Chap. 5: Lipids. FAT FACTS Lipids or “Fats” are essential to good health Fat is found in almost all foods Recommended intake of dietary fat: 20%-35%

Chap. 5: LipidsChap. 5: Lipids

FAT FACTSFAT FACTS

Lipids or “Fats” are essential to good healthLipids or “Fats” are essential to good health Fat is found in almost all foodsFat is found in almost all foods Recommended intake of dietary fat: Recommended intake of dietary fat:

20%-35% of kcal.20%-35% of kcal. 3,500 kcal = 1 lb. of fat3,500 kcal = 1 lb. of fat

Properties of LipidsProperties of Lipids

Do not readily dissolve in waterDo not readily dissolve in water Fats are solid at room temperatureFats are solid at room temperature Oils are liquid at room temperatureOils are liquid at room temperature Triglycerides are the main form of lipids in Triglycerides are the main form of lipids in

food and body (storage)food and body (storage) Energy dense (9 kcal /gm)Energy dense (9 kcal /gm)

Functions of Somatic FatFunctions of Somatic Fat

Stored Energy ReserveStored Energy Reserve InsulationInsulation CushioningCushioning Transport fat-soluble vitaminsTransport fat-soluble vitamins Forms Cell Membranes (cholesterol)Forms Cell Membranes (cholesterol)

Functions of Dietary LipidsFunctions of Dietary Lipids

Concentrated source of energy (kcal)Concentrated source of energy (kcal) Satiety (slows emptying of stomach)Satiety (slows emptying of stomach) Aroma, Flavor and mouth feelAroma, Flavor and mouth feel

Requirements for Dietary FatRequirements for Dietary Fat

20% to 35% of total caloric intake.20% to 35% of total caloric intake. This is approximately 44 to 77 grams of fat This is approximately 44 to 77 grams of fat

if you consume 2000 kcal per day.if you consume 2000 kcal per day. Less than 10% of the daily kcal intake Less than 10% of the daily kcal intake

should be from saturated fat.should be from saturated fat. This is approximately 22 grams of This is approximately 22 grams of

saturated fat if you consume 2000 saturated fat if you consume 2000 kcal/day.kcal/day.

A large percentage of fat intake should A large percentage of fat intake should come from monounsaturated oils.come from monounsaturated oils.

Sources of Dietary LipidsSources of Dietary Lipids

Types of FatTypes of Fat

TriglyceridesTriglycerides Make up 95% of all fatsMake up 95% of all fats Composed of a water soluble glycerol and three water Composed of a water soluble glycerol and three water

insoluble fatty acidsinsoluble fatty acids PhospholipidsPhospholipids

Composed of glycerol, 2 fatty acids and a Composed of glycerol, 2 fatty acids and a phosphorus.phosphorus.

Primary function is to emulsify fats.Primary function is to emulsify fats. SterolsSterols

Compounds composed of several carbon rings that Compounds composed of several carbon rings that has several biological functionshas several biological functions

TriglyceridesTriglycerides

The most common type of fat found in the The most common type of fat found in the body (95% of all fats are triglycerides)body (95% of all fats are triglycerides)

Triglycerides Triglycerides

H

H--C--OH

H--C--OH

H--C--OH

H

Fatty Acid

Fatty Acid

Fatty Acid

+

H O

H--C--O--C--

O

H--C--O--C--

O

H--C--O--C--

H

Fatty Acid

Fatty Acid

Fatty Acid

Condensation

Fatty Acid Structure Fatty Acid Structure (Fig. 5-1-A)(Fig. 5-1-A)

omega endomega end alpha endalpha endMethyl endMethyl end Acid endAcid end

H H H H H H H H H H H H H H H H H O

H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH

H H H H H H H H H H H H H H H H H

Saturated Fatty Acid Structure Saturated Fatty Acid Structure (Fig. 5-1-A)(Fig. 5-1-A)

omega endomega end alpha endalpha end

Note: All carbons connected by single bondsNote: All carbons connected by single bonds

