Food “combining” Some holistic medicine advocates have suggested that combining fats, proteins and carbohydrates in a meal prevents proper digestion of.

Food “combining”

• Some holistic medicine advocates have suggested that combining fats, proteins and carbohydrates in a meal prevents proper digestion of these macronutrients

• What do you think?

Digestion pathways

• Carbohydrates; enzymes in saliva begin the process

• Proteins: pepsins in stomach initiate breakdown

• Fats: Lipases excreted in walls of small intestine and pancreas

• So……………………triage results?

Conclusion

• It is not an issue to combine all 3 macronutrients in a single meal !!

8. Lipids – Fats & Oils

Chapter 15

Lipids

A lipid is an organic substance found in living systems that is insoluble in water but

is soluble in organic solvents.

Lipids vary widely in their structures. They have mostly C,H and some have a few polar atoms/

functional groups.

Lipids include:

fats and oils

steroids

waxes

Fats & oils make up 95% of the nutritional lipids, the other 5% are steroids. Waxes are functional

only.

Fats are solid triglycerides

Oils are liquid triglycerides

Fats and Oils The Triglycerides We Eat

Triglycerides/fatty acids are characterized/named by:

1) The length/number of carbons in the side chains

2) The number of carbon-carbon double bonds in the side chains(the degree of unsaturation).

CH2-O2C-R

CH2-O2C-R”

CH-O2C-R’ Fatty acid side chains

HOCH2-CHOH-CH2OH(glycerol)

Representative Fatty Acids C12-C18(also C20) Dietary Fats and Oils

CH3-(CH2)12-COOHCH3-(CH2)14-COOHCH3-(CH2)16-CO2H

CH3-(CH2)7-CH=CH-(CH2)7-CO2HCH3-(CH2)4-CH=CH-CH2-CH=CH-(CH2)7-CO2H

CH3-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH-(CH2)7-CO2H

(1)(2)(3)(4)(5)(6)

(1) Myristic acid 58 Saturated C-14(2) Palmitic acid 63 Saturated C-16(3) Stearic acid 71 Saturated C-18(4) Oleic acid 4 Monounsaturated C-18(5) Linoleic acid - 5 Polyunsaturated C-18(6) Linolenic acid - 11 Polyunsaturated C-18

Name Class Mp(oC)

Fatty Acid Content of some Fats/Oils

Canola (Canadian-oil-low acid)

• Oil from Canadian rapeseed

• Has “ideal ratio” of omega-6 to omega-3 fatty acids of 2:1

• Also very low in saturated fat

Olive oil

• Deemed to be the most “heart healthy”

• Highest % of monounsaturated fatty acids

• Extra virgin (1st press)

O2 -C=C-C-COOH -COH-COH-C-COOH unsaturated easy

Oxidation of Organic Compounds, eg. fatty acids

O2 -C-C-C-COOH -C-COH-C-COOH saturated difficult

oxidation = decomposition = rancidity

more saturated = more stable, ie. longer ‘shelf life’, eg. commercial baked goods more unsaturated = faster deterioration, ie. need antioxidants to protect compounds(in the body?)

Hydrolyse: to convert (lyse = to cleave) a compoundinto other substances through the action of water.

-H2OR-C=O R-C=O O-H HO-R’ +H2O O-R’

acid + alcohol ester

(fatty acid + glycerol triglyceride)

FATTY ACIDS (TRIGLYCERIDES) 

Solid: longer chains saturated(only C-C) eg. animal fat, butter  Liquid: unsaturations (C=C) eg. many vegetable oils (olive, sunflower)

Unsaturates can’t fit well into a solid lattice

R e a c t i o n s ( M e t a b o l i c )

O 2

*F a t t y A c i d

C 2 p i e c e s + C O 2 +

H 2 O + e n e r g y

H u m a n s c a n n o t m a k e :

* “ E s s e n t i a l ” F a t t y A c i d s : L i n o l e i c : 1 8 ( 9 , 1 2 ) L i n o l e n i c : 1 8 ( 9 , 1 2 , 1 5 )

Body fat is stored energy

The body converts the unused carbohydrates, proteins and triglycerides that make up our macronutrients into small globules of fat that end up in the specialized cells of adipose tissue, the fatty tissue of the body.

