Williams' Basic Nutrition & Diet Therapy Chapter 3 Fats Williams' Basic Nutrition & Diet Therapy 1

The Nature of Fats Dietary importance Classes of fats Concentrated fuel for energy Classes of fats Lipids Hyperlipidemia-elevated level of fat in blood Composed of carbon, hydrogen, oxygen Glycerides-majority of dietary fats Triglycerides-3 fatty acids attached to glycerol base Fatty acids-building blocks of triglycerides; classified by their length Lipoproteins-vehicles for lipid transport-to be able to get the fat to and from cells in the body; LDL carry fat and cholesterol to cells and HDL carry free cholesterol from body tissues back to the liver for metabolism Why is fat considered a backup fuel source for the body? (Carbohydrates are the primary fuel, followed by fat when needed.) Explain that each class of fat serves a different purpose in the body and all are considered lipids.

Fatty Acids Saturated fatty acids Filled or “saturated” with hydrogen-most are of animal origin; meat, dairy, and eggs More heavy, more dense-solid at room temperature Unsaturated fatty acids Found in plant foods Not completely filled with hydrogen Less heavy, less dense-liquid at room temperature Monounsaturated: one unfilled spot-examples olive, canola, peanut, avocados Polyunsaturated: two or more unfilled spots-examples vegetable oils, corn, sunflower; safflower oil has the least amount of saturated fat Saturated fats are heavier, denser, and more solid than unsaturated fats. Unsaturated fats are usually in oil form. What foods supply monounsaturated fats? (Olive and olive oil, peanuts and peanut oil, canola oil, almonds, pecans, and avocados)

Fatty Acids Essential fatty acids- Only fatty acids essential for complete human nutrition are linoleic acid and alpha-linolenic acid Linolenic acid is primarily found in soybean, canola, and flaxseed oil serve important functions related to tissue strength, cholesterol  metabolism, muscle tone, blood clotting, and heart action Must come from foods we eat Can develop essential fatty acid deficiency Nonessential fatty acids -with adequate dietary supply of essential fatty acids body is capable of manufacturing saturated, monounsaturated, and other polyunsaturated fatty acids, as well as cholesterol Saturated fats are heavier, denser, and more solid than unsaturated fats. Unsaturated fats are usually in oil form. What foods supply monounsaturated fats? (Olive and olive oil, peanuts and peanut oil, canola oil, almonds, pecans, and avocados)

Fatty Acids Trans-fatty acid Omega-3 and omega-6 fatty acids Naturally occurring Hydrogen atoms around carbon double bond are on opposite sides Hydrogenation-when the hydrogen atoms on the carbon double bond are moved to opposite sides-for longer shelf life-tend to become more solid Negative health consequences, cardiovascular disease Omega-3 and omega-6 fatty acids Determined by position of first carbon involved in double bond What are some of the sources of unnecessary trans fats? (Restaurant foods, fast foods, packaged foods)

Fatty Acids Phospholipids Sterols Lecithin-produced by the liver; key building block of cell membranes; ideal for transporting fats and cholesterol Eicosanoids-hormones that exert control over multiple functions in the body; messengers for the CNS Sterols Cholesterol-synthesized in the liver; vital for membranes; precursor for some hormones; important in human metabolism; occurs naturally in foods of animal origin; found in egg yolks, organ meats, and other meats What are some of the sources of unnecessary trans fats? (Restaurant foods, fast foods, packaged foods)

Functions of Fat in Foods Fat in foods provides: Energy-9 kcal/g (carbs 4 kcal/g) Essential nutrients-linoleic and alpha-linolenic acid Flavor and satisfaction Fat substitutes are not absorbed and therefore do not provide energy or essential nutrients but may provide flavor and satisfaction Fat provides 9 kcal/g versus 4 kcal/g for carbohydrates. Explain that this is an effective way to store energy.

Functions of Fat in the Body Adipose tissue Protects organs Helps regulate temperature by acting as an insulator Cell membrane structure Forms part of cell membrane Helps transport nutrients across cell membranes Fat is stored in adipose tissue. What are some common sites of adipose tissue deposits? Explain that a special fat covering protects nerve fibers and helps relay nerve impulses.

