EPHE 155 Spring 2025 Lec6 Macronutrients Protein Slides PDF

EPHE 155 Introduction to Nutrition: Concepts & Controversies Macronutrients Protein University of Victoria, School of Exercise Science, Physical and Health Education Dr.Kimberly McQueen, BSc ND Email: [email protected] Learning Goals ❏...

EPHE 155 Introduction to Nutrition: Concepts & Controversies Macronutrients Protein University of Victoria, School of Exercise Science, Physical and Health Education Dr.Kimberly McQueen, BSc ND Email: [email protected] Learning Goals ❏ Types and Sources: ❏ Differentiate between essential, nonessential, and conditionally essential amino acids. ❏ Identify foods that provide high-quality protein, including animal and plant sources. ❏ Role in the Body: ❏ Explain the functions of proteins, including tissue repair, enzyme production, immune defense, and hormone regulation. ❏ Digestion and Absorption: ❏ Describe how proteins are broken down into amino acids during digestion. ❏ Explain the absorption of amino acids in the small intestine and their transport to the liver and other tissues. ❏ Protein Quality and Needs: ❏ Discuss protein quality, nitrogen balance, and how protein needs vary based on factors like age, activity level, and health status. ❏ Health and Dietary Patterns: ❏ Summarize the health benefits and potential challenges of vegetarian diets and their impact on protein intake. Food Sources of Proteins The structure of Protein  * Use the mnemonic or another one to know which AA are in each category. PVT TIM HaLL was the one I was taught for the 9 EAA. The 20 Amino Acids (AA) Essential AA (AKA Indispensable): = the body cannot synthesize it at all or not in amounts sufficient to meet physiological needs. Nonessential AA (AKA dispensable): = an amino acid that the body can synthesize in sufficient amounts to meet its needs Conditionally Essential Amino Acids (also known as Conditionally Indispensable Amino Acids): These are amino acids that are typically classified as nonessential, meaning the body can normally produce them. However, under specific circumstances, they become essential because the body cannot produce them in sufficient amounts. Example: In Phenylketonuria (PKU), a genetic condition, the body has a defective gene that impairs the production of an enzyme required to convert phenylalanine (an amino acid) into tyrosine (another amino acid). As a result, phenylalanine accumulates in the body, and tyrosine becomes an essential amino acid since the body can no longer make it. Definitions Peptide = a strand of amino acids Peptide bond = the bond that joins one amino acid to another Dipeptide = protein fragments that are two amino acids long Tripeptide = protein fragments that are three amino acids long Oligopeptide = protein fragments that are 4-10 amino acids long Polypeptide = protein fragment of many (more than 10) amino acids Recycling Amino Acids Food and body proteins are dismantled to single amino acids These are used for: A pool of raw materials Energy The amino acids are then put back together to make a functional protein Each protein has a standard amino acid sequence. The sequencing is inherited (in our genetics) There can be alterations in the sequence ○ ex.Sickle-cell disease A mineral or a vitamin may join on to the unit and activate it Protein shapes enable the performance of different tasks in the body The Coiling and Folding of a Protein Molecule Hemoglobin Genetics Denaturation of Proteins Denaturation: This refers to the process where a protein loses its natural structure (shape) due to external factors. This structural distortion affects the protein's function but does not break its amino acid sequence.: In Digestion: Denaturation is an essential step in protein digestion. It unfolds the protein, making it easier for digestive enzymes to break it down into amino acids. In Cooking: Heat from cooking causes proteins to denature. For example, when an egg is cooked, its proteins unfold and solidify, changing from clear and runny to white and firm. Other: Acids and Bases: For instance, lemon juice can "cook" fish in ceviche by denaturing its proteins. Alcohol: Alcohol can denature proteins, which is why it is used to sterilize surfaces. Heavy Metals: Certain toxic substances, like mercury or lead, can denature proteins, disrupting their function. Protein Digestion and Absorption Protein digestion Begins in the strong acid of the stomach Protein in food is denatured ○ Uncoils protein strands Enzymes attack peptide bonds Small intestine ○ Many proteins are in the form of polypeptides ○ Further