Lipids Flashcards
What is a lipid?
- Soluble in non-polar solvents
- Linked to or can be linked to fatty acids
- Relatively non-toxic
Why are lipids important?
- Main storage for of energy
- Component of cell membranes
- Provide insulation
- Help control body temperature
- Provide protection to internal organs
- Form basis of many hormones
- Aids intestinal absorption of fat-soluble vitamins
Is quality or quantity more important?
The quality is important in terms of chronic disease risk
Why are lipids important in food?
- Enhance flavour and palatability of food
- Provide essential fatty acids
What are the types of lipids?
- Triacylglycerol
- Phospholipids
- Sphingolipids
- Sterols
- Fat soluble vitamins (A,D,E,K)
- Others
What are triglycerides?
- Most common type of lipid in our body and in food
- Glycerol + 3 fatty acids = triglyceride
What are the functions of triglycerides?
- Energy Store (37kJ per gram)
- Storage form of fatty acid
- Structural component of lipoproteins
- > 90% of dietary lipid
What are phospholipids?
- Major lipid class found in cell membranes
- Glycerol + 2 fatty acids + phosphate = phospholipid
What are the functions of phospholipids?
- Energy store
- Source of fatty acids
- Structural components: membranes, plasma lipoproteins
- Information molecules (eicosanoids)
- 5-10% of dietary lipid
Who consumes 0 cholesterol?
Vegans - because they only in animals. But the body makes its own cholesterol in the liver so we don’t need to consume it
What are the functions of cholesterol?
- Structural component of membranes
- Steroid backbone
- Vitamin D
- Bile acids (needed for fat digestion)
What are fatty acids?
- Major energy source
- Structural in phospholipid bilayer
- Membrane fluidity
- Information molecules (eicosanoids)
What are eicosanoids?
Substances that are important for inflammation, clotting and anti-clotting. Made in the essential fatty acids
What are the different classifications of fatty acids?
- Short chain fatty acid (C2-C6)
- Medium chain fatty acid (C8-C12)
- Long chain fatty acid (>C14)
- Very long chain fatty acid (>C22)
- Most fatty acids in diet (C10-C22)
What does saturation mean?
How saturated the carbons are with hydrogen
What does C18:0 mean?
- That there is 18 carbons and 0 double bonds
- Saturated fatty acid
What are the characteristics of saturated fatty acids?
- High melting points (solid at room temp)
- Fatty acid synthesis in body
What does C18:1n9 mean?
- Oleic acid
- 18 carbons
- 1 double bond after the 9th carbon
- Monounsaturated fatty acids
What are the characteristics of monounsaturated fatty acids?
- One cis or trans double bond
- Intermediate melting points
- Fatty acid synthesis in body (not essential)
What does C18:2w-6 mean?
- Linoleic acid (essential)
- 18 carbons
- 2 double bonds, the first after the 6th carbon and a methylene group (CH2) separates the two bonds
What does C18:3w-3 mean?
- Alpha-linolenic acid (essential)
- 18 carbons
- 3 double bonds, the first after the 3rd carbon and a methylene group separating them
What are characteristics of polyunsaturated fatty acids?
- Two or more cis/trans double bonds
- Low melting points
- Body cannot synthesise n-6 and n-3 PUFA which means they are essential and can’t be made in the body
What are essential fatty acids?
Humans aren’t able to produce a double bond before the 9th carbon from the methyl or omega end. Therefore, we must obtain the fatty acids that have double bonds before the 9th carbon from our diet
What are the essential fatty acids humans need?
- Omega 3 fatty acids (a-linolenic acid)
- Omega 6 fatty acids (linoleic acid)
How much of your energy should essential fatty acids make up?
At least 1-3% of daily energy intake
What are some essential fatty acid deficiencies?
- Growth retardation
- Reproductive failure
- Skin lesions
- Kidney and liver disorders
- Neurological and visual problems
- However, most diets meet the minimum requirements more than adequately
What is a trans fatty acid?
- Hydrogen are on opposing sides
- Act like a saturated fat in the body
- Causes your LDL cholesterol to increase
- Higher melting point
What sort of foods are mostly saturated fatty acids?