One pound of adipose tissue stores, and provides when needed, ~3500 Cal of energy.

The high energy density of fat - its ability to store energy (9 Cal/gram) compactly in relatively little space and with relatively little weight, compared with carbohydrates and proteins (4 Cal/gram), allows us to carry stores of energy with us.

It give humans and other animals the mobility and freedom necessary for survival

Water in the Camel’s Hump

C54H108O6 + 78O2 54CO2 + 54H2O + zillion Cal (triglyceride from C18H36O2 x 3 ie glycerol tristearate)

Metabolism requires oxygen, produces energy, carbon dioxide and water

Fat = Essential Energy

Most of our long term energy supplies operates via the formation, storage and metabolism of

body fat (triglycerides).

Short term energy storage, from one meal to another, occurs through a starch-like substance

called glycogen(a carbohydrate).

Adipose Tissue / Fat Adipose tissue forms cushioning shields around our major organs, protecting them against damage from physical shock and provides insulation to our bodies, guarding against a rapid loss of body heat to the external environment .

Fats carry the flavours and vitamins of many of our foods although fats have no flavours of their own, eg. carrying vitamins A, D, E and K from our foods to our tissues.

Fatty acids form not only the triglycerides but other compounds as well, including such vital classes as prostaglandins and phospholipids.

R e a c t io n s (“ S y n th e t ic ” )

Io d in e # ( s a t . u n s a t . )

C C C CI I

H H

C C C C

II

C C C C

H H

Io d in a t io n

H y d ro g e n a t io n u n s a tu ra te d s a tu ra te d

CH2 O R

O

CH

CH2

O

O

R'

O

O

R''

CH2 OH

CH

CH2

OH

OH

RO

O Na+

Na+

Na+

R'O

O

R''O

O

3NaOH / H2O

Heat

+

+

+

Saponification/Hydrolysis of a Triglyceride

triglyceride glycerol soaps

COOH

- alpha end

- omega end

Omega - 3 Fatty Acids - Especially in Fish Oils !

Eicosapentaenoic acid (EPA): 20(5,8,11,14,17) mp –50OC !

Docosahexaenoic acid (DHA): 22(5,8,11,14,17, 20)

also -linolenic: 18(9,12,15)

Mainly 20 & 22 C’s, polyunsaturated and 1st ‘ene’ is 3 from -end.

Why ‘Omega – 3’ FA ?

Low incidence of heart disease amongst populations that eat lots of fat BUT mostly as fish !

eg. Inuit & Greenlanders

Sat Mono Poly(16 &18) -3(20 &22)

Cod 15 29 20 35 Herring 20 5 21 53

Don’t like fish? Try omega 3 eggs!

Omega-3 eggs

• Chickens are fed flaxseed, which contains high levels of omega-3 fatty acids. After 10 days, this modifies the fat content in the egg yolk to contain more omega-3 fatty acids and less saturated and omega-6’s

• In 1997, this was the Canadian New Product of the year

Omega-3 Chickens

Omega-3 meats

• Present work (Guelph) on chickens, turkeys, pigs to obtain meat with high omega-3 fat content via diet alterations

• Coming soon to a supermarket near you!

Other omega -3 enriched products

• Orange juice

• Other fruit juices

Cis vs. Trans Fatty acids

• Almost all natural unsaturated fatty acids have cis stereochemistry in C=C’s.

• Small amounts of trans are produced in stomachs of ruminating animals by partial enzymatic hydrogenation of polyunsaturated fats, and thus are present in small amounts in milk and butter

C CR

HH

R

partial H2 catalyst

C CH

RH

RC C R

H

H

R

H

H

+

Commercial Hydrogenation of Fatty Acids

‘cis’ ‘trans’ unsaturated saturated unsaturatednatural natural unnaturalgood bad bad

An unwanted byproduct

• Trans fats increase the level of Low density lipoprotein (LDL).

