Chapter 6: Fats Flashcards
Fat
nutrition: fats are energy-containing nutrients found in food
medicine: fats are known as lipids, large fat-containing components in the blood
physiology: a fat is a long chain of carbon molecules
adipose tissue: the body’s long-term storage site for fats
Importance of fat
important energy source at rest and during exercise
fat from diet provides the essential fatty acids that the body cannot manufacture and is needed for the absorption of the fat-soluble vitamins (A, D, E, K)
fats in foods helps satisfy hunger
most concentrated form of energy
containing 9 kcal/g
fat intake needs to be relative to CHO and protein intakes
Different types of fats
fats vary in their chemical composition
lipids include 3 different classes of fat
1) triglycerides: three fatty acids attached to a glycerol molecule (95T% of fat in body)
2) sterols
3) phospholipids: phosphate containing fats; found in food and in the body
Differences in fatty acids
due to chemical composition
saturated fatty acids, unsaturated fatty acids
Saturated fatty acids
fat that is solid at room temperature
no double bonds between carbon atoms
saturated with hydrogen atoms
mainly found in animal foods
a few plant foods such as coconut, coconut oil, palm oil, and palm kernel oil
Unsaturated fatty acids
fat that is liquid at room temperature
have one or more double bonds between carbon atoms
monounsaturated (one double bonds) - olive, peanut, and canola oils, avocados, almonds, hazelnuts, and pecans, pumpkin, and sesame seeds
polyunsaturated (multiple double bonds) - sunflower, corn, soybean, and flaxseed oils, walnuts, flaxseeds, fish, canola oil
hydrogenated fats
omega 3, 6, 9
Hydrogenated fats
are made through a process to make liquid oils more solid and to increase shelf life of the product
produces trans fat
trans fat associated with an increased risk for cardiovascular disease and type 2 diabetes, increases bad cholesterol (LDL) and reduced good cholesterol, increases in insulin resistance
there are some naturally occurring trans fat found in beef, lamb, dairy products that may have some healthy benefits
Trans vs cis formation
trans formation of atoms results in atoms being on opposite sides of the double bond which allows for the trans fats to stack on top of each other and can build up into plaque in blood vessels
cis formation of atoms results in atoms being on same side of double bond allowing the fatty acid to bend and no stacking occurs
Omega 3, 6, 9
polyunsaturated fatty acids that have double bond between carbons at certain locations
Formation of fats in foods
in form of triglycerides
nearly 95% of all fat consumed in the diet
triglyceride is composed of four parts (3 fatty acids attached to a glycerol
individual fatty acids that make up a triglyceride influence the temperature at which fat will melt
foods are grouped based on the predominant fatty acids
Two essential fatty acids
widely found in food
linoleic = omega 6 fatty acids is in many vegetable oils such as corn, soy, safflower, and sunflower oils
alpha-linoleic = omega 3 family found in soy, canola, and flaxseed as well as leafy green vegetables, fatty fish, and fish oils
important because body cannot make them
omega 3 fatty acids = positive effects on immune and inflammation responses
omega 6 fatty acids = opposite effects
ratio between omega 6 to omega 3 fatty acids ration should be about 4:1 or less (western diet is 15:1)
Omega 3 fatty acids and recovery from strenuous exercise
1.5 hours or more of moderate to high intensity exercise (55-75% of VO2 max)
experience an increase in many of the compounds associated with inflammation - normal response to skeletal muscle injury and acute inflammation that occurs with exercise; increase in body’s anti-inflammatory compounds
goal for athlete is to have proper balance between inflammatory and anti-inflammatory compounds
trained athletes may not benefit from omega 3 supplementation because their anti-inflammatory responses may already be enhanced sufficiently as a natural response to their training
greatest benefit may be to those who have certain diseases or those who are untrained
Sterols and phospholipids
5% of fat found in foods
most common sterol found in food is cholesterol
cholesterol found only in animal foods such as meat, egg yolks in which the fat has not been removed
important component of cell membranes
phospholipids are structural component of all living tissues
Healthy fats
lower risk of CV disease
unsaturated fatty acids and omega 3 fatty acids
Unhealthy fats
saturated fatty acids
limit to less than 10% of the diet
Fat intake for athletes
appropriate amount will depends on overall energy need and macronutrient balance
What is the challenge of fat digestion and absorption?
