Lecture Notes Chapter 5 & 6
Lecture Notes Chapter 5 & 6 HS 331
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This 12 page Class Notes was uploaded by Sydney Brummett on Saturday September 24, 2016. The Class Notes belongs to HS 331 at Wichita State University taught by Dr. Lisa Wray in Fall 2016. Since its upload, it has received 45 views. For similar materials see Principles of Diet and Nutrition in Health Sciences at Wichita State University.
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Date Created: 09/24/16
Chapter 5 Lecture: Fats: Essential Energy-Supplying Nutrients, and In Depth 5.5, Cardiovascular Disease What are fats? o Fats are one type of lipid o Lipids: diverse class of organic substances that are insoluble in water Lipids (fats) do not dissolve in water Triglycerides o Most of the fat we eat is in the form of triglycerides o Triglycerides are composed of Three fatty acid molecules Fatty acids: long chains of carbon atoms surrounded by hydrogen atoms One glycerol molecule Glycerol: a three-carbon alcohol that is the backbone of a triglyceride o Fatty acids can differ in Length of their carbon chain Short (<6 carbons), medium (6-12 carbons), or long (<13 carbons) Level of saturation Saturation refers to how many hydrogen atoms surround each carbon Shape o Saturated fatty acids have hydrogen atoms surrounding every carbon in the chain; they have no double bonds o Monounsaturated fatty acids lack hydrogen atoms in one region; they have one double bond o Polyunsaturated fatty acids lack hydrogen atoms in multiple locations; they have two or more double bonds o Note: each double bond causes the loss of two hydrogen atoms o The shape of a triglyceride is determined by the saturation of the carbon chains o Saturated fatty acids can pack tightly together and are solid at room temperatures For example, coconut oil, animal fats, butter and lard are high in saturated fatty acids o Unsaturated fatty acids do not stack well together well and are liquid at room temperature The predominant type in plants Two exceptions are coconut and palm kernel oil o The hydrogen atoms at the unsaturated region can be arranged in different positions Cis: same side of the carbon chain Trans: opposite sides of the carbon chain. o Hydrogenation: the addition of hydrogen atoms to unsaturated fatty acids Converts liquid fats (oils) into a semisolid (spreadable) or solid form Used to create margarine from plant oil Often creates trans fatty acids Listed on food labels as partially hydrogenated oil Essential fatty acids o Essential fatty acids cannot be synthesized in the body and must be obtained in the diet Omega-6 and omega-3 fatty acids They are precursors to biological compounds called eicosanoids, which regulate cellular function o Linoleic acid is found in veggies and nut oils o Alpha-linolenic acid (ALA) is derived from dark-green leafy veggies, flaxseeds and flaxseed oil, soybeans and soybean oil, walnuts and walnut oil, and canola oil o Eicosapentaenoic Acid (EPA) and docosahexaenoic acid (DHA) have important health benefits and are found in fish, shellfish, and fish oils Phospholipids o Phospholipids: Composed of Glycerol backbone Two fatty acids Phosphate Soluble in water Manufactured in our bodies so they are not required in our diet Important components of cell membranes Sterols o Sterols: lipids containing multiple rings of carbon atoms Essential components of cell membranes and many hormones Manufactured in our bodies and therefore not an essential component of our diet Cholesterol is the major sterol found in the body Why do we need fats? o Energy Fat is very energy dense, providing 9 kcal/gram Much of the energy used during rest comes from fat Fat is used for energy during exercise, especially after glycogen is depleted Fat is also used for energy storage o Fat-soluble vitamins Vitamins A, D, E and K are soluble in fat; fat is required for their transport o Fat is essential to many body functions Cell membrane structure Nerve cell transmissions Protection of internal organs Insulation to retain body heat o Fat provides flavor and texture to foods o Fat contributes to making us feel satiated Fats are more energy dense than carbohydrates or protein Fats take longer to digest How does out body process fats? o As fat enters the small intestine: Bile is secreted from the gallbladder into the small intestine Bile is produced by the liver and stored in the gallbladder Bile disperses fat into smaller fat droplets Pancreatic enzymes break triglycerides into two separate fatty acids and a monoglyceride Fat enters the mucosal cell as a micelle (fatty acids, monoglyceride, phospholipids, and sterols) o In the intestinal mucosal cell: Fatty acids are reattached to the monoglyceride to re-form triglycerides A small amount of protein is added to the lipids, forming a chylomicron