dietary fats and lipids Flashcards
functions of fats
helps brain development and function
structural component of fat
support the absorption of vitamins
source of energy
good fro heart health and blood vessels
dietary fat
the fat we eat provides essential fatty acids
govt recommends that fat intake shouldnt exceed 35% of total daily energy
1 gram fat= 9kcal
triglycerides or fats
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
triglyceride structure
each triglycerides= glycerol + 3 fatty acid
fatty acid structure
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
number of bonds in FA
0= saturated
1= monounstaurated eg oleic acid in rapeseed and olive oil
>1= polyunsaturated eg linoleic acid in sunflower oil
structural characteristics of FA
melting point- solid or liquid at room temp (unsaturated liquid at room temp)
health effects- how they effect blood cholesteral
carbon chain length
short chain= <6 carbons
medium= 6-10 carbons eg coconut oil and some dairy products
long= >12= avo, dairy, meat, oil and nuts
saturated fatty acids
no double bonds
straight line- single bond- configuration allows them to pack together tightly on glycerol backbone
solid at room temp
unsaturated FA
double bonds that create kink so FA pack together loosely on glycerol backbone
liquid at room temp
digestion
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
emulsification in SI
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
enzymatic digestion
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
absorption
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
into bloodstream
SCFA and MCFA can be absorbed directly into bloodstream
LCFA and monoglycerides reassemble into triglycerides within intestinal cells incorporated into chlymicrones (lipid transport vehicles)
absorbed lipids
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
essential fatty acids
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
EFA defieciency
dry scaly rash
decreased growth in infants and children
increased susceptibility to infection
poor wound healing
EFA are important
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
very long chain omega 3
eg EPA and DHA - eicosapentanoic acid, docosahexaconic acid
salmon and sardines
can be synthesised from ALA but the rate of conversion is limited
EPA and DHA health benefits
regulate blood pressure
reduce circulating triaglycerol levels
improve brain function
support brain and eye development
sustainable alternatives
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
saturated fat intake and CVD risk
associated with increased LDL cholesterol
SACN systematic review- sat fats
- 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
saturated FA recommendations
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
beyond isoolated nutrients
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
food matrix
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
shiftting from sfa
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
specific saturated fats
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