H H H H H H H H H H H H H H H H H O

H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH

H H H H H H H H H H H H H H H H H

Monounsaturated Fatty Acid Monounsaturated Fatty Acid Structure Structure (Fig. 5-1-B)(Fig. 5-1-B)

omega endomega end alpha endalpha end

Note: Only ONE double bondNote: Only ONE double bond

H H H H H H H H H H H H H H H O

H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH

H H H H H H H H H H H H H H H H H

Polyunsaturated Fatty Acid Polyunsaturated Fatty Acid Structure Structure (Fig. 5-1-C)(Fig. 5-1-C)

omega endomega end alpha endalpha end

>> 2 double bonds 2 double bonds

H H H H H H H H H H H H H O

H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH

H H H H H H H H H H H H H H H H H

Triglycerides can contain a Triglycerides can contain a mixture of saturated, mixture of saturated,

monounsaturated and monounsaturated and polyunsaturated fatty acids.polyunsaturated fatty acids.Most of our dietary lipids are Most of our dietary lipids are

mixed triglycerides.mixed triglycerides.

Characteristics of Fatty AcidsCharacteristics of Fatty Acids

SaturatedSaturated fatty acids are fatty acids are solidsolid at room at room temperature and are resistant to oxidation. temperature and are resistant to oxidation. Should be consumed Should be consumed sparinglysparingly in diet. in diet.

MonounsaturatedMonounsaturated Fats are Fats are liquidliquid at room at room temperature. Rate of oxidation: low. temperature. Rate of oxidation: low. Consumption Consumption does not have to be limiteddoes not have to be limited..

PolyunsaturatedPolyunsaturated Fats are Fats are liquidliquid at room at room temperature. Rate of oxidation: High. temperature. Rate of oxidation: High. Should be consumed Should be consumed moderatelymoderately..

OxidationOxidation Oxidation: The removal of electron(s) from atoms of a Oxidation: The removal of electron(s) from atoms of a

compound or element by oxygen or another ion/atom.compound or element by oxygen or another ion/atom. Alters appearance or function of compound or elementAlters appearance or function of compound or element EX: Rust on iron EX: Rust on iron

Fat Oxidation ConcernsFat Oxidation Concerns

Fatty acid oxidation in the body increases Fatty acid oxidation in the body increases free radical production which destroys free radical production which destroys cellscells

Fatty acid oxidation in the body damages Fatty acid oxidation in the body damages arterial walls and increases CVD riskarterial walls and increases CVD risk

Fatty acid oxidation in foods is not harmful, Fatty acid oxidation in foods is not harmful, but is unpleasant to taste and smell. Oil but is unpleasant to taste and smell. Oil that is oxidized is called “rancid.”that is oxidized is called “rancid.”

Hydrogenation of Fatty AcidsHydrogenation of Fatty Acids

Process used to solidify an oil and Process used to solidify an oil and slow oxidation.slow oxidation.

Addition of H to C=C double bondsAddition of H to C=C double bonds Increases shelf lifeIncreases shelf life Formation of Formation of trans fatty acidtrans fatty acid (similar (similar

to shape of saturated fatty acid)to shape of saturated fatty acid)

Cis and Trans Fatty Acid Cis and Trans Fatty Acid

Health Dangers of Excessive Health Dangers of Excessive Trans Fatty AcidTrans Fatty Acid

Raises LDLRaises LDL Lowers HDLLowers HDL Increases risk for heart diseaseIncreases risk for heart disease Damages artery wallsDamages artery walls

Minimize Intake of Trans Fatty Minimize Intake of Trans Fatty AcidAcid

Limit use of solid oils Limit use of solid oils (margarine)(margarine)

Limit deep-fried foodsLimit deep-fried foodsLimit high fat baked goodsLimit high fat baked goodsLimit use of all processed foodsLimit use of all processed foods

Essential Fatty AcidsEssential Fatty Acids

Needed for production of hormone-Needed for production of hormone-like compounds called eicosanoids like compounds called eicosanoids which regulate inflammation, clotting,which regulate inflammation, clotting,

immune function, vision, and allergic immune function, vision, and allergic response.response.

