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Valerie Schulz, MMSc, RD, LD/N, CDE Compare essential to non-essential amino acids State the outcome if essential amino acids are missing Discuss various roles of protein in humans Describe fate of amino acids/protein consumed with sufficient carbohydrate vs a carb-poor diet Identify major forms of protein malnutrition Discuss why consuming too much protein is not recommended Summarize advantages/risks of vegan diet Amino acids (aa): links in the chains of proteins General structure of amino acids: (side group) - varies H–H-N – (amino C– H C–O-O-H (acid group) group) The nitrogen (N) makes protein different from carbohydrates or fats The side group makes each aa different, and more complex than carbs or fats (review of what was learned in HUN 2002) Unlike CHO and fat, protein contains ___________ Each building block of protein, the ________ __________, bind with ___________ bonds. Human bodies (can / cannot) make essential amino acids. What makes one amino acid different from another? The ______ group How many amino acids are there? ______ (Pg 191; heading is ‘How do Amino Acids Build Proteins?’) Primary sequence is determined by the _____ blueprint. Secondary structure caused by attractions of ___________ groups. Tertiary structure caused by folding of the protein as electrically charged side groups are attracted to __________ and orient to the outside of protein. The side groups that have a neutral charge are repelled by water and attracted to each other; they tuck themselves _________ the protein structure. (Review of Chapter 3 – you tell me) Mouth: (does any protein digestion happen here?) Stomach: (2 things happen here) Denatured/unfolded by ________ e_______________ break proteins into smaller chunks Small intestine: many e_________, secreted into the small intestine by the pancreas or made in the small intestine, break up the chunks (don’t need to know specific names) Absorbed as ________ __________, into the blood Large intestine: (does any protein absorption happen here?) Each human protein has a distinctive sequence, leading to a specific 3-D shape and function. The variety of possible sequences for amino acid strands is tremendous (compare 26 letters of alphabet, and how many words are in unabridged dictionary) A single human cell may contain as many as 10,000 different proteins, each one present in thousands of copies. The following slide shows the hemoglobin molecule, exemplifying: 3-D structure of proteins Function is related to shape: notice how the protein chains, shown in color, bend so that the heme molecule is held in place. Iron atom is held by heme. Function of hemoglobin is to carry iron, & oxygen Peer into the blue, green, purple and orange chains to see the primary sequence of the amino acids that determines the final shape of the protein, so it is perfect to carry heme Protein carriers transport amino acids into the intestinal cells. The aa might be used in the intestinal cell for its own purposes (intestinal cells are remade ~every 3 days) If not needed in the intestinal cell, aa move on into the blood on the way to the liver. Important point: EVERY protein we eat is broken down to amino acids before it is remade into human proteins. So we cannot eat an enzyme to help our digestion, because it would be denatured in the stomach. (Pg 194; the Variety of Proteins, Nutrients and Gene Expression) Every cell nucleus contains the DNA for making __________ human protein, but cells do not make them all. Some genes are “expressed” and others are not depending on the cell type. For example, only cells of the pancreas express the gene for the protein hormone insulin. Nutrients do not change DNA structure, but they greatly influence genetic expression (will not be tested on protein synthesis, Figure 6.6, pg 195) Those who suffered through HUN 2002 with me will remember the following cartoon slide It likens the long strand of DNA to a “sentence”, and then considers the smaller gene piece as a “word” in that sentence The blue part is the actual codes that stand for each amino acid The green parts are the all important control areas, where what we eat will have an impact on how often (or not) this protein is expressed. (Like omega-3 fats causing more anti-inflammatory proteins to be made.) Genes can be thought of as 'words' along the DNA 'sentences'. Amino acids with similar structures use the same transport systems to enter intestinal cells As a result, amino acids may compete with one another for absorption, ie, excess of one may slow absorption