2. Lipid
Nutrition and health
• Lipids play diverse and important roles in nutrition
and health.
• Many lipids are absolutely essential for life.
• However, there is also considerable awareness
that abnormal levels of certain lipids, particularly
cholesterol (in hypercholesterolemia)
Hypercholesterolemia
refers to levels of
cholesterol in the blood
that are higher than
normal hypercholesterolemia)
3. • cholesterol and trans fatty acids,
are risk factors for heart disease
amongst others.
• Consumption of industrially
produced trans-fatty acids (TFA) is
associated with substantial risk of
coronary heart disease (CHD).
• The magnitude of this
relationship, as well as emerging
associations with end points such
as diabetes and sudden cardiac
death
4. • Humans have a requirement for certain
essential fatty acids, such as linoleic acid (an
omega-6 fatty acid) and alpha-linolenic
acid (an omega-3 fatty acid) in the diet
because they cannot be synthesized from
simple precursors in the diet.
5. • Both of these fatty acids are 18-carbon
polyunsaturated fatty acids differing in the
number and position of the double bonds.
• Most vegetable oils are rich in linoleic acid
(safflower, sunflower, and corn oils).
• Alpha-linolenic acid is found in the green
leaves of plants, and in selected seeds, nuts
and legumes (flax, canola, walnuts and soy).
• Fish oils are particularly rich in the longer-
chain omega-6 fatty acids eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA).
6. • Most of the lipid
found in food is in
the form of
triacylglycerols,
cholesterol and
phospholipids.
phospholipids
cholesterol
7. • Most of the saturated fatty acids (as triacylglycerols) in the diet
are incorporated into adipose tissue stores, because the
absence of double bonds allows a higher energy yield per
carbon than is obtained from oxidation of unsaturated fatty
acids.
• The longer chain fatty acids are incorporated into cell
membranes as phospholipids regardless of degree of
saturation.
• Since dietary fatty acids are exchanged with membrane fatty
acids, dietary fat composition is reflected in membrane lipid
composition.
8. • Thus dietary fatty acids can influence cell
function through effects on membrane
properties.
• Dietary fat provides an average energy intake
which is approximately twice that of
carbohydrate or protein.
• A minimum amount of dietary fat is necessary
to facilitate absorption of fat-soluble vitamins
(A, D, E and K) and carotenoids.
• A minimal amount of body fat is also necessary
to provide insulation that prevents heat loss and
protects vital organs from shock due to ordinary
activities.
9. • High fat intake contributes to increased risk of
obesity, diabetes and atherosclerosis.
Atherosclerosis is the primary cause of coronary and
cardiovascular diseases and is primary due to the buildup of
plaque on the inside walls of arteries.
Plaque is made up of cholesterol-rich low density lipoproteins
(LDL), macrophages, smooth muscle cells, platelets, and other
substances.
10. • Atherosclerosis is the leading cause of illness
and death, almost doubling the number of
deaths from cancers.
• Despite significant medical advances,
coronary artery disease and atherosclerotic
stroke are responsible for more deaths than
all other causes combined
11. • A substantial amount of scientific evidence
supports the impact of dietary fatty acids on
cardiovascular health.
• Saturated fats have a profound
hypercholesterolemic (increase blood
cholesterol levels) effect and tend to increase
plasma LDL.
• They are found predominantly in animal
products (butter, cheese and meat) but coconut
oil and palm oil are common vegetable sources.
• Intake of monounsaturated fats in oils such as
olive oil is thought to be preferable to
consumption of polyunsaturated fats in oils such
as corn oil because the monounsaturated fats
apparently do not lower high-density-
lipoprotein (HDL) cholesterol levels
12. • Keeping cholesterol in the normal range not
only helps prevent heart attacks and strokes
but may also prevent the progression of
atherosclerosis.
• Some medicines are a class of drugs that
lowers the level of cholesterol in the blood by
inhibiting the enzyme HMG-CoA reductase.
• This is a key enzyme involved in the
biosynthesis of cholesterol in the liver.
