Nutrition Today NUTR SCI 132
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This 12 page Class Notes was uploaded by Ms. Jaylin Veum on Thursday September 17, 2015. The Class Notes belongs to NUTR SCI 132 at University of Wisconsin - Madison taught by Peter Anderson in Fall. Since its upload, it has received 25 views. For similar materials see /class/205266/nutr-sci-132-university-of-wisconsin-madison in Natural Sciences at University of Wisconsin - Madison.
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Date Created: 09/17/15
Chapter 5 What distinguishes protein from the other macronutrients Carbs and fat is the presence ofthe element nitrogen Only legumes can get around this limitation placed by fertility since they alone fix nitrogen a process by which they pull it out ofthe air Legumes for this reason are higher in protein than any other plant source Other plants can only make as much protein as the soil provides nitrogen for but legumes have no such dependence Plants die and return their nitrogen to the soil or are eaten by herbivorous animals Animals cannot synthesize amino acids from nitrogen and are dependent on plant proteins Proteins make up some ofthe largest and most complex molecules in nature but they are built from a limited number of very simple components the amino acids 20 amino acids combined in large numbers in a multitude ofways gives us the tens of thousands of proteins in our body Amino acids are composed of carbon hydrogen oxygen nitrogen and in a few cases sulfur When protein is used for energy its defining nitrogen is left over and must be disposed of This waste product in the form called urea is concentrated in the urine by the kidneys and excreted High protein diets tax the kidneys and cause water loss through urination These amino acids join together by what is known as a peptide bond Short chains of amino acids called peptides range in length from dipeptides to polypeptides One ofthese peptides composed of 51 amino acids is the hormone insulin Hormones are also peptides Very long chains of amino acids hundreds or even thousands of units are called proteins The collagen in connective tissue or the digestive enzyme amylase the amino acid constituents appear in a very specific sequence The chemical and physical properties ofthat protein depend on the sequence the functionality ofthat protein in turn depends on those properties Your DNA carries that sequence The properties of every protein are determined by the sequence of amino acids in it and the sequence of amino acids in that protein is carried in your genes The first thing you do when you eat protein is to undo all this delicate organization Strong hydrochloric acid present denatures proteins This breaks down the structure ofthe proteins opening it up to the action of proteases the digestive enzymes that break the peptide bonds between amino acids The stomach produces protease to get the job started as does the small intestine which finishes it Ifthis protein is inadequately digested you get an upset stomach or diarrhea Anything that is not fat or water is likely to be a protein Protein provides the structure ofthe body Muscle and various kinds of connective tissue consist of protein It should also be remembered that while protein is important for muscle Carbs and adequate energy are also important If either is in short supply the body breaks down muscle for blood glucose and energy Carbs is said to be proteinsparing Iron could do a great deal of damage in unleashed in the wrong place Transport proteins keep them sage Hemoglobin carrying oxygen and carbon dioxide is a transport protein Lipoproteins are a special case ofthis Lipids not being water soluble have to be encapsulated to travel the waterb ased bloodstream Lipoproteins essentially put them in a proteinbased bubble Homeostasis body tries to maintain constant conditions Proteins contribute to homeostasis by maintaining acidbase balance Acidity can be defined as an excess of hydrogen ions electrically charged hydrogen particles and basic or alkaline conditions can be defined as a deficiency of these hydrogen ions Proteins are also important in maintaining uid balance Proteins attract and retain uid in the bloodstream through the process of osmosis Osmosis is the movement ofwater from an area oflow solute concentration to an area of high solute concentration through a membrane Osmosis results from the attractive force called osmotic pressure generated by the solute on the water Enzymes are proteins that catalyze biochemical reactions such as those involved in digestion as well as many others Catalysts are chemicals that take part in chemical reactions without themselves being consumed A very small amount of enzyme is needed to react very large amounts of substrate the participant in the reaction 2 amino acids tryptophan and tyrosine are precursors ofthree neurotransmitters Neurotransmitters pass on and modulate nerve impulses Precursors are chemicals that themselves do not have the ability to perform the desired action but are chemically transferred by