Lipids Objectives 1 Understand the chemical composition and

Lipids

Objectives 1 - Understand the chemical composition and differences between fats. 2 - Explain the structural and functional processes of triglycerides, phospholipids, and sterols. 3 - Describe the process of fat digestion and absorption. 4 - Discuss the different types of lipoproteins in the body. 5 - Clarify the recommended intakes of fat and essential fatty acid requirements to meet daily nutritive needs 6 - Describe the health-risk factors with over consumption of lipids in the diet

What Are Lipids? Lipids – Diverse group of molecules that are insoluble in water Fats – The lipid content of diets and foods

Three types of lipids are found in foods and in body cells and tissues: – Triglycerides – Phospholipids – Sterols

Fatty acids are carboxylic acids with long-chain hydrocarbon side groups CH 3 (CH 2)n COOH. They are rarely free in nature but, rather, occur in esterified form as the major components of the various lipids.

Fatty Acids The Length of the Carbon Chain – long-chain, medium-chain, short-chain The Degree of Unsaturation – saturated, unsaturated, monounsaturated, polyunsaturated. – Carbons can be numbered: – Carboxyl end (COOH): -carbon (alpha—first) – Methyl end (CH 3): Ω-carbon (omega—last) The Location of Double Bonds – omega-3 fatty acid, omega-6 fatty acid

omega-3 fatty acid: a polyunsaturated fatty acid in which the first double bond is three carbons away from the methyl (CH 3) end of the carbon chain. omega-6 fatty acid: a polyunsaturated fatty acid in which the first double bond is six carbons from the methyl (CH 3) end of the carbon chain.

Essential fatty acids: fatty acids needed the body but not made by it in amounts sufficient to meet physiological needs and must be obtained from food - Linoleic Acid (Omega-6 fatty acid) - Found in vegetable and nut oils - Linolenic Acid (Omega-3 fatty acid) Found in vegetables, soy, flaxseeds, walnuts - Arachidonic acid.

linoleic acid Linolenic Acid │ arachidonic acid eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) The body uses arachidonic acid and EPA to make substances known as eicosanoids.

Eicosapentaenoic (EYE-cossa-PENTA-ee-N 0 -ick) acid (EPA): an omega-3 polyunsaturated fatty acid with 20 carbons and five double bonds; present in fish and synthesized in limited amounts in the body from linolenic acid. Docosahexaenoic (DOE-cossa-HEXA-ee-NOick) acid (DHA): an omega-3 polyunsaturated fatty acid with 22 carbons and six double bonds; present in fish and synthesized in limited amounts in the body from linolenic acid.

Eicosanoids (eye-COSS-uh-noyds): derivatives of 20 -carbon fatty acids; biologically active compounds that help to regulate blood pressure, blood clotting, and other body functions. They include prostaglandins (PROS-tah-GLAN D-ins), thromboxanes(throm-BOX-ains), and leukotrienes (LOO-ko-TRY-eens).

Fatty Acid Deficiencies: symptoms include growth retardation, reproductive failure, skin lesions, kidney and liver disorders, and subtle neurological and visual problems.

Triglycerides (try-GLl 55 -er-rides): the chief form of fat in the diet and the major storage form of fat in the body; composed of a molecule of glycerol with three fatty acids attached; also called triacylglycerols (tryay-seel-GLI 55 -er-ols). tri = three glyceride = of glycerol acyl = a carbon chain glycerol (GLl 55 -er-ol): an alcohol composed of a three-carbon chain, which can serve as the backbone for a triglyceride. 01 = alcohol

Triglycerides Fatty acids are classified by: – Carbon chain length – Saturation level – Shape

The degree of unsaturation influences the fats and oils in foods. Firmness The degree of unsaturation influences the firmness of fats at room temperature. polyunsaturated vegetable oils are liquid at room temperature, and the more saturated animal fats are solid. Cocoa butter, palm oil, palm kernel oil, and coconut oil are saturated even though they are of vegetable origin; they are firmer than most vegetable oils because of their saturation, but softer than most animal fats because of their shorter carbon chains (8 to 14 carbons long).

