Lipids, Fats, & Oils: What’s the Difference?Lipids Organic substances that are

relatively insoluble in water and soluble in organic solvents Fats

Solid at room temperature Oils

Liquid at room temperature

Major Lipid Classes Fatty acids Triglycerides Phospholipids Sterols Fat-soluble vitamins

Structure & Classification of Fatty AcidsFatty acid consists of: Chain of carbon atoms Carboxylic acid group

alpha end (α) -COOH

Methyl group omega end (ω)

Number of Carbons Short-chain fatty acids

< 8 carbons Medium chain fatty acids

8-12 carbons Long chain fatty acids

> 12 carbons

Fatty Acid Chain Length Affects

Chemical properties

Physiological functions

Solubility in water

Number & Position of Double Bonds Fatty acids

Saturated Single carbon-carbon bonds

Unsaturated Double bonds

Monounsaturated One double bond

Polyunsaturated ≥2 double bonds

Number of Double Bonds Influences

Physical nature of fatty acid Saturated (SFA)

Solid at room temperature Monounsaturated (MSFA)

Thick liquids or soft solids Polyunsaturated (PSFA)

Liquid

Cis versus Trans Fatty Acids Cis double bond

Hydrogen atoms positioned on same side of double bond

Trans double bond Hydrogen atoms are on opposite

sides of double bond Trans fatty acid

Fatty Acid Nomenclature Alpha (α) Nomenclature

Based on positions and types of double bonds relative to the carboxylic (α) end of the fatty acids

Omega (ω) Nomenclature Fatty acids categorized into groups

based on where the first double bond is located relative to methyl (ω) end

“n” system

Examples Omega-3 fatty acid

First double bond is between the 3rd-4th carbons from ω end

Omega-6 fatty acid First double bond is between the 6-7th

carbons

Common Names

The Essential Fatty Acids: Linoleic & Linolenic Acids Not produced in body Linoleic Acid

18 carbons, 2 cis double bonds, ω-6 fatty acid Makes arachidonic acid

Linolenic Acid 18 carbons, 3 cis double bonds, ω-3 fatty acid Converted to docosahexaenoic acid (DHA) &

eicosapentaenoic acid (EPA)

Optimal Lipid Nutrition During Infancy Conditionally Essential Fatty Acids

during infancy Arachidonic acid

ω-6 fatty acid DHA

ω-3 fatty acid

Optimal Lipid Nutrition During Infancy DHA & arachidonic acid

Assists with growth, development of eyes, nervous system, & mental function

Found in breast milk Fortification now occurring with infant

formula

Functions of the Essential Fatty Acids Eicosanoids

Lipid mediators of inflammation made from arachidonic acid and EPA

Includes Prostaglandins Prostacyclins Thromboxanes Leukotrienes

Functions of the Essential Fatty Acids Eicosanoids

Functions: Assist & regulate immune & cardiovascular

systems Act as chemical messengers

Linoleic acid ω-6 eicosanoids Inflammation

Linolenic acid ω-3 eicosanoids Dilation of blood vessels

Food for Thought Why do many Alaskans have enhanced

physiological responses? Why does it take extra time for them to

stop bleeding? Answers:

Alaskan natives eat high amounts of ω-3 fatty acids from fish and marine mammals.

This consumption enhances physiological responses that are stimulated by ω-3 eicosanoids.

