The LipidsThe LipidsTriglyceridesTriglyceridesPhospholipidsPhospholipids

SterolsSterols

LipidsLipids• Triglycerides (TG)Triglycerides (TG)

– Fats and oilsFats and oils

• PhospholipidsPhospholipids

• SterolsSterols

Fatty Acids (FA) & TGFatty Acids (FA) & TG

• glycerol-a sugar alcohol, glycerol-a sugar alcohol, backbone of a FA!backbone of a FA!

• REM: they have carbon REM: they have carbon (C), so they are organic!(C), so they are organic!

FA & TGFA & TG

glycerol + 3 FA glycerol + 3 FA TG + HTG + H22OO

Condensation of Glycerol & Fatty Acids to Form a Triglyceride

Fatty AcidsFatty Acids– Length (size matters)Length (size matters)– Saturated vs. unsaturatedSaturated vs. unsaturated

• Acetic Acid (most simple)Acetic Acid (most simple)

Saturated Fatty AcidsSaturated Fatty Acids• How many carbons?How many carbons?

Stearic acid – 18-carbon

Simplified structureSimplified structure

Fatty AcidsFatty Acids• Point of saturation (where?)Point of saturation (where?)

• Degree of saturation (how much?)Degree of saturation (how much?)– Saturated fatty acidSaturated fatty acid

•Monounsaturated Monounsaturated •Polyunsaturated Polyunsaturated

An impossible chemical structure: Why?

Oleic acid – 18-carbon, monounsaturated

Linoleic acid – 18-carbon, polyunsaturated

OMEGA NUMBER: Ω-3 vs. Ω-6 Fatty Acids

TG: Why Does Saturation Matter?TG: Why Does Saturation Matter?

• Unsaturation effects:Unsaturation effects:– FirmnessFirmness– StabilityStability

•OxidationOxidation–AntioxidantsAntioxidants

Triglycerides:What about Triglycerides:What about “hydrogenated oils?”“hydrogenated oils?”

– HydrogenationHydrogenation-hydrogen added to -hydrogen added to mono- or polyunsaturated fats to mono- or polyunsaturated fats to make them solid by reducing the make them solid by reducing the number of double bonds (C=C).number of double bonds (C=C).

– CisCis vs. vs. transtrans-fatty acids-fatty acids

Hydrogenation

Cis- and Trans-Fatty Acids Compared

So what? It’s a nice picture. So what? It’s a nice picture.

TransTrans fats are bad!!! fats are bad!!!

• In the body In the body transtrans fats behave like fats behave like saturated fats! Why?saturated fats! Why?

• They contribute to higher They contribute to higher LDL cholesterol and lower levels of "good" cholesterol and lower levels of "good" HDL cholesterol = heart disease. cholesterol = heart disease.

PhospholipidsPhospholipids

Phospholipids (PL)Phospholipids (PL)• Phospholipids in Phospholipids in

foodsfoods

• Roles of PLRoles of PL– Plasma membranePlasma membrane– Emulsifiers (help oil Emulsifiers (help oil

and water exist and water exist together)together)

Membrane Structure PLMembrane Structure PL

Hydrophobic tail vs. hydrophilic head: more on this later.

SterolsSterols

SterolsSterols• Roles of sterols: Roles of sterols: GoodGood

– Bile acidsBile acids– Sex hormonesSex hormones– Adrenal hormonesAdrenal hormones– Vitamin DVitamin D

• Roles of sterols: Roles of sterols: BadBad-Atherosclerosis-hardening of arteries.-Atherosclerosis-hardening of arteries.

Fat DigestionFat Digestion

Yummy...or not.Yummy...or not.

Fat DigestionFat Digestion• HydrolysisHydrolysis

– Triglycerides Triglycerides monoglycerides, monoglycerides, fatty acids, glycerol fatty acids, glycerol

Fat DigestionFat Digestion

Fat DigestionFat Digestion• MouthMouth

– MeltingMelting– Lingual lipase Lingual lipase

Fat DigestionFat Digestion• StomachStomach

– Churning and mixingChurning and mixing– Gastric lipase Gastric lipase

Fat DigestionFat Digestion• Small intestineSmall intestine

– CCK-hormone which signals bile CCK-hormone which signals bile release!release!•Bile emulsifies fats.Bile emulsifies fats.

Fat DigestionFat Digestion

Fat DigestionFat Digestion

Fat DigestionFat Digestion• Small intestineSmall intestine

– Pancreatic lipasesPancreatic lipases– Intestinal lipasesIntestinal lipases

Fat Fat DigestionDigestionOverviewOverview

Fat DigestionFat Digestion• Enterohepatic Enterohepatic

circulationcirculation

• Note how fiber Note how fiber helps remove helps remove excess excess cholesterol!!cholesterol!!

