Chapter 5 The Lipids: Triglycerides, Phospholipids, and Sterols

Transcription

1 5-1 Chapter 5 The Lipids: Triglycerides, Phospholipids, and Sterols IF NOTHING ELSE, MY STUDENTS SHOULD LEARN 1. The lipids include triglycerides (fats and oils), phospholipids, and sterols. In foods, fats provide flavour, tenderness, and palatability. Triglycerides in the diet provide fat soluble vitamins and add satiety. Triglycerides provide energy, insulation, and protection from shock, and help the body use protein and carbohydrate optimally. Sterols are found in both plant and animal foods, but cholesterol is found only in animal products. Phospholipids are used as emulsifiers in foods. 2. That the digestion of lipids involves multiple enzymes secreted from accessory digestive organs. Absorption of lipids occurs through the lymphatic system first, followed by movement into the cardiovascular system as packaged lipoproteins. 3. That dietary fats take on many forms, including saturated, monounsaturated, and polyunsaturated fatty acids, and have different implications on overall health. 4. How to recognize the presence of different levels and types of dietary lipids in food sources by reading nutritional labels. LEARNING OBJECTIVES Students should be able to: LO 5.1: Discuss the role of dietary lipids as a component of a healthy diet. [Understand/Apply] LO 5.2: Compare and contrast the physical properties and food sources of saturated, monounsaturated, and polyunsaturated fatty acids. [Remember/Understand] LO 5.3: Describe how dietary lipids are digested at various levels within the digestive system, as well as the role of the accessory digestive organs in accelerating lipid breakdown. [Remember/Understand] LO 5.4: Describe how dietary lipids are absorbed and transported throughout the body as lipoproteins. [Remember/Understand]

2 5-2 LO 5.5: Describe the roles of omega 3 and omega 6 fatty acids in the body and the importance of achieving a balanced intake. [Understand] LO 5.6: Explain the health implications of ingesting dietary lipids, as well as LDL and HDL and the factors that raise or lower levels of these lipoproteins. [Understand] LO 5.7: Describe the formation and structure of a trans fatty acid and discuss the possibility of eliminating them from the diet. [Understand/Apply] LO 5.8: Discuss the role of fat in the development of heart disease, cancer, and obesity. [Understand/Apply] LO 5.9: Outline examples of different choices that can be made within the food groups to reduce the amount of lipids in a diet. [Understand/Apply] W H Y I S T H I S C H A P T E R I M P O R T A N T T O S C I E N T I S T S A N D H E A LT H C A R E P R A C T I T I O N E R S? Of special interest to... symbol key: = Health Care Practitioners 2 = Science Majors Health care practitioners recognize that when monounsaturated or certain polyunsaturated fats replace saturated and trans fats in the diet, it protects against heart disease. Scientists continue to study the properties of various oils used in our diets in order to determine the health benefits. Elevated blood cholesterol is a major risk factor for cardiovascular disease. Scientists continue to study ways of lowering LDL cholesterol and/or increasing HDL cholesterol through diet, exercise, or a combination of both interventions. Health care practitioners typically advise patients of the cardiovascular disease risks posed by consuming excessive amounts of dietary fats/cholesterol. A deficiency in an essential fatty acid in the diet has adverse effects on the health of an individual. Research has established that increasing the intake of certain fatty acids (e.g., omega 3 fatty acid) can improve the health of the heart. Scientists also are reporting that omega 3 fatty acids may support immunity and inhibit the development of certain cancers.

3 5-3 WHY SHOULD STUDENTS CARE? Lipids not only serve as energy reserves but also cushion the vital organs, insulate the body from temperature extremes, enhance absorption of fat soluble nutrients and phytochemicals, and provide the major component of which cell membranes are made. Fat tissue also secretes hormones and produces enzymes. Students should be aware that lipids provide more energy per gram than carbohydrate and protein, enhance the aromas and flavours of foods, and contribute to satiety, or a feeling of fullness, after a meal. It is important for students to know that the body s storage form of fat is triglyceride, which is made up of three fatty acids and a single glycerol molecule. Fatty acids differ in chain length and degree of hydrogen saturation. Fatty acids can be saturated (filled with hydrogens), monounsaturated (with one point of unsaturation), or polyunsaturated (with more than one point of unsaturation). The degree of saturation of the fatty acids will determine how liquid or solid that food item will be at room tempreature. Students need to know that unsaturated fats are liquid at room temperature and become solid as more hydrogen atoms are added. Phospholipids, including lecithin, play key roles in cell membranes; sterols play roles as part of bile, vitamin D, the sex hormones, and other important compounds. Students should be aware that in order to absorb lipids from a meal after digestion, they are packaged into a specialized form of lipoprotein called chylomicrons, and move into the lymphatic system. Chylomicrons then move into the cardiovascular system a short time following absorption. Students should know that there are different forms of lipoproteins which are chylomicrons, very low density lipoproteins (VLDL), low density lipoproteins (LDL), and high density lipoproteins (HDL). It is LDL and HDL concentrations in the blood that determine cardiovascular disease risk. Students should know that elevated blood cholesterol is a risk factor for cardiovascular disease. Among the major dietary factors that raise blood cholesterol, saturated and trans fat intakes are the most influential, while dietary cholesterol actually raises blood cholesterol to a lesser degree. It is important for students to be aware of two polyunsaturated fatty acids, linoleic acid (an omega 6 acid) and linolenic acid (an omega 3 acid), are essential nutrients used to make substances that perform many important functions. The

