lipids refer to a category of compounds that include
-sterols
-triglycerides
-phospholipids
3 molecules that lipids are made of
-oxygen
-hydrogen
-carbon
lipids are hydrophobic, meaning...
they do not dissolve in water
6 basic functions of lipids in the body
� Store and provide energy
� Provide insulation
� Help manufacture steroids and bile
� Play a role in transporting fat-soluble
nutrients in the blood
� Used to manufacture major sex hormones
� Key to the structure of cell membranes
lipids are comprised of fatty acids, which are...
� Building blocks for triglycerides and phospholipids
� A chain of carbon and hydrogen atoms with a carboxyl group at the alpha end and a methyl group at the omega end
why does fat have more kilocalories than protein and carbohydrates?
the ration of hydrogen and carbon to oxygen is higher.
the many different fatty acids vary by...
�Length of the carbon chain
�Degree of saturation
�Shape
what is the carbon length of fatty acids?
2-20 carbons long
-the most common fatty acids contain 12-24 carbons
short chain fatty acids carbon length
2-4 carbons
medium chain fatty acids carbon length
6-10 carbons
long chain fatty acids carbon length
12+ carbons
what is the most common type of fatty acid?
long chain; this type takes longer to digest than short chain and medium chain
how is the degree of saturation determined in fatty acids?
whether the carbons are held together by a double or single bond.
saturated fatty acids
� All the carbons on the fatty acid are bound to hydrogen.
� There are no double bonds.
� They are solid at room temperature.
� They have a higher melting point.
unsaturated fatty acids
Some carbons on fatty acid form a double bond with each other instead of binding to hydrogen.
-liquid at room temp
-lower melting point
mono-saturated fatty acid (MUFA)
Has one double bond
poly-saturated fatty acid (PUFA)
has two or more double bonds
rancidity
spoiling of fats through oxidation
� Double bonds are less stable than single bonds.
� Foods with unsaturated fats become rancid faster than foods with saturated fats.
how have manufacturers enhanced the stability of fatty acids by reducing rancidity?
� Adding antioxidants
� Limiting food exposure to oxygen, heat, and light
� Hydrogenation
Omega-3 fatty acids
� First double bond is between the third and fourth carbons from the omega end.
� Example: Alpha-linolenic acid
Omega-6 fatty acids
� First double bond is between the sixth and seventh carbons from the omega end.
-linoleic acid
Unsaturated fatty acids form two different shapes based on...
the position of the hydrogen atoms around the double bond
-cis: hydrogens are on the same side of double bond
-trans: hydrogens are on opposite sides of the double bonds
examples of saturated fats
white marbling on beef and bacon, chicken skin, whole milk dairy products, coconut products
examples of trans fats
manmade saturated fats that have been banned from processed foods( margarine,desserts, fried foods)
examples of polyunsaturated fats
mostly found in plant products; liquid at room temperature
Omega 3 Fatty acids: Fish and Fish oils, flaxseeds, soy
Omega 6 Fatty Acids: vegetable oils, nuts, seeds
examples of monounsaturated fats
canola oil, olive oil, avocados, nuts, seed
what is the most common lipid?
triglyceride
triglycerides
make up 95% of lipids found in food
-A triglyceride molecule has three fatty acids connected to a glycerol backbone
4 functions of triglycerides
� Add texture to baked goods
� Make meats tender
� Preserve freshness
� Stored as adipose tissue
for energy
phospholipids
� Made of a glycerol backbone and two fatty acids, a phosphate group, and different nitrogen-containing compounds
� Hydrophilic on one end; hydrophobic on the other
� Make up the phospholipid bilayer in the cell membrane
lecithin definition and functions
(aka phosphatidylcholine) is a type of phospholipid.
-synthesized by the liver
�Used as an emulsifier
in foods (e.g., salad
dressing)
�A major phospholipid in the cell membrane
sterols
� Made of four connecting rings of carbon and hydrogen
� They do not contain glycerol or fatty acids.