Lipoproteins and healthLipoproteins and healthFactors that lower LDL and raise HDLFactors that lower LDL and raise HDL

– Weight controlWeight control– Replace saturated fat with monounsaturated Replace saturated fat with monounsaturated

fat and polyunsaturated fat in the dietfat and polyunsaturated fat in the diet– Soluble fibersSoluble fibers– PhytochemicalsPhytochemicals– Moderate alcohol consumptionModerate alcohol consumption– Physical activity (biggest helper)Physical activity (biggest helper)

• Genes influence lipoprotein activity.Genes influence lipoprotein activity.

Roles of TriglyceridesRoles of Triglycerides• Fat storesFat stores

– EnergyEnergy– ProtectionProtection– InsulationInsulation

Essential Fatty AcidsEssential Fatty Acids

Fat MetabolismFat Metabolism

• Storage as fatStorage as fat– Adipose tissueAdipose tissue– LPL = LPL =

lipoprotein lipoprotein lipaselipase...fat ...fat storage.storage.

Lipid MetabolismLipid Metabolism• Using fat for energyUsing fat for energy

– Hormone-sensitive Hormone-sensitive lipaselipase...triglyceride ...triglyceride release.release.

– Provides very little Provides very little glucose...problem glucose...problem during fasting?during fasting?

Health Effects Health Effects of Lipidsof Lipids

• Blood lipid profileBlood lipid profile

• Heart diseaseHeart disease

• Risks from saturated fatsRisks from saturated fats

Health Effects of Lipids:US DietHealth Effects of Lipids:US Diet

Dietary CholesterolDietary Cholesterol

Health Effects Health Effects of Lipidsof Lipids

• Benefits:monounsaturated and Benefits:monounsaturated and polyunsaturated fatspolyunsaturated fats

• CancerCancer

• ObesityObesity

Health Effects and Health Effects and Recommended Intakes of LipidsRecommended Intakes of Lipids

• Recommended Intakes of FatRecommended Intakes of Fat– DRI: 20-35% of energy intake (400-700 kcalories DRI: 20-35% of energy intake (400-700 kcalories

of a 2,000-kcal diet).of a 2,000-kcal diet).

– FDA recommends 10% of energy intake from sFDA recommends 10% of energy intake from s

• Linoleic acid AILinoleic acid AI Linolenic acid AILinolenic acid AI5-10% of energy intake5-10% of energy intake 0.6-1.2% of energy intake 0.6-1.2% of energy intake– aturated, 30% of energy intake total fataturated, 30% of energy intake total fat

Health Effects and Health Effects and Recommended Intakes of LipidsRecommended Intakes of Lipids– Daily Values Daily Values

• 65 g fat based on 30% of 2000-kcal diet65 g fat based on 30% of 2000-kcal diet• 20 g sat. fat based on 10% of 2000-kcal diet20 g sat. fat based on 10% of 2000-kcal diet• 300 mg cholesterol300 mg cholesterol

– USDA Food Guide considers saturated fats USDA Food Guide considers saturated fats discretionary kcalories. discretionary kcalories.

– Too little fat can be detrimental to health.Too little fat can be detrimental to health.

Health Effects and Health Effects and Recommended Intakes of LipidsRecommended Intakes of Lipids

• Health Effects of LipidsHealth Effects of Lipids– Blood lipid profileBlood lipid profile

• Reveals concentrations of lipids in the bloodReveals concentrations of lipids in the blood• Desirable levels Desirable levels

– Total cholesterol < 200 mg/dLTotal cholesterol < 200 mg/dL– LDL cholesterol < 100 mg/dLLDL cholesterol < 100 mg/dL– HDL cholesterol ≥ 60 mg/dLHDL cholesterol ≥ 60 mg/dL– Triglycerides < 150 mg/dLTriglycerides < 150 mg/dL

Cutting Fat Cuts kCalories and Saturated FatCutting Fat Cuts kCalories and Saturated Fat

Guidelines to GroceriesGuidelines to Groceries• Milk and milk productsMilk and milk products• Vegetables, fruits, and grainsVegetables, fruits, and grains• Invisible fatInvisible fat

High-Fat FoodsHigh-Fat Foods• Changing guidelines for fat intakeChanging guidelines for fat intake

High-Fat FoodsHigh-Fat Foods• Cook with olive oilCook with olive oil

• Nibble on nutsNibble on nuts

• Feast on fishFeast on fish– But beware of mercury?But beware of mercury?

High-Fat FoodsHigh-Fat Foods• Mediterranean diet?Mediterranean diet?