4 5-4 omega 6 family includes linoleic acid and arachidonic acid. The omega 3 family includes linolenic acid, EPA, and DHA. Students should know that hydrogenated fats, as found in vegetable oils, resist rancidity better, are firmer textured, and have a higher smoking point than unsaturated oils, but also lose the health benefits of unsaturated oils. W H AT A R E C O M M O N S T U D E N T MISCONCEPTIONS/STUMBLING BLOCKS? 1. Students may initially have difficulty understanding the differences between saturated and unsaturated fatty acids. Giving students an illustration of the differences between the two types of lipids is useful when presenting the topic. 2. Many students who start an introductory nutrition course have the misconception that cholesterol is bad. It is important for students to be aware that cholesterol has different forms and that not all forms of cholesterol are bad (distribute Handout 5 3). 3. It is often difficult for students to gain an appreciation of the vast health benefits associated with the ingestion of omega fatty acids. Distribute Handout 5 4: Why Omega 3 Fatty Acids Are Considered Good Fats and discuss in class the health benefits of these fatty acids. W H AT C A N I D O I N C L A S S? There are a variety of activities that can be done in class. Listed below are some activities that will help introduce the topic of nutrition, and the students to each other. Classroom Activity 5 1: Chapter Opening Quiz Objective: Introduction to chapter Class size: Any Instructions: As a way of introducing any new chapter, give a quiz to the class. This is a quiz designed to be projected overhead using available technology. For details, please see Chapter 1, Classroom Activity

5 5-5 Classroom Activity 5 2: Compare Energy Values of Food Prepared by Different Techniques Key concept: Effect of food preparation method on fat content Class size: Any Instructions: Instruct students to calculate and compare the kcalories in a baked, broiled, or steamed food versus the same food after frying. Use the table of nutrient value of foods in APPENDIX H of the textbook. Classroom Activity 5 3: How to Modify a Recipe1 Key concept: Strategies for cutting fat in recipe Class size: Any Materials needed: A copy of Handout 5 1 for each student Instructions: Recipes can be modified to retain flavour and texture while the fat content is reduced during food preparation. Provide students with a copy of Handout 5 1: How to Modify a Recipe Lasagna. Discuss the items substituted for fat. Instruct students to bring in their own traditional recipes and practise modifying them according to these suggestions. You can even designate a day for students to bring in food items they prepared from a modified recipe. Classroom Activity 5 4: Discussion of Changing Guidelines for Fat Intake Object: Exploring beliefs about fat Class size: Any Instructions: At the beginning of discussion of this chapter, ask students to write on a sheet of paper their beliefs about fat intake recommendations. Instruct them to be as specific as possible. Give them 5 10 minutes to complete this exercise. Then ask students to share what they believe and compile a list. You can tell them that they will explore these statements in this chapter and can talk about the challenge of presenting nutrition information to the public. Classroom Activity 5 5: Trans Fat Label Analysis Key concept: Trans fat; reading food labels Class size: Any Materials needed: Copy of Worksheet 5 1 for each student Instructions: Trans fat has major health implications, and food labels include information regarding this fat. Distribute Worksheet 5 1 and have students complete the questions. Classroom Activity 5 6: Review of Fats Objective: Review Class size: Any Materials needed: Copy of Worksheet 5 2 for each student. Instructions: Distribute Worksheet 5 2 and have students complete the questions. 1 Activity provided by Sandra Woodruff, MS, RD.

6 5-6 Critical Thinking Questions2 These questions will also be posted to the book s website so that students can complete them online and their answers to you. 1. Lipids are chemically classified into three different categories: triglycerides, phospholipids, and sterols. Discuss the details of these three different categories and the role they play in our bodies and in the food industry. 2. As your textbook points out, lipids are hydrophobic, which could be problematic as regards their absorption. However, lipid enzymes are hydrophilic, enhancing the ability for lipids to be digested and absorbed. Discuss the variety of factors that are involved in the absorption and transport of lipids in the body. How can some of these factors be confusing to the average health consumer? 3. Lipids have many important functions. Discuss what important roles lipids have in our bodies. 4. Differentiate between all the various components in a blood lipid profile. Discuss how different types of lipids can affect the blood lipid profile, and how diet and exercise habits can be modified to improve it. 5. It is clear that many Canadians consume too much fat or too many lipids in their diets. This might be evidenced by the high prevalence of obesity, average cholesterol and LDL levels, and dietary intake patterns of the Canadian consumer. There are individuals who become fearful of obesity because of the prevalence of such statistics, and therefore select diets almost void of fats. (a) What might this type of diet look like, (b) what might be the outcome of such a dietary pattern on the body s physiology given the importance of fat, and (c) how might you counsel patients to include lipids in their diets in a healthful manner? 6. Dietary fads are as plentiful as the choices of unprocessed foods we have to select and consume in our diets. Yet neither selection appears to be winning weight loss battle for the Canadian consumer. Highlight 5 recaps the chapter s information on lipids and introduces the Mediterranean diet. Do you feel this diet might stand out from other diet trends in being able to accomplish healthy weight loss for the Canadian consumer? Why or why not? Support your opinion with literature citations. W H A T O T H E R R E S O U R C E S A R E AVA I L A B L E? You can look up information about government policy as well as any health condition that you are interested in learning more about. Consult the following websites to get reliable information on the following: 2 Contributed by Kathleen Rourke. 6