the body into the active compound be it vitamin neurotransmitter or whatever The gap between nerve cells is the synapse Proteins are important components ofthe immune system Foreign proteins called antigens on the surface of an invading organism such as bacterium we respond with antibodies also proteins as well as other elements Effect ofa protein deficiency is a decrease in the effectiveness of this immune response and an increased risk of infection Even protein gets used as fuel Protein as fuel is most important when we run out of carbohydrate stores You create that glucose from certain amino acids using the process of gluconeogenesis It turns body protein muscle into Carbs something you cant do with fat Protein recommendations are based on age and body weight 5863 grams for adult males and 4650 grams for adult females about 1215 of calories Protein adequacy is not an issue for most of us Put another way ifyou get adequate calories you will probably be getting adequate protein as well Average protein intakes in the US 70 grams for females 90 for males Compare this to RDAs of 50 and 63 grams Protein deficiency is rare in the US and generally requires extraordinary circumstances Children who have higher needs on a body weight basis Pregnant women also have higher needs and for similar reasons high rates of maternal and fetal tissue synthesis Protein does not make muscles grow Appropriate strength training stimulates muscle growth and this does require some extra protein This extra protein requirement of athletes can be as high as 1218 grams per kg body weight for those at the highest levels oftraining about twice the protein needed ofthe normal individual The typical diet supplies twice the protein needed by an average person Practically all foods contain protein High protein foods meats fish poultry and dairy products Usually overlooked are the plant proteins especially the legumes And quality in protein means the essential amino acids Nine ofthe 20 are essential What makes these nine amino acids essential is the fact that the human body does not synthesize them While the other 11 we can make these 9 must be present in out diet ifwe are to have them A high quality protein has all 9 in the correct proportions a low quality protein has insufficient quantity of one or more One way to assess the quality of a protein is through its effect on nitrogen balance Nitrogen balance describes whether we are gaining or losing protein using nitrogen as a surrogate Ifwe are in positive nitrogen balance we are gaining or accumulating protein ifwe are in negative nitrogen balance we are losing or excreting protein Positive nitrogen balance can be achieved in childhood growth pregnancy or muscle building exercise Negative nitrogen balance is seen in starvation If we eat a low quality protein however we soon run out of an amino acid while synthesizing protein This is the limiting amino acid and protein synthesis stops Running out of an amino acid completely stops the process If we feed a high quality protein we see a very little nitrogen excretion Biological value nitrogen retainedJnitrogen absorbed Chemical score a chemical analysis ofthe protein with a comparison to some standard usually egg protein or human milk protein Protein DigestibilityCorrected Amino Acid Score also allows for the digestibility of the protein Animal proteins are much higher quality than plant proteins Milk meat poultry and fish are very high quality while grains seeds beans and veggies are low Health vegetarians lowering their cholesterol or increasing their fiber intake Ethical vegetarians avoiding all animal foods because they just don39t believe in eating them Lactovegetarians eat dairy products along with their plants goods Lactoovovegetarians add in eggs Dairy and egg have the best quality protein to be found Veganseaters ofplant food only Plant proteins often contain much less fat with little saturated fat and no cholesterol rich in complex Carbs and fiber both entirely lacking in animal protein Incomplete plant proteins become whole through protein complementarily This is the practice of combining two proteins to improve their amino acid proportions Through complementarily each protein supplements the other39s limiting amino acid and the right combination yields a high biological value Classic combo is grains and legumes Combining these 2 goods gives a complete protein Protein complementarily makes it entirely practical for vegetarians to get adequate protein from plant foods Plant foods have a lower energy and protein density and lesser amounts ofthese micronutrients What we do see is protein deficiency accompanied by energy deficiency as well We call this Protein Energy Malnutrition PEM PEM is caused not by diets low in protein but by insufficient food across the board It cannot be relived by simply adding more protein to the diet but rather by more of all kinds of food It is caused not by poor food but usually by disruptions in the food supply caused by war poverty or famine PEM comes in two types marasmus and kwashiorkor Both are