Proteins

1. Proteins The Body’s Building Blocks

2. Question • Which of the food groups from the Food Pyramid provide the most protein in a diet? • Answer: The meat/beans group and the milk products group

3. Familiar Protein Sources

4. Other Protein Sources

5. What Is Protein? • It is an energy-yielding nutrient composed of carbon, hydrogen, oxygen, and nitrogen • The presence of nitrogen is what makes it differ from carbohydrates and fats • Proteins are made up of amino acids • The body has at least 30,000 types of proteins; each type does a different job

6. Amino Acids • The building blocks of protein • Most proteins are made up of different patterns and combinations of 20 amino acids, which are linked in strands • The 20 amino acids are like letters in the alphabet – just as you use different letter combinations in different sequences to make different words, you combine different amino acids in different sequences to make different proteins

7. Amino Acid Structure

8. How do amino acids combine to make proteins? • Every cell contains DNA; this DNA provides the instructions for how the amino acids will be linked to form the proteins in your body • In this way, your body can take amino acids from the breakdown of foods that you eat and make the required proteins to perform required body functions, such as tissue and cell repair, disease fighting, growth and development, etc.

9. Analogies • DNA is to proteins, as ____ is to a model airplane kit • Amino acids are to proteins, as ____ are to the alphabet

10. Shape Changers • Proteins can change their shape and take on new characteristics • This is called denaturation • Heat, acids, bases, and alcohol are among the factors that can denature proteins • E.g. : Frying an egg – applying heat to an egg changes it from a runny fluid to a solid mass • The shapes of the protein molecules in the egg have changed • Once a protein is denatured, it can never return to it’s original state

11. Types of Amino Acids • You need all 20 amino acids for good health • Your body can synthesize 11 of the amino acids from other amino acids • The amino acids your body can make are called nonessential amino acids • The remaining 9 amino acids that your body can’t make are called essential amino acids

12. Question • What is the difference between essential amino acids and nonessential amino acids? • Answer: Your body can make nonessential amino acids, while it has to obtain essential amino acids from foods

13. Protein in the Body • Bite, chew, swallow • Stomach acids denature the protein • Move to the small intestine, where they are broken down by enzymes into single amino acids • Amino acids are absorbed into the bloodstream, and are carried to the body cells that need them

14. Functions of Proteins • Your cells can use amino acids from food proteins to build new proteins • Cells can also convert amino acids to other compounds, including other amino acids • The proteins built by cells are custom designed to perform a wide range of functions • The roles proteins play depend on where they are located and how your body needs them • Proteins have 6 main functions

15. 1. Build and Maintain Tissues • As your body grows, it uses protein to help make new tissue, which is why it is important for people to get enough protein during the growth years • When you eat a nutritious diet, your body uses protein to build lean muscle mass • Protein makes up about 18-20% of the body • About 3% of this protein is broken down each day • You also need protein to maintain existing tissue

16. 2. Make Important Compounds • Your body uses proteins to make enzymes, which cause specific chemical reactions in the body (e.g. digestive enzymes for food breakdown) • Proteins are used to make some hormones, which are released in the bloodstream to control specific body processes • Your body’s immune system uses proteins to make antibodies, which defend the body against infection and disease

17. 3. Regulate Fluid and Mineral Balance • Proteins help carry the minerals sodium and potassium from one side of cell walls to another • These minerals and other proteins control the flow of water through cell membranes • A balance of fluid inside and outside the cell is crucial

18. 4. Maintain Acid-Base Balance • Acid-base balance refers to the maintenance of the correct level of acidity of a body fluid • If blood becomes too acidic, it can be life-threatening • Proteins in the blood act as chemical buffers • A buffer is a compound that can counteract an excess of acid or base in a fluid

19. 5. Carry Vital Substances • Proteins linked with fat form lipoproteins, which are the compounds used to carry fats in the bloodstream • Proteins also transport iron and other nutrients • Oxygen transport in the blood is reliant upon protein as well

20. 6. Provide Energy • The body’s number one priority is to provide the cells with the energy they need to exist • Even though only proteins can perform cell growth and repair, the body will use proteins for energy when it lacks carbs and fats • The body will also burn proteins for energy when there is excess protein taken in; this is hard on the liver and kidneys • * A Billboard For Proteins

21. Animal Sources of Protein • Animal flesh – Beef, pork, poultry, lamb, veal, and fish • Other sources – Eggs, milk, yogurt, cheese, and ice cream • Meat and some dairy are problematic due to high fat content • Most of the fat is saturated • No fiber is obtained from these foods • The cost of protein from animal sources can be high

22. Plant Sources of Protein • Found in grains, nuts, seeds, and legumes • Legumes are peanuts, black-eye peas, kidney beans, black beans, chickpeas, etc. • Soy beans are a large source of plant protein • They are a legume • They can be modified to form a variety of food products, such as tofu and soy burgers

23. Vegetarianism • The practice of eating a diet consisting entirely or largely of plant foods • Beneficial to health in that most of the fat in plant foods are polyunsaturated, plants foods contain no cholesterol, and these foods are generally high in fiber • The eating patterns of vegetarians vary greatly; there are four main types

24. Types of Vegetarians • 1. Vegans – eat no food from animal sources; their diet is limited to plant foods • 2. Lacto-vegetarians – eat animal protein in the form of dairy products, but no meats, fish, poultry, or eggs • 3. Lacto-ovo vegetarians – eat animal protein in the form of dairy and eggs, but no meats, fish, or poultry • 4. Semivegetarians – eat dairy, eggs, poultry, and seafood, but no red meat

25. Reasons for Vegetarianism • Religious reasons – Buddhists, Hindus, Seventh-Day Adventists, Trappist monks • Health reasons – avoid fat and cholesterol, hormones and chemicals, and foodborne illnesses • Socioeconomic reasons – eating meat is wasteful • Environmental reasons – animal grazing is hard on the land • Humanitarian reasons – can’t stand the idea of eating Bambi, Flipper, Chicken Little, etc.