7 5-7 The Dietitians of Canada (DC) provide excellent summaries related to fat intake. Go to and type fatty acids in the search engine. To learn more about the effects/developments of omega fatty acids, visit the DHA EPA Omega 3 Institute: To learn more about fish oil, see Health Canada s Natural Health Products Ingredients Database: sc.gc.ca/nhpid bdipsn/monosreq.do? lang=eng. Scroll down the alphabetical list to find fish oil. For the levels in mercury in fish and those permitted in these fish, visit Health Canada: sc.gc.ca/fn an/pubs/mercur/merc_fish_poisson eng.php ANSWER KEY FOR ALL I N S T R U C T O R S M A N UA L AC T I V I T I E S Critical Thinking Questions3 1. Answer: Triglycerides: Triglycerides are the predominant category of lipids in the body. Triglycerides are composed of one glycerol molecule and three fatty acids. The number of double bonds within the chain of carbons that make up a fatty acid determines the degree of saturation or unsaturation of a particular fatty acid. The end points of the fatty acid are an acid (COOH) and a methyl group (CH3). The greater the number of double bonds, the greater the unsaturation of the fatty acid. The more unsaturated the fatty acid, the more liquid the fatty acid will be at room temperature. The more saturated the fatty acid, the more solid the fatty acid will be at room temperature. For instance, animal fats, cocoa butter, and coconut oil are all saturated fats and all solid at room temperature, whereas vegetable oils are polyunsaturated fatty acids and liquid at room temperature. Monounsaturated fatty acids, which are also liquid at room temperature, exhibit their first double bond at the omega 9 carbon instead of the omega 3 or 6 carbon. Peanut and olive oils are examples of monounsaturated fatty acids. Fatty acids are organic acids that vary in length from 4 24 carbons, with an 18 carbon unit oleic acid being most typical. Oleic acid is a monounsaturated fatty acid found in olive and peanut oils. Linolenic acid and linoleic acid are both essential fatty acids that are 18 carbons long and polyunsaturated. They help to regulate blood pressure and blood clotting in the body as well as many other functions. Naming of these fatty acids is based upon where their first point of unsaturation occurs. For linolenic acid, this occurs at the omega 3 spot, and for linoleic acid, at the omega 6 spot. Because unsaturated fatty acids tend to spoil readily when exposed to oxygen, they are quite unstable. The more unsaturated the fatty acid, the more readily it will become rancid. Therefore, manufacturers package their products in containers that are airtight and non metallic. It is also important to protect fatty acids from sunlight. 3 Contributed by Kathleen Rourke.

8 5-8 Food manufacturers add antioxidants to oils so that the antioxidants can compete for the oxygen, preventing the oxidation of the fats. Hydrogenation is another common process that saturates the fatty acid as well as improves the texture of the food product. In this process, hydrogen molecules are added to an unsaturated product, converting it to a saturated or partially saturated state. Chemically, a cis configuration is transformed into a trans configuration, whereby the two hydrogen molecules that were both on the same side of the molecule are now opposed to one another on the same molecule. Much debate has surfaced over the health consequences of this type of manufacturer food alteration! Phospholipids and Sterols: Phospholipids and sterols make up approximately 5 percent of the body s lipid composition. Phospholipids (e.g., lecithin) retain a backbone of one glycerol molecule with two fatty acids attached. The remaining site is occupied by choline and a phosphate molecule. This unique structure allows phospholipids to be soluble in both fat (via the fatty acids) and water (via the phosphate molecule) and therefore be used as an emulsifier. While emulsifiers are agents that oil and water to combine together, the primary importance of the phospholipid s structure in the body is for its work at the cell membrane site. They are an important part of the cell membrane and enable fats, fat soluble vitamins, and hormones that are made up of sterols to move across the cell membrane from aqueous environments with their lipid components. Sterols are ring structures, and include sex hormones, vitamin D (a fat soluble vitamin), and bile acids. Cholesterol, a sterol itself, is the building block for all of these substances. Endogenous cholesterol or cholesterol made by the body is sufficient to meet the body s needs. There also exist plant sterol sources that can be helpful in clearing excessive exogenous cholesterol from the body. Overall, it is important to point out that lipids are chemically composed of oxygen, carbon, and hydrogen, similar to carbohydrates. However, lipids provide twice the kcalories or energy of carbohydrates or proteins. While lipids are typically viewed as bad in the diet, lipids are necessary as noted above for cell membrane structure, composition of hormones, digestion and absorption of fat soluble vitamins, blood clotting mechanisms, and blood pressure regulation mechanisms, as well as thermal insulation, protection of the vital organs, and extra energy in times of starvation. Although it is the excess of lipid ingestion that is truly the problem in Canada, some lipid or fat ingestion in the diet is necessary for health and physical well being. 2. Answer: One fascinating point cited in the textbook was that on average from the food we eat, grams of triglycerides, and 4 to 8 grams of phospholipids and 200 to 350 milligrams of cholesterol are processed by the body. Think about how remarkable our bodies are to process all of these lipids in this challenging environment! And then think about all the individuals who eat well beyond the average! The result is a body always working overtime. The goal of the body in the digestion of any food is to break the food down into the smallest units possible for processing and absorption. This is similar with lipid digestion, beginning in the mouth where lingual lipase, released from the salivary 8