characterized by fatigue exhaustion and reduced work capacity Both leave the victim prone to infection Both produce emaciation Kwashiorkor however gives its victims the bloated bellies that are caused by abdominal edema a buildup of uid in the abdominal cavity This edema is a failure of the homeostatic action ofprotein discussed previously Normally protein in the blood attracts water to generate an osmotic pressure which draws uid into the bloodstream and retains uid in the blood With insufficient protein in the blood caused by a very low protein intake no force exists to balance blood pressure and uid leaks from the blood vessels accumulating in the abdominal cavity Protein in excess of needs will be stripped of its nitrogen and used for energy or stored as fat This nitrogen compounds formed are excreted in urine High intakes of protein require more urine formation and can contribute to a more rapid deterioration ofthe kidneys in those with kidney disease which often develops as a result of diabetes High intakes ofprotein particularly animal proteins stimulate diuresis This cases higher urinary losses of calcium and may contribute to osteoporosis Diuresis urine formation by the kidney High intake of protein particularly animal protein have been linked to heart disease and various kinds of cancer Excess energy whether protein fat or carbohydrate will contribute to obesity and many protein foods as rich sources of fat Chapter 6 Lipids are hydrophobic and lipophilic literally fatloving Lipids in foods are more commonly referred to as fats and oils fats being solid at room temperature and oils being liquid High fat are important contributors to chronic diseases like cancer heart disease and obesity Most plans actually contain relatively little liquid Complex chemicals containing carbon and hydrogen are called organic compounds re ecting this presence of carbon in life Inorganic carbon in the form of carbon dioxide in the atmosphere Fossil fuels behind the warming trend Three kinds oflipid line in the world triglycerides phospholipids and sterols Most ofthe lipid in our diet as well as in our bodies is triglyceride It is made up of fatty acids Omega end simply terminates in a third hydrogen atom forming what is known as a methyl group The other end known as the alpha end terminates in a carboxyl group Saturated fatty acids a fatty acid in which all ofthe carboncarbon bonds are single bonds It is saturated with hydrogen atoms that is it contains all the hydrogen it can in its structure Found in animal products Fairly linear straightline molecule A linear molecule freezes more readily at a relatively high temperature This property makes saturated fats solid at room temp Having a lot of fatty acids in the membrane provided by a diet rich in saturated fat makes the membrane less effective at removing cholesterol from the blood Saturated fats are the worst dietary contributors to the development of heart disease Saturated fats are more or less synonymous with animal fats coconut oil are highly saturated Fish is not saturated Unsaturated fatty acid has a point on unsaturation that is there is a point a double bond that is not saturated with all the hydrogen it could be One point of unsaturation we call it a monounsaturated fatty acid lower freezing point that saturated fatty acids It takes a colder temp to freeze them Liquid a room temp but will cloud or get stiffifput in the fridge Unlike saturated fats monounsaturated actually lower blood levels of cholesterol A polyunsaturated fatty acid two to six double bonds Remain uid at even lower temps most in fact stay liquid in the freezer An omega3 has its first double bond at the 3rd carbon from the omega end 183 fatty acid has 18 carbons with three double bonds Most common omega6 are vegetable oils which are rich in linoleic acid Omega3s are the fish oils and some ofthem are highly unsaturated Natural fat sources rarely consist of a single fatty acid Increasing saturation raises the melting point of a fat At a given temperature the less saturated a fat is the more uid it is Saturated fats get still at low temperatures Saturated fats make less uid membranes at old temperatures Cold climate plants like corm soybeans and sun owers are highly polyunsaturated They have to be They grow at temperatures just above freezing Triglycerides are nothing more than 3 fatty acids hung on he backbone ofglycerol an alcohol Hydrogenation is a process that saturates unsaturated fats Some of the double bonds are broken and replaced by single bonds to new hydrogen atoms Shortening and margarine are made this way Tansfatty acid do not exist in nature but only in our food supply Fats can become rancid as a result ofperoxidation Double bonds are not as stable as single bonds and are liable to attack by free radical oxygen a particularly reactive species of oxygen Free radicals have an unpaired electron in their outer shell which is not a very stable state Phospholipids show up in soybeans and egg yolks and are frequently added in processing as emulsifiers Like all lipids phospholipids contain