Food Sources of Fat Animal fats Plant fats most concentrated of which include meat fats (e.g., bacon, sausage), dairy fats (e.g., cream, ice cream, butter, cheese), and egg yolks lean portions do not have the same hypercholesterolemic effects as their full-fat counterparts when they are consumed with diets that are high in fiber Plant fats mostly monounsaturated and polyunsaturated fats, including the essential fatty acids. Food sources for unsaturated fats include vegetable oils (e.g., safflower, corn, cottonseed, soybean, peanut, olive. How much of a daily dietary intake needs to be from fat to supply adequate amounts of essential fatty acids? (10%)

Characteristics of Food Fat Sources Visible fats  include butter, margarine, separate cream, salad oils and dressings, lard, shortening, fatty meats (e.g., bacon, sausage, salt pork), and the visible fat of any meat Easier to control Invisible fats include cheese, the cream portion of homogenized milk, nuts, seeds, olives, avocados, and lean meat Basically those that you cannot cut out of food Ask students to name some of the obvious fats. Ask students to identify some of the sources of invisible fats. Are any of the students surprised by these sources of fats?

Food Label Information Calories from fat Calories from saturated fat Total fat Saturated fat Polyunsaturated fat Monounsaturated fat Cholesterol Voluntary information The FDA regulates food labeling. Explain how and why it does so. Do the students think that food manufacturers would add the voluntary information if it showed an amount of a nutrient the consumer would see as “bad”?

Digestion of Fats Mouth Stomach Small intestine Bile produced diluted in the liver Bile from the gallbladder concentrated- stimulated to be released by cholecistokinin Bile is an emulsifier Bile breaks down fat into smaller particles to be able to be used in the body Enzymes from the pancreas Enzymes from the small intestine Absorption The primary digestion action occurring in the mouth is mechanical. Foods are broken up into smaller particles through chewing and are moistened for passage into the stomach. Little, if any, chemical fat digestion takes place in the stomach. Why do you think this is? (Prompt the students to remember the principle of “like attracts like”; stomach acid is more attracted to hydrophilic compounds than hydrophobic compounds.)

The primary digestion action occurring in the mouth is mechanical The primary digestion action occurring in the mouth is mechanical. Foods are broken up into smaller particles through chewing and are moistened for passage into the stomach. Little, if any, chemical fat digestion takes place in the stomach. Why do you think this is? (Prompt the students to remember the principle of “like attracts like”; stomach acid is more attracted to hydrophilic compounds than hydrophobic compounds.)

Dietary Fat and Health The American diet is high in fat. Increases risk for obesity, elevated blood fats, diabetes, arteriosclerosis, among other complications Excess calories are stored as fat. Animal food sources contribute to excess cholesterol and saturated fat in the diet such as lard A decrease in saturated fat reduces serum total cholesterol. Monounsaturated fats reduce LDL cholesterol when substituted for saturated fat. Why are excess calories stored as fat and not carbohydrate or protein? (Explain that storing excess energy as fat is the way the body is supposed to work. It is a machine meant to store the most energy in the least amount of space.) Heart disease continues to be one of the leading causes of death in developed countries. Much attention is focused on reducing risk factors leading to this disease.

Dietary Guidelines for Americans Control saturated fat and cholesterol Use only lean cuts of all meats; use more poultry and seafood Limit eggs to two or three per week Use low-fat or fat-free milk and milk products Avoid adding too much fat in food preparation Remember that end products of fat metabolism will be fatty acids, glycerols, or diglycerides By using these tips, people can significantly reduce their fat intake. Ask students to describe some other tips that can help reduce fat in the diet.

FDA Health Claims A diet low in total fat may reduce the risk of some cancers Diets low in saturated fat and cholesterol may reduce the risk of coronary heart disease Other claims are pending How could an individual follow some of the FDA’s recommendations contained in its pending claims?

Dietary Fat Requirements Healthy diet guidelines: Stress the health benefits of a diet low in fat, saturated fat, and cholesterol Recommend that the fat content should not exceed 20% to 35% of total kilocalories Less than 10% of kilocalories should be from saturated fat Dietary cholesterol should be limited to 300 mg/day Example: 1500 calorie= 300 calories to 525 calories of fat Tell the class how much cholesterol is in one egg. According to these guidelines, can one egg be eaten every day?