� They do not provide energy.
most common sterol and it's functions
cholesterol
� Found in every cell in the body
� Helps with numerous body processes
� Precursor to vitamin D, sex steroids, and adrenal corticoids
major plant sterols
Phytosterols and phytostanols
During digestion, fatty acids form a combination of...
free fatty acids, glycerol and monoglycerides
lipases
the enzymes that digest lipids
where does fat digestion begin?
in the mouth with chewing
� Food mixes with saliva and lingual lipase.
� Lingual lipase hydrolyzes the medium-chain fatty acids.
once the bolus of food travels through the esophagus into the stomach...
� Gastrin is released from the gastric pits lining the stomach and stimulates the release of gastric juices, rich in gastric lipase.
� Gastric lipase hydrolyzes one fatty acid from the triglyceride, which produces a free fatty acid and a diglyceride.
once in the intestine....
bile acid emulsifies larger fat droplets into smaller fat droplets.
� This allows pancreatic lipase to digest the lipids easily.
micelle
the resulting lipid complex after the bile acid in the intestine emulsifies the larger fat droplets into smaller ones
-transport the lipid complex across the small
intestinal wall.
Cholecystokinin (CCK)
the hormone that stimulates the gallbladder to release bile acid.
-CCK is released by the cells of the duodenum in the presence of lipids.
digestions of phospholipids (4 steps)
� Emulsified by bile during digestion
� Dismantled into two free fatty acids and the phospholipid remnant
� Packaged as micelles
� Transported through intestinal wall
digestions of sterols
� Not digested
� Carried by the micelle and absorbed intact through intestinal wall
� Bile emulsifies sterols.
what happens to lipids that are not digested?
� Bind with fiber
� Are eliminated in the feces
chylomicrons
-facilitate lipid absorption
Glycerol and short- to medium-chain fatty acids are absorbed...
directly into the bloodstream
Long-chain fatty acids combine with...
cholesterol and phospholipids to for a chylomicron. Chylomicrons are too large to be absorbed into the bloodstream
chylomicron flow
� Travel through lymph fluid first
� Exit the lymph and enter bloodstream through thoracic duct next to the heart
� Lipoprotein lipase (LPL) hydrolizes triglycerides in the chylomicrons as they travel to the liver via the bloodstream.
Lipoprotein lipase (LPL)
hydrolizes triglycerides in the chylomicrons as they travel to the liver via the bloodstream.
lipoproteins
carry lipids into the circulatory system
four different lipoproteins that carry lipids into the circulatory system
-HDLs: high density lipid proteins
-LDLs: low density lipid proteins
-VLDLs: very low density lipid proteins
-Chylomicrons
HDLs, LDLs, VLDs
� Globular molecule with a lipid center surrounded by a plasma membrane
� Density determines function.
� More protein = higher density
-the more density the better
VLDLs
�Transport triglycerides (TGs) and cholesterol from the liver to the cells
�Lipoprotein lipase located on the outside of adipocytes and muscle cells cleave fatty acids (FAs) from TGs.
�FAs move into the adipocyte and muscle cells and stored for later use.
LDLS
� Carry cholesterol from the liver to the tissues
� "Bad cholesterol"
� "Lousy" DLs
HDLs
� Carry cholesterol from the cells to the liver
� "Good cholesterol"
� "Healthy" DLs
6 lipid functions in the body
� Used as a source of energy
� Form body structures (including cell membranes)
� Regulate metabolism
� Enhance the absorption of fat-soluble vitamins
� Provide a layer of insulation to help regulate body temperature
� Help cushion the major organ
energy function of lipids
-bodies main function of energy throughout the day
-readily available when the body needs energy
-excess fat is stored as adipocyte cells
-unlimited fat storage
�Fat cells can grow up to 1,000 times their original size.
�Additional fat cells are made when
fat is the preferred energy source of...
the heart, liver, and resting muscle
fat spares glucose so it is only used by the
central nervous system and red blood cells
why is fat not able to sustain life during starvation?
glucose is needed to metabolize fat
the ________ portion of fat can make small amounts of glucose
glycerol
Several essential nutrients require dietary fat for absorption.
