Transcript Lipids - 35-206-202

LIPIDS
CHAPTER 6
LEARNING OUTCOMES
• Explain the basic chemical structure of fatty acids
and how they are named
• Describe the functions of triglycerides, fatty acids,
phospholipids and sterols in the body
• Classify and evaluate the different fatty acids based
on their health benefits or consequences
• Identify food sources of triglycerides, fatty acids,
phospholipids and sterols
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LEARNING OUTCOMES
• Describe the recommended intake of lipids
• Identify strategies for modifying total fat, saturated
fat, and trans fatty acids intake
• Explain the digestion, absorption and transport of
lipids in the body
• Discuss health concerns related to dietary fat intake
• Describe dietary measures to reduce the risk of
developing cardiovascular disease
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TRIGLYCERIDES
• Most common lipid in
food and the body
• Make up 95% of what
we eat and what is in
our bodies
• FA can all be the same
or all be different, the
fatty acids are long
chains of carbons with
hydrogens attached
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FUNCTIONS OF TRIGLYCERIDES
• Provide energy
• Provide compact energy source
• Insulate and protect the body
• Aid fat-soluble vitamin absorption and
transport
• Essential fatty acid functions
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FOOD SOURCES OF TRIGLYCERIDES
• Fruits and Vegetables
• Low fat except avocados and coconuts
• Dairy
• Low fat products are available
• Grains
• Low-fat except when fat is added e.g. pastries, pancakes
• Fats
• Usually a combination of many-described by the
predominate fat
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STRUCTURE
• Esterification
• Joining 3 fatty acids to a glycerol unit
• De-esterification
• Release of fatty acids-results in free fatty acids
• Diglyceride
• Loss of one fatty acid
• Monoglyceride
• Loss of two fatty acids
• Re-esterification
• Reattaching a fatty acid to a glycerol that has lost a fatty acid
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CARBON CHAIN LENGTH
• Long chain fatty acids
• 12 or more carbons (ex. Beef, lamb, plant oils)
• Medium chain fatty acids
• 6-10 carbons (ex. coconut and palm oils)
• Short chain fatty acids
• Less than 6 carbons (ex. dairy products)
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SATURATION
Each molecule wants to form as many bonds as it can
• Carbon- 4
• Oxygen- 2
• Hydrogen-1
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SATURATION
• Saturated fatty acids
• This 18 carbon fatty acid is fully saturated with hydrogen
atoms.
• No double bonds
• Increase blood levels of cholesterol
• Example: red meat, high fat dairy, coconut and palm oil- solid at
room temperature.
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SATURATION
• Monounsaturated fatty acids
• One double bond
• Decrease blood levels of cholesterol
• Example: olive oil, canola oil, peanut oil
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SATURATION
• Polyunsaturated fatty acids
• Many double bonds (at least 2)
• Decrease blood levels of cholesterol
• Example: Vegetable oils and fish oil
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SHAPE
• Cis fatty acids
• Bent carbon chain
• Trans fatty acids
• Straight carbon chain
• Hydrogenation: Adding
hydrogen to make an
unsaturated fat more
saturated-yields: trans fatty
acids
• Solidifies the lipid, increases
shelf life of product (tub
margarine, baked goods)
• Increases cholesterol even
more than saturated fat
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TRANS FATS
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TRANS FATS
1902- Scientist Wilhelm Normann finds that liquid oils can
be hydrogenated to form trans fatty acids.
1911- Procter & Gamble introduces Crisco vegetable
shortening in grocery stores.
1937- As World War II progresses, the use of margarine
(yellow colored vegetable shortening) rises sharply due
to butter rationing.
1984- Consumer advocacy groups campaign against
using saturated fat for frying in fast-food restaurants. In
response, most fast-food companies begin using partially
hydrogenated oils containing trans fat instead of beef
tallow and tropical oils high in saturated fats.
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TRANS FATS
1990s there were several studies correlating trans fatty
acids and increased LDL (bad) cholesterol levels
and a higher incidence of heart disease.