of the other that uses the same system When single amino acid supplements are consumed, the supplemented aa may overwhelm the transport system This reduces the absorption of the other amino acids using the same system. Joe takes an excess of amino acid “A”, which uses the same transport or carrier proteins as amino acids “B” and “C” All the carrier proteins get filled up with “A”, because there is so much of it There is not enough space on the carrier proteins to transport “B” or “C”, so less of those two are absorbed Especially if “B” or “C” are essential amino acids, Joe will be creating a deficiency by taking an excess of “A” Building materials: for growth/maintenance [muscle, collagen] Hormones: messengers; some are proteins Regulators of fluid balance: proteins hold 1. 2. 3. water in the cells or in the plasma (blood). In protein malnutrition, blood levels fall too low, water ‘leaks out’ in between the cells, causing edema Enzymes: 4. 1. 2. 3. 4. Digestion (break down) Build (ex: bones) Transform (ex: amino acid into glucose) Enzyme action: figure 6-7 (changed from 6.9) 1. Acid-Base regulators: proteins have negatively charged surfaces, can attract loose H+ ions “buffers” 2. Transporters: 1. hemoglobin carries oxygen from lungs to all cells; 2. lipoproteins carry lipids in the watery blood; 3. special transport proteins carry vitamins & minerals 3. Antibodies: designed to destroy specific antigen (ex: virus) 4. Source of energy (glucose): gluconeogenesis – making glucose from protein When insufficient carbohydrate and fat are consumed to meet the body’s energy need, food protein and body protein are sacrificed to supply energy. The ____________ part is removed from each amino acid, and the resulting fragment is oxidized for energy. No storage form of amino acids exists in the body. When an amino acid arrives in a cell, it can be: Used as is to build protein Altered somewhat to make another needed compound, such as the vitamin niacin Dismantled to use its amine group to build a nonessential amino acid The remaining carbon, hydrogen and oxygen atoms can be converted to glucose or fat In a cell starved for energy with no glucose or fatty acids: The cell strips the amino acid of its amine group (nitrogen part) and uses the remainder of its structure for energy The amine group is excreted from the cell and then from the body in the urine In a cell that has a surplus of energy and amino acids, the cell takes the amino acid apart excretes the amine group converts the rest to glucose or fat for storage Amino acids are “wasted” (won’t be used as protein) when: Energy is lacking from other sources (either not enough kcal and/or not enough carb). Protein is overabundant (can’t store it) An amino acid is oversupplied in supplement form. The quality of the diet’s protein is too low (too few essential amino acids). © 2012 John Wiley & Sons, Inc. All rights reserved. To be used efficiently as protein, protein must be accompanied by: ample carbohydrate and fat (kcal) (“Protein-sparing” effect of carbohydrate) vitamins and minerals. Protein quality is influenced by a protein’s digestibility and its amino acid composition. Amino acids from animal proteins are most easily digested and absorbed (over 90%) Amino acids from legumes are next (80 to 90%) Amino acids from plant foods vary (70 to 90%) High-quality proteins – provide enough of all of the essential amino acids needed to make new proteins Low-quality proteins – do not provide all the essential amino acids If a nonessential amino acid is unavailable from food, the cell synthesizes it If the diet fails to provide an essential amino acid, the cells begin to conserve the amino acid and reduce their use of amino acids for fuel. If a person does not consume all essential amino acids needed, the body’s pools of essential amino acids will dwindle: First, blood and muscle proteins are dismantled to provide the needed essential amino acids Finally, body organs are compromised. If food “A” lacks essential amino acids (if it is a low-quality protein), then the amino acids in food “A” can be used only if essential amino acids are present from another source. If food “A” is paired w/another low-quality protein food that fills in the gap, then the two together provide all essential amino acids, giving the same benefit as a high quality protein. See following slide (you will not be tested on the names of the amino acids that are complementary, just know the concept) The DRI recommendation for protein intake depends on size and stage of growth recommended intake is 0.8 gram per kilogram