Lipids Flashcards
The Functions of Fats in Foods (7)
- Nutrient (food fats provide essential fatty acids and other raw materials)
- Energy (food fats provide a concentrated energy source)
- Transport (fats carry fat-soluble vitamins A, D, E, and K along with some phytochemicals and assist in their absorption)
- Sensory appeal (fats contribute to the taste and smell of food)
- Appetite (fats stimulate the appetite)
- Satiety (fats contribute to feelings of fullness)
- Texture (fats make fried foods crisp and other foods tender)
Functions of Fat in the body (6)
- Energy stores
- Muscle fuel
- Padding
- Insulation
- Cell membranes
- Raw materials
Functions of Fat in the body: Energy stores
fats are the body’s chief form of stored energy
Functions of Fat in the body: Muscle fuel
Fats provide much of the energy to fuel muscular work
Functions of Fat in the body: Padding
Fat pads inside the body cavity protect the internal organs from shock
Functions of Fat in the body: Insulation
Fats insulate against temperature extremes by forming a fat layer under the skin
Functions of Fat in the body: Cell membranes
Fats from the major material of cell membranes
Functions of Fat in the body: Raw materials
Fats are converted to other compounds, such as hormones, bile, and vitamin D, as needed
Lipids: Organic compound meaning it contains…
Carbon
Lipids: Predominantly
triglycerides
Triglycerides
Tri = 3 fatty acids + glyceride = glycerol backbone
Fatty Acids: 2 main features
- Chain length (number of carbons)
- Saturation (number of hydrogens)
Hydrogenation
Adding hydrogen atoms to unsaturated fats
3 Types of fatty acids
- Saturated
- Monounsaturated (one double bond)
- Polyunsaturated (multiple double bonds)
TransFats
- spreadable oil products (margarine)
- Shelf life
- partially hydrogenated oils
- Significant negative impact on heart health
Trans fat vs cis fat
Trans fats are unsaturated fats with trans double bonds instead of cis bonds. The type of bond affects the shape of the fatty acid chain. A trans bond creates a straight chain, whereas a cis bond results in a chain that is bent. Trans fats may be monounsaturated or polyunsaturated.
Essential =
body requires but cannot make; must be consumed
Essential fatty Acids
Omega 6 Fatty Acids
Omega 3 Fatty Acids
Omega 6 Fatty Acids
- Linoleic acid (vegetable oils, nuts, whole grains)
- most canadians exceed required intakes –> inflammation
Omega 3 Fatty Acids
Linolenic Acid (alpha linolenic acid = plant) needs to be converted to EPA/DHA
- EPA = fish/algae
- DHA = fish/algae
Most Canadians do not get enough omega 3s
Phospholipids (another type of lipid)
- includes phosphorus atom
- component of lipoproteins
- emulsifiers (allow oil + water to mix)
- cell membrane structure
Sterols (another type of lipid)
- composed of multiple chemical rings
- precursors to bile, vit D, sex hormones, cells in brain & CNS system
- Chole-sterol (made by liver)
Fat Digestion and Absorption: Mouth and salivary glands
some hard fats begin to melt as they reach body temperature. The sublingual salivary gland in the base of the tongue secretes lingual lipase. The degree of hydrolysis by lingual lipase is slight for most fats but may be appreciable for milk fats
Fat Digestion and Absorption: Stomach
The stomach’s churning action mixes fat with water and acid. A gastric lipase accesses and hydrolyzes (only a very small amount of) fat
Fat Digestion and Absorption: Small intestine and pancreas
Cholecystokinin (CCK) signals the gallbladder to release bile (via the common bile duct): Fat –> bile —> emulsified fat
- Pancreatic lipase flows in from the pancreas (via the pancreatic duct):
Emulsified fat (triglycerides) –> pancreatic and intestinal lipase –> monoglycerides, glycerol, fatty acids,
Fat Digestion and Absorption: Large Intestine
Some fat and cholesterol, trapped in fiber, exit in feces
5 steps of lipids being transported and absorbed
- In the stomach, the fat and watery GI juices tend to separate. The enzymes are in the water and can’t get at the fat.
- When fat enters the small intestine the gallbladder secretes bile. Bile has an affinity for both fat and water, so it can bring the fat into the water.
- Bile’s emulsifying action converts large globules into small droplets that repel each other
- After emulsification, the enzymes have easy access to the fat droplets
- once in the enterocyte (cells of large intestine) Triglycerides, cholesterol, phospholipids, fat-soluble vitamins become lipoproteins known as chylomicron enters lymph system before entering blood stream and ultimately the liver
Lipoproteins: Very-low-density lipoproteins (VLDL)
- made primarily by liver cells to transport lipids to various tissues in the body
- composed primarily of triglycerides
Low-Density lipoproteins (LDL)
- Derived from VLDL as cells remove triglycerides from them
- carry cholesterol and triglycerides from the liver to the cells of the body composed primarily of cholesterol
- Larger, lighter, filled with more lipid
- Deliver cholesterol and triglycerides from liver to the tissues
- High LDL predictor of fatal heart attack or stroke
High Density lipoproteins
- Transport cholesterol back to the liver from peripheral cells
- composed primarily of protein
- smaller, denser, packaged with more protein
- scavenge excess cholesterol from the tissues and return to the liver for metabolism or disposal
- Low blood concentration of HDL signifies higher disease
Cholesterol
Cholesterol travels through the blood on proteins called “lipoproteins.” Two types of lipoproteins carry cholesterol throughout the body: HDL, LDL
- cholesterol is a type of lipid
Saturated Fats
- Ongoing research into how saturated fats affect our heart health
- saturated fat can raise LDL cholesterol levels in the blood which is a risk factor for heart disease and stroke
- replacing saturated fats with mono or poly unsaturated fats decreases LDL-C.
- there are different dietary saturated fatty acids. There is emerging evidence to suggest that the health effects of saturated fats could vary depending on the food sources they come from
Healthy Fats: Beneficial
- Salmon, tuna, fatty fish (seafood omega 3 fats)
- walnuts, canola oil, flax seeds (plant omega 3 fats)
- corn, soy, safflower & sunflower oils (plant omega 6 fats)
- Olive & peanut oils, nuts, avocados (monounsaturated fats)
Unhealthy fats
- Red meat, butter, cheese, ice cream (saturated fats)
Partially hydrogenated oil (industrial trans fats)
Recommendations
- the DRI suggests a diet that is: low in saturated fat, trans fat, and cholesterol, and provides 20-35% of one’s daily energy from fat
- try to replace solid fats with liquid oils whenever possible
- be aware that all high-fat foods are high in kcalories
- select the most nutrient-dense from all food groups
- consume fewer and smaller portions of foods and beverages containing solid fats
- choose unsaturated fats
- don’t overdo fat restriction
- regarding fat replaces: fat alternatives must actually replace fat and every in the diet
Ultra low fat diets: risk for
- essential fatty acid deficiency
- decreased hormone and vit D production
- Dyslipidemia (increases LDL-C and lowers HDL-C)