calories and despite being emulsifiers do not dissolve fat from body as is sometimes claimed Antioxidantssubstance which protects cellular components against oxidation by reacting with free radical oxygen itself Sterols consist of or are derived from a fourring structure Cholesterol we need it Fortunately we can synthesize our own which keeps it from becoming an essential nutrient It is only made in animals Fake fats Olestra trade name Olean is the primary lipid fat substitute currently on the market It feels tastes and cooks like fat but because it is not digestible it yields no calories Lipids are not soluble in water Triglycerides are broken by lipase into monoglycerides and free fatty acids for absorption They are absorbed into the intestinal mucosal cells where they are reassembled into triglycerides Phospholipids are similarly broken down for absorption and reassembled in the mucosa Sterols are absorbed unchanged All these dietary lipids are packaged into chylomicrons are large droplets oflipid sealed into a shell of cholesterol protein and phospholipids Most ofthe lipid in your diet is triglyceride An enzyme known as lipoprotein lipase present on the arterial wall breaks triglyceride down into free fatty acids and glycerol VLDLs are also most triglyceride the lightweight substance behind their low density lipoprotein formed in the liver which transports endogenous triglyceride to body cells It also receives cholesterol from HDL for return to the liver Endogenousmade within the body Stripped oftheir triglyceride the VLDL remnants return to the liver but not before they pick up cholesterol from HDL So endogenous cholesterol dietary cholesterol and scavenged cholesterol from HDL are all returned to the liver by VLDL The liver packages all this cholesterol into LDL Whereas chylomicrons and VLDLs delivered triglyceride to the body via the bloodstream LDL delivers cholesterol Liver cells also have LDL receptors Saturated fats block this process preventing the liver from clearing LDL from the blood Consequently diets high in saturated fats elevate blood levels of LDL Cholesterol remains in circulation Accumulation of cholesterol forming arterial plaques Because LDLs deliver this cholesterol to the arteries high levels of LDLs are closely associated with the risk of developing heart disease however the LDL s delivery of cholesterol to other body cells is a beneficial and normal process HDL are made by the liver getting their high density from the high protein content HDL pulls cholesterol out ofthe arterial plaques and transfers it back to the liver high levels of HDL are associated with a lowered risk of heart disease Like the other macronutrients fat supplies energy and has a high energy density We store triglyceride in adipose tissue Eicosanoidlipid regulatory substance with a local effect Made from longchain polyunsaturated fatty acids Our bodies can make any saturated fats we need We can elongate shorter fatty acids chains and we can add double bonds to the 9th carbon or later We can39t make omega 3 or 6 fatty acids though we can make existing ones longer So the only two fatty acids essential in our diet are the omega 3 fatty acid alphalinoleic acid and the omega 6 fatty acid linoleic acid A deficiency ofthese essential fatty acids seen only in adults on long term fatfree intravenous feeding shows up as dermatitis and as the effects ofinadequate eicosanoid production Cholesterol turns out to be vital for our continued operation Dietary fats have been linked to heart disease and cancer CHD resulting in heart attack is the leading cause of death in this and most other industrialized nations Heart attacks rarely strike young people Pathology is the study of disease processes Atherosclerosis is a thickening and narrowing ofthe arterial walls caused by the growth of arterial plaques This causes chest pain known as angina Ischemia insufficient blood ow It the tissue supplied by this artery was heart muscle we call it a myocardial infarction or heart attack and if it was brain we call it a stroke Ischemia of this sort can happen anywhere and is often seen in intestines or legs Etiology is the study ofthe causes of disease Uncontrollable risk factors for heart disease include age gender especially in middle age since estrogen protects women After menopause women lose this protection and with increasing age their risk catches up with that of men Controllable factors smoking high blood pressure and obesity Saturated fats prevent the uptake of LDL from the blood by the liver and have a powerful elevating effect of LDL Transfatty acids those intruders in hydrogenated fats also raise LDL cholesterol Dietary cholesterol will not raise blood cholesterol levels Monounsaturated fats and omega6 polyunsaturated are good Both lower LDL though the omega quot6 PUFAs may do so somewhat more Omega 3 polyunsaturated the fish oils reduce your chances of having a heart attack Lower blood triglycerides Reduce blood clotting thorough their effect on eicosanoid synthesis Reduce the risk of sudden death Moderate alcohol use