Saturation also influences stability. All fat s become spoiled when exposed to oxygen. Polyunsaturated fat s spoil most readily because their double bonds are unstable; monounsaturated fat s are slightly less susceptible. Saturated fat s are most resistant to oxidation and thus least likely to become rancid. The oxidation of fats produces a variety of compounds that smell and taste rancid. Other types of spoilage can occur due to microbial growth. oxidation (OKS-ee-day-shun): the process of a substance combining with oxygen; oxidation reactions involve the loss of electrons.

Manufacturers can protect fat-containing products against rancidity in three ways First, products may be sealed in air-tight, nonmetallic containers, protected from light, and refrigerated. Second, manufacturers may add antioxidants to compete for the oxygen and thus protect the oil (examples are the additives BHA and BHT and vitamin. Third, manufacturers may saturate some or all of the points of unsaturation by adding hydrogen molecules-a process known as hydrogenation.

Antioxidants: as a food additive, preservatives that delay or prevent rancidity of fats in foods and other damage to foo dcaused by oxygen. Hydrogenation (HIGH-dro-jen-AY-shun or high. DROJ-eh-NAY-shun): 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) and more resistant to oxidation (protecting against rancidity). Hydrogenation produces trans-fatty acids. Increase risk of cardiovascular disease.

Cis-fatty acid: H’s on same side of the double bond; fold into a U-like formation; naturally occurring; Trans-fatty acid: H’s on opposite side of double bond; more linear; occur in partially hydrogenated foods;

Trans-fatty acids: fatty acids with hydrogen's on opposite sides of the double bond.

Classification of Fats in Foods: Saturated Monounsaturated Polyunsaturated │ │ Animal Fat Olive Oil Corn Lard Canola Oil Soybean Butter Peanut Cottonseed Palm Avocado Safflower Palm Kernal Sunflower Coconut Fish oil Whole milk sesame cheese

Roles of Triglycerides: In the body, triglycerides: 1 - Provide an energy reserve when stored in the body's fat tissue 2 - Insulate against temperature extremes 3 - Protect against shock 4 - Help the body use carbohydrate and protein efficiently

Phospholipid (FOS-foe-L 1 P-id): a compound similar to a triglyceride but having a phosphate group (a phosphoruscontaining salt) and choline (or another nitrogen containing compound) in place of one of the fatty acids. Glycerol + 2 fatty acids + phosphate group Soluble in water. Transport fat in the bloodstream Manufactured in our bodies (not required)

lecithin (LESS-uh-thin): one of the phospholipids. Both nature and the food industry use lecithin as an emulsifier to combine water-soluble and fat-soluble ingredients that do not ordinarily mix, such as water and oil. Choline (KOH-Ieen): a nitrogen-containing compound found in foods and made in the body from the amino acid methionine. Choline is part of the phospholipid lecithin and the neurotransmitter acetylcholine.

Phospholipids in Foods: phospholipids used by the food industry as emulsifiers, phospholipids are also found naturally in foods. The richest food sources of lecithin are eggs, liver, soybeans, wheat germ, and peanuts.

Roles of Phospholipids: 1 - The lecithins and other phospholipids are important constituents of cell membranes. 2 - Phospholipids are soluble in both water and fat , they can help lipids move back and forth across the cell membranes into the watery fluids on both sides such as vitamins and hormones, to pass easily in and out of cells. 3 - The phospholipids also act as emulsifiers in the body, helping to keep fats suspended in the blood and body fluids. Lipid transport as part of lipoproteins.

Sterols: (STARE-ols or STEER-ols): compounds containing a four ring carbon structure with any of a variety of side chains attached. The most famous sterol is cholesterol.