9 5-9 glands, hydrolyzes short and medium length lipids/fats. The mouth melts other solid fats to body temperature. In the stomach, gastric lipase breaks up larger fat molecules into smaller particles before the chyme mixture is released into the small intestine. In the small intestine, bile is released from the gallbladder upon the signal of the hormone cholescystokinin. Bile acts as an emulsifier (can suspend fatty substances in an aqueous environment) and attracts the fat molecules to it. At the same time, the pancreas releases pancreatic lipase and intestinal lipase is also released. Both enzymes work to fully digest the triglyceride molecule for absorption. Triglycerides and phospholipids are broken down by enzymatically removing one fatty acid at a time while the sterol is absorbed whole. While small molecules can be absorbed independently, larger molecules must be packed into complexes known as micelles. These are emulsified fat droplets of bile, fatty acids, and monoglycerides that can now move into the intestinal cells. Once in the intestinal cells, these micelles are disassembled and triglycerides are reconstructed and attached to a protein carrier. These new units are called chylomicrons. Chylomicrons transport fats through the lymph system and enter the bloodstream at the thoracic duct, close to the heart. At that point, lipids are transported throughout the body for use or storage. Chylomicrons are one of four types of lipoprotein carriers that help to carry fats around the body, thus providing lipid transport in an aqueous environment. The other three are VLDL or very low density lipoproteins, LDL or low density lipoproteins, and HDL or high density lipoproteins. The greater the proportion of fats in the bloodstream, the less dense the lipoproteins will be; the less fats in the bloodstream, the higher the density of the lipoproteins. Therefore, as the chylomicrons begin their distribution cycle, they change in character and density, depending on the individual diet, activity level, health status, genetics, etc. Triglycerides, sterols, and phospholipids are distributed, stored, and picked up and as the lipoprotein goes about its business it may become more or less dense. Consumers often become confused by the various interchanging terms for lipoproteins. What is good and what is bad cholesterol? Where do VLDL and LDL and HDL come into the picture with all of this? What about the proportions between them? Is cholesterol in all foods? First, it is important to help patients to understand that their bodies can make cholesterol and that even if they try extremely hard to avoid high fat and high cholesterol food, they may be genetically prone to a higher cholesterol level. Helping patients to read and differentiate among different types of food labels is very helpful, as manufacturers often say that a product does not have cholesterol when it never did, while a product can certainly have a significant amount of saturated fatty acids that will not be helpful to a patient s cholesterol. Frequently, the most straightforward approach is the best for most patients; therefore, explaining the role of cholesterol and perhaps HDL is more than most patients can handle. Assess the patient s educational level to ascertain if he or she is capable of handling a great deal of complex information before providing additional information.

10 5-10 For most patients, explaining the role of cholesterol, foods to avoid, and foods to encourage in the diet such as complex carbohydrates and fruits and vegetables is most important in helping them to get a handle on high cholesterol. Also, the role of exercise in lowering their cholesterol level (pending the MD approval) should be mentioned. Next, discussing the role of HDL in improving a patient s cholesterol level and the role of exercise in improving HDL is also important. Beyond this, discussing each lipoprotein may be too confusing to most consumers. The RD needs to assess and judge when the patient is able and ready to handle more detailed information that will support their nutrition education advancement. 3. Answer: As noted earlier, lipids or fats (the terms are being used interchangeably) are very important in our bodies. First, extra layers of fat in our bodies protect against extreme negative temperatures (cold). Many distance swimmers that have attempted to swim the English Channel have added additional layers of fat to protect themselves against the cold temperatures of the water as well as to provide them with energy during their long swim. In some native tribes in northern climates, one will see greater body fat densities, again assumed to protect these tribes during the harsh winters supply energy during long winters without food. One will generally find that swimmers retain greater fat density than other athletes. Researchers believe that the fat serves thermal purposes as well as provides buoyancy. This phenomenon is consistently seen in swimmers and is being studied. Most individuals believe that both buoyancy and thermal protection are the primary rationale for the noted phenomena. Women have a higher fat density that protects their unborn infant and provides energy for the mother in the event of starvation. Nature s mechanisms are in place in the event of harm to the mother and are very important protective mechanisms for the unborn infant. These extra calories are also important in the production of the mother s milk. During the entire pregnancy process, the mother does not require that many more calories (an additional 340 kcalories/ day in the second trimester). However, for lactation, an additional 500 kcalories/ day are required to be successful. Added fat stores found around the body protect its internal organs against injury in the event of a traumatic impact. While these stores do not need to be massive, they are important to the body and its protection. Fat stores can be found under the skin, in the muscle tissues, and around vital organs. In the event of starvation, these fat stores supply energy to the body as triglycerides. As noted earlier, stored fat is a dense source of energy, supplying twice the number of kcalories per gram compared to protein and carbohydrate sources. Lipids or fats are also used by the body to manufacture sterols, which include the important sex hormones and other hormones that are extremely important in regulating and helping to provide homeostasis in our bodies. Fats are an important component of the cell membrane. Sterols themselves are also interesting components that can act as emulsifiers and enter the cell membrane easily via their unique emulsifier function. The important role of fat in the cell membrane cannot be underestimated in its role in the diet. Without fat in the diet, our bodies as a totality would not be able to function correctly over a long period of time. 10