increases HDL and lowers heart attack risk Soluble fiber binds with bile acids made with cholesterol in the guy forming an insoluble compound this prevents the reabsorption ofthe bile acids and hence their recirculation by causing them to be excreted Soluble fiber therefore tends to lower blood cholesterol Animal studies tell us that high fat intakes and particularly high polyunsaturated fat intakes spur the onset of cancer Animals on high fat diets and particularly high polyunsaturated fat diets get more cancer Result of higher fat or of lower carbohydrate Countries with high fat intake have more breast cancer The nurse39s study also produced typical results in this case no correlation between fat intake and breast cancer incidence The researchers concluded that high fat intakes DO NOT cause breast cancer Among plant foods lipids can be found in nuts and oilseeds from where we get vegetable oils Very few grains legumes vegetables or fruits contain significant fat No minimum requirement for fat High intakes of saturated fat say over 10 of calories are directly implicated in heart disease even though saturated fat contains no more calories than other fats Low fat diets probably reduce cancer risks Asian style diet lots ofgrain products rice noodles and breads high in vegetables and legumes as well with lesser amounts of most animal foods though fish is consumed frequently Fat intakes can be in the range of 1020 with most of that being mono and polyunsaturated fat The bulk of calories come from carbohydrate Mediterranean diet is about a high in fat as a conventional North American dies The big difference is in the type of fat Unlike the highcarbohydrate Asian diet a Mediterranean diet substitutes monounsaturated fat for saturated fat Is higher in grains legumes and vegetables than the US diet and lower in animal foods though fish may be consumed frequently Chapter 7 Thrifty metabolism a genetically determined energy efficient metabolism requiring few calories for daily activities In an environment of scarce food such as found in prehistoric times a thrifty metabolism allowed the storage of seasonally abundant food as body fat for use in times of food shortage In a modern environment with a large surplus of calories a thrifty metabolism contributes to the development of obesity Obesity is the product ofgenetics and environment Most body processes could be described as anabolic those that create more complex chemical compounds for energy storage or synthesis oftissue or as catabolic those that break down complex compounds for energy release or tissue breakdown During weight gain we see anabolism while in weight loss we are hoping to stimulate catabolism Anabolism is the bodybuilding itself We see anabolism in infant growth pregnancy weight gain and muscle building Glycogen synthesis is an anabolic process Insulin is the hormone that directs anabolism Catabolism is the body breaking itself down Catabolism occurs during exercise fasting or physiological stress when the body needs energy ATP is used to translate chemical energy from nutrients into the life processes that sustain us When you go for a run you can produce the ATP necessary for that run from blood sugar muscle glycogen body fat stores or breakdown of muscle protein Fat only supports low intensity exercise Energy can readily change form however going from nuclear energy to heat and light to chemical energy to mechanical energy and heat to the energy ofmotion kinetic energy and finally to heat 1000 calories equals one kilocalorie We take in energy only in the form of chemical energy store in macronutrients If we are in energy balance we are neither gaining nor losing energy Energy intake energy expenditure We expend energy in 3 ways through basal metabolism physical activity and the Thermic Effect of Food TEF The rate of your expenditure under these conditions is your BMR and your day39s total expenditure by these activities is your Resting Energy Expenditure REE makes up around 23 oftotal energy expenditure in the average person Almost all your BMR is generated by lean tissue Physical activityenergy expenditure through voluntary physical effort For a given activity the heavier you are the more calories it will cost you TEF is the energy cost of eating TEF is the energy expended digesting absorbing transporting storing and metabolizing nutrients Total Energy Expenditure TEE is the sum of REE physical activity and TEF Obesity contributes significantly to heart disease Type II diabetes hypertension cancer stroke and arthritis Heightweight tables were originally developed by insurance companies BMI also compares height and weight BMI weightheightquot2 A BMI ofgreater than 25 is overweight and a BMI ofmore than 27 is obese Prevalence is the number of cases in a given pop or the proportion ofthe population suffering from the stated condition Relative risk is the increase in risk seen in a higher risk group over than seen in the lowest risk group BMI fails to discriminate between fat and lean tissue Total body mass is the sum oflean tissue mass and fat mass