Chylomicron: a lipoprotein produced by cells lining the small intestine Composed of triglycerides surrounded by phospholipids and proteins Soluble in water Chylomicrons are the transport vehicles that remove absorbed fats from the small intestine Travel through the lymphatic system Are transferred to the bloodstream Short and medium-chain fatty acids are absorbed more quickly because they are not arranged into chylomicrons One the chylomicron gets to a cell in the body, the triglycerides in the chylomicrons must be disassembled by lipoprotein lipase into two fatty acids and a monoglyceride before they can pass through the cell membrane After entering the cell, the two fatty acids and monoglyceride re-form a triglyceride The triglyceride can be: Used immediately for energy Used to make lipid-containing compounds Stored in liver and muscle cells How much fat should we eat? o The Acceptable Macronutrient Distribution Range (AMDR) for fat 20 – 35% of calories should be from fat o Athletes and highly active people may need more energy from carbs and can reduce their fat intake to 20-25% of total calories o The type of fat consumed is important Intake of saturated and trans fatty acids should be minimized as much as possible We typically get enough linoleic acid in our diets from salad dressings, veggie oils, margarines, and mayonnaise To ensure an adequate amount of omega-3 fatty acids, we need to consume more dark-green leafy veggies, walnuts, flaxseeds, and fish or fish oils Recognize the Fat in Foods o Visible fats are those we can see in foods or can easily see have been added to foods, such as dressing or chicken skin o Hidden fats are those added to processed or prepared foods to improve texture or taste, which may not be aware of, or that occur naturally o Read the Nutrition Facts Panel on foods carefully Lower-fat versions of foods may not always be lower in calories Limit Saturated and Trans fats o Reduce your intake of saturated fats Be conscious of the saturated fat content of meats, baked goods and snack goods, and foods including veggies that are fried, breaded, or drenched in sauce o Avoid trans fatty acids o Limit your intake of dietary cholesterol, which will also help limit your intake of saturated fats Select Beneficial Fats o Consume and cook with leafy green veggies, avocados, soybeans, soybean oil, and flaxseed oil o Add walnuts, almonds, flaxseeds, and chia seeds to your diet, and try almond milk in your cereal o Consider including fish in your diet at least twice a week or consider taking a fish oil supplement Fish can contain mercury, PCBs, and other environmental contaminants, so be selective Fat Replacers o Snack foods are frequent targets for fat replacers, substances that can reduce the fat content o Fat replacers such as olestra have not proved very popular or effective because of potential gastrointestinal side effects o Our growing obesity problems indicate that fat replacers do not help Americans lose weight Role of Fats in Chronic Disease o The chronic disease most closely associated with diets high in saturated fat is cardiovascular disease o The role of dietary fat in the development of cancer has been extensively researched, but the relationship between some cancer types and dietary fats is controversial (e.g., breast cancer) o The strongest association between dietary fat and cancer is for prostate cancer In depth: cardiovascular Disease o Cardiovascular disease (CVD) Dysfunction of the heart or blood vessels The most common forms: Coronary heart disease, or coronary artery disease Stroke Hypertension, or high blood pressure Peripheral vascular disease o Atherosclerosis is a disease in which artery walls build up lipid deposits and scar tissue, impairing blood flow The stiffness that results is commonly called “hardening of the arteries” The result is that the heart must work harder to push blood through the vessels o Hypertension is a major chronic disease in the US o It functions as a warning sign for a person’s risk for developing heart disease or stroke o For many people, hypertension is hereditary; for others, it can be induced through poor nutrition and exercise habits or a combination of poor habits and heredity o Modifiable risk factors for cardiovascular disease include: Being overweight Physical inactivity Smoking Type 2 diabetes mellitus Inflammation in the body Abnormal blood lipids o The intake of certain types of fats can protect against heart disease Diets high in omega-3 fatty acids (along with moderate exercise) can reduce inflammation and increased HDL (“good”) cholesterol levels Low-density lipoproteins (LDLs) are often called “bad” cholesterol because of their role in transporting cholesterol throughout the body o Diets high in saturated fats Decrease the removal of LDLs from the blood Contribute to formation of plaques that