11 5-11 There are two fatty acids that the body cannot manufacture and must be provided by the diet: linoleic acid and linolenic acid. Both 18 carbon compounds can be found in vegetable oils, nuts, and seeds and are important to blood clotting and blood pressure functions, among other activities. Eicosanoids, which have longer carbon chains than linoleic acid and linolenic acids, are noted to play a role in heart wellness, growth and development, and immune responses. 4. Answer: Normal Blood Lipid Profile: Total cholesterol: Less than 200 mg/dl LDL cholesterol: Less than 100 mg/dl HDL cholesterol: Greater than or equal to 60 mg/dl Triglycerides: Less than 150 mg/dl As we know, our bodies manufacture cholesterol in the liver using fat, protein, and carbohydrate. Additional dietary sources of cholesterol are digested, absorbed, and circulated, with their fate decided based upon the body s need for cholesterol components, genetics (which may increase one s risk of maintaining a higher cholesterol level), exercise levels, and other components in the diet. Individuals who exercise more will increase their levels of HDL, the lipoprotein that will help to move free cholesterol out of the blood so that it can be cleared from the body. There are some limitations to an individual s ability to increase his or her HDL level and if the individual stops exercising on a regular basis, the HDL level will decline to their previous levels. LDL Cholesterol: LDL cholesterol is a lipoprotein that carries cholesterol to the cells. The higher the LDL level, the higher the association with cardiovascular disease. Selecting a diet that is low in saturated fat with a preference toward monounsaturated and polyunsaturated fatty acids usually serves to keep LDL levels low. Selecting a diet high in complex carbohydrates with soluble fibres is also important. Triglycerides: Triglycerides are the predominant lipid in the body. Diet, exercise, and lifestyle all impact triglyceride level. A diet high in simple sugars, including fruit juices, can easily increase triglyceride levels as can lack of activity and stress. To maintain normal triglyceride levels, it is important to eat a diet that is high in complex carbohydrates, especially fibres. Choose lean meats, fish, and poultry. Alcohol should always be used in moderation and a preferred alcoholic beverage would be red wine instead of distilled beverages. Plenty of exercise serves to maintain a good cholesterol profile and dissipate stress hormones, relieving stress. Overall, to maintain the best cholesterol profile, a diet that is full of complex carbohydrates is best. This allows for plenty of intake of soluble and insoluble fibre. Be sure to select plenty of fruits and vegetables and well as legumes and nuts for valuable sources of phytochemicals. Choose low fat meats, fish, and poultry as well as legumes for protein sources. Select monounsaturated and polyunsaturated fatty acids for the diet and stay away from saturated fats and trans fats when selecting food products, meats, and cooking products. Plenty of exercise is important to help raise

12 5-12 HDL levels that support cholesterol clearance from the body. These activities should assist patients in maintaining the correct weight for their body type and frame. Moderating alcohol consumption is always important, as alcohol is metabolized as a fat and adds to depression. If selecting alcoholic beverages, red wine is a good choice for its health benefits. 5. Answer: (a) A diet that is totally void of fats would be a diet free of any processed foods, dairy products, meats, poultry, nuts, and of course oils, etc. Clearly, whole food groups are being left out of such a diet, which would result in the individual becoming deficient in many micronutrients as well as the macronutrient lipid. To perhaps take a slightly different approach toward a minimal fat diet, which is not unusual to see in patients with fat phobias, the patient may be eating fruits and vegetables (no sauces or dressings on vegetables); salads with no dressing; meats, fish, and poultry with all fat removed; no dairy products or perhaps fat free dairy products; no processed foods, etc. An important point to remember here is that women who follow such restricted diets frequently impose the same rules on their young children and infants. Some failure to thrive infants come from families that are obsessed with fat and weight control. (b) Depending on the age, health, and weight of the individual, this dietary approach has some merits. When taken to the extreme, however, it limits the micronutrients the individual can receive in their diet. Consuming a diet of non processed foods is not a negative, in and of itself. Plenty of fruits and vegetables provide for a great source of vitamins and minerals and lean sources of protein should always be recommended. Yet the diet is void of calcium, and the individual will have to work hard to consume legumes for protein without nuts as a source. For women and young children, these are two nutrients that are important for growth and development as well as for strong bones. With regard to fat, while the body does not require a great deal of fat to function at its optimum, some fat in the diet is important to support physiological functions. Fat is needed for the phospholipids in the cell membranes, for the sterols that support hormone production, for the bile acids that break down fats for transport to body tissues, and for the various other functions of fats such as insulation, energy supply, and metabolic functions such as blood clotting, etc. Canadians clearly eat too much fat, yet we must not forget that some fat is not a bad thing for the body. It has many important activities to perform every minute of the day to keep us going! (c) Individuals who are fat phobic can be difficult to work with; therefore, counselling them to add small amounts of fat sources to their diets needs to be a baby steps process. In counselling these patients, start with adding a small amount of a food product that has minimal observable fat and allow them to work for a good month on that addition. Prior to that addition, it is important for the RD to fully educate patients on all the functions of fat in the diet. Key in on activities that patients are most interested in and that would benefit from the addition of the nutrient. Help them view 12