relatively large molecules
do not mix well with water which means transport in blood requires most fat to be bound to protein
Digestion
begins in the mouth and continues in stomach, but most occurs in small intestine
undigested fat in the stomach delays the emptying of the stomach contents and results in a feeling of fullness
athletes may limit their fat intake temporarily in certain situations when they do not want gastric emptying delayed
athletes may include fat containing foods when they want to avoid feeling hungry for several hours
fats are exposed to bile salts and digestive enzymes before they cross the membranes of the intestinal cells (because don’t mix well with water)
triglycerides are broken down by enzymes to diglycerides, monoglycerides, and free fatty acids; digestion reduces the size of the fat particles and readies them for absorption by the mucosal cells of the intestine
digestion of phospholipids is similar process as triglycerides but with different enzymes
sterols are not broken down at this point
Bile salts
part of bile
emulsifier to help breakdown fats
Pancreatic lipase
secreted by pancreas into the small intestine and helps break down the large fatty acids into smaller components
is used once the bile salts breakdown the fat molecule into many smaller molecules
Absorption
once in mucosal cells, monglycerides are resynthesized into triglycerides
become part of chylomicron which is a lipoprotein (triglycerides, cholesterol and phospholipids become part of chylomicron)
lipoproteins transport fat throughout the body
chylomicrons are transported out of the mucosal cells of the intestine into the lymph system
Transportation
body’s main transport fluids are blood and lymph
chylomicrons released slowly into lympathetic vessels
blood lipid levels are usually highest about 3 hours after fat consumption, but may take as long as 6 hours for the dietary fat to be transported into the blood (because too big to go into the bloodstream directly)
some fatty acids in mucosal cells are not incorporated into chylomicrons and are released right into the blood via portal veins, where each will be bound to plasma protein (albumin)
chylomicrons circulate through all the tissues
triglyceride portion of the chylomicron can be absorbed by adipose and muscle cells by lipoprotein lipase stimulating the release of the fatty acids from the triglyceride which are then rapidly absorbed by the fat and muscle cells (occurs when pass near muscle/adipose cell)
absorption into muscle cells occurs if needed in the muscle for energy
in the liver, triglyceride portion of chylomicron is broken down and becomes part of the fatty acid pool
cholesterol portion of the chylomicron remains and is transported to the liver to be processed
Difference between blood and lymph
blood consists of water, red and white blood cells, and many other constituents like oxygen and nutrients
some components of blood are filtered out of the capillaries into the spaces of the tissue known as interstitial fluid
most this fluid is returned to capillaries but the amount that is not returned is referred to as lymph
lymph consists of white blood cells, proteins, fats, and other compounds and it moves through its own set of vessels that are separate from capillaries
eventually lymph and blood vessels are joined near the heart
Storage
stored in body largely in the form of triglycerides in adipose tissue, liver, muscle, and small amount in the blood
chylomicron flows through blood stream after they go through lympathetic vessels
capillaries near fat cells have lipoprotein lipase in their walls
when activated the triglycerides in the chylomicron are broken into monoglycerol and fatty acids
monoglycerides and fatty acids pass into the fat cells and then are reformed into triglycerides
activity of LPL and the process of triglyceride formation are primarily stimulated by insulin
pancreas secretes insulin in response to food consumption - in hours after a meal, the body has the hormonal environment and the substrates that favour triglyceride formation and fat storage
muscle can also store fate (intramuscular triglycerides) - occurs primarily in muscle that is highly aerobic; same process with adipocytes
fats are very energy dense vs CHO or proteins - every gram of glycogen stores 2g of water (increases weight without increasing energy content