1993- Health advocacy groups call for fast-food
restaurants to stop using partially hydrogenated oils
in their deep fryers.
1999- The U.S. government proposes a law requiring
food manufacturers to list trans fat amounts on
nutrition labels. The proposal is not passed as law.
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TRANS FATS
2002- The government agrees with researchers for the
first time on record: that there is likely no safe level
of trans fat and that people should eat as little as
possible.
2003- The FDA passes a law requiring that trans fat be
listed on the Nutrition Facts label on food products;
food manufacturers have three years to comply.
2006- Trans fat labeling becomes mandatory in the
United States.
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SHOULD TRANS FATS BE LEGAL?
Illegal
• Denmark, 2003
• Banned in almost all foods
• Heart disease has fallen by 20%
between 2001 (before the ban) and
2006 (two years after the ban)
• NY City, 2006
• Restaurants/food service
establishments
• Switzerland, 2008
Legal or limited
• Some restrict the
amount of trans fat in
foods (Canada, Boston)
• Others mandate
labeling
• Others have no laws
concerning trans fat
• Banned in almost all foods
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TRANS FAT LABELING LOOPHOLE
Any food that contains 0.5 grams or less of trans fat
can be listed as zero grams on the Nutrition Facts
label. It may seem like a small amount, but there is
no safe amount and all those half grams can add
up.
You must read the ingredients label: “partially
hydrogenated” is in the list, it is a food that contains
trans fats and should be avoided.
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NAMING FATTY ACIDS
(OMEGA AND DELTA)
• Omega System
• Double bond closest to omega (methyl) end
• Omega-3 fatty acid is 18:3 ω3
• Omega-6 is 18:2 ω6
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OMEGA 6 AND OMEGA 3 FATTY ACIDS
Eicosanoid “Local
hormone”
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TWO ESSENTIAL FATTY ACIDS
Linoleic (Omega-6)
• Polyunsaturated
• Major source of Omega
6 fatty acids in foods
• Used to make
Arachidonic acid, and
Eicosanoids
Alpha-linolenic (Omega3)
• Polyunsaturated
• Major source of Omega
3 fatty acids in foods
• Used to make EPA and
DHA and Eicosanoids
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TWO ESSENTIAL FATTY ACIDS
• Linoleic
• Beef, poultry, safflower
oil, sunflower oil, corn
oil, mayonnaise
• Regulates blood
pressure, can increase
blood clotting and
inflammation
• Alpha-linolenic
• Cold water fish (salmon,
tuna, sardines),
walnuts, flax, canola oil
• Reduces inflammation,
thins blood, and
reduces plasma
triglycerides
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ESSENTIAL FATTY ACID NEEDS
• Body unable to synthesize so Adequate Intake has been
established
• Approximately 2-4 Tablespoons daily
• Omega 6 intake usually high, Omega 3 intake usually too
low-this in balance has health consequences
• Deficiency
• Unlikely
• Could result in slowed growth, flaky and dry skin,
delayed wound healing
• Toxicity
• No upper level set
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AHA
1000mg of DHA + EPA = 2
servings of fish/week
Alpha linolenic acid ALA
(flax, mayo), lower
cholesterol but no
relationship w/heart
disease and may increase
risk of prostrate cancer
500 mg as ALA
32 mg DHA
3000 mg of
DHA+EPA in 6oz
3 soft gels=900mg
of DHA + EPA
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DIETARY FATS
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DIETARY FAT RECOMMENDATIONS
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AMERICAN HEART ASSOCIATION
RECOMMENDATIONS
• Limit saturated fats to 10% of total calories
• Limit polyunsaturated fats to 10% of total
calories
• Minimize trans fat intake
• Limit cholesterol intake to less than 300 mg
• Eat at least two servings of fatty fish/week
(tuna, salmon, mackerel, lake trout, herring,
and sardines)
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FAT INTAKE
• North American fat intake has doubled in
the last century
• Too high
• Saturated fat, trans fat, Omega 6
• Too low
• Omega 3
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MEDITERRANEAN DIET
• Up to 40% fat if comprised of
monounsaturated fatty acids
• Diet is high in
• Olive oil, fruits, vegetables, whole grains, beans,
nuts and seeds
• Small to moderate amounts of cheese, yogurt and
fish
• Limit eggs and red meat
• Exercise
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MEDITERRANEAN DIET
• Breakfast: Greek yogurt topped