Sources: -Endogenous(en-DOGDE-eh-nus): cholesterol that is made in the body. liver makes about 800 to 1500 milligrams of cholesterol per day. • Exogenous (eks-ODGE-eh-nus): cholesterol from outside the body (from foods, animal sources only such as cholesterol-meats, eggs, fish, poultry, and dairy products). endo = within gen = arising exo = outside (the body)

Roles of Sterols: 1 - structural component of cell membranes: more than 90 percent of all the body's cholesterol. 2 - Precursor to other substances - Sterol hormones the sex hormones (such as testosterone, progesterone and estrogen), the adrenal hormones (such as cortisol). - Vitamin D - Bile acids

Lipid Absorption: Small molecules of digested triglycerides (glycerol and short- and medium-chain fatty acids) can diffuse easily into the intestinal cells; they are absorbed directly into the bloodstream. Larger molecules (the monoglycerides and long-chain fatty acids) merge into spherical complexes, known as micelles. Micelles are emulsified fat droplets formed by molecules of bile surrounding monoglycerides and fatty acids. This configuration permits solubility in the watery digestive fluids and transportation to the intestinal cells.

Sterols other than cholesterol are naturally found in all plants. Being structurally similar to cholesterol, these plant sterols interfere with cholesterol absorption, thus lowering blood cholesterol levels. ? Food manufacturers have fortified foods such as margarine with plant sterols, creating a functional food that helps to reduce blood cholesterol.

Micelles (MY-cells): tiny spherical complexes of emulsified fat that arise during digestion; most contain bile salts and the products of lipid digestion, including fatty acids, monoglycerides, and cholesterol.

lipoproteins (L 1 P-oh-PRO-teenz): clusters of lipids associated with proteins that serve as transport vehicles for lipids in the lymph and blood. 4 - main types of lipoproteins – 1. Chylomicrons – 2. VLDL – 3. LDL – 4. HDL

Lipoproteins • 1. Chylomicrons – transport diet-derived lipids (mostly TG) from intestine to rest of the body; – cells from all over the body remove lipids as the chylomicrons pass by; get smaller; protein remnants left; go to liver; • 2. VLDL (Very Low Density Lipoprotein) – liver site of lipid synthesis; lipid packaged with proteins shipped to other parts of the body; cells remove TG; become more dense;

Lipoproteins • 3. LDL (Low Density Lipoproteins) – derived from VLDL; circulate throughout body; content available to cells to build new membranes, make hormones, or store; – LDL receptors on liver cells remove LDL from circulation; • 4. HDL (High Density Lipoproteins) – carries cholesterol and other lipids from the cells back to the liver for recycling or disposal – mostly protein;

Health Implications • LDL (lousy): linked to heart disease • HDL (happy): protective from heart disease • Factors that improve LDL-HDL ratio: – weight control – Monounsaturated or polyunsaturated, instead of saturated, fat in the diet – Soluble viscous fibers. – Phytochemicals (Antioxidants) – Physical activity – Moderate alcohol consumption

The Roles of Fat • • • 9 kcal per gram Major fuel at rest Endurance exercise Stored energy Essential fatty acids Fat-soluble vitamins Regulates cell function Maintains membrane Protects the body Provides flavors and textures of foods • Helps us feel satiated • •

DRI and 2005 Dietary Guideline s for fat: 20 to 35 0/0 of energy intake (from mostly polyunsaturated and monounsaturated fat sources such as fish, nuts, and vegetable oils.