break down to strands of dipeptides and tripeptides Liver ○ Chemically alters nutrients How Proteins in Food Become Amino Acids in the Body After Protein is Digested, the Fate of the Amino Acids Absorbed by cells of small intestine ○ As single amino acids ○ Most dipeptides and tripeptides are reduced to single amino acids ○ Some larger molecules escape the digestive process Separate sites for absorption of different amino acids Released into the bloodstream ○ Carried to the liver The larger molecules may also stimulate an immune response and thus play a role in food allergy. When a person ingests a large dose of any single amino acid, that amino acid may limit absorption of others of its general type. Role of Body Proteins Supporting Growth and Maintenance Amino acids must be continually available to replace old or build new proteins Protein turnover: Process of breakdown, recovery, and synthesis of protein ○ In adults, about 300 - 400 grams of protein turns over each day, accounting for about 20% of our resting energy needs Building and replacing tissue: muscle, bone, hair, skin and nails, blood Red Blood Cells have a lifespan of about 120 days and Intestinal cells live only about 3 days. Cells arise, live, and die. Cells must also replace their internal functional proteins Role of Body Proteins Enzymes, Hormones, and Other Compounds Thousands of enzymes reside in a single cell - each one facilitating a different reaction. Hormones are chemical messengers and some are made from amino acids (others are made from lipids). Thyroid hormone (thyroxine), Insulin and Glucagon are a few examples. The AA tyrosine is also used to synthesize thyroxine, epinephrine and norepinephrine (AKA adrenaline and noradrenaline). Tyrosine also contributes to making melanin which is responsible for the colour of hair, skin and eyes. The AA tryptophan is a building block in the synthesis of the neurotransmitter, Serotonin. Enzymes -among the most important proteins formed in living cells Enzymes are catalysts: they speed up reactions that would happen anyway. This enzyme works by positioning two compounds, A and B, so that the reaction between them will be especially likely to take place. Compounds A and B (the substrates) are attracted to the enzyme’s active site and park there for a moment in the exact position that makes the reaction between them most likely to occur. They react by bonding together and leave the enzyme as the new compound, AB (the product). A single enzyme can facilitate several hundred such reactions in a second. Other enzymes break compounds apart into two or more products or rearrange the atoms in one compound to make another one. Proteins Transport substance into and out of the cells Role of Body Proteins Fluid & Electrolyte Balance Acid - Base Balance Blood pH is tightly regulated at 7.35-7.45 Proteins cannot move freely in and out of Normal body processes constantly produce cells but water can. Protein attracts water. acids and bases. The blood must carry these By maintaining intracellular proteins (and byproducts for excretion mineral balance), cells retain the fluid they Acids release Hydrogen need. Bases are compounds that accept Hydrogen Transport proteins reside in the cell Negatively charged side chains of amino acids membrane to assist with balance. These can pick up extra hydrogen and release them proteins help maintain a balance of when needed. In this way the protein in the Potassium inside the cell and Sodium bloodstream can help buffer and maintain the right pH regulation. outside the cell. Disturbances in the mechanism can lead to Acidosis or Alkalosis are serious health conditions that are medical emergencies. They edema, the swelling of body tissue by can lead to coma or death leakage of fluid from the blood vessels. Role of Body Proteins Blood Clotting Energy Under adequate nourishment, protein Proteins respond to injury and bleeding as contributes to about 15% of energy a part of blood clotting. production. Protein forms the netting that traps Protein can also contribute to the creation platelets at the site and also contribute of glucose in a process called collagen to the healing process. gluconeogenesis. When a protein is used for energy, it’s amine group (the group containing nitrogen), is stripped off and used elsewhere or the liver incorporates it into urea and sends it to the kidney for elimination. Role of Body Proteins Antibodies Macronutrients storage Glucose is stored as Glycogen Fat is stored as Triglycerides Protein has no specialized storage compound so we if we are deficient then we can just draw on active, working molecular or structural proteins. If carbohydrate and protein are lacking in nutrition then the body must dismantle proteins from the muscle, liver and other organs. Thus, energy deficiency (starvation) always creates wasting of lean body tissue as well as fat loss. ○ The End Game for Protein Protein-containing food is ingested and digested into amino acids. These amino acids can: 1. Be used to build proteins (e.g., enzymes, hormones, or structural components). 