What do proteins do?Build new tissueFunctional unit (a few to thousands amino acids)EnzymesHormonesAntibodiesPhysiology/metabolismFluid and electrolyte balanceAcid-base balanceEnergyTransportationBlood clottingHow much protein do we need?The dietary Reference Intakes recommendation for protein intake depends on size and stage of growthDRI recommended intake is .8 grams per kilogram of body weightMinimum is 10 percent of total caloriesAthletes may need slightly more (1.0 gram per kg)Classification of Amino AcidsEssential AA’sPhenylaline, valine, tryptophan, threonine, isoleucine, methionine, histidine, leucine, lysineOther AA’sAlanine, arginine, aspagarnine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine, selenocysteineProtein StructureThe amine group links with the acidic end of the next amino acidAA with electrically charged side chains are attracted to H2OAA with neutral side chains are repelled by water- seek each otherConsequently, proteins have very convoluted shapesPeptide BondsValine, Leucine, Tyrosine are single amino acids with different side chainsThey can bond to form a strand of amino acids, part of a proteinHemoglobinQuaternaryA heme structure holds the ironProtein DenaturationProtein structure and function are disrupted by a variety of things.Heat, acid, alcohol, base, saltsAmino Acid MetabolismCarried to the liverUsed by the liver or released into the blood to be taken up by other cellsCells can then use the amino acids toMake their proteins for their own useMake proteins that are released into the lymph or blood for other usesWhen necessary, body cells can use amino acids for energyProtein deficienciesMarasmus- chronic inadequate food intakeInadequate energy, vitamin, mineral, and protein intakePerson is shriveled and lean all overKwashiorkorSwollen belly and skin rash are presentSevere acute malnutritionToo little protein to support body functionsMalnutrition in the United StatesPEM is not unknown in the US, where millions live on the edge of hunger.Inner cities, US indian reservations, rural areas, some elderly people, hungry and homeless children, people suffering from anorexia nervosa, people with AIDs or cancerProtein QualityIf a diet does not contain the essential amino acids in adequate quantities, protein synthesis in the body can be slowed.A food that contains all nine essential amino acids is called a complete proteinMost plant foods do not contain all 9 essential amino acidsLegumes are the exception, notably soybeansThis may have implications for vegetariansComplimentary ProteinsTwo or more proteins whose amino acid assortments complement each other in such a way that the essential amino acids missing from one are supplied by the otherProtein QualityProbably not an issue in countries where overall dietary intake is adequateIf it is an issue its only for vegansMore of an issue in countries where dietary sources of protein are limitedBenefits of Vegetarian DietStrong evidence links vegetarian diets with reduced incidences of chronic diseasesSome benefits includeLess obesityDefense against certain cancersLess heart diseaseLess high blood pressureMay help prevent diabetes, osteoporosis, diverticular disease, gallstones, and rheumatoid arthritisAre vegetarian diets healthier?Some of these effects may arise more from what vegetarians include in the diet- abundant fruit, legumes, veggies, and whole grains – than from what they emitA balanced, adequate diet in which lean meats and seafood, eggs, and milk play a part in addition to fruits, vegetables, and whole grains can be very healthyBoth meat eaters and lacto-ovo vegetarians can rely on their diets during critical times of lifeA vegan diet can pose challengesMeat provides abundant iron, znc, and vitamin b needed by everyone, but in particular by pregnant women, children, and adolescentsBoth vegetarian and meat containing diets, if not properly balanced, can lack nutrientsPoorly planned meat eater’s diets may lack vitamin A, vitamin C, foliate, and fiber among othersPoorly planned vegetarian diets typically lack iron, zinc, calcium, omega-3 fatty acids, vitamin D, and vitamin BAre vegetarian diets more environmentally friendly?Meat industry responsible for more greenhouse gas emissions than the transportation industryRaising livestock also leads to land and water degradation due to overgrazing, waste products in the environmentGrowing corn for feed contributes to monoculture, less land to grow fruits/ vegetablesMeat raised locally and/or organically will have lower impact on the environmentCows fed grass have lower impact on the environment and the nutritional content of the meat is more favorable for humans (expensive)What about fruits and veggies grown far away and transported? Is this better than meat raised locally?Protein excessDiets high in protein-rich foodsOften associated with obesity and its many accompanying health risksAnimal protein sources in particular can be high in saturated fatA known contributor to atherosclerosis and heart diseaseThe effect of animal protein itself on heart health is uncertainSubstituting plant protein for animal protein improves indicators of heart disease riskAnimals fed experimentally high protein diets often develop enlarged kidneys or liversIn humans- a high protein diet worsens existing kidney problems and may accelerate a decline in only mildly impaired kidneysOne of the most effective treatments for people with established kidney problems is to reduce protein intakes to slow the progression of their disease.Peotein of high biological valueProtein excessProtein intake and calciumEvidence is mixed about whether high intakes of protein from animal sources, especially when accompanied by very low calcium and low fruit and vegetable intakes, can accelerate adult bone loss.No doubt exists that feeding purified protein to human subjects causes calcium to be spilled from the urine.Diets high in protein, particularly animal protein, correlate with a higher incidence of hip fractures in some populationsHowever, the reverse may be true in malnourished elderly individuals in whom protein deficiency and hip fracture often occur together.Restoring dietary protein and giving certain calcium and vitamin D supplements can improve bone statusHigh protein dietsForces body to use proteins for energyTissue proteins and dietary proteinsLimit overall food intakeNot a healthy long term dietPotential short term side effectsMuch research
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