Download Lipids What Are Lipids?

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Lipids
Types, Food Sources, Functions
What Are Lipids?
• Lipids
– Diverse group of molecules that are insoluble in water
• Fats
– The lipid content of diets and foods
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Lipids in Body Cells and Tissues
• Types of Lipids in body cells and tissues:
 Triacyglycerols or Triglycerides (or TGs)
 Glycerolphospholipids
 Sphingolipids
 Eicosanoids
 Cholesterol
Functions of Lipids Stored in the Body
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TGs serve as fuels providing the body with energy
•
Glycerolphospholipids and sphingolipids are found in membanes and in blood
lipoproteins at the interfaces between the lipid components of these
structures and surrounding water.
– These membrane lipids form hydrophobic barriers between subcellular
compartments and between cellular constitutes and extracellular milieu
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Eikosanoids regulate many cellular processes, mainly inflammation
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Triglycerides (or TGs)
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TGs contain:
– Three fatty acid molecules
– One glycerol molecule
Triglycerides (or TGs)
• Fatty acids are determinant for classification
of TGs
• Fatty acids are classified by:
1. Carbon chain length
2. Saturation level
3. Shape
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Triglycerides: Saturation
• According to saturation, fatty acids can be
divided into three categories:
1. Saturated fatty acids have hydrogen atoms
surrounding every carbon in the chain
2. Monounsaturated fatty acids lack one
hydrogen atom (one double bond)
3. Polyunsaturated fatty acids have more
than one double bond
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Triglycerides
• Hydrogenation: hydrogen atoms are added
to unsaturated fatty acids. As a result:
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oils become more solid and more saturated
trans fatty acids are created
risk of cardiovascular disease increases
risk of cancer development may also increase
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Hydrogenated fat-rich foods
Essential Fatty Acids
The Essential Fats are a group of fatty acids that
are essential to human health.
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Omega-3 (3) – Linolenic acid
Omega-6 (6) – Linoleic acid
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Structure of EFAs
LINOLEIC ACIDS (Omega 6)
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Eighteen-carbon essential fatty acids that
contain two double bonds.
18:2 (9,12)
LINOLENIC ACIDS (Omega 3)
Eighteen-carbon essential fatty acids that
contain three double bonds
18:3 (9,12,15)
Function of EFAs
• Formation of healthy cell membranes
• Proper development and functioning of the brain and
nervous system
• Production of the Eicosanoids
–Thromboxanes
–Leukotrienes
–Prostaglandins
Responsible for regulating blood pressure, blood viscosity,
vasoconstriction, immune and inflammatory responses.
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Essential Fatty Acid Deficiency Side
Effects
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hemorrhagic dermatitis
skin atrophy
dermatitis
dry skin
weakness
impaired vision
mood swings
edema
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high blood pressure
high triglycerides
hemorrhagic folliculitis
hemotologic disturbances (ex:
sticky platelets)
• immune and mental
deficiencies
• impaired growth
Who are at risk for deficiency?
• Long-term TPN patients
without adequate lipid
• Cystic Fibrosis
• Low Birth Weight Infants
• Premature infants
• Severely malnourished patients
• Patients on Long-term MCT as
fat source
• Patients with fat malabsorption
• Hepatorenal Syndrome
• Sjogren-Larsson Syndrome
• Multisystem neuronal
degradation
• Crohn’s disease
• Cirrhosis and alcoholism
• Reye’s Syndrome
• Short bowel syndrome
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Triene:Tetraene Ratio
• T/T ratio is the marker used to diagnose essential fatty
acid deficiency. Characterized by:
• A decrease of Arachidonic (20:4 6)acid
• An increase of Mead’s acid (20:39).