Essential Fatty AcidsEssential Fatty Acids Omega 6 Omega-3

Linoleic acid Alpha-linolenic acid(corn, soybeans, nuts, seeds, greens) (canola oil, walnuts, flaxseed)

Gamma-Linolenic acid DHA (borage oil, primrose oil) (docosahexanoic acid)

Fish oil

Arachidonic Acid EPA

(meat) (eicosapentaenoic acid)

Fish oil

The Different EffectsThe Different Effects

Omega-6 Omega-6 increases blood clottingincreases blood clotting increases inflammatory responsesincreases inflammatory responses promotes activation of leukocytespromotes activation of leukocytes

Omega-3Omega-3 reduces heart attackreduces heart attack Inhibits inflammationInhibits inflammation Inhibits cancer growthInhibits cancer growth decreases blood clottingdecreases blood clotting excess may cause hemorrhagic strokeexcess may cause hemorrhagic strokeRatio of Omega 6: Omega 3 4:1Ratio of Omega 6: Omega 3 4:1

Essential Fatty Acid- Omega-6 (alpha-Essential Fatty Acid- Omega-6 (alpha-linoleic acid)linoleic acid)

omega endomega end alpha endalpha end

1st double bond is located on the 6th carbon 1st double bond is located on the 6th carbon from the omega endfrom the omega end

H H H H H H H H H H H H H O

H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH

H H H H H H H H H H H H H H H H H

Omega-6 Fatty AcidOmega-6 Fatty Acid

Found in vegetable oilsFound in vegetable oils Only need ~ 1 Only need ~ 1

tablespoon a daytablespoon a day About 14g per dayAbout 14g per day

Essential Fatty Acid- Omega-3 (alpha-Essential Fatty Acid- Omega-3 (alpha-linolenic acid)linolenic acid)

omega endomega end alpha endalpha end

1st double bond is located on the 3rd carbon 1st double bond is located on the 3rd carbon from the omega endfrom the omega end

H H H H H H H H H H H H H H H H H O

H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH

H H H H H H H H H H H

Omega-3 Fatty AcidOmega-3 Fatty Acid

EPA and DHA Primarily from fish oil, EPA and DHA Primarily from fish oil, Omega 3 eggs.Omega 3 eggs.

Alpha-Linolenic found in canola oil, Alpha-Linolenic found in canola oil, soybean oil, flaxseed oil, enriched cereals, soybean oil, flaxseed oil, enriched cereals, and walnutsand walnuts

Recommend intake of ~2 servings of fish Recommend intake of ~2 servings of fish per week or 6-10 oz.per week or 6-10 oz.

About 2 grams per day.About 2 grams per day.

PhospholipidPhospholipid

Built on a glycerol backboneBuilt on a glycerol backbone Has at least one fatty acid replaced with Has at least one fatty acid replaced with

phosphorus compoundphosphorus compound Found in bodyFound in body Synthesized by the body as neededSynthesized by the body as needed

Functions of PhospholipidsFunctions of Phospholipids

Make up cell membraneMake up cell membrane EmulsifierEmulsifier

Bile acidsBile acids LecithinsLecithins Improves food productsImproves food products

EmulsifierEmulsifier

Hydrophilic end Hydrophilic end (attracts water)(attracts water)

Hydrophobic end Hydrophobic end (attracts lipid)(attracts lipid)

Emulsification Emulsification

Sterols: CholesterolSterols: Cholesterol

Essential component of cell Essential component of cell membranemembrane

Produced by the liverProduced by the liver Found only in animal productsFound only in animal products Forms important hormonesForms important hormones

Estrogen, testosterone, vitamin DEstrogen, testosterone, vitamin D

Precursor to bile acidsPrecursor to bile acids

Structure of CholesterolStructure of Cholesterol

Dietary CholesterolDietary Cholesterol

Dietary cholesterol is found only in animal Dietary cholesterol is found only in animal products. Since the liver makes products. Since the liver makes cholesterol, only things with a liver have cholesterol, only things with a liver have cholesterol.cholesterol.

