Fats And Lipids Flashcards
What are the functions of fat in the body
Cell membrane structure- integral to cell membranes and cholesterol synthesis
Protect vital organs
Growth and development, function of brain, eyes and heart
Energy storage and insulation
Absorption of fat soluble vitamins
What is the energy content of fat
9
What is the recommended daily fat intake
35%
Provides essential fatty acids
Explain the types of triglycerides
Triglycerides + the main form of fat in our foods
Visible fats, oil, meat
Hidden fats, baked goods, dairy, fried food
Naturally occurring, avocado, olives, corn, nuts
Explain the structure of fats
Each triglyceride = glycerol (backbone)+ 3 x fatty acid
Exactly lain fatty acid structure
- A hydrocarbon chain - a chain of carbon atoms bonded to hydrogen atoms, typically even numbered and insoluble in water
- Carboxyl group (-COOH) at one end of the molecule, this is the acidic part
- Methyl group (CH3) at other end
What factors affect fatty acid structure and physical properties
- chain length
- number of double bonds
Saturated = 0
Monounsaturated = 1
Polyunsaturated = >1 - position of double bond
= impact health and melting point
How are fatty acids classified on their carbon chain length
Short chain <6
Medium 6-10
Long 12+
Explain fatty acids and fat state at room temp
Saturated = no double bonds
- straight line, single bond only, allows for tight packing on glycerol backbone
- solid at room temperature
Unsaturated = double bonds, creates a link, loose packing on glycerol backbone
- liquid at room temp
Why are lipids complex to digest
Non polar molecules so hydrophobic
Explain fat digestion at the mouth
Lingual lipids released but is still inactive in the mouth, needs acidic environment to activate
Explain fat digestion in the stomach
Lingual and gastric lipase starts breaking triglycerides into diglycerides and fatty acids
Explain fat digestion in the small intestine
Emulsification
Lipid droplets are broken down into smaller, emulsified fat droplets
By bile salt, released from gall bladder
Increased SA for enzyme digestion
Enzymatic digestion by pancreatic lipase
= triglycerides to mono, some free glycerol also formed
Explain the role of micelles
Transport fat digestion products (fatty acids and moniglycerides) to intestinal cell membranes for absorption
Across the brush border
Into enterocytes
Explain the fate of absorbed lipids
Liver: synthesises lipoproteins, cholesterol and phospholipids for body functions
Metabolic date depends on dietary intake and energy needs :
When intake excessive - liver coverts for storage as subcutaneous tissue through lipogenesis
When energy and glucose levels are low - broken down into glyceryl and fatty acid through lipolysis for energy use
What are the fat soluble
ADEK
Explain vitamin A
Immune system function
Vision in dim light
Skin
Whole meat, cheese
Carrots, green leafy veh
Explain vitamin D
Bone health
Oily fish, eggs, meat, cereal
Sunlight
Explain vitamin e
Protect cells in our bodies against damage
Vegetables and seed oils, nuts and seeds
Explain vitamin K
Blood clotting
Bone health
Green leafy
Meat
Dairy
What are essential fatty acid
Body can’t synthesise itself
Which are the essential fatty acids
Linoleic acid (omega 6 polyunsaturated)
Alpha-linolenic
Explain essential fatty acid requirements
Linoleic acid 1% intake
- nuts and seeds, in uk get enough
Alpha- Linoleic 0.2%
Seed oil
Not enough
Explain deficiencies of essential fatty acids
Dry scaly rash
Less froth children
More infection
Poor wound healing
What are the key roles of essential fatty acids
- structural components of cell membranes
- production of eicosanoids (hormone like substances) act as mediators to regulate biological processes
- can be converted into longer chain fatty acids
Explain very long chain omega 3 fatty acids
EPA and DPA
Can both be synthesised from alpha Linoleic acid
( not essential trial as synthesise from ala)
Requires elongate and desaturated enzymes
Conversion rate limited so recommended that we include in diet
Fatty fish
What are benefits of EPA and DHA
Regulate blood pressure
Anti inflammatory
Reduce circulating triglyceride levels
Improve brain function
Support brain and eye development, reduce Alzheimer’s
What are dietary recommendations for very long chain fatty acids
2 portions fish per week, one oily
450mg EPA DHA daily
What is the association between omega 3 fatty acids and health
Higher circulating levels add associated with lower risk of all cause premature death, cvd and cancer
Explain traditional sources of very long chain omega 3 PUFAd
Not sustainable
Oily fish and fish oil supplements
Overfishing and climate change
24% decrease 1974-2017
1 third fishes at unsustainable levels
What are overfishing alternatives
Algae oil or algae based products
Fish obtain EPA from algae
Suggest reduce triglycerides levels circulating in blood
Comparable to original sources
Genetically modified plants e.g camelina
8 week RCT showed consuming camelina seed oil as effective in increasing EPA and DHA
Explain saturated fat and cvd risk
Should make up less than 10% intake
Based on evidence of increased ldl cholesterol in the blood
However some evidence finds no such association, the replacement nutrient should be considered
What did the SACN 2015 report say about saturated fat
Reducing consumption reduces
- cvd and chd
- lowers total ldl cholesterol levels
- improves indicators of glycemic control
No more than 10%, continue from 1991
Should substitute with unsaturated especially polyunsaturated
What did the isocaloric replacement of saturated fats study find
Replacing 5% of energy with PUFA, MUFA or carbohydrates = less risk chd
Explain the divas study
Substitution of 10% of dietary sat fats with unsaturated
= lower cholesterol
= 17-20% reduction CVD mortality
Explain individual effects of specific SFAs
Replace 1% of energy with lauric, palmitic or myristic acid raised ldl compared to stearic acid
= coconut oil not better, raises ldl
Explain issues with reductionist approach, looking at isolated nutrients
Unsuitable for chronic disease prevention, too simple
People consume food not single
Should look at a holistic approach e.g sat fats
What is the food matrix
Look at complex physical structure of whole foods
Look at digestion and absorption
How nutrients organised and interact effect value
E.g cheese, fermented, protein, calcium vs butter
Blood lipid response to butter
Calcium rich sources can reduce ldl cholesterol