� Fat-soluble vitamins
� Carotenoids
� Cholesterol
� Phospholipids
__ per day are needed to stimulate chylomicrons that transport fat-soluble vitamins.
20 grams
Fat in subcutaneous tissue...
-insulates the body
-maintains body temperature
Too much stored fat can be detrimental to health and increase risk for...
heart disease, hypertension and diabetes
linoleic acid is converted to...
arachidonic acid
Alpha-linolenic acid (ALA) is converted to ____ and elongated to ____
eicosapentanoic acid (EPA); docosahexanoic acid (DHA)
EPA and arachidonic acid make _____
eicosanoids
eicosanoids
Hormone-like substances that regulate blood
clotting, immune system, inflammation, blood
pressure
ALA is needed to make
healthy cell membranes, particularly in the nerve tissues and retina
The body uses cholesterol as starting material for
-Vitamin D and sex hormones such as estrogen and testosterone
-Bile acid
how phospholipids helps make up cell membrane
Part of the phospholipid bilayer in cell membranes
how cholesterol helps make up cell membrane
A structural component in cell membranes
Recommendations of triglycerides and cholesterol
AMDR: 20-35% of daily kilocalories should come from fat
excess fat consumption leads to excess weight gain only if
excess kilocalories are consumed; however, since fat has a high concentration of kilocalories, it is likely to gain weight.
for heart health, consume no more than...
also, replace ___ with ____ and ____
10% of kilocalories from saturated fat (less than 7 is ideal)
saturated fats; polyunsaturated and monounsaturated
trans fats should be limited to
less than 1 percent of total kilocalories
AMDR for essential fatty acids (linoleic acid, alpha-linoleic acid)
linoleic acid: 5-10% of total kilocalorie intake
alpha-linoleic acid: .6-1.2% of total kilocalorie intake
for people diagnosed with heart disease, they should aim to consume _ grams of fatty acids daily. Also, __ to __ grams of EPA and DHA daily may reduce triglycerides in the blood
1; 2 to 4
what organ synthesizes cholesterol needed for the body?
the liver; 900 mg/d
cholesterol levels in the blood are regulated by
a feedback system
to reduce the risk of cardiovascular disease, daily cholesterol intake should be limited to less than
300 mg/d
the most common dietary lipid in the diet
lecithin; it is digested in the GI tract and does NOT enter the small intestine intact
-supplements of this do not provide health benefits; claims include weight loss, improving fat metabolism, cardiovascular health, and
exercise performance.
which organ makes all of the phospholipid the body needs? including lecithin
liver
to replace saturated fats with unsaturated fats, consume more of the following:
� Vegetable oils: soybean, corn, canola oils
� Soybeans
� Walnuts, flaxseeds, wheat germ
increase alpha-linoleic acids (omega-3 fatty acids) by consuming ______. Avoid ______
� Walnuts, flaxseeds, canola oil
� Fatty fish such as salmon, tuna, mackerel
�All fish contain EPA and DHA.
� Avoid cod-liver oil, as it is very high in vitamin A, which can be detrimental.
it is impossible to eliminated all saturated fats from the diet. Primary sources of saturated fat include:
� Animal foods: Fatty cuts of meat, whole-milk
dairy products, and the skin on poultry
� Plant sources: Coconut, palm, and palm kernel oils
how to lower consumption of saturated fats
� Limit intake of foods rich in saturated fat.
� Consume lower fat versions of fat-containing foods.
