Chapter 5 The Lipids: Fats, Oils, Phospholipids, & Sterols Basic Nutrition 10/1/07 Dr. Fralinger.

Chapter 5The Lipids: Fats, Oils, Phospholipids, & Sterols

Basic Nutrition

10/1/07

Dr. Fralinger

Introduction

Lipids– Family of organic compounds soluble in organic solvents

but not in water– Include triglycerides, phospholipids, and sterols

Cholesterol– Member of sterols– Soft, waxy substance made in the body

Fats– Lipids solid at room temp.

Oils– Lipids liquid at room temp.

Introduction

CVD– Disease of the heart and blood vessels

Triglycerides– Chief form of fat in foods and the human body

Phospholipids– Similar to triglycerides, except have a

phosphorous containing acid – Present in all cell membranes

Introduction

Lecithin– Phospholipid manufactured by the liver and found

in many foods– Major constituent of cell membranes

Sterols– One of the 3 classes of dietary lipids– Structure similar to cholesterol

Usefulness of Fats in the Body

Fat is the body’s chief storage form for the energy from food eaten in excess of need

Fats in the body Fats in food

Energy stores Nutrient

Muscle fuel Energy

Emergency reserve Transport

Padding Raw materials

Insulation Sensory appeal

Cell membranes Appetite

Raw materials Satiety

Texture


Fat vs. Glucose– Glucose stored as glycogen– Glycogen holds lots of water, so it’s bulky and

heavy body can’t store enough to provide energy for very long

– Fats pack tightly w/o water and can store much more energy in a small space

– Fats provide more than twice the energy of carbs, so efficient storage form of energy


Essential fatty acids– Fatty acids that the body needs but cannot make

in amounts sufficient to meet physiological needs– Serve as raw materials for body to make

molecules required


Lipids not only serve as energy reserves but also – cushion vital organs– protect body from temp. extremes– carry fat-soluble nutrients & phytochemicals– serve as raw materials– provide major component of cell membranes


Lipids – provide more energy per gram than carbohydrate

and protein– enhance the aromas and flavors of foods– contribute to satiety after a meal

Triglycerides: Fatty Acids & Glycerol

Fatty acids– Organic acids composed of carbon chains of

various lengths

Glycerol– Organic compound three carbons long– Serves as the backbone for triglycerides

Body combines 3 fatty acids w/ one glycerol to make a triglyceride, the storage form of fat

Saturated vs. Unsaturated Fatty Acids

Saturated fatty acid– Carries max possible # of hydrogen atoms (no

points of unsaturation)

Point of unsaturation– Site in a molecule where the bonding is such that

additional hydrogen atoms can easily be attached


Unsaturated fatty acid– Lacks some hydrogen atoms and has one or

more pts. of unsaturation

Monounsaturated fatty acid– Contains one point of unsaturation

Polyunsaturated fatty acid– Has two or more pts. of unsaturation


Saturated fats– Triglycerides where most fatty acids are saturated

Trans fats– Contain unusual fatty acids (trans f.a.) formed

during processing


Monounsaturated fats– Triglycerides where most of the fatty acids have

one pt. of unsaturation

Polyunsaturated fats– Triglycerides where most of the fatty acids have

two or more pts. of unsaturation


Therefore, fatty acids are energy-rich carbon chains that can be: – saturated (filled with hydrogens)– monounsaturated (w/ one pt. of unsaturation) – polyunsaturated (w/ more than one pt. of

unsaturation)

Degree of saturation of the fatty acids in a fat determines the fat’s softness or hardness

Phospholipids and sterols

Phospholipids– Soluble in water and fat– Can serve as an emulsifier

substance that mixes w/ fat and water permanently disperses fat in water, forming an emulsion


Emulsification– Process of mixing lipid with water by adding an

emulsifier

Phospholipids help fats travel back and forth across the lipid-containing membranes of cells into the watery fluids on both sides


Sterols – Cholesterol is an example– Serves as the raw material for making bile

Bile– Another emulsifier important to digestion– Made by the liver from cholesterol and stored in

the gallbladder– allows enzymes to split fatty acids from glycerol

for absorption


Sterols play roles as part of bile, vitamin D, the sex hormones, and other important compounds