13 5-13 the small amount of lipid as a nutrient that will improve their body s ability to perform. It is important to assess the extent of the prescribed use of the plan in the household. It may not be unusual to find a child who has also been prescribed such a plan. In that case, it is important to try to see the child in your clinic or to have the child seen by his or her own doctor. The RD may want to make a confidential call to the child s doctor if there is extensive avoidance of lipids by the mother, as the child may be suffering from some growth and development issues. Frequently, the child s physician can be alerted to make special observations at the child s next visit. 6. Answer: This question asks students for their opinion, which may or may not support the dietary program. Primary literature review citations have been requested for their write up, which is important in helping students to establish their professional work ethic as one centred on evidenced based practice. While there is certainly a considerable body of evidence to support the Mediterranean diet, students who can support, with primary references, either perspective should be given credit for their work, as there are always two sides to any research question. In Support of the Mediterranean Diet: In support the Mediterranean diet, significant evidence suggests that the diet encourages choices of fresh and unprocessed foods. Many of the food choices are in the fruit and vegetable category, with additional choices of complex carbohydrates such as whole grains. Proteins come mainly from legumes, nuts, seafood, and cheeses, with very little meat or poultry as part of the diet. The diet is very low in saturated fats or trans fats and very high in monounsaturated fats. Phytochemicals are also abundant from the legumes and vegetables. Omega 3 fatty acids are provided abundantly through the fish eaten. The Mediterranean culture upon which the diet was originally based is extremely active, not as automated as in Canada and the United States. Meals are a spiritual and family event to be shared and excessive portions do not really exist. Meals consist of small portions of salads, cheese, etc. as opposed to the North American family where, by and large, many individuals do not really know what an appropriate portion of any food category might be. Most foods also come fresh from open markets as opposed to grocery chains that supply processed foods that must be able to retain a long shelf life. It is possible to follow a Mediterranean program in Canada with careful attention. As noted, the diet has several positive attributes,such as low saturated fat and trans fat intake and high monounsaturated fatty acid consumption. The diet is rich in complex carbohydrates as well as fibre that help to rid the vascular system of plaque formation and provide important nutrients. Many vegetables and fruits also provide fibre and nutrients, while nuts, cheeses, legumes, and fish provide a great source of protein and important omega 3 fatty acids. Portion control is particularly important. Small, regular meals are important to maintain a consistent blood sugar level. With these meals, a source of protein, vegetable/fruit, and complex carbohydrate are recommended. Snacks can consist of milk or dairy products with fruit and or protein source.

14 5-14 It is important to minimize or curtail processed foods and any significant consumption of beef, and all visible fat should be removed from poultry. In addition, attention to an exercise regime is important to keep weight down and muscles toned for health and fitness. Exercise is an important component to this overall program. Not in Support of the Mediterranean Diet: While there are many great attributes to this diet and a body of research to support its use, some individuals may find it difficult to follow for cultural, religious, or health reasons. One example would be a preference for consumption of more meat, which is not forbidden from the Mediterranean diet but is not the norm. For some individuals, there may be issues with nut allergies and lactose intolerances. For individuals who are not used to consuming much fibre, caution should be taken to start slowly in consuming small amounts of fibre and slowly move up total fibre volume. Another issue that can be problematic for Canadian consumers is their ability to pursue the Mediterranean diet under terms of portion control and with the inclusion of plenty of physical activity. The diet includes foods such as nuts and cheese that are very high in fat and calories. Given that most Canadians do not practise portion control, they may experience an increase in weight if they were to follow a diet such as the Mediterranean diet. A successful dietary plan would have to provide for more guidance on portion sizes per meal and per day. However unfortunate, this is something that is required for Canadian consumers, who need help to re educate them as to a more moderate eating plan. Most successful plans in Canada and the United States require intensive human resource time in educating individuals as to portion size, dealing with stress, adding exercise or physical activity into their daily activities, and a variety of psychological self esteem work. Worksheet Answer Key Worksheet 5 1: Trans Fat 1. To help consumers identify which foods contain trans fats, so that they can limit their intake of this type of fat through their food choices. 2. The term trans refers to a type of double bond within a fatty acid in which the hydrogen atoms adjacent to the double bond are on opposite sides of the carbon chain. 3. During the hydrogenation process, which is used to solidify liquid vegetable oils and make them more resistant to oxidation, hydrogen molecules are added to unsaturated fatty acids. This usually results in partially hydrogenated fats. At the same time, this process changes some of the double bonds that still remain from the cis configuration (more common in nature) to the trans configuration, creating trans fats. 4. Trans fatty acids behave more like saturated fats than unsaturated fats in the body. They raise LDL cholesterol and lower HDL cholesterol (at high intakes), and seem to increase inflammation and insulin resistance. Dietary trans fatty acids are associated with heart disease risk. 14

15 5. Answers will vary. Worksheet 5 2: Do You Know Your Fats? All 10 statements are false. Worksheet 5 3: Check Your Lipid Choices Answers will vary. Worksheet 5 4: Chapter 5 Crossword Puzzle 1. olestra 4. endogenous 7. micelles 2. antioxidants 5. choline 8. sterols 3. hydrogenation 6. hydrophobic 9. exogenous 10. fatty acid Worksheet 5 5: Dietary Fat Recommendations (Internet Exercise) 1. False 4. True 6. a) Sunflower oil, b) Corn oil, c) 2. False 5. c Partially hydrogenated oils 3. False 5-15