� Read the Nutrition Facts panel to help you choose foods that are low in fat
why were trans fats and hydrogenated oils the substitute for saturated fat in cooking commercials?
they provide a similar function of making the food flaky and reduces rancidity but these two reduce cholesterol in the diet
hydrogentation and how it works
replacing saturated fat with hydrogenated fat; unstable cis fatty acids in double bond form trans fatty acids, which are worse for your health than saturated fat. trans fats are required on nutrition labels by the FDA
trans fats raise ____s and lower ____s
LDL;HDL
dietary cholesterol comes mainly from
animal products
phytosterols and stanols
� Lower LDL levels by competing with cholesterol for absorption
� Are found in soybean oil, many fruits, vegetables, legumes, sesame seeds, nuts, cereals, and other plant foods
� Food manufacturers are fortifying foods with them to help lower cholesterol.
due to health concerns, a survey showed that over ___ million americans (__% of the adult population) chose lower-fat foods and beverages
160; 79
fat substitutes and its three categories
designed to provide the creamy properties of fat for fewer kilocalories and total fat grams.
� There are three categories of fat substitutes: carbohydrate based, protein based, fat based.
carbohydrate based
� Majority of fat substitutes
� Use plant polysaccharides to help retain moisture and provide a fatlike texture
protein based
� Created from the protein in eggs and milk
� Provide a creamy texture in the mouth
fat based
� Modified fats that provide the physical attributes of fat for fewer kilocalories than regular fat or interfere with the absorption of fat
true or false; low fat, fat free and regular fat products ALL lead to weight gain if too many kilocalories are consumed
true
____ is the number one killer of adults in the US, and begins with _____
heart disease; atherosclerosis
atherosclerosis in the arteries leading to the brain can cause ____
stroke
progression of atherosclerosis
� Injury to the lining of the arteries promotes
inflammation.
� LDLs and other lipid substances accumulate at the injured site and become oxidized by reacting with free radicals and metal ions.
� Macrophages are attracted to the oxidized LDLs and then for
primary risk factor for heart disease
elevated blood lipids
how to reduce risk of heart disease
� Starting at age 20, have a blood lipid profile analysis every 5 years.
� Measure cholesterol-to-HDL ratio.
� Have a risk score calculated.
diets high in ____ raise LDLs, however diets high in ____ do not.
saturated fats; cholesterol
the types of saturated fats effect whether LDLs are raised. Which 2 types of saturated fats raise LDLs and which one does not?
� Myristic and palmitic acids raise LDLs.
� Stearic acid doesn't raise LDLs.
� It is difficult to isolate foods by saturated fatty acid type; recommend lowering overall saturated fatty acid intake.
consume more fish: how and why
� Eat at least two, 3.5 ounce servings of fatty fish rich in omega-3 fatty acids per week.
� Choose baked, broiled, or poached fish.
� Pregnant women and children should consume no more than 12 oz of fatty fish per week.
why is it important to limit consumption of EDAs and DHAs to less than 3 grams per day?
�Increases risk for excessive bleeding
�May raise both blood glucose and LDL levels �Intakes >3 g only occur with supplementation. �Omega-3 fatty acid supplements should be taken with medical supervision.
how to consume more plant foods to consume less trans and saturated fat
� Canola oil, soy, flaxseeds, and walnuts are
rich in ALA.
� Choose plant foods rich in soluble fiber.
� Consume at least 2 grams of plant sterols a day.
why is it important to consume at least 2 grams of plant sterols per day?
�Shown to lower LDL levels by 10 percent
�Foods rich in plant sterols include soybean oil, many fruits, vegetables, legumes, nuts, and other plant foods as well as margarine made with plant sterols.
how does consuming antioxidants and phytochemicals help? give examples
Antioxidants and phytochemicals neutralize free radicals, stimulate the immune system to repair tissue damage, and reduce heart disease risk.
� Vitamin E, vitamin C, and beta-carotene
� Garlic may help lower cholesterol.
� Flavonoids may help prevent LDLs
how does exercise help?
raises HDLs, lowers LDLs, and reduces high blood pressure and insulin resistance.
what does smoking do to your body
� Smoke damages the walls of the arteries and accelerates atherosclerosis.
� Smokers are three times more likely to have a heart attack than nonsmokers
benefits of moderate alcohol
� Increases HDL levels
� Decreases blood clotting
� Moderate amounts are defined as no more than:
� 1 serving of alcohol per day for females
� 2 servings of alcohol per day for males