of body weight per day DRI Minimum is 10 percent of total calories 2000 kcal x 10% = 200 kcal 200 kcal / 4 kcal per g protein = 50 g protein 50 g protein spread over 3 meals is ~15-20g/meal Athletes may need slightly more (1g per kg) I just wanted you to be exposed to the concept on the following slide It is used more in intensive care and research situations than it would be in day-to-day nutrition care or education Now that we have covered all the basics of protein, will consider the effects of lack of protein or too much protein on disease. PEM occurs in two main forms: K___________________ (acute protein deficiency) M_____________ chronic food (protein & energy) deficiency PEM is not unknown in the United States, where millions live on the edge of hunger. Inner cities Rural areas Some elderly people, especially those living alone Hungry and homeless children People suffering from anorexia nervosa People with wasting illnesses such as AIDS, cancer, or drug and alcohol addictions GI issues that have slowed or stopped the intake of food: esophageal strictures, intestinal blockages Variable Marasmus Kwashiorkor Onset Earlier, usually in first year Later, after breastfeeding has stopped Growth Failure significant Not much Edema No yes Blood protein concentration Not much change Very low Skin changes Not usually Red patches & boils Fatty liver no yes Marasmus - without adequate nutrition: Muscles, including heart, weaken Brain development in children stunted, learning impaired Metabolism slows, body temperature is subnormal Person is apathetic, does as little activity as possible Growth ceases; child is no larger at 4 than was at 2 Digestive enzymes in short supply, intestinal cells cannot replenish, absorption fails Blood proteins, incl hemoglobin, not produced: anemia Antibodies degraded to provide amino acids for other synthesis, leaving the person an easy target for infection, including ones that cause diarrhea Infections w/PEM cause 2/3 of child death in developing world Kwashiorkor Without severe wasting of body fat Proteins that maintained fluid balance diminished, fluid leaks out of blood, accumulates in belly and legs, resulting in edema Skin loses elasticity, cracks; sores develop, fail to heal Fatty liver, caused by lack of protein carriers to transport fat out of liver Fatty liver loses some function, including ability to clear toxins, which accumulate, reducing appetite There is no benefit from eating excess protein: Why? In human beings, a high-protein diet increases the kidneys’ workload but this alone does not appear to damage healthy kidneys or cause kidney disease. (What does?) In people with kidney problems, a high-protein diet may speed the kidneys’ decline. People with Stage 1 – Stage 4 can slow progression to Stage 5 (dialysis) by eating lower protein. Diagnosed by comparing BUN with creatinine to estimate GFR: glomerular filtration rate According to the National Kidney Foundation, normal results range from 90 - 120 mL/min/1.73 m2. (not necessary to memorize) GFR decreases with age Levels below 60 mL/min/1.73 m2 for 3 or more months are a sign of chronic kidney disease (CKD) GFR below 15 mL/min/1.73 m2 is a sign of kidney failure; requires immediate medical attention. Dialysis usually when GFR <7. Eat a healthy diet: Include a variety of grains, especially whole grains, fresh fruits and vegetables Choose a diet that is low in saturated fat and cholesterol and moderate in total fats Limit intake of refined and processed foods high in sugar and sodium Choose and prepare foods with less salt or high sodium ingredients Aim for a healthy weight, consume adequate calories and include physical activity each day Consume the DRI for vitamins and minerals Keep protein intake within the Daily Reference Intake (DRI) level recommended for healthy people (0.8g/k) (potassium ,phosphorus usually not restricted unless blood levels above normal) Including grains, fruits and vegetables, but limiting whole grains and certain fruits and vegetables if blood tests show phosphorus or potassium levels are above normal. A diet that is low in saturated fat and cholesterol Limiting intake of processed foods high in sodium; prepare foods with less salt or high sodium ingredients. Aiming for a healthy weight by consuming adequate calories, including physical activity Limiting protein intake to the level determined by the dietitian’s assessment of individual needs (as low as 30g/day) Consuming DRI for water soluble vitamins; C limited Vitamin D and iron may be tailored to individual requirements. Limiting phosphorus