even lean protein in excess can lead to weight gain Copyright 2005 Wadsworth Group, a division of Thomson Learning

Protein Quality High-quality proteins Digestibility –Animal vs. plant Amino acid composition –Limiting amino acid Copyright 2005 Wadsworth Group, a division of Thomson Learning

Protein Quality Reference protein –Protein source that can support health of preschool children –Rapid growth rate at that age Complementary proteins –Proteins that provide all essential amino acids in combination Copyright 2005 Wadsworth Group, a division of Thomson Learning

Protein Quality PDCAAS –Protein digestibility- corrected amino acid score –Compares amino acids composition to human requirements and accounts for digestibility Copyright 2005 Wadsworth Group, a division of Thomson Learning

Food Labels Quantity of protein –Infants -14g –Children under age four – 16g –Older children and adults – 50g –Pregnant women – 60g –Lactating women – 65g Daily Value –50 g protein 10% of a 2000 kcal diet So if you are on a lower calorie diet this amount would be a little less Also the quality of the protein needs to be considered Copyright 2005 Wadsworth Group, a division of Thomson Learning

Recommended Intakes RDA –0.8 g/kg/day –10% - 35% of energy intake Copyright 2005 Wadsworth Group, a division of Thomson Learning

When there is not enough protein – extreme cases Protein-Energy Malnutrition (PEM) Not enough protein, energy or both Adult PEM –Among drug abusers (alcohol and other drugs) –AIDS or tuberculosis patients (hospital stays) –Anorexia nervosa patients Biggest effect on children Acute PEM –Short term starvation –Children are thin for their height Chronic PEM –Long term starvation –Children are short for their age –Seen among poor people in the world whether in Africa, Southeast Asia or the urban poor in the US. Copyright 2005 Wadsworth Group, a division of Thomson Learning

Protein-Energy Malnutrition (PEM) Marasmus –“dying away” Kwashiorkor –“the evil spirit that infects the first child when the second child is born” Marasmus-kwashiorkor mix Copyright 2005 Wadsworth Group, a division of Thomson Learning

Protein-Energy Malnutrition (PEM) Infections –Antibodies are broken down to provide amino acids for other uses –So the body is unable to ward of infections –Dysentery (diarrhea) makes it worse since you lose nutrient PEM can lead to heart failure and death Rehabilitation –Treat diarrhea with fluids –Slowly introduce proteins and other appropriate nutrients (as digestion improves) Copyright 2005 Wadsworth Group, a division of Thomson Learning

Protein-Energy Malnutrition (PEM) The Sad Truth Ending PEM is not a medical problem It is a sociological and political problem Copyright 2005 Wadsworth Group, a division of Thomson Learning

When there is not enough protein – mild cases Vegetarians/Vegans –It is possible to be a vegetarian and get enough protein –Not enough good quality protein unless careful about including multiple vegetarian protein sources –Ovo-lactovegetarians and lactovegetarians may be fine –Vegans have the biggest problem

Vegetarian Diets Copyright 2005 Wadsworth Group, a division of Thomson Learning

When there is too much protein Heart disease –High protein animal foods are also high in fat (esp. saturated fat) –Substitute soy and other plant proteins –Elevated homocysteine levels in the blood are associated with heart disease (homocysteine is an amino acid) Cancer Adult bone loss –osteoporosis Copyright 2005 Wadsworth Group, a division of Thomson Learning

Health Effects Weight control Kidney disease Copyright 2005 Wadsworth Group, a division of Thomson Learning

Recommended Intakes Adequate intake Protein in abundance Copyright 2005 Wadsworth Group, a division of Thomson Learning

Supplements Protein supplements Amino acid supplements Copyright 2005 Wadsworth Group, a division of Thomson Learning

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Vegetarian Diets Health benefits Copyright 2005 Wadsworth Group, a division of Thomson Learning

Vegetarian Diets Diet planning –Protein Lacto-ovo-vegetarians Meat replacements –Texturized vegetable protein Copyright 2005 Wadsworth Group, a division of Thomson Learning

Vegetarian Diets Vitamins and minerals –Lactovegetarians –Vegans Copyright 2005 Wadsworth Group, a division of Thomson Learning

Vegetarian Diets Omega-3 fatty acids Copyright 2005 Wadsworth Group, a division of Thomson Learning

Vegetarian Diets Vegetarian diets through the life span –Pregnancy and lactation –Infancy –Childhood and adolescence Copyright 2005 Wadsworth Group, a division of Thomson Learning

Vegetarian Diets Healthy food choices –Macrobiotic diets Copyright 2005 Wadsworth Group, a division of Thomson Learning