26. Protein Quality • Proteins in different foods differ in quality • Plant foods provide lower quality proteins and are sources of incomplete proteins • These proteins are missing one or more of the essential amino acids • Animal foods have high quality proteins and are sources of complete proteins • Means that all the essential amino acids humans need are present in the proteins • Animal products such as eggs, cheese, milk and yogurt are also complete proteins

27. Incomplete Vs. Complete Proteins • Your body needs the right balance of all 20 amino acids to build tissues and other compounds • If one or more essential amino acids is missing your cells will not be able to make needed proteins • Have to find a way to complete the incomplete proteins • *Animal Vs. Plant Protein

28. Complementary Proteins • You can get the amino acids missing from one incomplete source by combining it with another incomplete source • Two or more incomplete proteins which can be combined to provide all the essential amino acids are called complementary proteins • In general, combining grains, nuts, or seeds with legumes will give you complementary proteins (e.g. peanut butter and whole wheat bread) • Can also get a complete protein when eating a small amount of a complete protein with a large amount of an incomplete protein (e.g. pork with rice) • * A Good Match

29. How Much Protein Do You Need? • Your body does not store protein, so you need some every day • The amount depends upon your age, gender, body size, and health • Children and teens need more • Pregnant and nursing women need more • Teenage boys and men need more • Sick and injured people need more • Why do the above groups need more?

30. Protein Needs • Children need more protein due to rapid growth • Pregnant women need more protein for fetal development • Nursing mothers need more to make milk • Males need more due to a higher amount of muscle mass • People who are sick need more in order to make antibodies • People who are injured need more to repair damaged tissue

31. RDA for Protein • 14-18 year old males – 52 grams per day • 14-18 year old females – 46 grams per day • To meet the RDA, 10-35% of daily calories should come from protein (do the math)

32. Do Athletes Need More Protein? • Well-trained athletes do need a little more protein per day • An extra half a glass of milk or a chicken wing will provide the extra that athletes need • Remember – an athlete’s primary need is for energy • Athletes should focus on the high end of the calorie range for carbs (~55-65%) and the low end of the range for fats (~20-25%) • That leaves 10-25% of an athletes calories for protein

33. Protein Supplements? • So much of what is out there is unproven • Not enough research at this point, so long term effects are still largely unknown • (transparency)

34. The Risks of Too Little or Too Much Protein • As with all nutrients, moderation is key • Nitrogen balance is a comparison of the nitrogen a person consumes with the nitrogen they excrete • Protein is the only nutrient that provides nitrogen, so nitrogen balance is used to evaluate a person’s protein status • Nitrogen equilibrium – take in as much as you excrete (e.g. healthy adult) • Positive nitrogen balance – take in more than you excrete (e.g. when you are growing tissue, such as a child or a pregnant woman) • Negative nitrogen balance – take in less than you excrete (e.g. losing body tissue due to starvation) • * Protein Balance

35. Protein Deficiency • Deficiency diseases develop when you lack an essential nutrient • Common among people fighting poverty • Protein-energy malnutrition (PEM) – condition caused by a lack of calories and protein in the diet • Kwashiorkor – protein-deficiency disease; common in poor countries when a mother weans one child to feed the next; characterized by stunted growth and immune system weaknesses • Marasmus – calorie and protein – deficiency disease; most often affects infants in poor countries; characterized by wasting away of the body and infant mortality

36. Excess Proteins • Most people in the U.S. consume too much protein • Leads to: • Liver and kidney problems – excess proteins must be excreted as nitrogen; overworks the liver and kidneys, causing them to age prematurely • Calcium loss – diets high in protein from animal sources contribute to calcium loss from the bones, leading to fractures, osteoporosis, etc. • Excess body fat – many high-protein foods are also high-fat foods; since the body cannot store excess protein, it converts it to fat and stores it in the adipose tissue, leading to weight gain • * Not Too Little, Not Too Much

37. 4 ounces extra-lean ground beef patty 290 calories 112 mg cholesterol High in saturated fat 0 g fiber 44% protein 56% fat 0% carbohydrates ½ cup pinto beans 116 calories 0 mg cholesterol Low in saturated fat 7 g fiber 24% protein 1% fat 75% carbohydrates Comparing Protein Sources

38. Review Questions • What is the difference between an essential and a nonessential amino acid? • What role do stomach acids play in protein digestion? • How can a diet low in carbohydrates and fats affect the way the body uses proteins? • Name three specific animal sources and three specific plant sources of protein.

39. Review Questions • About what percentage of daily calories should come from protein? • What type of nitrogen balance would describe the protein status of a healthy teen? • What are the 3 problems associated with high-protein diets?