Lipids Flashcards
Lipids in the Body
Lipids exist in the body in various forms with each form having a different structure and function. Lipids include:
- Individual fatty acids.
- Triglycerides.
- Phospholipids in every cell membrane.
- Cholesterol and steroid based compounds ( e.g. oestrogen).
- Sphingolipids found in nerve cell membranes, e.g. myelin.
- Glycolipids involved in cell identity (like a cell ‘passport’).
- Cerebrosides glycosphingolipids found in the brain.
- Fat soluble vitamins A, D, E, K.
Phospholipid
phosphate + fatty acids
Glycolipid
carbohydate + lipid
Cerebroside
waxy lipid + sugar
Sphingolipid
long chain amino alcohol + fatty acid + sugar
Function of Lipids
- Energy (ATP) production - each gram of fat supplies the body with about nine calories.
- Storage of energy reserves - fats are a more efficient form of storage energy than carbohydrates or proteins, so the body stores any excess energy as fat.
- Cell membrane structure - phospholipids and cholesterol stabilise cell membranes, whilst allowing a degree of fluidity which is crucial to the function of every cell.
- Thermal insulation in subcutaneous tissue and protection around organs.
- Steroid hormones - progestogens, androgens, glucocorticoids, mineralocorticoids and oestrogens are derived from cholesterol.
- Formation of eicosanoids - signalling molecules involved in a range of processes such as blood coagulation and inflammation.
- Growth and development - the brain is rich in arachidonic acid (AA) and docosahexaenoic acid (DHA).
- Constituents of nervous tissue structure (sphingomyelin).
- Aid to cell signalling processes.
- Required for the absorption of fat soluble vitamins.
Fatty Acids
Fatty acids are hydrocarbon chains with an acid group at one end and a methyl group at the other.
- Short chain fatty acids (up to 5 Cs) and medium chain fatty acids (6-12 Cs) travel directly to the liver where they can be used to create energy or ketones. Medium chain triglycerides (MCTs) can be used as a source of energy before exercise (e.g. 1 tbsp).
- Long chain fatty acids (14-22 Cs) and very long chain fatty acids (> 22 Cs) are used to build cell membranes.
Short
Chain Fatty Acids
Short chain fatty acids (SCFAs) have fewer than six carbon atoms.
• SCFAs are produced when dietary fibre is fermented in the colon.
• Acetate, propionate and butyrate are the most common SCFAs.
• Butyrate is particularly important for colon health because it is the primary energy source for colonocytes. It supports the intestinal tight junctions .
• SCFAs are speculated to have a role in the microbiota gut brain axis crosstalk.
• Butyrate is thought to have an anti-inflammatory effect on the colon.
Hydrogenation
- Unsaturated fats can be saturated by the addition of hydrogen as in hydrogenation when oils are made into solid spreads.
- Hydrogenation turns the natural fatty acid into unnatural forms (i.e. trans fats ) which are damaging to health
Saturated fatty acids
Contain no C-C double bonds. All the carbons are completely saturated with hydrogen bonds. Solid at room temperature.
Saturated fat intake has been a fiercely debated topic.
- A lot of studies about high saturated fat diets and health, have reported on dietary intake of saturated fats from junk foods.
- A recent review by the Journal of the American College of Cardiology found that there was inadequate scientific evidence to keep advising against foods high in saturated fats, including coconut, unprocessed meat, eggs and dark chocolate.
Types of Saturated Fats
Butyric acid 4-C Caprylic acid 8-C Lauric acid 12-C Palmitic acid 16-C Stearic acid 18-C
Butyric acid 4-C
Butter, Dairy Produced in the gut
Caprylic acid 8-C
Coconut
Palm Kernel
Breast milk
Anti-fungal properties
Coconut oil
Coconut oil contains medium chain triglycerides (MCTs) which the body uses as a source of fuel or turns them into ketones. • MCTs increase the number of calories burned compared to longer chain fatty acids. • Coconut oil contains 50% lauric acid. Monolaurin is formed from lauric acid. Both substances have antibacterial , antiviral and antifungal properties. • ↑ HDL cholesterol, ↓ LDL • Preliminary studies show positive outcomes in epilepsy and Alzheimer’s disease.
