Nutrition Chapter 6

Protein Equilibrium

healthy adult meeting nutrient needs, notably protein and calorie needs

Learning Objectives

-Distinguish between essential and nonessential amino acids and explain why adequate amounts of each of the essential amino acids are required for protein synthesis -Describe how amino acids form proteins -Identify food sources of protein, distinguish between high-quality and low-quality proteins, and describe the concept of complementary proteins -Describe how protein is digested, absorbed, and metabolized in the body -List the primary functions of protein in the body -Apply current recommendations for protein intake to determine protein needs for healthy adults -Describe the harmful effects of a high-protein diet and describe what is meant by positive protein balance, negative protein balance, and protein equilibrium -Describe how protein-calorie malnutrition eventually can lead to disease in the body -Develop vegetarian diet plans that meet the body's nutritional needs

Other Potentially Harmful Aspects of a High-Protein Diet

-Excessive intake of processed red meat is linked with colon cancer -Increased burden on the kidney -May increase loss in the urine -Increase urine production -> increase risk for dehydration

Environmental Burden

-Increased demands for beef, poultry, and milk has resulted in "factory farms" -Significant environmental impact as a result of large amount of land and water use, along with high level of waste produced -DGAs recommend a decrease in protein consumption from animal foods Not just for our health, but for health of the planet

Factors that determine protein final shape:

-Side chain electrical charge -Side chain polarity -Some proteins require the addition of a mineral, vitamin, or carbohydrate to be activated

Protein as a source of energy

-Typically, carbohydrates and fats are metabolized for fuel, but in some circumstances, proteins can yield energy Prolonged exercise Calorie restriction and or/low carb dieting -Amino group from amino acid is removed, and remaining carbon skeleton is metabolized for energy needs -Increase in urea production -Protein is costly source of calories

Protein Turnover

-maintaining constant supply of amino acids Body is in constant state of breakdown, rebuilding, and repair Protein turnover: a process by which a cell responds to its changing environment by either producing proteins that are needed and disassembling proteins that are not needed ->much of this has to do with the fact that there is no storage tissue for amino acids Estimated that an adult makes and degrades nearly 250 grams of protein a day!

marasmus

-severe energy and protein deficit -severe weight loss -wasting of muscle and body fat (skin and bones appearance) -severe growth impairment (less than 60% of normal weight for age) -develops gradually

kwashiorkor

-severe protein with moderate energy deficit -often accompanied by infections or other diseases -edema -mild to moderate weight loss -maintenance of some muscle and subcutaneous fat -growth impairments (60%-80% of normal weight for age) -rapid onset -fatty liver

Caution with Amino Acid Supplements

1. Marketed heavily to athletes and dieters 2. Proven that the right amount of protein in diet is essential to athlete performance -Can easily meet (and exceed) protein needs through whole foods and protein rich beverages like milk 3. Using single amino acid supplementation is NOT considered safe -Single amino acids can compete for absorption of other amino acids, and lead to potential deficiency -In Canada, the sale of single amino acids to consumers is banned

Essential amino acid names (need to know all 9)-PVT MT HILL

1. Phenylalanine 2. Valine 3. Threonine 4. Methionine 5. Tryptophan 6. Histidine 7. Isoleucine 8. Leucine 9. Lysine

Protein Synthesis

1. Signal to cell that protein "x" is needed ; DNA responds by "typing" the code for protein "x" 2. in nucleus of cell, transcription of DNA results in mRNA, which contains a copy of the "code" for protein "x" 3. mRNA leaves nucleus of cell into cytoplasm; ribosomes attaches to mRNA 4. ribosome "reads" or "translates" mRNA "code" for protein "x"; every codon indicates particular amino acid 5. tRNA selects appropriate amino acid and brings into place; ribosome continues to read mRNA and tRNA continues to select amino acids 6. Protein is eventually formed

What is a branched chain amino acid?