can block arteries Increase triglyceride levels (chylomicrons and very-low- density lipoproteins, or VLDLs) o Recommendations to improve blood lipid levels Keep total fat intake level to within 20-35% of your daily energy intake Decrease your dietary saturated fat to less than 7% of total energy intake Increase your consumption of dietary omega-3 fatty acids from foods (e.g., green veggies, fish) Consume 400 micrograms/day of folate Increase dietary intakes of whole grains, fruits, and veggies Maintain blood glucose within normal ranges Eat meals throughout the day rather than eating most of your Calories in the evening before bed Limit alcohol consumption Don’t smoke Maintain an active lifestyle Maintain a healthful body weight Limit dietary sodium Follow the DASH diet Dietary Approaches to Stop Hypertension If needed, use doctor-prescribed medications Chapter 6 Lecture: Proteins What are proteins? o Proteins Large, complex molecules found in the cells of all living things Critical components of all the tissues of the human body Functions in metabolism, immunity, fluid valance, and nutrient transport In certain circumstances, provide energy Contain a special form of nitrogen our bodies can readily use Amino acids o Amino acids are the nitrogen-containing molecules that combine to form proteins o Essential amino acids Cannot be produced by our bodies Must be obtained from food Nine of 20 amino acids in our bodies are essential o Nonessential amino acids Can be made by our bodies (11) How are proteins made? o When two amino acids join together in a peptide bond, they form a dipeptide o Ten or more amino acids bonded together form a polypeptide o Proteins are made by combining multiple amino acids o Transcription: use of the genetic information in DNA to make RNA mRNA copies the genetic information and carries it to the ribosome o Translation: conversion of genetic information in RNA to assemble amino acids in the proper sequence to synthesize a protein on the ribosome Protein Organization Determines Function o Protein structure has four levels Primary structure Sequential order of amino acids Secondary structure Spiral shape due to chemical bonding between the amino acids Tertiary and quaternary structure Further folding into a unique 3D shape that may be globular or fibrous Protein function o Proteins lose shape (denaturation) when subjected to Heat Acids and bases Heavy metals Alcohol Protein synthesis can be limited o Incomplete protein: does not contain all essential amino acids in sufficient quantities Growth and health are compromised Considered a “low-quality” protein o Complete protein: contains sufficient amounts of all nine essential amino acids Considered a “high-quality” protein Protein synthesis can be enhanced o Mutual supplementation: combining two incomplete proteins to make a complete protein o Complementary proteins: two protein sources that together supply all nine essential amino acids Example: beans and rice Why do we need proteins? o Cell growth, repair, and maintenance o Enzymes o Hormones o Fluid and electrolyte balance o pH balance o Antibodies to protect against disease o Energy source o Transport and storage of nutrients o Compounds such as neurotransmitters, fibrin, and collagen How do we break down protein? o Stomach acids and enzymes break proteins into short polypeptides o Digestion of proteins continues in the small intestine, where the polypeptides are further broken down Pancreatic enzymes called proteases complete the digestion of proteins into single amino acids o Protein digestibility affect protein quality o Animal protein sources (meat, dairy), soy products, and legumes are highly digestible o Grains and vegies proteins are less digestible How much protein should we eat? o People who require more protein include Children Adolescents Pregnant or lactating women Athletes Vegetarians o Nitrogen balance describes the relationship between how much nitrogen (or protein) we consume and excrete each day o Recommended Dietary Allowance (RDA) 0.8 grams of protein per kilogram of body weight per day 10-35% of total energy intake should be from protein o Most Americans meet or exceed the RDA for dietary protein o This is true for many athletes as well o Certain groups of athletes, such as distance runners, figure skaters, female gymnasts, and wrestlers who are dieting, are at risk for low protein intake Too much dietary protein can be harmful o The risks of too much dietary protein include High cholesterol and heart disease Diets high in protein from animal sources are associated with high blood cholesterol Kidney disease High-protein diets are associated with an increased risk of kidney disease in people who are susceptible o There is no evidence that high-protein diets lead to bone loss, except in people consuming inadequate calcium Protein: much