- Coconut oil
- Butter
- Beef tallow
- Palm oil
- Lard
What sort of foods are mostly monounsaturated fatty acids?
- Olive oil
- Canola oil
- Peanut oil
What sort of foods are mostly polyunsaturated fatty acids?
- Safflower oil
- Flaxseed oil
- Walnut oil
- Sunflower oil
- Corn oil
- Soybean oil
- Cottonseed oil
Mechanisms of saturated fatty acids?
Increase cholesterol which decreases LDL receptor activity
Mechanisms of trans fatty acids?
Increase cholesterol synthesis
What is the AMDR of Fat?
- 20-35%
- Saturated and trans fats <10%
What types of lipids transport directly into blood?
- Glycerol
- Short-chain fatty acids
- Medium-chain fatty acids
What types of lipids transport through lymph system, the blood?
- Triglycerides
- Cholesterol
- Phospholipids
What are metabolic adaptations to exercise with a high fat diet?
- Increase capillarisation of muscle (increase blood flow)
- Increase IMTG content
- Increase sensitivity of adipose and muscle cells to epinephrine
- Increase in number and size of skeletal muscle mitochondria
- Increase in enzymes involved in fat transport and metabolism
- Increase activity of oxidative enzymes
Adaptation to endurance exercise with high fat diet?
Allowed a trained individual to use proportionally more fat and less CHO at a given workload
Why would you want to enhance fat metabolism?
- Increase the proportion of fat used during exercise will decrease the rate of CHO utilisation and therefore spare muscle glycogen for later
- Unlike CHO there is virtually unlimited storage of fat
- Fat is energy dense
What’s a potential limitation with high CHO diets?
That CHO oxidation is increased, reducing fat oxidation
When may a high fat diet be important?
Where energy expenditure is large and time for recovery is limited
What are some advantages of fat as a fuel?
- Energy dense
- Extensive body stores
What are some disadvantages of fat as a fuel?
- Oxygen cost. CHO produces great ATP yield per unit of oxygen
- Transportation in blood (fat - via lymph system, CHO - intestinal absoprtion)
- Cannot be used anaerobically
- Potential health consequences
What are some factors affecting fat oxidation during exercise?
- Exercise intensity
- Exercise duration
- Preceding diet
- Training status
- Endogenous and exogenous CHO availability
How much fat is being used at rest?
~50%
How much fat is being used at 25% VO2max?
Fat dominant ~80%
How much fat is being used at 65% VO2max?
~50%
Increased IMTG use
How much fat is being used at 85% VO2max?
~25%
Decreased plasma FFA and decreased IMTG use
What happens after 1-3 days of a high fat diet?
- Decreased resting muscle and liver glycogen stores
- Decreased CHO oxidation during subsequent exercise
- Impairment of endurance capacity and performance of prolonged exercise
- Reductions in well-being
What happens after 5-10 days of a high fat diet?
- Increased fat oxidation during exercise
- Compensate for decreased CHO availability
- Little support for any performance benefit
What happens after 3 weeks ketogenic?
- Studies have shown that training capacity can be restored within 2-3 weeks, but very variable between athletes
- Exercise at intensities >70%VO2max lead to higher HR and perceived effort, even after 4 weeks
- Maximal rates of fat oxidation shift from 45% to 75%VO2max
What’s the long term adaptation to high fat diets non-ketogenic?
- Majority of studies show no difference in endurance -performance when comparing adaptation to high-fat and high CHO diets
- At best endurance performance can only be maintained after long-term adaptation to high-fat vs high-CHO diets
What diet is best for athletes?
Neither is best. Since both seem to show similar results, need to take a more individualised approach when working with athletes
When should eating patterns provide high CHO availability?
When training involves high intensity/volume/quality/technique
When is it less important to achieve high CHO availability?
When training involves exercise of lower intensity
What are some factors to consider when designing diets for endurance athletes?
- Individual preference
- Total energy expenditure
- Time for recovery
- Nature of the sporting event
