dietary fats and lipids

Question 1

functions of fats

Answer 1

helps brain development and function
structural component of fat
support the absorption of vitamins
source of energy
good fro heart health and blood vessels

Question 2

dietary fat

Answer 2

the fat we eat provides essential fatty acids
govt recommends that fat intake shouldnt exceed 35% of total daily energy
1 gram fat= 9kcal

Question 3

triglycerides or fats

Answer 3

main form of lipids in food
visible fats= concentrated fats eg butter and veg oil
hidden fats= baked goods, dairy + fried food
naturally occuring triglycerides= avo, olives, corn and nuts

Question 4

triglyceride structure

Answer 4

each triglycerides= glycerol + 3 fatty acid

Question 5

fatty acid structure

Answer 5

hydrocarbon chain chemically bonded together
one end of molecule: carboxyl/carboxyl acid group
other end: methyl group

can differ by: chain length, number of bonds, position of double bonds

Question 6

number of bonds in FA

Answer 6

0= saturated
1= monounstaurated eg oleic acid in rapeseed and olive oil
>1= polyunsaturated eg linoleic acid in sunflower oil

Question 7

structural characteristics of FA

Answer 7

melting point- solid or liquid at room temp (unsaturated liquid at room temp)
health effects- how they effect blood cholesteral

Question 8

carbon chain length

Answer 8

short chain= <6 carbons
medium= 6-10 carbons eg coconut oil and some dairy products
long= >12= avo, dairy, meat, oil and nuts

Question 9

saturated fatty acids

Answer 9

no double bonds
straight line- single bond- configuration allows them to pack together tightly on glycerol backbone
solid at room temp

Question 10

unsaturated FA

Answer 10

double bonds that create kink so FA pack together loosely on glycerol backbone
liquid at room temp

Question 11

digestion

Answer 11

triglycerides are non polar- hydrophobic
lingual lipase in mouth starts to break down fats
in stomach–> lipase activity helps to start breaking triglycerides into diglycerides and fatty acids

Question 12

emulsification in SI

Answer 12

in small intestine
lipid droplets are broken down into smaller, emulsified fat droplets
bile released from gall baldder into SI
break down fat globule into smaller droplets
emulsification helps to increase SA to allow enzymes to attach and break down triglycerides

Question 13

enzymatic digestion

Answer 13

pancreatic lipase is secreted into small intestine
takes triglycerides and breaks it down into monoglycerides and FFA, sometimes a free glycerol is formed
forms monoglyceride

Question 14

absorption

Answer 14

micelles help fats to get close enough to microvilli of intestinal cells so that they can be absorbed
bile salts cluster around the products of fat digestion to form micelles
micelles are transporters for monoglycerides and FFA
fatty acids and monoglyceides leave micelles and enter intestinal epithelial cells

Question 15

into bloodstream

Answer 15

SCFA and MCFA can be absorbed directly into bloodstream
LCFA and monoglycerides reassemble into triglycerides within intestinal cells incorporated into chlymicrones (lipid transport vehicles)

Question 16

absorbed lipids

Answer 16

liver is involved in fat metab and synthesises lipoproteins, cholesterol anf phospholipids essential for many body functions
metabolic fate of lipid depends on dietary intake levels and energy expenditure
if fat intake is in excess, liver prepares for storage in subcutaneous tissue/ other storage depots via lipogenesis
if energy and glucose levels are low, stored fat is converted back into glycerol and fatty acids via lipolysis

Question 17

essential fatty acids

Answer 17

fatty acids that we cant synthesise so need to consume in diet
polyunstaurated and essential FA
N-3 FA eg alpha linoelic acid- omega 3= flaxseed, walnuts, chia seed
N-6 FA- linoleic acid- omega 6= sunflower oil, soybeans and corn oils

Question 18

EFA defieciency

Answer 18

dry scaly rash
decreased growth in infants and children
increased susceptibility to infection
poor wound healing

Question 19

EFA are important

Answer 19

important for structural components of cell membranes
prod of hormone like substances called eicosanoids- act as mediators that regulate biological processes eg blood pressure, vasocontriction, immune and inflammatory responses
can be converted into other longer chain fatty acids

Question 20

very long chain omega 3

Answer 20

eg EPA and DHA - eicosapentanoic acid, docosahexaconic acid
salmon and sardines
can be synthesised from ALA but the rate of conversion is limited

Question 21

EPA and DHA health benefits

Answer 21

regulate blood pressure
reduce circulating triaglycerol levels
improve brain function
support brain and eye development

Question 22

sustainable alternatives

Answer 22

traditional sources of very long chain omega 3 PUFA are not sustainable
- algae oil or algae based products
- can be used in supplements

genetically modified plants eg camelina sativa- consuming this is as effective as fish oil for increasing EPA and DHA concentrations in humans

Question 23

saturated fat intake and CVD risk

Answer 23

associated with increased LDL cholesterol

Question 24

SACN systematic review- sat fats

Answer 24

• meta analysis of saturated fats, health outcomes and risk factors
• health outcomes- CVD mortality, T2D + selected common cancers
• intermediate markers= blood lipids, blood pressure, markers of glycaemic control, anthropometric measures, cognitive function

results- reducing saturated fats significantly reduced risk of CHD and CVD events
similar results seen for reducing saturated fats and replacing them with PU

Question 25

saturated FA recommendations

Answer 25

in all UK all age groups are consuming more than recommended SF
population average contribution to total dietary energy should be reduced to no more than 10%
SFA should be substituted with unsaturated fats

Question 26

beyond isoolated nutrients

Answer 26

need to look at health effects of whole foods
nutrition science has traditionally focused on isolated nutrients - reductionist approach but is needed for certain advances in nutrition
but people consume foods, not single nutrients

Question 27

food matrix

Answer 27

can we predict health effects of whole foods based on nutritional labelling or by their staurated fat content
whole foods consist of many nutrients that are contained in a complex physical structure
the nature of the food structure and nutrients will determine nutrient digestion and absorption thereby altering the overall nutritonal and health properties of the food

Question 28

shiftting from sfa

Answer 28

suggestions to shift from SFA based food dietary guidelines for CVD health
previous advice to resrrict SFA intake to reduce risk of CVD
current advice- health effects of SFA depends on the interacting effects from naturally occuring food componenets and from unhealthy compounds introduced by processing

Question 29

specific saturated fats

Answer 29

different sat fats will have different effects on the body
isoenergetic replacement (1% energy intake) from carbs with lauric, palmitic and mystiric avid increased LDL cholesterol whereas stearic acid had neutral effects