Dietary cholesterol serves no purpose Dietary cholesterol serves no purpose since the liver makes all your body needs.since the liver makes all your body needs.

Dietary cholesterol has little affect on Dietary cholesterol has little affect on blood cholesterol.blood cholesterol.

LIPID DIGESTIONLIPID DIGESTION

Digestion of Fat in the StomachDigestion of Fat in the Stomach

Gastric lipaseGastric lipase works only in an acidic works only in an acidic environment environment

Gastric lipase acts on triglycerides Gastric lipase acts on triglycerides containing short & medium chain fatty acidcontaining short & medium chain fatty acid

Longer fatty acid chain is not affected by Longer fatty acid chain is not affected by the stomachthe stomach

Digestion of Fat in the Small Digestion of Fat in the Small IntestineIntestine

Primary site of fat digestionPrimary site of fat digestion CCKCCK stimulates pancreas to release stimulates pancreas to release pancreatic pancreatic

lipaselipase Pancreas release lipasePancreas release lipase Bile acid emulsifies digested fatBile acid emulsifies digested fat Fat is broken down to Fat is broken down to monoglyceridesmonoglycerides and and

fatty acidsfatty acids

Absorption of LipidsAbsorption of Lipids

Diffuse into the absorptive cellsDiffuse into the absorptive cells Short and medium chain (<12 C) fatty Short and medium chain (<12 C) fatty

acids are water solubleacids are water soluble Enters the blood stream, sent to liver via the Enters the blood stream, sent to liver via the

portal veinportal vein Long chain fatty acids reforms into Long chain fatty acids reforms into

Triglycerides for special transport via the Triglycerides for special transport via the lymphatic system.lymphatic system.

Carrying Lipids in the BloodstreamCarrying Lipids in the Bloodstream

Triglycerides are too large to be Triglycerides are too large to be transported in the blood.transported in the blood.

Unique system of fat transportation is Unique system of fat transportation is needed called “lipoproteins.”needed called “lipoproteins.”

Lipoproteins are packaged lipids with a Lipoproteins are packaged lipids with a protein exterior and are transported to the protein exterior and are transported to the bloodstream via lymph. bloodstream via lymph.

LipoproteinsLipoproteins

Types of LipoproteinsTypes of Lipoproteins ChylomicronsChylomicrons. Largest of the lipoproteins carry . Largest of the lipoproteins carry

mostly triglycerides from the intestines to the mostly triglycerides from the intestines to the rest of the body via lymph. rest of the body via lymph.

VLDL.VLDL. Very low density lipoproteins. Carry Very low density lipoproteins. Carry mostly chylomicron remnants and lipids mostly chylomicron remnants and lipids assembled by the liver.assembled by the liver.

LDL.LDL. Low density lipoprotein. The remnant of Low density lipoprotein. The remnant of VLDL. Carries mostly cholesterol. Has a VLDL. Carries mostly cholesterol. Has a propensity to oxidize and damage arteriespropensity to oxidize and damage arteries

HDL.HDL. High density lipoprotein. Carries some High density lipoprotein. Carries some lipids, but is mostly protein. Retrieves cholesterol lipids, but is mostly protein. Retrieves cholesterol from the cells and delivers to the liver for from the cells and delivers to the liver for recycling.recycling.

Dangers of too much fatDangers of too much fat

ObesityObesity DiabetesDiabetes HypertensionHypertension cancercancer

Elevated Triglycerides and CholesterolElevated Triglycerides and Cholesterol DiabetesDiabetes Heart diseaseHeart disease