Digestion and Absorption of Fats

In the stomach, fats separate from other food components

In the small intestine, bile emulsifies the fats, enzymes digest them, and the intestinal cells absorb them

Monoglycerides– Products of the digestion of lipids– Consist of glycerol molecules with one fatty acid

attached

Transport of Fats

Glycerol and shorter-chain fatty acids pass directly through the cells of the intestinal lining into the bloodstream where they travel unassisted to the liver

Large lipids are incorporated into chylomicrons for transport in the lymph and blood

Blood and other body fluids are watery, so fats need lipoproteins to carry them in these fluids

Transport of Fats

Lipoproteins– Clusters of lipids associated with protein– Serve as transport vehicles for lipids in blood and

lymph– Major classes are the chylomicrons, the VLDL,

the LDL, and the HDL

Transport of Fats

Chylomicrons– Clusters formed when lipids from a meal are

combined with carrier proteins in the cells of the intestinal lining

– Transport food fats through the watery body fluids to the liver and other tissues

How can I use my stored fat for energy?

Fat depots-– Muscles– Breasts– Insulating fat layer under the skin


1. When a person’s body starts to run out of available fuel from food, begins to retrieve stored fat to use for energy

2. Fat cells respond to the call for energy by dismantling stored fat molecules and releasing fat components into the blood


3. Cells break them down further into small

fragments

4. Each fat fragment is combined with a

fragment derived from glucose

5. Energy-releasing process continues,

liberating energy, CO2, and water


Therefore, to use the energy stored as fat, must create a greater demand for it in the tissues by decreasing intake of food energy, increasing the body’s expenditure of energy, or both

When low on fuel, the body draws on its stored fat for energy; carbs are necessary for the complete breakdown of fat

Dietary Fat, Cholesterol, and Health

Choosing a diet too high in saturated fats or trans fats invites the risk of heart and artery disease (CVD)

Cancer Obesity

Lipoproteins and Heart Disease Risk

The chief lipoproteins are chylomicrons, VLDL, LDL, and HDL

Blood LDL and HDL concentrations are among the major risk factors for heart disease


VLDL– Carry triglycerides and other lipids made in the liver to the

body cells for their use

LDL– Transport cholesterol and other lipids to the tissues– Made from VLDL after they have donated many of their

triglycerides to body cells

HDL– Critical in the process of carrying cholesterol away from

body cells to the liver for disposal


The more of the following factors present, the more urgent the need for changes in diet, etc. to reduce heart disease risk:

– High blood LDL cholesterol– Low blood HDL cholesterol– High blood pressure (hypertension)– Diabetes (insulin resistance)– Obesity– Physical inactivity– Cigarette smoking– An “atherogenic” diet

High in sat. fats, including trans fats Low in veggies, legumes, fruit, and whole grains

What does food cholesterol have to do with blood cholesterol?

Most saturated food fats raise blood cholesterol more than food cholesterol does

High blood cholesterol is an indicator of risk for CVD

Main dietary factors associated with elevated blood cholesterol are high saturated fat and trans fat intakes


LDL cholesterol indicates a risk of heart disease because the LDL are carrying cholesterol, made mostly from saturated fat in the diet, to the body tissues to be deposited there


Dietary cholesterol makes a smaller but still significant contribution to elevated blood cholesterol

Five food that contribute about 70% of the food cholesterol in the US diet:

– Eggs, 30%– Beef, 16%– Poultry, 12%– Cheese, 6%– Milk, 5%


Genetic inheritance modifies everyone’s ability to handle dietary cholesterol somewhat

Many people exhibit little increase in their blood cholesterol even with a high dietary intake

Lowering LDL Cholesterol

Trimming fat from food trims calories and, often, saturated fat and trans fat as well

Oxidation– Interaction of a compound with oxygen– LDL is susceptible to damage by oxidation,

thereby making it dangerous to the arteries of the heart

Lowering LDL Cholesterol

Dietary antioxidant– Substance in food that significantly decreases the

damaging effects of reactive compounds– Adequate intakes of these, such as vitamin C,

vitamin E, selenium, and antioxidant phytochemicals, may slow LDL oxidation

Recommendations Applied

Dietary measures to lower LDL in the blood involve reducing saturated fat and trans fat and substituting monounsaturated and polyunsaturated fats

