Lipids as Dietary Supplements

how are lipids biosynthesized

by living organisms

polarity of lipids

non polar molecules

-> insoluble in water but soluble in non-polar organic solvents

6 biological functions of lipids

energy storage

cell membrane structure

signalling

emulsifying agents

vision

protection and insulation

energy storage

high calorific content

beta oxidation of constituent FA releases energy

cell membrane structure

lipid bilayer provides structure to the cell

cholesterol alter structure/permeability where embedded in the lipid bilayer

signalling

eicosanoids are mediators of cellular signalling

- prostaglandins, thromboxanes, leukotrienes

emulsifying agents

bile acids and salts are steroidal lipids that help solubilize dietary lipids in the GI tract

vision

phospholipids/ fatty acids are abundant photoreceptor cells

protection/insulation

fat stored in the form of triglycerides within the subcutaneous tissue

thermal, electrical and mechanical insulation

cholesterol involved in myelination for the transmission of signals in nerve tissue

2 steps in fat digestion

emulsification

digestion

emulsification

the physical chopping

occurs in the duodenum and jejunum

larger dietary fats are broken down by amphipathic bile acids into micelles

digestion

micelles increase SA

this allows lipases to hydrolyse TG -> MG + FFA

TG are partially hydrolysed in the stomach by gastric lipase but predominantly in duodenum by pancreatic lipase

2 steps in fat absorption

absorption

transport

absorption

FA + MG - absorbed into enterocytes through simple diffusion and FA transporter proteins

once inside enterocytes - FA + MG -> TG

transport

TG are packaged with lipoproteins, cholesterol and other lipids --> chylomicrons

these are absorbed into lymphatic system and venous blood -> transported to tissues

what does dietary fat/ fat storage in human mostly consist of

triglycerides

components of tryglycerides

glycerol + fatty acid = ester

3 types of triglycerides

depends on FA residues, they can be

fats

oils

fixed oils

fats

long chain saturated FA

oils

short chain saturated FA

fixed oil

long and short chain unsaturated FA

types of triglycerides

simple - 3 hydrocarbon side chain are the same

mixed - 3 diff hydrocarbon side chain

complex - contain PO3

draw structures slide 14

structural features of FA

carboxylic acid with hydrocarbon side chain

usually even no of carbon atoms

can be saturated/ unsaturated

double bonds in FA

usually cis configuration

not conjugated

monounsaturated FA

one C=C bond

polyunsaturated FA (PUFAs)

2+ C=C bond

3 diff systems used to name FA

common name

systematic name

shorthand

shorthand name

alpha - first carbon after main func group

then beta, gamma etc

last carbon = omega

omega 3 -> first double bond is 3 positions away from omega carbon

cis configuration

introduces bend in the alkyl chain

interferes with molecules aggregating

important for membrane fluidity

what is hydrogenation in fats

addition of H2 to C=C bonds converting them into unsaturated C-C bonds

effect of trans fats on human health

increase LDL

decrease HDL

increase risk of heart diseasew

effects of unsaturated fats on health

considered cardioprotective

cheese, butter,cream

saturated fats

avocado

high in unsaturated FAs

phytosterols - role in lowering cholesterol

dark chocolate

equal amounts of oleic acid (unsaturated) and stearic + palmitic acid (saturated fats)

nuts seeds, olive oil

oily fish

n/s/oo: monounsaturated fats

oily fish: omega 3

2 essential FA

alpha linolenic acid (omega 3)

linoleic acid (omega 6)

alpha linolenic acid

essential omega 3

source: plants - seed oil, walnut oil, rapeseed oil

Biosynthesised to longer chain omega-3 eicosanoids --> reduced inflammation + thrombosis

linoleic acid

essential omega 6 FA

source - plants: veg oils

biosynthesized to long chain omega 6 eicosanoids

--> increased inflammation and thrombosis

draw omega 3 eicosanoid pathway

ls 26

draw omega 6 eicosanoid pathway

ls 26

recommended ratio of omega 6:3

2:1 or lower

what does an imbalance towards omega 6 cause

weight gain

arthritis

inflammatory conditions

thrombus formation

2 biologically important omega 3

EPA

DHA

sources of EPA + DHA

oily fish: mackerel, sardines, tuna, salmon

clinical importance of omega 3

cardiovascular protective effects

rheumatoid arthritis

cognitive function

cardiovascular protective effects

reduce: inflammation, atherosclerosis, platelet aggregation, TG synthesis, hospitalisation + death in HF

increase: HDL

rheumatoid arthritis

decrease inflammation and reactive oxygen species

3 ways omega 3 help with cognitive function

neurodevelopment - foetal brain development - *DHA

ADHD

Alzheimers

phytosterols

steroid compounds including plant stanols/sterols

source: veg oils, nuts, cereals

RDA: 2g/day

what do phytosterols do

inhibit intestinal absorption of cholesterol

decrease LDL

FA supplements

Eskimo 3

Eskimo brain 3.6.9

udos oil

borage oil

evening primrose oil

FA + pregnancy

decrease risk of : preterm birth (< 37 weeks), premature birth (<34 weeks), low weight babies

possible reduced risk of perinatal death and neonatal admissions