Linoleic acid (omega-6) AI: Men: 19 -50 yr: 17 g/day 51+ yr: 14 g/day Women: 19 -50 yr: 12 g/day 51+ yr: 11 g/day Linolenic acid (omega-3) AI: Men: 1. 6 g/day Women: 1. 1 g/day

Food Sources of Fat: Visible fats: – Fats we add to foods – Butter, cream, mayonnaise, salad dressings Invisible fats: – Fats hidden within foods – Occur naturally or added during processing – Baked goods, dairy, meats, fast foods

Cardiovascular disease «(CVD): a general term for all diseases of the heart and blood vessels. Atherosclerosis is the main cause of CVD. When the arteries that carry blood to the heart muscle become blocked, the heart suffers damage known as coronary heart disease «(CHD). cardio = heart vascular = blood vessels

Blood lipid profile: results of blood tests that reveal a person's total cholesterol, triglycerides, and various lipoproteins. Desirable blood lipid profile: Total cholesterol: < 200 mg/d. L LDL cholesterol: < 100 mg/d. L HDL cholesterol: 2: 60 mg/d. L Triglycerides: < 150 mg/d. L

Major Risk Factors for CHD (not modifiable) 1 - Increasing age 2 - Male gender 3 - Family history of prema ture heart disease

Major Risk Factors for CHD (modifiable) 1 - Cholesterol accumulates in the arteries, restricting blood flow and raising blood prssure. 2 - Saturated Fats raises LDL chol esterol the risk saturated fatty acids that raise blood cholesterol are lauric, myristic, and palmitic acids (12, 14, and 16 carbons, respectively). In contrast, stearic acid (18 carbons) does not seem to raise blood cholesterol. Fats from animal sources are the main sources of saturated fats. diets (see Some vegetable fats (coconut and palm) and hydrogenated fats provide smaller amounts of saturated fats.

3 - Trans Fats Research also suggests an association between dietary trans-fatty acids and heart disease. '? In the body, trans-fatty acids alter blood cholesterol the same way some saturated fats do: they raise LDL cholesterol and, at high intakes, lower HDL cholesterol. Transfatty acids also appear to increase inflammation and insulin

Major Risk Factors for CHD (modifiable) 4 - High blood LDL cholesterol 5 - Low blood HDL cholesterol 6 - High blood pressure (hypertension) 7 - Diabetes 8 - Obesity (especially abdominal obesity) 9 - Physical inactivity 10 - Cigarette smoking 11 - An "atherogenic" diet (high in saturated fats 9 - Inflammation

How lower saturated fat intake: 1 - Selecting poultry or fish 2 - Fat-free milk products helps to lower saturated fat intake and heart disease risk. 12 - Using nonhydrogenated margarine and unsaturated cooking oil.

Cardiovascular Disease Lifestyle changes can prevent or reduce cardiovascular heart disease: – Total fat intake: 20− 35% total calories – Saturated fat: less than 7% total calories – Cholesterol: less than 300 mg per day – Trans fat: reduce to absolute minimum – Increase omega-3 fatty acids – Dietary fiber: 20− 30 grams per day – Folate: 400 micrograms/day

Fat replacers: ingredients derived from carbohydrate, protein, or fat that replace some or all of the functions of fat and mayor may not provide energy. Artificial fats: zero-energy fat replacers that are chemically synthesized to mimic the sensory and cooking qualities of naturally occurring fats but are totally or partially resistant to digestion. Fat replacers. - Used to lower fat content of foods. - Found in chips, cakes, cookies. - May cause GI side effects in large amounts

Example:

Olestra: a synthetic fat made from sucrose and fatty acids Indigestible – provides zero kcals also known as sucrose polyester. Sucrose + fatty acids So many fatty acid chains are crowded around the core, the digestive enzymes cannot find a breaking point

The FDA's evaluation of olestra's safety addressed two questions. First: is olestra toxic? Research on both animals and human beings supports the safety of olestra as a partial replacement for dietary fats and oils, with no reports of cancer or birth defects. Second: does olestra affect either nutrient absorption or the health of the digestive tract? - Olestra binds with some of the fat-soluble vitamins A, D, E, and K and carries them out of the body. - Some consumers experience digestive distress with olestra consumption, such as cramps, gas, bloating, and diarrhea

Food Sources of Fats in Food