16 5-16 W O R K S H E E T AC T I V I T I E S Worksheet 5 1: Trans Fat N ut rit ion Fa c t s Wheat Squares Sweetened Serving Size 1 Box Servings Per Container Corn Flakes Not Sweetened Mixed Grain Flakes Sweetened (35g) 1 (19g) 1 (27g) %Daily Value* 70 0 % Daily Value* 0g 0g 0g 0mg 8% 200mg 25mg 1% 17g 6% 1g 4% 6g 1g % Daily Value* 0g 0g 0g 0mg 5% 120mg 30mg 1% 24g 8% 1g 4% 13g 1g 1 15% 6% 15% 15% 15% 15% Amount Per Serving Calories Calories from Fat Total Fat Saturated Fat Trans Fat Cholesterol Sodium Potassium Total Carbohydrate Dietary Fibre Sugars Protein 0g 0g 0g 0mg 0mg 125mg 29g 3g 8g 4g * Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs: Calories: 2,000 2,500 Total Fat Less than 65g 80g Sat Fat Less than 20g 25g Cholesterol Less than 300mg 300mg Sodium Less than 2,400mg 2,400mg Potassium 3,500mg 3,500mg Total Carbohydrate 300g 375g Dietary Fibre 25g 30g Vitamin A Vitamin C Calcium Iron Thiamin Riboflavin Niacin Vitamin B6 4% 1 12% Source for label information: U.S. Food and Drug Administration Trans Fat Label Implications 1. Why was Trans Fat added to the Nutrition Facts Label? 2. What does the term trans fat mean with respect to structural composition? 3. What does the term trans fat mean with respect to food processing? 4. What does the term trans fat mean with respect to one s daily diet? 5. Do you think that trans fat will be replaced by some other processing mechanism leading to other potential health problems? 16

17 5-17 Worksheet 5 2: Do You Know Your Fats? Please indicate whether each of the following statements is true or false by circling the appropriate word. Then tally the total number of true and false statements. True False Fat Statement: 1. All margarine products have the same fat content. True False 2. Hydrogenated food products are healthier than those that are not hydrogenated. True False 3. If you see fat free on the food product label, then the food is guaranteed to have no fat. True False 4. You can live without fats in your diet. True False 5. A saturated fat is better for you than a polyunsaturated fat. True False 6. In order to be healthy, you should have no cholesterol in your body. True False 7. Eicosanoids do not provide any health benefits. True False 8. All fatty acids can be synthesized in the body. True False 9. There are no clinical deficiencies seen from too little fat in one s diet. True False 10. As long as your LDL cholesterol is within normal range, you need not worry. Totals:

18 5-18 Worksheet 5 3: Check Your Lipid Choices Fats give foods their flavour, texture, and palatability. Unfortunately, these same characteristics entice people to eat too much from time to time. Do you know how to select low fat foods that help you meet dietary fat recommendations? Look at these examples of foods and consider how often you select the item that is lower in fat. Which of these pairs are you most likely to select: Peanuts or pretzels? Hot dog or turkey sandwich? Whole milk or low fat milk? Fried chicken or baked chicken? Tuna packed in oil or tuna packed in water? Spaghetti with alfredo sauce or with marinara sauce? Croissants or bagels? Sausage pizza or mushroom pizza? The second item in each pair is lower in fat and making such fat free or low fat food choices regularly can help you meet dietary fat recommendations. In addition, eating plenty of whole grain products, fresh vegetables, legumes, and fruits daily will help to keep your fat intake under control. Contributed by Sharon Rady Rolfes. 18

19 5-19 Worksheet 5 4: Chapter 5 Crossword Puzzle Across Down 1. A synthetic fat made from sucrose and fatty acids that provides 0 kcalories per gram; also known as sucrose polyester. 7. Tiny spherical complexes of emulsified fat that arise during digestion. 8. Compounds containing a four carbon ring structure with any of a variety of side chains attached. 9. An adjective describing cholesterol that originates outside the body (from foods). 10. An organic compound composed of a carbon chain with hydrogens attached and an acid group (COOH) at one end and a methyl group (CH3) at the other end. 2. Compounds that protect others from oxidation by being oxidized themselves. 3. A chemical process by which hydrogens are added to monounsaturated or polyunsaturated fatty acids to reduce the number of double bonds, making the fats more saturated (solid). 4. An adjective describing cholesterol that is made in the body. 5. A nitrogen containing compound found in foods as part of lecithin and other phospholipids. 6. A term referring to water fearing, or non water soluble, substances.

20 5-20 Worksheet 5 5: Dietary Fat Recommendations (Internet Exercise) Go to the following website to answers questions 1 3: Click on Dietary Fat. Do not close the window until you have answered all of the questions. 1. The highest total fat limit is for the adult population. a. True b. False 2. Non fat milk is recommended for children under the age of 2 in order to prevent excessive fat deposits later on in life. a. True b. False 3. Trans fats can increase high density lipoproteins and are therefore considered to pose significant cardiac problems. a. True b. False Now, scroll down the page to the links under More Information on Fats. Use the web pages on the different types of dietary fats to answer questions Trans fat is listed on the Nutrition Facts panel on food labels as of a. True b. False 5. Which of the following recommendations is accurate with regard to the intake of saturated fats? a. Consuming 15 percent of energy from saturated fats presents with minimal cardiac risk. b. Omega 3 and omega 6 fatty acids are considered to be excellent sources of saturated fats. c. Increased consumption of saturated fats can lead to increased incidence of cardiac events. d. The majority of fats in your diet should include high percentages of saturated fatty acids. 6. Match the food example with the type of fat. a. Monounsaturated b. Omega 6 polyunsaturated c. Trans fat Corn oil Sunflower oil Partially hydrogenated oils 20

