cholesterol and the role of plant oils
by Caroline Stokes
Nutrition Scientist, British Nutrition Foundation
Cholesterol is a lipid which in small CHD. The average blood cholesterol of the different types of fatty acids are
amounts is essential for many body
concentration in England is currently summarised in Table 1.
processes. For example, it is a struc-
5.5 mmol/l for men and 5.6 mmol/l for PUFAs, found in plant oils such as
tural component of cell membranes
women, compared to the target con- sunflower, rapeseed and soya bean
and nerve sheaths. Cholesterol is
centration of less than 5 mmol/l (British oil and in some types of fat spreads,
also required for the synthesis of bile
Heart Foundation 2007). can help to lower LDL cholesterol and
acids and steroid and adrenocorti-
Several lifestyle factors may con- also slightly raise HDL cholesterol con-
cal hormones such as oestrogen
tribute to high cholesterol levels in centrations (Lunn & Theobald 2006).
and cortisol.
the blood, such as physical inactivity, Trans fatty acids are found in small
The synthesis of cholesterol occurs
overweight or obesity, smoking, exces- quantities in milk, beef and lamb but
predominantly in the liver. Animal
sive alcohol intake, family history and are also produced through a process
foods such as meat, poultry, shellfish
diet. Contrary to popular belief, foods of hydrogenation when margarines
and particularly organ meats are the
containing cholesterol, which are and spreads are manufactured from
primary source of dietary cholesterol.
primarily animal foods such as meat, oil. However, there has recently been
shellfish and eggs, do not significantly a reduction in Trans fatty acids in many
However, cholesterol is mainly synthe-
influence blood cholesterol concen- manufactured products in the UK. If
sised in the body from dietary fat and
trations. In fact, it is the amount and consumed in high amounts (e.g. over
so the above foods contribute very
type of fat in the diet which particu- two percent of dietary energy intake),
little to cholesterol levels in the body.
larly affects blood cholesterol levels. Trans fatty acids can raise LDL cholester-
Cholesterol is carried round the
All fats in the diet provide saturated ol and reduce HDL cholesterol concen-
body with the help of proteins known
trations (Aisbitt & Buttriss 2006).
as apoproteins which
transport cholesterol in the
Type of fatty acid Main dietary sources include
In line with the public
health messages to reduce
blood. These lipid-protein
Butter, margarine, lard, fatty meats
total fat and SFA intake and
complexes, known as lipo-
Saturated
and meat products, full-fat dairy
proteins can be classified
products, biscuits, cakes and
to increase the proportion
based on their density. The
pastries.
of unsaturated fatty acids
in the diet, there have been
three main types of lipopro-
Monounsaturated
Olive oil, rapeseed oil, avocados,
some substantial changes to
teins are: very low-density
nuts and seeds; milk and meat.
the balance of fatty acids in
lipoproteins (VLDL), which
supply the body with energy
Polyunsaturated
Sunflower oil, corn oil, soya oil,
our diets. In the UK, intakes
polyunsaturated fat spreads.
of SFAs have decreased
from triglycerides during the
Small amounts in milk, beef and
which has been coupled
fasting state. Secondly, low-
by increases in PUFA (in
density lipoproteins (LDL) are
Trans
lamb; hard margarines, frying oils
and bakery products (containing particular omega-6 PUFAs)
derived when the triglycer-
partially hydrogenated oils). over recent years (see Lunn
ide is removed from VLDL,
with the remaining choles-
Table 1 Types of fatty acids and main dietary sources in the UK.
& Theobald 2006). The move
away from food sources of
terol being concentrated
(SFA), monounsaturated (MUFA) and SFAs has been facilitated by the wide
and transported to peripheral tissues.
polyunsaturated fatty acids (PUFA) availability of sources of unsaturated
Finally high-density lipoproteins (HDL)
in varying proportions. These fatty fatty acids such as vegetable oils from
are small dense particles of choles-
acids can influence both LDL and HDL a wide range of oilseed crops.
terol, protein and phospholipids whose
cholesterol. SFAs are mainly found in The fatty acid composition of seed
function is to transport cholesterol from
animal products, with butter, marga- oils vary widely, as shown in Figure 1,
around the body back to the liver.
rine and lard, fatty meats and meat therefore the consumption of different
Although there are several risk fac-
products, full fat dairy products and types can have a significant effect on
tors for coronary heart disease (CHD),
cakes, biscuits and pastries being the blood cholesterol levels. Typically, one
high blood cholesterol concentrations
major sources in the UK diet. Of the type of fatty acid usually dominates
are one of the principal risk factors,
three fatty acids, SFAs pose the great- within a given oil. To briefly summarise
with mortality data indicating that 45 est risk as they raise LDL cholesterol the figure below, olive, and rapeseed
percent of people in Western Europe levels in the body. However, a diet rich oil predominantly contain MUFAs
and 35 percent from Central and in MUFAs can help lower LDL choles- whilst soya bean, corn, sunflower and
Eastern Europe who die from heart terol slightly (but has little effect on the safflower oil contain mainly PUFAs. PU-
attacks have abnormal blood lipids ‘good’ HDL cholesterol levels). Oils of FAs can be further divided into alpha
(British Heart Foundation 2007). High plant origin (e.g. olive oil, rapeseed linolenic acid (omega-3) and linoleic
levels of LDL in the blood stream are oil), avocados, nuts and seeds are acid (omega-6). Most oils contain
a risk factor for CHD. HDL can remove good sources of MUFAs, but meat, linoleic acid such as soya bean, corn,
cholesterol from the blood and hence milk and dairy foods also provide sunflower and safflower oil and linseed
is associated with a reduced risk of MUFAs. Main dietary sources in the UK oil contains alpha linolenic acid.
NHDmag.com May ‘08 - issue 34 17
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