Proteins are made up of amino acids and perform many essential functions in the body. They are needed for growth, maintenance, as enzymes, hormones, and for fluid balance regulation. There are 20 amino acids, 9 of which the body cannot synthesize and must obtain through diet. High quality proteins come from animal sources like meat and dairy, while plant proteins may be limiting in some amino acids. Recommended daily protein intake is 0.8 grams per kilogram of body weight.

1. Protein Charles Lohman

2. Amino Acids Amino Acids Side groups of amino acids vary from one amino acid to the next These differing side groups are what make proteins more complex than either carbohydrates or lipids (fats) Proteins are made up of 20 different amino acids , each with a different side group Nonessential amino Acids Amino acids the body can synthesize Consist of more than half of the 20

3. Amino Acids Essential Amino Acids Amino acids the body CANNOT synthesize There are 9 of them Conditionally Essential Amino Acids When a nonessential amino acid becomes essential under special circumstances Such as with the disease phenylkentonuria when the body is unable to make the conversion of phenylalanine to tyrosine. So tyrosine becomes a conditionally essential amino acid

4. Roles of Protein Growth and Maintenance Proteins form the building blocks of muscles, blood, and skin from the time of conception Collagen is a protein that provides the material for bones, teeth, ligaments, and tendons. Collagen is also the strengthening glue between the cells of the artery walls that enables the arteries to withstand the pressure of the blood surging through them with each heartbeat Proteins are also needed for replacing dead or damaged cells

5. Roles of Protein Enzymes Some proteins act as enzymes Enzymes not only break down substances, but they also build substances such as bone, and transform one substance into another Enzymes themselves are not altered by the reactions they facilitate, but act as catalysts, permitting reactions to occur more quickly and efficiently

6. Roles of Proteins Hormones Some hormones are proteins , regulating a variety of actions in the body For example insulin stimulates the transport proteins of the muscles and the adipose tissue to pump glucose into the cells faster than it can leak out Fluid balance Disruption of fluid balance can cause edema Edema is when there are excessive amounts of interstitial fluid (spaces between the cells) Edema can be caused by excessive protein loss caused by kidney disease or large wounds, inadequate protein synthesis caused by liver disease inadequate dietary intake of protein

7. Roles of Proteins As Acid base Regulators Proteins help to maintain the balance between acids and bases within the body fluids The body’s acid base balance is tightly controlled The extremes of acidosis and alkalosis leads to coma and death because they denature (disturbing the shape of the protein) working proteins As Transporters Some proteins move about the body fluids, carrying nutrients and other molecules The protein hemoglobin carries oxygen from the lungs to the cells Lipoproteins transport lipids Some transport proteins carry vitamins and minerals

8. Roles of Proteins As Antibodies Antibodies are large proteins of the blood and body fluids, produced by the immune system in response to the invasion of a body by foreign molecules As a Source of Energy and Glucose During times of starvation or insufficient carbohydrate intake, protein will be sacrificed tom provide energy and glucose The body will break down its tissue proteins to make amino acids available for energy and glucose production Protein can therefore maintain blood glucose levels, but at the expense of losing lean body tissue

9. Protein Quality Digestibility Proteins must be digested before they can provide amino acids This depends on such factors as the proteins source and other foods eaten with it Digestibility of animal proteins is about 90 to 99 percent Digestibility of plant proteins is about 70 to 90 percent Digestibility of soy and legumes is over 90 percent digestibility High Quality proteins Foods derived from animals (meat, fish, poultry, cheese, eggs, yogurt, and milk) provide high quality protein Soy is also considered a high quality protein Plant proteins (vegetables, nuts, seeds, grains, and legumes) tend to be limiting in one or more essential amino acids A limiting amino acid is an amino acid in less than the amount needed to support protein synthesis

10. Protein Quality Complementary Proteins Two or more dietary proteins whose amino acid assortments complement each other in such a way that the essential amino acids missing from one are supplied by the other When used by vegetarians it can help them receive all the amino acids needed over the course of a day by eating a variety of whole grains, legumes, seeds, nuts, and vegetables

11. Health Effects and Recommended Intakes of Protein Protein Energy Malnutrition (PEM) A deficiency of protein, energy, or both PEM can be classified in two forms, marasmus, and kwashiorkor which differ in their clinical features Marasmus means “dying away” and reflects a severe deprivation of food over a long period of time Occurs commonly in children from 6 to 18 months in all overpopulated and impoverished areas of the world Physically characterized as skin and bones

12. Health Effects and Recommended Intakes of Protein Kwashiorkor Sudden and recent deprivation of food Usually develops rapidly as a result of protein deficiency or, more commonly, is precipitated by an illness such as measles or another infection Some muscle wasting may occur Proteins and hormones that previously maintained fluid balance diminish, and fluid leaks into the interstitial spaces Child’s limbs and abdomen become swollen with edema which is a distinguishing feature of the disease

13. Health Effects of Protein Heart Disease A high protein diet may contribute to the progression of heart disease There is a correlation between animal protein intake and heart disease Substituting vegetable protein for animal protein improves blood lipids and decreases heart disease mortality Cancer Population studies suggest a correlation between high intakes of animal proteins and some types of cancers notably, cancer of the colon, breast, kidneys, pancreas, and prostate Adult Bone Loss When protein intake is high, calcium excretion increases. Whether excess protein depletes the bones of their chief mineral depends upon the ratio of calcium intake to protein intake Some research suggests that animal protein may be more detrimental to calcium metabolism and bone health than vegetable protein However excess protein whether from animal or vegetable sources increase calcium excretion

14. Health Effects of Protein Weight Control Dietary protein may play a role in increasing body weight Protein rich foods are often fat rich foods that contribute to weight gain with accompanying health risks Weight loss gimmicks that encourage a high protein, low carbohydrate diet may be temporarily effective Diets that provide adequate protein, moderate fat, and sufficient energy from carbohydrates can better support weight loss by providing satiety Kidney Disease High protein intake increases the work of the kidneys, BUT does not appear to diminish kidney function or cause kidney disease Restricting dietary protein, however, may help to slow the progression of kidney disease and limit the formation of kidney stones in people who have these conditions

15. Recommended Intakes of Protein Protein RDA Food protein is the only source of the essential amino acids and second it is the only practical source of nitrogen Protein RDA for adults is 0.8 (10% to 35% of energy intake) grams per kilogram of healthy body weight per day For infants and children, the RDA is slightly higher For teens 14 to 18, RDA is 0.85g/kg/day

16. Protein Supplements Protein Powders Body builds muscle from amino acids so many athletes take protein powders with the false hope of stimulating muscle growth Muscle work builds muscle; protein supplements do not, and athletes do not need them They do not improve athletic performance Protein powders can supply amino acids to the body, but nature’s protein sources – lean meat, milk, eggs, and legumes – supply all these amino acids and more Remember excess protein will just get stored as FAT