Problems of obesity stem from fat mass We generally see women with higher body fat than men and body fat increasing with age in adulthood A desirable range for men might be around 1020 and for women about 1825 Males having more than 25 fat and females having more than 30 can be considered obese Underwater weighing fat oats and lean tissue sinks density predicts fatness which explains the necessity of exhaling to get an accurate reading Skinfold calipers used to measure thickness of the fat layer under the skin in several locations such as triceps shoulder blade and abdomen Body Impedance Analysis BIAJ small electrodes are attached to hand and foot and a minute amount of electricity is passed through the body Body water containing electrolytes conducts electricity well Adipose tissue with little water does not Like skinfolds measures this works best on people who need it little Subcutaneous fat is right under the skin And skinfolds measure this Visceral or abdominal fat occurs inside the abdominal cavity Under the abdominal muscles inside the gut Intramuscular fat is interspersed with muscle fibers in the muscle In android obesity the so called apple shapequot most fat is carried abdominally This distribution is more common in men In gynecoid obesity the so called pear shapequot more fat is carried lower on the body on the hips and thighs We see this pattern more often in women Android obesity carries a substantially higher risk of hypertension Type II diabetes and heart disease than does gynecoid obesity These fat distributions are defined by the hiptowaist ratio A ratio greater than about 111 can be considered android obesity Over 60 of US adults are overweight 20 human genes link to obesity Set point theory is the notion that one39s body tends to gravitate to a particular weight Body resists changes in weight Having lost weight you also burn fewer calories That weight tends to come back Set point is also governed by the hormone leptin Adipose cells produce Leptin when they have reached a particular level of fat content Leptin diminishes appetite Body39s principle site for energy storage adipose Adipose tissue is essential for normal reproductive function in women Amenorrhea this cessation of menstruation is associated with lower levels of estrogen Combination of amenorrhea eating disorder and low bone density has been referred to as the female athlete triad Adipose tissue cushions internal organs from blows and absorbs shock Adipose tissue gives us insulation from the elements Adipose tissue grows in two ways through an increase in the number of cells hyperplasia and through an increase in cell size hypertrophy Wight gain due to hyperplasia tends to be harder to lose since the number offats cells crying out to be filled remain high Hyperplasia tends to occur more in growing children Many defeat themselves by lowering metabolism Ifyou lower your metabolism you lower your caloric requirement Rapid weight loss tends to be a loss ofbody water and lean muscle mass The only way to lose fat is to burn it off A pound ofbody fat and the water associated with it contains about 2700 kcals Muscle loss lowers metabolism Any reduction in food intake triggers metabolic slowdown A slower metabolism means you need fewer calories to maintain your weight and it gets harder to lose weight Very Low Calorie Diets lowering metabolism and training yourself not to eat while increasing binging High protein Lowcarbohydrate diets promotes losses of water and lean tissue as well as fat lowering metabolism and producing rebound weight gain Highmeat diets have to be very high in saturated fat the biggest promoter of heart disease Gastric bypass operations stomach stapling and the like are collectively called Bariatric surgery Sibutrimine phentermine and orlistat are drugs When in energy balance energy intakeenergy expenditure Reduce intake and increase expenditure to lose weight A thirty minute walk will be the same as three ten minute walks in terms of energy consumption Cardiovascular benefits will not be the same however during makes a difference there Any time you raise heart rate and breathing you are burning calories at a high rate Strength exercises rarely consume many calories during exercise since much of the session is spent recovering but have a great longterm effect on weight Activities that build muscle will indirectly raise metabolism as the muscle is built The other way to increase energy expenditure is to keep your metabolism high Weight loss to do any good must be fat loss Loss oflean body mass lowers metabolism Food restriction lowers basal metabolism Lower the energy density ofyour diet Energy density is the amount of energy or calories carried in a measure of food Replace that fat with complex carbohydrate Starch should be the biggest single component ofyour diet Vegetables are perhaps the ideal weight loss food Great advantage of low energy density foods is being able to eat way more food for the same number of calories Greater volume gives greater satiety
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