• Thus they are deemed to be “heart unhealthy” since LDL tends to deposit cholesterol in the arteries rather than transport it (as does HDL) to cells for use in cell membrane construction.

How are trans fats metabolized?

• Catabolism (breakdown) of all fats

• Catalyzed by lipases to free FA’s and glycerol

• FA’s split by beta oxidation into 2C units (Acetyl Co), or propionyl CoA if odd #C’s

• Need bile salts to emulsify fats and allow absorption by the intestine (occurs 1st)

Also have anabolism

• Macromolecules (ie Proteins) synthesized using 2C units derived from fat metabolism, amino acids etc

• Essential link between energy producing (catabolic) and energy utilizing (anabolic) pathways is ATP (adenosine triphosphate)

• Details much beyond the scope of this course!!

‘Trans’ = Saturated; in shape and ‘badness’ !

Incomplete Labels !

‘Trans Fats’ - Misleading Labels

‘Trans Fats’ – an Informative Label

CH3

CH3

OH

CH3

CH3

CH3

Cholesterol (animal "fat")

Cholesterol - a steroidal alcohol (atherosclerosis!)

High – red meat, egg yolks, dairy products Low – egg whites, yoghurt

None ! – fruits, veggies, vegetable oils

Properties of Cholesterol

very insoluble in water, C27H46O

solid, mp. 149o

compact, stiff/rigid

Cholesterol is Absolutely Essential !

The average male (80kg/170lb) contains ~220gm

About:

50% in cell membranes

40% converted to bile acids to ‘emulsify/ transport’ lipids (liver> gall bladder> intestines)

some converted to hormones (testosterone, estrogens, cortisone)

in 80kg male (~gms)

blood 16 muscle 45 brain 50 adipose tissue 45

skin 18 liver 8 heart/kidney, etc. 8

adrenal glands 2 alimentary tract 7

Cell Membrane Structure (lipid bilayer)

Cholesterol Transport in vivo

• Cholesterol is insoluble in water, hence to transport it through the bloodstream, our bodies wrap it in a sheath of proteins and varying amounts of triglycerides to form lipoproteins.

• High Density Lipoproteins (HDL’s) transport excess cholesterol to the liver for disposal “good cholesterol”

• LDL’s (Low Density Lipoproteins) and VLDL’s tend to deposit cholesterol on arterial walls “bad cholesterol”

Structural features: HDL vs LDL

• HDL contains unsaturated cis Fatty acids

• LDL contains more saturated and trans fatty acids

• Both contain apolipoproteins and phospholipids which are oriented with hydrophobic part on inside and outer hydrophilic edges exposed

Cholesterol in gallstones

• Bile : used in fat digestion• Contains water, cholesterol, bile salts , proteins

and bilirubin (waste product)• If bile contains too much cholesterol, it can

harden into gallstones• Extraction of cholesterol from gallstones

(removed by surgery) is a common lab experiment!

• Size can range from grains of sand up to golf ball!

Source of bile acid

• Produced in liver

• Stored and concentrated in the gallbladder

• Secreted into small intestine

• If gallstone blocks exit duct, then gallbladder may need to be removed

• Fat digestion becomes more difficult, but not impossible

Gallstones

Some real ones!!

• Courtesy of the Ottawa Hospital!

Some Risk factors for gallstones

• Gender: Women 2x as likely; excess estrogen from pregnancy, BC pills, HRT all may increase cholesterol levels