if blood levels of phosphorus or PTH are above normal. Limiting calcium if blood levels are above normal. Limiting potassium if blood levels are above normal. Alcohol abuse Drug-induced: http://www.medicinenet.com/liver_disease/ page2.htm#what_are_the_causes_of_liver_di sease (from above link): start reading at ‘What are the causes of liver disease?’, read down through alcohol abuse, cirrhosis. Under drug induced, just notice the part about acetaminophen. Start again at infectious hepatitis, then stop at hemochromatosis. Limited amount of protein. A damaged liver cannot process protein very well. This causes a build-up of ammonia in the bloodstream. More carbohydrate. Carbohydrate is the body's energy supply. A healthy liver makes glycogen from carbohydrate. The glycogen is then broken down when the body needs energy. A damaged liver can't do this. Without glycogen, more carbohydrate is needed from the diet to make sure the body has enough energy. A moderate amount of fat. Fat provides calories, essential fatty acids, and fat-soluble vitamins. A limited amount of fluids and sodium. Liver damage can cause high blood pressure in the major vein of the liver. This can result in ascites, a fluid build-up in the abdominal cavity. Limiting fluids and sodium can help prevent this. (you saw the ascites picture in Chap 3 controversy on alcohol ) Common diet prescription for ESLD (End stage liver disease): 30-60g protein (usually works out to 8-15% of kcal); lower amounts if history of high blood ammonia, or encephalopathy. High quality protein is more desirable (why?) 60-70% kcal as carbohydrate; fruit is encouraged. Usually have to demonstrate how to add extra. Carbs do not need protein carriers for absorption. 25-30% kcal from fat (about same as is recommended for population at large). Fat needs protein carriers. 2gm (2000mg) Na+ or less. This is the difficult part to implement Fluid restriction: not always What constitutes a vegetarian diet? Many subsets of reducing/omitting animal foods Describe varieties : “flexitarian” Lacto-ovo Lacto vegan People who eat well-planned vegetarian diets suffer less often from chronic diseases than people whose diets center on meat Strong evidence links vegetarian diets with reduced incidences of chronic diseases. Benefits include: Less obesity Defense against certain cancers (colo-rectal associated with red and processed meats. Fish eaters had lowest levels of cancer in a UK study) Less heart disease (blood lipids stepwise: vegan, lacto-ovo, meat-eating) Less high blood pressure (specific etiology unclear: lower body weight and higher K+ probable) May help prevent diabetes, osteoporosis, diverticular disease, gallstones, and rheumatoid arthritis When meat (animal muscle) is omitted, USUALLY see these changes: Lower saturated fat Increased whole grains (is whole wheat bread a whole grain? You have discussed this!) Increased fruit, vegetable, legumes - all associated with improved health Positive changes associated with a vegetarian diet are the same changes associated with a WHOLE foods pattern of eating A 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 healthy. On the other hand: Meat lovers who shun all vegetables have no adequate substitutions for these foods (unlike vegetarians who can find suitable replacements for meat). Both vegetarian and meat-containing diets, if not properly balanced, can lack nutrients. Poorly planned meat eater’s diets may lack: vitamin A vitamin C Folate fiber Poorly planned vegetarian diets typically lack: Iron Zinc Calcium omega-3 fatty acids vitamin D vitamin B12. Area Vegan Meat consuming Pregnancy If start pregnancy too thin, need extra kcal. Choose well to get enough B12 and iron. Receive enough B12, iron, zinc. If also consume dairy, usually enough Ca++, Vit D Childhood Vegan foods higher fiber, child may get full before achieve all nutrients. Same Adolescence Teens wisely choosing lots of fruits & vegs can meet national dietary objectives, rare in US. Iron still an issue. Very easy to choose foods that exclude fruits and vegetables, initiate fatty streaks, etc. Aging Poor dentition leads to problems chewing meat; texture change not well liked. Softer cooked vegetable proteins aesthetically pleasing Nutrient Vegan Meat consuming Protein Legumes, seeds, nuts, soy Animal muscle, egg, dairy Iron Dark green leafy, dried fruits (hi kcal), legumes (w/ Vit C) Animal muscle, egg (w/ Vit C) Zinc Legumes, nuts, seeds Animal muscle, dairy Calcium Dark green leafy, nuts, Dairy seeds (fortified plant milk) Omega-3 Marine algae, flaxseed, walnuts Fatty fish