The Lipids:
Triglycerides,
Phospholipids, and
Sterols
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Introduction

Poor health
 Too much fat
 Too little fat
 Too much of some kinds of fat

Family of lipids
 Triglycerides (fats and oils)
 Most abundant in food and body
 Phospholipids
 Sterols
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Triglycerides
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Triglycerides
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Triglycerides
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Phospholipids

Phospholipids
 Soluble in fat and water
 Emulsifiers in food industry
 Promote mixing of oil and fats in watery solution
 Lecithin is a phospholipid
 Food sources
 Eggs, liver, soybeans, wheat germ and peanuts
 Roles
 Part of cell membranes
 Emulsifiers
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Sterols

Sterols (most famous is cholesterol)
 Food sources
 Meats, eggs, fish, poultry and dairy products
 Cholesterol is found almost exclusively in animals
 Roles of sterols
 Body compounds made from cholesterol




Bile acids
Sex hormones
Adrenal hormones
Vitamin D
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Digestion
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Emulsification of Fat by Bile
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Hydrolysis of a Triglyceride
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Enterohepatic Circulation of Bile
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Absorption of Fat
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Transport
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
•
Dietary fats more strongly influence the incidence of coronary
heart disease (CHD)
•
Research indicates that the type of fat is more important than the
total amount of fat consumed
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Plasma Lipids and CHD
•
Plasma cholesterol may arise either from diet or from endogenous biosynthesis
•
Cholesterol is transported between the tissues in combination with protein and
phospholipids as lipoproteins
Lipoprotein structure
(chylomicron)
ApoA, ApoB, ApoC, ApoE
(apolipoproteins);
T (triacylglycerol);
C (cholesterol);
green (phospholipids)
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Plasma Lipids and CHD
1. Low density lipoprotein (LDL) and high density lipoprotein (HDL)
•
The level of plasma cholesterol is not precisely regulated, but rather varies in
response to the diet
•
Elevated levels of LDL cholesterol result in an increased risk for CHD
•
Elevated levels of HDL cholesterol result in a decreased risk for CHD
•
Abnormal levels of plasma lipids (dyslipidemia) act in combination with smoking,
obesity, sedentary lifestyle, insulin resistance and other risk factors to increase
the risk of CHD
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Plasma Lipids and CHD
2. Beneficial effect of lowering plasma cholesterol
•
Clinical trials have demonstrated that dietary or drug treatment of
hypercholesterolemia is effective in decreasing LDL, increasing HDL, and
reducing the risk for cardiovascular events
•
Diet induced changes are typically 10-20% decrease in cholesterol
•
Treatment with statin drugs decreases plasma cholesterol by about 30-60%
- HMG-CoA-reductase inhibitors
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Dietary fats and plasma lipids
•
Triacylglycerols (TAGs) are quantitatively the most important class of dietary fats
•
The influence of TAGs on blood lipids is determined by the chemical nature of
their constituent fatty acids
– Absence or presence of double bonds
– Number of double bonds (saturated vs. mono- and polyunsaturated)
– Location of the double bonds (ω-6 vs. ω-3)
– Cis vs. trans configuration of the unsaturated fatty acids
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Dietary fats and plasma lipids
1. Saturated fat
•
Triacylglycerols composed primarily of fatty acids whose hydrocarbons chains
do not contain any double bonds
•
Consumption is positively associated with high levels of total plasma cholesterol
and LDL cholesterol, and an increased risk of CHD
•
Main sources are
– Dairy and meat products
– Some vegetable oils such as coconut and palm
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Dietary fats and plasma lipids
1. Saturated fat
•
Chain lengths of 14C (myristic) and 16C (palmitic) are most potent in increasing
serum cholesterol
•
Stearic acid (18C) found in many foods including chocolate has little effect on
blood cholesterol
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Dietary fats and plasma lipids
2. Monounsaturated fats
•
TAGs containing primarily fatty acids with one C=C
•
When substituted for saturated fatty acids, lowers both total plasma cholesterol
and LDL cholesterol, but maintain or increase HDL cholesterol
•
Diets rich in olive oil (high in monounsaturated oleic acid) show a low incidence of
CHD (e.g. Mediterranean cultures)
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Mediterranean Diet
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Dietary fats and plasma lipids
3. Polyunsaturated fats (PUFAs)
•
Triacylglycerols containing primarily fatty acids with more than one C=C
•
Effect on cardiovascular disease is influenced by the location of the C=C within the
molecule
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
3. Polyunsaturated fats (PUFAs)
ω-6 Fatty acids
•
Long chain PUFAs with the first C=C beginning at the 6th bond position when starting
from the CH3 end of the fatty acid molecule
•
Consumption of fats containing ω-6 PUFAs, principally linoleic acid, 18:2(9,12), obtained
from vegetable oils, lowers plasma cholesterol when substituted for saturated fats
•
Lowers plasma LDL and HDL
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
3. Polyunsaturated fats (PUFAs)
ω-6 Fatty acids
•
Linoleic acid is an essential fatty acid
•
5-10% of total calories recommended
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
3. Polyunsaturated fats (PUFAs)
ω-3 Fatty acids
•
Long chain PUFAs with the first C=C beginning at the 3rd bond position from the CH3 end
•
Suppress cardiac arrthymias, reduce serum TAGs, decrease the tendency for thrombosis,
lower blood pressure, and substantially reduce the risk of cardiovascular mortality, but
have little effect on LDL or HDL cholesterol levels
•
Found in plants, principally α-linolenic acid (essential fatty acid)
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
3. Polyunsaturated fats (PUFAs)
ω-3 Fatty acids
•
Included in infant formulas to promote brain development
•
A deficiency of essential fatty acids is characterized by scaly dermatitis, hair loss and poor
wound healing
•
0.6-1.2% of total calories recommended
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Dietary fats and plasma lipids
4. Trans fatty acids
•
Do not occur naturally in plants but in small amounts
in animals
•
Formed during the hydrogenation of liquid vegetable
oils e.g. in the manufacture of margarine and partially
hydrogenated vegetable oil
•
Elevate serum LDL but not HDL
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Disease
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Disease
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Dietary Fats
Other dietary factors affecting CHD
•
Moderate consumption of alcohol (e.g. 2 drinks a day) decreases the risk of CHD, because
there is a positive correlation between moderate alcohol consumption and the plasma
concentration of HDL
•
Because of the potential dangers of alcohol abuse, health professionals are reluctant to
recommend increased alcohol consumption to their patients
•
Red wine contains phenolic compounds that inhibit lipoprotein oxidation
•
These antioxidants are also present in raisins and grape seed
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Recommended Intakes of Fat

Dietary Guidelines
 Diet low in saturated and trans fat
 Diet low in cholesterol
 20 to 35 percent of daily energy from fat
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Butter and Margarine Labels Compared
The closer the
“partially
hydrogenated
oils” is to the
beginning of the
ingredients list,
the more trans
fat it contains
Whitney & Rolfes – Understanding Nutrition, 12th Edition