Food Sources of the Essential Fatty Acids & Their Metabolism

Linoleic acid Nuts & seeds

Linolenic acid Oils (soybean, safflower,

corn, flaxseed)

Longer-chain fatty acid sources

EPA & DHA Fatty fish & seafood

Arachidonic acid Variety of plant &

animal foods

Essential Fatty Acid Deficiency Irritated & flaky skin Gastrointestinal problems Compromised immune system Slow growth for children

Food Sources of Saturated & Unsaturated Fatty Acids

Guidelines for Saturated Fatty Acids (SFA) Consumption SFA intake positively related to risk

for cardiovascular disease

Dietary Guidelines for Americans SFA should constitute no more than

10% of total kilocalories

Trans Fatty Acids Partial hydrogenation

Process by which some carbon-carbon double bonds found in PUFAs are converted to single bonds

Produces trans fatty acids Formed in rumen Reduces spoilage & improves texture

Food sources Shortening, margarine, crackers, pastries,

bakery products

Guidelines for Trans-Fatty Acid Consumption Can increase risk for

cardiovascular disease U.S. Dietary Guidelines

Consume less than 1% of kilocalories from trans fatty acids

2006 – Required on food labels

Mono-, Di-, & TriglyceridesFunctions:

Source of energy (ATP), insulation, protection Monoglycerides

Lipid made of a glycerol bonded to 1 fatty acid

Diglycerides Lipid made of a glycerol bonded to a 2 fatty

acids Triglycerides

Lipid made of a glycerol bonded to 3 fatty acids

Structure of Mono-, Di-, & Triglycerides

Functions of Triglycerides Provide essential fatty acids for

body functions Energy production Insulation Protection

Use as an Energy Source Lipolysis

Breakdown of triglycerides into fatty acids & glycerol

Stimulated by: Low levels of insulin during hypoglycemia Exercise Physiological stress

Hormone-sensitive lipase Enzyme that catalyzes the hydrolysis of ester

bonds that attach fatty acids to the glycerol molecule

Mobilizes fatty acids from adipose tissue

Use as an Energy Source cont. 1 g fatty acids yields 9 kcal Ketogenesis

Occurs when body’s supply of glucose becomes limited

Ketones produced Used by brain, heart, skeletal muscle,

kidneys Spares protein

Use as an Energy Reserve Adipocytes

Specialized cell that is part of adipose tissue

Subcutaneous adipose tissue Found directly under the skin

Visceral adipose tissue Surrounds vital organs

Use as an Energy Reserve cont.

Energy excess

Insulin stimulates triglyceride storage

Lipogenesis(Synthesis of fatty acids & triglycerides)

Storage of Excess Energy Large amount of triglyerides can

be stored in small space Energy yield from lipids relatively

high Body has infinite ability to store

excess energy in adipose tissue

Insulation & Protection Adipose tissue:

Insulates body Protects internal organs

Phospholipids

Phospholipids Major components of cell membranes Play roles in digestion, absorption,

transport of lipids, cellular metabolism Act as biologically active compounds Amphipathic

Contains both polar and nonpolar portions

Phospholipids are Components of Cell Membranes

Phospholipids are Carriers of Hydrophobic CompoundsExample Lipoproteins

Transport lipids in the blood

Sources of Phospholipids Found naturally in most foods Phosphatidylcholine

Stabilizer to foods Mayonnaise & ice cream

Soy products Common name “lecithin”

Phospholipids & Mental Health in the Elderly Dementia

Influences ability to think, speak, reason, remember & move

Phosphatidylserine Found in brain Important in neural development & function FDA

“Very limited & preliminary scientific research suggests that phosphatidylserine may reduce risk of dementia in elderly”

Sterols & Sterol Esters

Sterol Lipid with distinctive

multiring structure Cholesterol

Sterol ester Chemical compound

of a sterol molecule bonded to a fatty acid via ester linkage

Cholesterol & Cholesteryl Esters Cholesterol

Sterol found in animal foods & made in body Substrate for the synthesis of bile acids &

steroids Component of cell membranes

Cholesteryl ester Sterol made of a cholesterol molecule

bonded to a fatty acid Component of cell membranes

Sources of Cholesterol in the Body: Synthesis & Diet Cholesterol

Made from glucose + fatty acids Influential dietary factors

Low-kilocalorie & low-carbohydrates Diet + genetics influences cholesterol

synthesis Statin drugs

Decrease blood cholesterol by inhibiting 1 of the enzymes needed for synthesis