more than meat! o Many foods besides meat can be good protein sources, including dairy products, eggs, legumes, whole grains, and nuts o “New” good sources of protein include quorn, quinoa, amaranth, teff, millet, and sorghum Can vegetarian diets provide protein? o Vegetarianism: restricting the diet to foods of plant origin There are many versions of vegetarianism There are many reasons to adopt a vegetarian diet Why Vegetarianism? o People choose vegetarianism because of: Health benefits Ecological reasons Religious reasons Ethical reasons Concerns over food safety Health benefits of vegetarianism o Lower intake of fat and total energy o Lower blood pressure o Reduced risk for heart disease o Reduced risk for some types of cancer o Fewer digestive problems o Reduced risk for kidney disease, kidney stones, and gallstones Challenged of vegetarianism o Diets can be low in some vitamins and minerals (iron, calcium, zinc, vitamins D and B12) o Must plan a balanced and adequate diet o Soy products are an excellent protein source o Should include complementary proteins o Can find healthy eating tips for vegetarians at MyPlate online Disorders related to protein in take o Protein-energy malnutrition: a disorder caused by inadequate intake of protein and energy o There are two common, serious forms: Marasmus Kwashiorkor o Marasmus: disease resulting from severely inadequate intakes of protein, energy, and other nutrients It is characterized by extreme tissue wasting and stunted growth and development o Kwashiorkor: disease resulting from extremely low protein intake Symptoms include: Some weight loss and muscle wasting Edema resulting in distention of the belly Retarded growth and development Often seen in children in developing countries Disorder related to Genetic abnormalities o Phenylketonuria (PKU) is a disorder in which a person does not have the ability to break down the amino acid phenylalanine o Sickle cell anemia causes red blood cells to be shaped in a way that impedes their transport to body tissues o Cystic fibrosis causes an alteration in chloride transport, leading to a sticky mucus that causes life-threatening respiratory and digestive problems In depth: vitamins and minerals o Macronutrients: Carbs Fats Protein Provide energy Required in relatively large amounts o Micronutrients: Vitamins Minerals Do not supply energy Required in relatively small amounts Assist in body functions (energy metabolism, maintenance of healthy cells and tissues) Absorption may be very low (2-10%) when compared to macronutrients (85-99%) Many micronutrients need to be chemically altered before they are active in the body o Vitamins Organic compounds 13 are essential Nine are soluble in water Four are soluble in fat o Characteristics of fat-soluble vitamins Large storage capability Toxicity is possible Deficiency symptoms may take many months to develop May occur in numerous chemical forms o Characteristic of water-soluble vitamins: Minimal storage capability Toxicity is rare Deficiency symptoms occur quickly Excreted in urine when tissues are saturated o General properties of minerals Inorganic Cannot be synthesized by plants or animals Not digested or broken down prior to absorption Two classifications based on need o Characteristic of major minerals Required in amounts of at least 100 mg/day Body contains 5 g or higher Seven major minerals o Characteristics of trace minerals Required in amounts of less than 100 mg/day Body contains less than 5 g Eight trace minerals are essential for human health o Absorption of micronutrients depends on numerous factors Chemical form (e.g., absorption of heme iron from meats, fish, poultry is ~25%, whereas non-heme iron from plant products is ~3-5%) Numerous factors in foods bind micronutrients and prevent absorption Other nutrients within a meal alter absorption o Supplementation of micronutrients is controversial: Easier to develop toxicity with supplements Some may be harmful to certain subgroups of consumers Most minerals are better absorbed from animal food sources Eating a variety of foods provides many other nutrients (e.g., phytochemicals) Supplements may alter the balance between nutrients o Adequate intake of these minerals had been associated with lowered disease risk Vitamin D and colon cancer Vitamin E and complications of diabetes Vitamin K and osteoporosis Calcium and hypertension Chromium and type 2 diabetes in older adults Magnesium and muscle wasting in older adults Selenium and certain types of cancer o Do more essential micronutrients exist? We don’t think so o Nutrition researchers continue to explore the possibility of other substances being essential o Vitamin-like factors (e.g., carnitine) and numerous minerals (e.g., boron, nickel, silicon) may prove to be essential in our diet
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