(This acid is produced in excess during EFAD)
• Triene:Tetraene ratio of >0.4 is considered EFAD
• Some studies suggest a lower threshold of 0.2
• EFAD development: can be as early as 2 to 4 weeks
on TPN without lipids
Phospholipids
• Phospholipids contain
– Glycerol backbone, two fatty acids, phosphate
• Soluble in water
• Transport fat in the bloodstream
• Manufactured in our bodies (not required)
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Sterols
• Sterols contain multiple rings of carbon atoms
• Plant sterols appear to block the absorption of
dietary cholesterol
• Cholesterol is made in our bodies and
therefore is not necessary in the diet
– Sex hormones, vitamin D, bile
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Cholesterol
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The main sterol compound, essential to
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life
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100g in human body, most in cell
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membranes, in myelin layers around
neurons
Cell membrane structure
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Human skin barrier (toxins, water loss)
Precursor of steroid hormones
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(testosterone,
estrogen, progesterone, cortisone)
Precursor of bile acids
Formation of vitamin D (with UVs)
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Dietary sources
All foods containing animal fat contain
cholesterol to varying extents
Major dietary sources of cholesterol
include cheese, egg yolks, beef, pork,
poultry
Human breast milk also contains significant
quantities of cholesterol
From a dietary perspective, cholesterol is
not found in significant amounts in plant
sources
OPTIMAL CHOLESTEROL LEVELS (AHA)
Total Cholesterol
Less than 200 mg/dL
Desirable level that puts you at lower risk for coronary heart disease
200 to 239 mg/dL
Borderline high
240 mg/dL and above
High blood cholesterol. Twice the risk of CAD as below 200 mg/dl
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Estimates of the percentages of CVD attributable to some
modifiable risk factors
Risk factor
Chol 200mg/dl or greater
Physical inactivity
BP 140/90 mmHg or greater
Cigarette smoking
Estimate
43%
35%
25%
22%
Obesity
Diabetes
7%
8%
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• Blood lipids include:
– Chylomicrons—present only after a meal
– Very-low-density lipoproteins (VLDL)
– Low-density lipoproteins (LDL)
– High-density lipoproteins (HDL)
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OPTIMAL CHOLESTEROL LEVELS (AHA)
HDL Cholesterol
LDL Cholesterol
Less than 40 mg/dL
Low level. A major risk factor for CAD
Less than 100 mg/dL
Optimal
40 to 59 mg/dL
The higher the level the better
100 to 129 mg/dL
Near or above optimal
60 mg/dL and above
High level. Considered protective
against CAD
130 to 159 mg/dL
Borderline high
160 to 189 mg/dL
High
190 mg/dL and above
Very high
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Chylomicron
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Plant sterols reduce serum cholesterol levels. Eur Heart J. 2009, 30(4):
404–409
Lipids
Beta oxidation breaks down fatty
acids to form acetyl Coenzyme A
Lipids have more potential
chemical energy and can be
more fully oxidized as an energy
fuel
Therefore, we gain more energy,
gram for gram, from fats than
from carbohydrates
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Lipids and Health
The Roles of Fat
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9 kcal per gram
Major fuel at rest
Fuel at exercise
Stores energy
Provides the body with
essential fatty acids
• Essential for absorption
of at-soluble vitamins
• Regulates cell function
• Maintains membrane
stability
• Provides insulation
• Provides flavors and
textures of foods
• Helps us feel satiated
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How Much Fat?
• Acceptable Macronutrient Distribution
Range (AMDR) for fat: 20−35% of calories
• Minimize saturated and trans fatty acid
intake to lower risk of heart disease
• Active people may need more energy from
carbohydrates and can reduce their fat
intake to 20−25% of total calories
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How Much Fat?
• Dietary Reference Intakes (DRIs) set for
essential fatty acids
– Linoleic acid: 5-10% of total calories
– Alpha-linolenic acid: 0.2-1.2% of total calories
– A lower ratio of omega-6/omega-3 fatty acids is
more desirable in reducing the risk of many of the
chronic diseases of high prevalence in Western
societies
• Saturated fat: less than 8% of energy
– Trans fats: reduced to the absolute minimum
Food Sources of Fat
• Visible fats
– Fats we add to foods
– Butter, cream, mayonnaise, salad dressings
• Invisible fats
– Fats hidden within foods
– Occur naturally or added during processing
– Baked goods, dairy, meats, fast foods
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Food Sources of Fat
• Beneficial fats
– Omega-3 fatty acids may be low in diets
– Fish, walnuts, canola are of high content in
omega-3 fatty acids
• Switching to more healthful fats without
increasing total fat intake
– Use olive in place of butter or margarine
– Select low-fat or nonfat dairy products
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Food Sources of Fat
• Fat replacers
– Used to lower fat content of foods
– Found in chips, cakes, cookies
– May cause GI side effects in large amounts
– Example: olestra (Olean)
Fats in Food
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Cardiovascular Disease
• Cardiovascular disease
– Dysfunction of the heart or blood vessels
– Can result in heart attack or stroke
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Cardiovascular Disease
• Risk factors for cardiovascular disease:
– Being overweight
– Physical inactivity
– Smoking
– High blood pressure
– Diabetes mellitus
– Inflammation
Cardiovascular Disease
• Dietary fats increase blood lipids
• Highly saturated and trans fat intakes increase
blood cholesterol
• Omega-3 fatty acids reduce inflammation and
blood triglycerides
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Cardiovascular Disease
• Diets high in saturated fats
– Decrease the removal of LDLs from the blood
– Increase blood cholesterol levels
– Contribute to the formation of plaques that can
block arteries
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Cardiovascular Disease
• Diets high in trans fatty acids:
– Can raise blood levels of LDL-cholesterol as much
as saturated fat
– Are abundant in hydrogenated vegetable oils
(margarine, baked goods, fried foods)
• FDA requires that trans fatty acid content be
listed on labels for conventional foods and
some dietary supplements
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Cardiovascular Disease
• Lifestyle changes can prevent or reduce
cardiovascular heart disease
– Total fat intake: 20−35% total calories
– Saturated fat: less than ≤8% total calories
– Monounsaturated fat: more than ≥12%
– Polyunsaturated fat: more than ≥10%
– Cholesterol: less than 200 mg per day
– Trans fat: reduce to absolute minimum
– Increase omega-3 fatty acids
– Dietary fiber: 20−30 grams per day
Cardiovascular Disease
• Lifestyle changes can prevent or reduce
cardiovascular heart disease
– Maintain normal blood glucose level
– Eat throughout the day
– No more than 2 alcoholic beverages per day for men and 1
drink per day for women
– Maintain an active lifestyle
– Maintain a healthful body weight
– Decrease salt intake
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