FNH 250 Notes

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University of British Columbia
Food, Nutrition and Health
FNH 250

Lipid Nutrition and Metabolism Part 1Lipid soluble in organic solvents generally insoluble in waterLipids of nutritional concern triglycerides TG phospholipids and sterolsGeneral Functions oSource of energy for bodyoComponents of cell membranesoRegulation of physiological and biochemical processesTG composed of glycerol and 3 fatty acidsoMake up most of the lipids in the dietoFunctionTo provide and store energy for the boyInsulation Protection of organsoMonoglycerides MG and diglycerides DGformed during digestion and as intermediates in reactions not present in high quantities in diet or body tissuesMG may be added to processed foods as emulsifying agents cake mixes salad dressingsoTG insoluble in water at room tempConsistency varies from liquid to solidMostly solid fatMostly liquid oilSimple triglycerides all the same type of fatty acidsMixed TG different types of fatty acidoPhospholipidsComposed of glycerol and 2 fatty acids and phosphate group plus small charged group attached to phosphateAmphipathic head portion polar and soluble in water tail nonpolar and insoluble FunctionsStructuralcomponent of cell membraneComponent of bilelipid emulsification and formation eg PhosphatidylcholinelecithinComponent of lipoproteinstransport of lipids in bloodRegulation of various processes in the body eg Blood vessel dilation and contraction inflammation blood clottingoSterolsC skeleton has 4 interconnected ringsCholesterol and compounds derived from sterolsCholesterol only found in animal tissueFound free or with fatty acid attached cholesterol esterFunctionsStructuralcomponent of cell membranePrecursor of bile saltslipid digestion and absorption Precursor of steroid hormonesregulation of various processes in the bodyoEg Estrogens progesterone testosterone cortisol vitamin D etcoFatty acidsCarbon chains with H and a carboxylic acid group on one endUsually found as components of other lipids in the body or in the diet not as free fatty acidTheir physical and chemical properties influence the properties of the lipids that contain them Most natural fats have fatty acids with an even number oof carbons ranging from 4 to 24Chain length for most edible oils 1618 coconut oil 12CThe higher the chain length the higher the melting pointSaturated only single carbon to carbon bondsImportant propertiesChain lengthoRanges from 424 C in food and bodyoShort chain fatty acids those 6C long made by microorganismsfound in dairy foodsoMedium chain 610 C made by mammary gland human milk and dairyoLong chain 12 CPresenceabsence of double bondsoSaturated fano double bondsoUnsaturated fa1 or more double bondsMonounsaturated fa MUFAs1 double bondPolyunsaturated fa PUFAs2 or more double bondsoAffects melting pointPresence of double bonds decreases MPPUFAs tend to be liquid at room tempSaturated fa tend to be solid at room tempDouble bond causes a bend in the shape of the faPrevents tight packing of moleculesless solidoPractical significance in bodyAffects fluidity of cell membranes and functionIncreases PUFAs and membrane will be more fluidIncrease saturated fatty acid and especially long chain then membrane will be stifferoIncreases susceptibility of fa to being oxidized by free radicals lipid peroxidationPUFAs at greater risk for damage by free radicals than MUFAs or saturated faCauses rancidity in foodstaste and smells badAntioxidants added to food to increase shelf lifeFree radicals from toxic compounds damage cell membrane results in nonfunctional lipidsBody has antioxidant systemGeometric isomerism oCis or trans formationoOrientation of H atoms around double bondoMost fa are in cis conformation H on same side of the bondoFa in trans configuration Produce by microorganisms Found in dairy products in small amountsProduced by partial hydrogenation of margarinesChanges shape of moleculenot bend at double bond molecules tighter and pack more tightlyShape is more like a saturated faacts like a saturated fa increase MPoImplications for cardiovascular disease CVDoMost unsaturated fatty acids are in the cisconformationoTrans fatty acids occur as a result ofRumen bacterial fermentationhence in beef lamb and dairy produceIsomerization during catalytic hydrogenation cisoHydrogenation of oils is the reaction of hydrogen with the double bond in unsaturated fa catalyzed by nickel Hydrogenated oilsHigher melting pointMore resistant to oxidative changes and heat than unreacted unsaturated faSome trans fatty acids are produced during hydrogenation higher melting pointLocation of the double bondoInfluences fa metabolism in the bodyoIn particular whether or not the fa can be synthesized in the body or notoEnzymes in the body can only make certain faoCannot put double bonds in all positionseg cant put double thbonds in between and C beforethe 9 C from Ch3 endNomenclature of fatty acidsoNeed to specify chain lengthof double bonds and position of double bondsoPosition of double bondscan be specified relative to the methyl end omega system or the carboxyl end delta systemoOmega systemstOnly gives position of the 1 bondstthth1 double bond is between 6 and 7 from methyl endAssumes any other double bond are 3 C away ie There is a methylene group between double bondstrue for most fatty acids except conjugated faConjugated fadouble bonds are not separated by a methylene group produced by micoorganism also in some dairy foodsoCLA significance Conjugated linoleic acid CLA a naturally occurring anticarcinogen found in dairy productsis an intermediary product of ruminal biohydrogenation of polyunsaturated fatty acidCLA concentration in milk fat can be enhanced by the addition of polyunsaturated fatty acids to the diet especially oils high in linoleic acidCLA inhibits growth of mammary tumors in ratsOther in virto and experimental animal studies protection against other types eg human malignant melanoma colorectal tumor cell growth liver cancer intestinal cancer prostate canceroEssential Fatty AcidoCHO can be converted and stored as fat soHow can fats be essentialEssential means that humansaminals cannot synthesize it in a sufficient level to meet their requirements must be supplied in the diet oOmega3 fatty acids especially EPA and DHA are required for optimal function of brain CNS and membranes
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