with berries and walnuts; Coffee or
tea
Lunch: Lentil soup with swish chard
topped with taziki sauce; hummus
and pita
Snack: Whole grain crackers and
cheese
Dinner: Roasted cod paired with a
wheat berry salad consisting of
olive oil vinaigrette, feta, parsley,
and tomatoes and a glass of red
wine
Dessert: Fresh fruit drizzled with
honey
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FAT REPLACEMENTS
• Water, Protein, Air (soft serve ice cream)
• Carbohydrates
• Fiber (Ztrim)
• Corn syrups, syrup solids, and high-fructose corn
syrups are used as fat replacers in many fat-free
and reduced-fat cookies
• Engineered fats
• Olestra (Lays's Light, Ruffles Light, Doritos Light,
and Tostitos Light)
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OLESTRA
• Olestra is synthesized from
sucrose, it can bond with six,
seven, or eight fatty acids,
making it too large and
irregular to move through the
intestinal wall and be
absorbed.
• Because olestra is undigested,
it inhibits absorption of fat
soluble vitamins (fun side
effects of this!)
• FDA requires manufacturers to
add vitamins A, D, E and K to
products made with olestra to
counter that effect.
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PHOSPHOLIPIDS
• Hydrophobic and
Hydrophilic Ends
• Functions
• Component of cell
membranes
• Emulsifier
• Sources
• Synthesized by the body
• Food: lecithin in egg yolks,
wheat germ and peanuts
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PHOSPHOLIPIDS
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STEROLS
• Ring structure, most known is cholesterol
• Plant sterols block cholesterol absorption sites in the human
intestine, thus helping to reduce cholesterol in humans, but
there is some concern that they may block absorption of
other important nutrients as well
• Functions
• Steroid hormones, bile, cell membranes, chylomicrons
• Sources
• Synthesized by the body
• Food: animal origin (meat, fish, eggs, dairy)
• Food additive: Benecol and Take Control
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STEROLS NEEDED TO MAKE STEROID
HORMONES
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FAT DIGESTION
• Stomach
• Gastric lipase
• Triglycerides are broken down into monoglycerides and
free fatty acids
• Liver-makes bile
• Gall bladder
• CCK triggers bile release from gall bladder
• Pancreas
• Pancreatic lipase, phospholipase, cholesterol lipase
into common bile duct, which empties to SI
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FAT DIGESTION
• Small Intestine
• Bile emulsifies fat to form micelles (acted upon
by pancreatic lipase)
• Phospholipids are broken down into free fatty
acids, glycerol and phosphoric acid by enzymes
from the SI and pancreas
• Cholesterol esters are broken down into
cholesterol and free fatty acids by enzymes from
SI and pancreas
• Most digestion in duodenum and ileum
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FAT DIGESTION
Bile emulsifies fat:
breaks it into tiny
droplets called
micelles (keeps the fat
suspended in the
water-based intestinal
contents
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FAT ABSORPTION
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FAT ABSORPTION
• The lipid portion of micelles is absorbed by the brush
border of the absorptive cells in the duodenum and
jejunum
• Short and medium chain fatty acids are absorbed via the
portal vein
• Long chain fatty acids are re-esterified and enter the
lymphatic system
• Bile is recycled via enterohepatic circulation
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TRANSPORTING FAT
• Transporting fat through water based blood and
lymphatic system is a challenge
• Short and medium chain fatty acids travel via cardiovascular
system to liver
• Long chain enter lymph system
• Fat is transported lipoproteins
• Lipid core
• Shell composed of protein, phospholipid and cholesterol
that allow transportation
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TYPES OF LIPOPROTEINS
• Chylomicrons
• Transport of dietary triglycerides from small intestine to
cells
• VLDL
• Carries mainly triglycerides from liver to cells
• LDL
• Made mostly of cholesterol, carries cholesterol to cells
• HDL
• Made mostly of protein, pick up and recycle or dispose of
cholesterol
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TYPES OF LIPOPROTEINS
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PATHWAYS FOR CHOLESTEROL UPTAKE
• Receptor Pathway
• LDL is removed from
blood by cells via the LDL
receptor
• In cells the LDL is broken
down and utilized in the
body (to do what?)