Lauric acid 12-C
Coconut
Palmitic acid 16-C
Coconut Palm Palm kernel
Stearic acid 18-C
Beef, Pork, Lamb, Mutton Cocoa and shea butter Butter
Unsaturated fatty acids
Contain one or more double bonds between carbons. Liquid at room temperature.
Monounsaturated fatty acids
Have one double bond in the chain.
Monounsaturated Fats
Palmitoleic acid Omega - 7
Oleic acid Omega - 9
Polyunsaturated fatty acids
Have several double bonds.
The more double bonds there are in a fatty acid, the less stable it is, increasing susceptibility to oxidation.
Omega System
- The omega system uses the number of carbon atoms, the number of double bonds, and the number of carbons from the omega end to the first carbon in the double bond.
- The omega 6 fatty acid, arachidonic acid , is referred to as 20:4 w6.
20 = no. of carbons
4= no. of double bonds
6= no. of carbons to first double bond
Polyunsaturated Fats Omega 3
Alpha linolenic acid (ALA) Stearidonic acid (SDA) EPA and DHA
Palmitoleic acid Omega - 7
Sea buckthorn berries Coconut Coconut, palm kernel Macadamia nut
Oleic acid Omega - 9
Olive, avocado Almond, peanut, pistachio Brazil nuts, pecan, cashew Hazelnuts, neem, macadamia Animal fat, butter
Alpha linolenic acid (ALA)
Flaxseeds (richest source 50% of its fatty acids are ALA) Chia seeds, hemp seeds, dark green leaves Pumpkin seeds, soybean, rapeseed (canola) Walnuts, wheat germ
Stearidonic acid (SDA)
Blackcurrant seeds
EPA and DHA
Cold water fish oil Salmon, trout, tuna, anchovies, mackerel Sardines, herring Spirulina, chlorella
Polyunsaturated Fats Omega-6
Linoleic acid (LA) Gamma linolenic acid (GLA) Arachidonic acid (AA)
Linoleic acid (LA)
Safflower Sunflower, hemp, soybean, walnut Pumpkin seed, sesame, almond, chia, cashew Rapeseed, wheat germ, avocado, Brazil nut Borage oil Evening primrose and hemp oil Blackcurrant seed oil Meat Other animal products
Gamma linolenic acid (GLA)
Borage oil Evening primrose and hemp oil Blackcurrant seed oil
Arachidonic acid (AA)
Meat Other animal products
Unnatural Trans Fats
Unnatural trans fatty acids are produced by high temperatures and hydrogenation.
• They are found in margarine, processed foods and refined vegetable oils.
• Trans fats stiffen cell membranes, making them prone to oxidation. This also alters their protective action and permeability, impeding normal cell function.
• Trans fats alter blood triglyceride and cholesterol profiles and are linked to an increased risk of cardiovascular disease, insulin resistance and cancer.
Cis and Trans Fatty Acids
At each double bond, two possible isomeric forms exist.
– Cis configuration = the H atoms are on the same side of the double bond. The majority of natural fats are cis.
– Trans configuration = the H atoms are on separate sides of the double bond.
• Conjugated linoleic acid (CLA) is a natural trans fat found in grass fed meat and dairy products. Studies
indicate CLA helps increase lean muscle mass and decrease body fat.
Essential Fatty Acids (EFAs)
There are two fatty acids that cannot be made in the body and so are essential in the diet. They are: 1. Linoleic acid (an omega-6 fatty acid). 2. Alpha linolenic acid (an omega 3 fatty acid). • Arachidonic acid was once thought to be essential in the diet, but we now know it can be made from linoleic acid. • Humans lost the ability to introduce double bonds into fatty acids between the carbon atoms 6‒7 and 3‒4, making LA and ALA essential in the diet.