Abbreviated BCAAs R-group has a branched structure Play key role in muscle protein synthesis Whey protein (from milk) is a rich source of the BCAA leucine

Denaturation of Proteins (Deactivate protein)

Alteration of a protein's three-dimensional structure; loses biological activity -heat -enzymes -Acid/alkaline solutions -Agitation -Cooking Digestion- breaks down protein to make amino acids available

Producing Vital Body Structures

Amino acid pool within cells can be used to form body proteins -Structural components -muscle -bone Blood proteins Transport proteins -Enzymes -Hormones -Immune proteins

The Basics

Amino acids linked together form a protein Bond formed between amino acids = peptide bond Synthesis of protein begins at cellular level Dependent upon ample essential amino acids supplied by diet

Vegan Diets

Complementary proteins Nutrient deficiency concerns Vitamin B12 Iron Zinc Calcium Omega-3 fatty acids

DNA Errors may cause disease

Conditions such as sickle cell anemia arises from malformation of red blood cell because of an incorrect structure in part of its hemoglobin protein chains -code for red blood cells

Bottom line on protein in diet...

For majority of healthy adults, enough protein is supplied from a well balanced diet that follows the Dietary Guidelines for Americans and MyPlate For individuals who do not fall into the "healthy adult" category, protein requirements may vary

Protein Quality of Foods

High-quality (complete) proteins Lower-quality (incomplete) proteins

Negative Protein balance

Inadequate protein intake (fasting, intestinal tract disease) inadequate calorie intake fevers, burns, infections, increased protein loss

Health Benefits of Plant Proteins

Low in saturated fat No cholesterol No trans fat High in fiber High in antioxidants Vitamin A Vitamin E Vitamin C Carotenoids High in magnesium Reduced risk of chronic diseases Cardiovascular disease Hypertension Cancer Type 2 diabetes Obesity Lower carbon foot print compared to animal proteins

Potentially harmful aspects of high protein diet?

Most proposed harmful aspects of a high protein diet have to do with a high protein diet pattern Typically, high protein diet pattern : -low in fiber, some vitamins (folate for example), and phytochemical (which are found mostly in plants) -high in saturated fat and cholesterol

Protein Digestion Overview

Mouth-Relatively inactive protein digestion, mechanical digestion Stomach- Step 1: Denaturation by Stomach Acid (HCL) Step 2: Chemical digestion by Pepsin(ogen) (-HCl secretion stimulated when bolus enters stomach -HCl stimulates/activates pepsinogen -> pepsin) Small Intestine - lumen, Pancreatic Protease further digests polypeptides in small intestine, pancreas is the accessory organ Small Intestine - Enterocyte, Final digestion of amino acid chains to single amino acids takes place within cells of small intestine

Protein Organization

Order of amino acids in a protein determines its ultimate shape Protein's final shape determines its function in the body

Important roles of protein

Protein considered "special forces" in the body Important roles of protein include: -Building blocks of body components -Fluid balance -Acid/base balance -Building blocks of hormones and enzymes -Immune function -Forming glucose -Energy yielding (non-preferred source) -Contributing to satiety

Dangers of too little protein

Protein deficiency is rarely isolated Usually accompanied by deficiencies of total calories and other key nutrients Significant problem in hospitalized patients and in developing parts of the world Areas where starch (rice or starchy root vegetables) is primary source of energy

Amino Acids - building blocks of life

Proteins are made of amino acids 20 different amino acids exist -9 essential amino acids -11 non essential amino acids

Peptide Bonds

Proteins linked together peptide bonds Bonds form between amino group of one amino acid and acid (carboxyl) group of another -Dipeptides - 2 amino acids -Tripetides - 3 amino acids -Oligopeptides - 4 to 9 amino acids -Polypeptides - 10 or more amino acids Most proteins are polypeptides, 50 to 2000 groups