21 5-21 Handout 5 1: How to Modify a Recipe Lasagna* Original 75 ml (1/3 c) olive oil (to sauté vegetables) 34 ml(11/2 c) diced onions 2 cloves garlic 680 g (11/2 lb) ground chuck 10 ml (2 tsp) salt 907 g (2 lb) tomato sauce 794 g (28 oz) canned tomatoes g (6 oz) canned tomato paste 15 ml (1 Tbsp) oregano 10 ml (2 tsp) onion salt 454 g (1 lb) lasagna noodles 30 ml (2 tbsp) olive oil (to cook noodles) 454g (16 oz) ricotta 227 g (8 oz) mozzarella 284 ml (10 oz) parmesan oil to grease pan Modified [omit oil] 34 ml (11/2 c) onion, 1 green pepper, 227g (1/2 lb) mushrooms 2 cloves garlic 340 g (3/4 lb) ground round [omit salt] use no added salt type tomato sauce use no added salt type canned tomatoes use no added salt type tomato paste 10 ml (2 tsp) oregano, 10 ml (2 tsp) basil, 125 ml (1/2 c) fresh parsley [omit salt] 454 g (1 lb) whole wheat lasagna noodles [omit oil] 454 g (16 oz) low fat cottage cheese, pureed 227g (8 oz) part skim mozzarella 113 g (4 oz) parmesan spray to grease pan Yield 16 servings ( pans) Analysis Energy (kcal) Protein (g) Fat (g) Sodium (mg) Cholesterol (mg) % of calories from fat Original (6 tsp) Modified (1.4 tsp) *Source: Culinary Hearts Kitchen Course, Tallahassee, Florida, as taught by Sandra Woodruff, MS, RD, with permission.

22 5-22 Handout 5 2: Why All Cholesterol Is Not Created Equally! What Is Cholesterol? Cholesterol is a wax like substance that is made up of sterol lipids. It is needed for cell membrane stability and for nerve cell membrane function. Cholesterol can be converted into bile which aids in fat digestion and can be converted into hormones such as estrogen and testosterone. Where Is Cholesterol Produced? Cholesterol is transported in the blood as a lipoprotein since blood is water based. Cholesterol is produced in the liver and allows lipids to travel through the lymphatic system into the bloodstream. What Types of Cholesterol Are There? Very low density lipoproteins (VLDL) are made in the liver and converted into low density lipoproteins (LDL). LDL have a higher proportion of lipids and cholesterol to protein. High density lipoproteins (HDL) have a higher proportion of protein to lipid and cholesterol. What Do LDL and HDL Do in the Body? What Can Be Done to Lower LDL and Raise HDL Levels? LDL carries lipids and cholesterol from the liver to the body s cells. LDL molecules can get deposited on the walls of the blood vessels. Oxidation of LDL molecules can trigger inflammation in the blood vessels that can lead to clot formation. Oxidized LDL molecules can also attract white blood cells called macrophages that try to remove the LDL. This can lead to clots being released from the blood vessel walls. HDL carries cholesterol from the blood to the liver where cholesterol is converted into bile. Higher levels of HDL are associated with lower incidence of cardiovascular disease. Reduce saturated fats in the diet to lower LDL levels. Studies suggest that high amounts of dietary saturated fatty acids may reduce the ability of the liver to remove excess LDL from the blood. Reduced body weight and moderate alcohol consumption may decrease the levels of VLDL molecules that are converted into LDL molecules in the liver. Increasing dietary plant sterols may interfere with the absorption of cholesterol from food. This could reduce the amount of LDL getting into the bloodstream. Increased physical activity has been associated with increased levels of HDL. Eating foods rich in vitamins C and E may also increase the levels of HDL. References: How Safe Are Statins?: Dr. Weil s Self Healing Letter. October 2003, p. 1; Cholesterol Busters: University of California, Berkeley Wellness Letter. Volume 20 (5), February 2004, p. 4; Controlling Elevated Cholesterol & Triglycerides: Dr. Weil s Self Healing Letter. December 2002, pp. 4 5; Merck Manual, 16th Edition. 1992: Rahway, N.J. pp Contributed by Mary Ellen Clark. 22

23 5-23 Handout 5 3: Why Omega 3 Fatty Acids Are Considered Good Fats What Is the Main Omega 3 Fatty Acid? It is an essential fatty acid called linolenic acid, and is found in fish oils that have many points of unsaturation (polyunsaturated) along the carbon hydrogen backbone. What Happens to Linolenic Acid in the Body? What Are Other Sources of EPA and DHA? The body converts some Linolenic acid into EPA (Eicosapentaenoic acid) and DHA (Docosahexanenoic acid). Why Are EPA and DHA So Good? How to Get Enough Linolenic Acid? Cold water fish such as salmon or mackerel contain EPA and DHA. Vegetable sources include flaxseed, walnuts, pecans, tofu, and green leafy vegetables. They encourage the production of prostaglandin G1 series, which are cyclic fatty acids that decrease platelet stickiness and overall inflammation in the blood vessels and other tissues. People with higher levels of EPA and DHA in their blood may have a lower level of inflammation in their tissues as shown by lower CRP levels. C reactive protein (CRP) is a marker of inflammation that may predict who is at risk of cardiovascular disease and other types of chronic inflammation. EPA may be released from cell membranes especially in the heart muscle where higher EPA levels may protect against deadly arrhythmias. People should get 3 grams a day from a variety of sources such as cold water fish, ground flaxseeds (flaxseed oil), pecans, walnuts, tofu, and green leafy vegetables. References: Tuft s University Health & Nutrition Letter, Volume 21 (12), February 2004; Special Supplement: Tuft s University Health & Nutrition Letter. Volume 20 (3) May 2002; Face the Fats: Nutrition Action Health Letter. Volume 29 (6) July/Aug 2002, pp. 3 7; Merck Manual. 16th Edition. 1992: Rahway, N.J., pp Contributed by Mary Ellen Clark.