• Weight: even moderate obesity • Diet: high fat, low fibre diet increases level of

cholesterol in bile• Rapid weight loss: crash diets as body tries to

metabolize fat• Age.>60: body secretes more cholesterol into bile

Lipid Content (mg) per servingof common foods

• Includes cholesterol

• Saturated fatty acids

• Unsaturated fatty acids

Fat and Oil Content

Food Cholesterol Saturated Monounsaturated PolyunsaturatedBeef 91 2.7 2.7 0.5Butter 219 50.5 23.4 3Cheese ,cheddar 105 21.1 9.4 0.9Cheese , cottage dry 7 0.3 0.1 0.02Chicken (no skin) 85 1.3 1.5 1Corn oil 0 12.7 24.2 58.7Eggs , whole 548 3.4 4.5 1.4Frankfurter (all beef) 51 12.7 14.8 1.2Margarine,stick(coin oil ) 0 13.2 45.8 18Milk , skim 2 0.1 0.05 0.007Milk whole 14 2.3 1.1 0.1Olive oil 0 13.5 73.7 8.4Peanut butter 0 9.7 23.3 15.2Peanut oil 0 16.9 46.2 32Safflower oil 0 9.1 12.1 74.5Salmon (pink , canned) 35 1 1.8 2.7Tuna (canned in water ) 63 0.2 0.1 0.2Turkey (no skin ) 69 1 0.6 0.9Yogurt (plain , lowfat) 6 1 0.4 0.04

Note

• No cholesterol in products derived from plant sources!!

Canada (Cholesterol, mmol/L)

Risk Level Total LDL HDL

Low <4.5 <3.5 1.2

Border-line 5.0-6.0 4.0 1.0

High >6.0 >4.5 0.9

Total / HDL should be 4.0 or less

USA (Cholesterol, mg/dL)

Risk Level Total LDL HDL

Low <200 <130 50

Border-line 200-239 130-159

High >240 >160 35

Cholesterol Related compounds

• 7-dehydrocholesterol (functions as a cholesterol precursor in blood serum) gets converted in vivo (epidermal cells) to Vitamin D by the action of sunlight

Are you getting enough Vitamin D?

• Deficiency leads to poor teeth and bone development (rickets) in children

• Vitamin D is added to milk to offset lack of sunlight in winter ; aids in Ca absorption

• Darker skin prevents UV action • Some MS connection (2009)-all people

should be taking supplements of it.

Can one get too much Vitamin D?

• Yes-overuse of Vitamin D supplements can lead to excessive absorption of Calcium and formation of Ca deposits in kidneys

• Exposure to sunlight is not a problem; Melanin formation (tanning) stops the UV induced reaction

• Recent claims re: Cancer retardation are controversial

Conclusions?

• Drink your milk (and less carbonated sodas)

• Take cod liver supplements if no exposure to sunlight

• Some exposure to sunlight is good (~1 hour per day)

• Avoid mega doses of any fat soluble vitamin

Phospholipids

Phospholipids

a phosphatidic acid

‘-’ or R polar head (charged)

nonpolar tails (HC)

Phospholipid Bilayer = Cell Membrane/Wallhydrophilic surface

hydrophobicinterior of cell wall

-water outside cell-

-water inside cell-

Phosphoglyceride Aggregate = Cell Wall

-cell interior-

-cell exterior-

Lecithin - Another Phospholipid

(emulsifying agent in egg yolks for mayonnaise, candy, cake dough)

Egg yolks

• Yolk; weighs~20 grams; 33% of weight of total egg liquid

• 50% water, 16% protein, 34% lipid• ~6.8 x9 =61.2 Cal from fat; 3.2 x4=12.8 Cal from

protein• Total ~74 Cal. vs. 15 Cal in egg white• Functions as stored food for the embryo• Supermarket eggs do not contain an ovum, since

they have not been fertilized (no rooster!)

Egg structure

Lipids in Egg yolk

• ~ 66% fat, 30% phospholipid (lecithin), 4% cholesterol

• Lecithin (~2 grams per yolk) acts as an emulsifier to “solubilize’’ the fat in the water of the yolk

• Egg yolks used commercially to produce mayonnaise, an emulsion

Origin of Phospholipids

• Biosynthesized in humans from glycerophosphate and Fatty acid CoA

• ATP (adenosinetriphosphate) is needed as a phosphorylating agent

Emulsifying power of an egg yolk

• 2 grams per yolk of lecithin (MW~800)

• # of moles =2/800= 1/400

• # of molecules=1/400 x Avogadro’s number

• 1/400 x 6.02 x 1023~ 1.5 x1021 molecules!