2. Be dismantled to: ○ Use the amine group for making other amino acids or urea (excreted by the liver). ○ Use the remaining backbone for energy, or convert it to glucose or fat. Key Points: Amino acids can be converted to glucose (unlike fatty acids) to help maintain blood glucose levels. If energy or carbohydrate intake is insufficient, amino acids provide energy. Excess amino acids cannot be stored. The body removes the nitrogen (excreted as urea) and uses the residues to: ○ Meet energy demands. ○ Convert to glucose for glycogen storage. ○ Convert to fat for long-term energy storage. Protein Quality To make the required proteins, the cell has the proteins from food, and a small amino acid pool. If an essential amino acid is in low supply then the protein synthesis is down regulated. It will upregulate the synthesis again if the amino acid becomes abundant again but if the deficiency is chronic, the cell will dismantle its protein-making machinery - making circumstances less than optimal. The cell can reconstruct the machinery but there is a lag time. Also the unused amine groups are eliminated which can compound the ability to regain optimal synthesis Amino acids from Animal-source proteins are considered to be 90% digested and absorbed. Amino acids from Plant-source proteins are considered to be 70-90% digested and absorbed. Complementary Proteins = two or more proteins whose AA assortments complement each other in such a way that the missing essential amino acids of one are supplied by the other. Protein Targets DRI is 0.8g/kg (I use 0.8-2g/kg) AMDR is 10-35% as percentage of calories The amount needed depends on body size, stage of development, and circumstances. Nitrogen Balance = compares the amount of nitrogen consumed against the the amount excreted over time (by measuring urinary urea nitrogen). Positive Nitrogen Balance = more protein is being built than broken down (anabolic). This is important in instances where growth is important: children, pregnancy, and in some athletic populations or people where you want to build muscle. Negative Nitrogen Balance = when people are losing more protein than they are ingesting (catabolic). This can be seen in astronauts and in surgical patients, or older adults. Nitrogen Equilibrium = when protein consumption matches protein excretion. Controversy: Vegetarian vs Meat-Containing Nutrition Definitions Vegetarian = includes plant-based foods and eliminates some or all animal-based foods. Lacto-ovo Vegetarian = Includes dairy and eggs with plant-based food. Excludes Flesh and Seafood. Lacto-Vegetarian = Includes dairy with plant-based foods. Excludes Flesh, Seafood, and Eggs. Ovo-Vegetarian = Includes eggs with plant-based foods. Excludes Flesh, Seafood, and Dairy. Pescatarian = Includes seafood with plant-based food. Excludes Flesh, and may exclude Dairy and Eggs too. Vegan = Only plant-sourced food. Excludes all things that had a mother: Flesh, Seafood, Dairy, Eggs, and sometimes Honey Omnivore = includes food of both animal and plant origin Possible Benefits of a Vegetarian Path A recognition that people who eat a In general vegetarians maintain a well-planned vegetarian nutrition often healthier weight, and this can contribute have lower rates of obesity, heart to keeping blood pressure in check. disease, high blood pressure, or cancer. Often, a vegetarian will have other Often, a vegetarian will eat more healthful lifestyle habits that helps vegetables and fruit, increased fibre compound the benefits and mitigate intake and have a reduced intake of health risk i.e. they typically do not saturated fat. smoke, may maintain an active lifestyle, and Due to the increased intake of vegetables and fruit their intake of phytochemicals will be up. The Omnivore Path Maybe food choices are more abundant which could make nourishing more convenient and effective Enjoyment - the person enjoys the foods they are eating The protein can be considered easier to absorb or digest Perhaps easier to obtain some of the micronutrients such as Iron, Calcium, Zinc, Vitamin D, Vitamin B12