• Excess builds up and
becomes oxidized
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PATHWAYS FOR CHOLESTEROL UPTAKE
High Density Lipoproteins
(HDL or good cholesterol)
• How does it get its name?
• Picks up cholesterol
throughout the bodyeventually this leads to
excretion of LDL
• Blocks oxidation of LDL
“Scavenger” WBC embed in
blood vessels and engulf
and digest LDL
• Can build up over timeplague develops (what is
this called?)
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ATHEROSCLEROSIS
• What can you do to
prevent plaque
buildup?
• What do cholesterol
lowering medications
do?
• How can you remove
an existing plaque to
prevent heart attack
and stroke?
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CARDIOVASCULAR DISEASE (CVD)
• Development of CVD
• Atherosclerotic plaque forms
• Result: Heart attack and stroke
• Risk factors
• Cannot change age, gender, race and genetics
• Can change blood triglyceride and cholesterol
levels, hypertension, smoking, physical inactivity,
obesity, diabetes and other diseases
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BLOOD LIPOPROTEIN LEVELS
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PREVENTING CVD (LIMIT)
• Total fat 20-35% total calories
• Saturated fat < 7 % total calories
• Trans fat low
• Polyunsaturated < 10% total calories
• Monounsaturated < 20% total calories
• Cholesterol < 200 mg daily
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PREVENTING CVD (EMPHASIZE)
• Include 2 grams plant stanols/sterols
• Soluble fiber 20-30 g
• Eat fatty fish 2x/week
• Keep body weight at a healthy level
• Increase physical activity
• Do things to increase your HDL (exercise)
• Eat foods that prevent oxidation
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PREVENTING CVD
• Nuts
• “scientific evidence suggests but does not prove that eating
1.5 oz of nuts/day as part of a diet low in saturated fat and
cholesterol may reduce risk of heart disease.” (almonds,
hazelnuts, peanuts, pecans, some pine nuts, pistachio nuts
and walnuts)
• Serving sizes: 1.5 oz is ~ 40 unshelled nuts, 1/3 cup, or 1 large
handful
• Nutrition info for 1.5 oz almonds: 250 kcal, 9 grams protein, 5
grams fiber, 1.5 grams sat fat, 13.5 g mono fat, 50% of Vit E
needs, and magnesium, riboflavin, copper, phosphorus
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PREVENTING CVD
• Supplements
• B vitamins like folic acid, B12, and B6 (homocysteine?)
• Niacin or Vitamin B3 (raise HDL?)
• Vitamin E (antioxidant), may prevent but NOT treat
• Garlic (lower cholesterol, less clumping of platelets,
antioxidant)
• Fish oil (omega 3, DHA + EPA)- AHA advises 1000 mg of DHA
+EPA for those who have heart disease
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HEALTH CONCERNS
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Dangers of low fat diet?
High polyunsaturated fat intake
Excessive omega 3 fat intake
Imbalances in omega 3 and omega 6 fats
Diets high in trans fats
Diets high in total fat
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MAKING RECOMMENDATIONS
• Breakfast: Everything Bagel
w/cream cheese, coffee
w/cream and sugar
• Lunch: 12 inch Italian sub,
Diet Coke, Baked Lays
• Snack: Quaker Granola bar
• Dinner: Easy Mac w/hotdogs
• Snack: Ice cream
• Changes if you
were normal
weight but
have high
cholesterol
• Changes if you
were
interested in
Mediterranea
n diet
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