Surface Area

• Consider a layer of lecithin one molecule thick on the surface of water

• The polar head of one lecithin molecule takes up about 1.6 x 10-15 square inches

• Thus the total surface area of oil protected by lecithin=1.6 x10-15 x 1.5x1021 sq inches

• Or 2.4 million square inches

How big is a football field (US)

• 100 yards x 50 yards= 5000 square yards

• In a square yard there are 36 x 36 =1296 square inches

• Thus in 2.4 million square inches, there are 2,400,000 /1296= 1851 square yards (or about 1/3 of a football field)

So………….

• The surface area of oil protected by the lecithin in an egg yolk covers over 1/3 of a football field

• Hence huge emulsifying power

• Ref. “The Curious Cook” by Harold McGee, McMillan 1990

Salmonella Enteritidis (SE bacteria)

• From fecal matter ; egg comes out by same path as fecies; eggs are washed and sanitized before sale

• Can get into yolk or white, before the shell is formed if the hen’s ovaduct or ovaries have been contaminated

• Raw eggs should not be consumed• SE causes severe abdominal pain, nausea in humans,

particularly if taking antacids• SE can be destroyed by acid, antibiotics• Not fatal but can cause ~2 weeks of discomfort!

Commercial mayonnaise

• Made with Pasteurized eggs to avoid SE

• Heat at 55-70oC kills bacteria

Soy Lecithin: comes from soybean oil

Lecithin in Chocolate

• Acts as surfactant (0.5 to 1%) to aid in the flow of liquid chocolate

• Polar end surrounds sugars ( OH groups)• Non polar end interacts with fat• Hershey Plant (Smiths Falls) closing 2006 due to

Salmonella in soy lecithin (Dec 2/06 reopening)-then permanent closure in 2007.

• Salmonella bacteria (normally from undercooked poultry) enter small intestine causing infection

How can Salmonella get into soy Lecithin products?

• Soybeans are often left to dry on open ground, hence are subject to soil fecal contaminant unless sterilized (roasted)

Waxes = (large mol.wt.) Esters (R-COOR’)

Birds/insects - water repellant feathers/exoskeletonsLeaves/fruit - minimize water evaporationHumans - to plug up ears!  beeswax; R= C15, R’= C30; carnauba wax(Brazilian palm): R= C31, R’= C34

*spermaceti(whales): R= C15, R’= C16(mp.31oC)

Whales have 4 tons*(in head). While swimming on surface(37oC) it is a liquid. When they dive (1000m) to feed, the oil solidifies, increases in density, and whale can stay submerged without effort until ready to return to surface where oil remelts for buoyancy.

Density of solids vs. liquids

• Behavior of whale oil is normal-ie liquid is less dense than the solid

• Water is the only substance on the planet in which the solid (ice) is less dense than the liquid

• Water at 4oC is the most dense!

Soaps/Detergents

Chp.13

Contain a nonpolar fat component (tail) and a polar head

Bipolar Behaviour of Soaps, etc.

Detergents = Synthetic Soaps

ie. hydrocarbon tail + polar/charged head

CH3(CH2)13OSO3– Na+

alkyl sulfate(anionic)

CH3(CH2)8 SO3- Na+

alkylbenzene sufonate(anionic)

CH3(CH2)11N+(CH3)Cl –

trimethylalkylammonium(cationic)

CH3(CH2)8O(CH2CH2O)nH (nonionic)

A Typical Soap Molecule

hydrophyllic

‘loves’ H2O

hydrophobic

‘hates’ H2O

Soap makes Grease ‘water-soluble’

Soaps in Hard water

• Curd formation due to insoluble Fe, Ca and Mg carboxylates

• Water softeners: exchange Na for Fe, Ca and Mg ions, increasing solubility of the carboxylates

• Detergents function better in hard water because sulfonates are soluble

Problem Set #3

• Chapt 15 # 1,8,9,10,11,25,29

• Chapt 13#1

• Chapt 16 #1,9,11,12,18