Cholesterol-containing foods are nutritious and are best used in moderation by most people

Essential Polyunsaturated Fatty Acids

Linoleic and linolenic acid– Essential; body does not make them on its own– Serve as raw materials from which eicosanoids

are made

Eicosanoids– Biologically active compounds that regulate body

functions

Essential Polyunsaturated Fatty Acids

Eicosanoids– Act somewhat like hormones, affecting

muscle relaxation and contraction blood vessel dilation and constriction blood clot formation blood lipid regulation immune response to injury and infection including fever,

inflammation and pain

Deficiencies of Essential Fatty Acids

Leads to observable changes in cells When diet is deficient in all of the

polyunsaturated fatty acids:– Reproductive failure– Skin abnormalities– Kidney and liver disorders– Infants

Growth hindered and vision impaired

Omega-6 and Omega-3 Fatty Acid Families

Omega-6– Linoleic acid – Endmost double bond six carbons from the end of the

carbon chain Arachidonic acid

– Omega-6 derived from linoleic acid Omega-3

– Linolenic acid, EPA, DHA (fish oils)– Endmost double bond three carbons from the end of the

carbon chain


A diet that includes two meals of fatty fish each week can reduce deaths and illness from heart disease, especially in those who have already suffered a heart attack

Fish is more beneficial than supplements of fish oil

Evidence that omega-3 may support immunity and inhibit development of certain cancers


For healthy people a normal diet to prevent deficiencies must have– Grains– Seeds– Nuts– Leafy veggies– Oils– Fish

Fish oil supplements

FDA does not permit labels to claim that they can prevent or cure diseases

May raise LDL cholesterol Excessive amounts can interfere with normal

functions Made from fish skins and livers, which may

have toxic concentrations of pesticides, mercury, etc

Fish oil supplements

Species most heavily contaminated with mercury:– Shark– Swordfish– King mackerel– Fresh tuna steaks– tilefish

Lower in mercury:– Shrimp– Canned light tuna– Salmon– Pollock– catfish

Effects of Processing of Unsaturated Fats

Vegetable oils make up most of the added fat in the US diet because fast-food chains use them for frying, food manufacturers add them to processed foods, and consumers tend to choose margarine over butter

Hydrogenated Vegetable Oil

Hydrogenation– Process of adding hydrogen to unsaturated fatty acids to

make fat more solid and resistant to the chemical change of oxidation

– Makes fats stay fresher longer and also chages physical properties

– Points of unsaturation are weak spots that are vulnerable to attack by oxygen

– When unsat. pts. In the oils of food are oxidized, the oils become rancid and the food tastes “off”

– Cooking oils should be stored in tightly covered containers that exclude air

Hydrogenated Vegetable Oil

Vegetable oils become more saturated when they are hydrogenated

Hydrogenated fats resist rancidity better, are firmer textured than unsaturated oils, but they also lose the health benefits of unsaturated oils

Trans fatty acids

Fatty acids with unusual shapes that can arise when polyunsaturated oils are hydrogenated

Consuming these poses a risk to the health of the heart and arteries by raising LDL and lowering HDL

Fat in the Diet

Fats added to foods during preparation or at the table are a major source of fat in the diet

Majority of added fats in the diet are invisible– They are the hidden fats of fried foods and baked

goods, sauces and mixed dishes, and dips and spreads

Fat in the Diet

Meats account for a large proportion of the hidden fat and saturated fat in many people’s diets

Most people consume meat in larger amts. Than recommended

The choice between whole and fat-free mild products can make a large difference to the fat and saturated fat content of a diet

Cheeses are a major contributor of saturated fat

Fat in the Diet

Fat may be added to grains during manufacturing, processing, or cooking

Chapter 5 The Lipids: Fats, Oils, Phospholipids, & Sterols Basic Nutrition 10/1/07 Dr. Fralinger.

Documents

unsaturation slide

body lipids

fatty acids w

triglycerides body

usefulness of fats

cholesterol slide

body fats lipids solid

fralinger slide