Protein Requirements

RDA: -For sedentary adults: 0.8 g/kg -Athletes may required up to 1.7 g/kg AMDR: 10% to 35% of total kcal Most of us eat more than the RDA for protein Excess protein cannot be stored as protein -Most health care providers and nutrition experts do not recommend consuming more than 2x's the RDA for protein

Protein Intake Recommendations from the 2015 - 2020 Dietary Guidelines

Recommendations for how we should be getting protein from foods 1. Increase variety in protein food choices -Incorporate seafood twice per week in place of meat, poultry, or eggs -Use legumes, nuts, or seeds in place of some meat and poultry in mixed dishes 2. Make more nutrient-dense choices within the protein foods group -Lean -Lower-sodium 3. Some population groups may need to reduce excessive intake of protein foods -Teenage boys -Adult men

Amino Acid Metabolism

Requires additional energy to process and get rid of excess urea produced as result of amino acid catabolism

American Institute for Cancer Research - New American Plate

Resembles MyPlate guidelines Emphasis on more vegetables, fruits, whole grains, and beans De-emphasis on animal protein

Protein Absorption

Single amino acids absorbed into portal circulation and transported to liver Once in liver, aa's can undergo several modifications, depending on the needs of body tissues ->combine amino acids into proteins ->dismantle amino acids to be used for energy ->release amino acids into blood stream for other tissues ->converted to non-essential amino acids ->excess converted to glucose or fat

Trends in Protein Consumption

Top five sources of protein in North American diet: -beef -poultry -milk -white bread -cheese American meat and poultry consumption has declined in recent years Worldwide meat consumption has been increasing, especially in developing countries (East and Southeast Asia in particular)

How do I increase Plant Proteins?

Try the veggie burger Sprinkle seeds, nuts on salad Eat soy nuts, edamame Peanut butter on bagel Choose beans with taco seasoning instead of beef or chicken for taco filler Use soy milk instead of dairy Try "Meatless Monday"

Getting enough protein in the diet

Typical North American protein intakes 100 grams of protein for men 65 grams of protein for women Both groups well exceed RDA for protein through food alone A well balanced diet will result in adequate protein for most healthy adults; no additional protein supplementation required!

Why protein?

Unique composition sets protein apart from other macronutrients -Contains: carbon, hydrogen, oxygen, and nitrogen Functions -Regulates and maintains body functions -Provides essential form of nitrogen (in the form of amino acids

Food Planning for Vegetarians

Vegan - eats only plant foods Fruitarian - eats fruits, nuts, honey, and vegetable oils Lactovegetarians - eats plant and dairy products Lactoovovegetarians - eats plant products, dairy, and eggs Concerns for infants and children? Not usually an issue if planned right Iron, vitamin B12, vitamin D, and calcium

Protein as a source of glucose

What? Certain amino acids can be converted into glucose in the liver When? During times of glycogen depletion Why? Must supply adequate glucose for tissues to thrive (RBC, nervous tissue and brain cells) Outcomes? muscle wasting Swelling and edema

Conditionally essential amino acids

amino acids made from essential amino acids if insufficient amounts are eaten

Essential Amino Acids

cannot be synthesized by humans in sufficient amounts or at all, must be included in the diet

Lower-quality (incomplete) proteins

dietary proteins that are low in or lack one or more essential amino acids -Most plant protein lack one or more "limiting" amino acid -All-or-none principle of protein synthesis -Complementary proteins - dietary strategy that pairs plant protein sources based on amino acid content to become a complete protein lack one or more of the nine essential amino acids whole grain, vegetable, fruits

High-quality (Complete) proteins

dietary proteins that contain ample amounts of all nine essential -animal protein poultry, fish, beef, dairy

Limiting amino acids

essential amino acid in lowest concentration in food or diet relative to body needs

Fun Fact

estimated that only about 8% of dietary protein goes toward muscle synthesis

Positive Protein Balance

growth pregnancy recovery stage after illness, injury athletic training

types of malnutrition

kwashiorkor marasmus