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Linda Lazarides'
Nutritional Health Bible
an essential reference book for everyone serious about health and nutrition
Treat Yourself with
Nutritional Therapy
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Cholesterol
Uses and sources
Cholesterol is a fatty substance found in animal tissues and in eggs. It is a
vital component of cell membranes, and especially of the myelin sheath which
insulates nerves, and is used to make bile acids which play a part in fat
digestion. It is also required for the production of steroid hormones and vitamin D. Very little of our blood cholesterol
is obtained from dietary sources, the majority is synthesized by the liver.
Elevated blood cholesterol levels are not therefore necessarily linked with a
high cholesterol consumption, but they do tend to be associated with a diet high
in saturated fat. This tendency depends to some extent on the types of saturated
fat consumed. The formation of different prostaglandins and leukotrienes which have different regulatory effects on metabolism and
physiological function probably plays a part in this.
Excretion
Cholesterol once made cannot be broken down by the body except into bile acids.
It can only be excreted via the stools, in the form of bile acids (which are
released into the gut during the process of digestion) and cholesterol
molecules. When adequate dietary fibre, especially pectins and other soluble
fibre, is consumed in the diet, it binds bile acids and carries them out of the
body via the stools. The reduced transit time of the gut contents, which is
promoted by a high-fibre diet, also helps to enhance the excretion of bile
acids. If bile acids are not removed from the gut, they are reabsorbed and
eventually re-converted to cholesterol. Low fibre diets therefore encourage this
reabsorption.
Forms of cholesterol
Like all fats, cholesterol is not soluble in water and
therefore has to be transported in the blood in the form of fat/protein
complexes known as lipoproteins. This gives rise to several common forms of
blood cholesterol:
- VLDL (very low density lipoproteins). These transport
triglycerides and cholesterol out of the liver and deposit them in
peripheral tissues and arteries. VLDLs eventually become LDLs.
- LDL (low density lipoproteins, or 'bad cholesterol'). These
contain predominantly cholesterol, which they deposit in the peripheral
tissues and arteries and in the liver.
- HDL (high density lipoproteins or 'good cholesterol'). These
consist of mainly phospholipids and 35-40 per cent cholesterol. The
phosopholipid picks up cholesterol from the peripheral tissues and arteries
and deposits it in the liver.
It is thought that LDL cholesterol may have to be oxidized
before it can form harmful atherogenic deposits in the arteries, which is the
reason why a high intake of antioxidant nutrients such as vitamins A, C, E,
selenium and beta-carotene is thought to be valuable in preventing heart
disease.
Methods of reducing
blood cholesterol levels
Increasing fibre
intake
Increasing the rate of loss of bile acids and cholesterol
through the stools by increasing fibre intake can reduce blood cholesterol
levels by 10-25 per cent. Pectin, found mainly in fruit, is the most effective
type of fibre for this purpose. Bran and cellulose are not so effective. Fibre
also enhances the production of propionic acid by intestinal bacteria. Once
absorbed into the blood, propionic acid may inhibit the synthesis of cholesterol
by the liver.
Increasing
consumption of plant foods
- Substances known as sterols, found in many vegetable and seed
oils, inhibit the absorption (or reabsorption) of cholesterol.
- Vitamin E-like substances known as tocotrienols, also found in many plants, particularly palm oil and barley oil,
also help to inhibit enzymes involved in cholesterol synthesis, resulting in
a lowering of cholesterol. It is thought that the often-observed
cholesterol-lowering effect of palm oil and cocoa butter - which are, paradoxically, saturated fats - may be
due to their tocotrienol or plant sterol content.
Correcting nutritional deficiencies
- Copper-, vanadium- or chromium-deficient diets or a diet with a
high ratio of zinc to copper, can result in hypertriglyceridaemia and high
blood cholesterol.
- Inuit Eskimos are notoriously free of heart disease, and consume
a great deal of oily fish. It is now known that the synthesis of VLDLs
(cholesterol-depositing lipoproteins which eventually form LDL, or 'bad
cholesterol') is reduced by EPA, a substance found in the oils from these
fish. Fish oils may also depress the synthesis of cholesterol by the liver.
Dietary
supplementation
- Large doses of supplementary vitamin C can reduce blood
cholesterol levels, possibly by stimulating the conversion of cholesterol to
bile acids.
- Niacin supplementation (3,000-9,000mg per day) may be prescribed
by doctors to reduce serum cholesterol through a reduction in sythesis of
VLDL. Niacin is also thought to enhance HDL ('good cholesterol') synthesis.
However most holistic practitioners believe that because of the association
of such large doses of niacin with possible liver damage, other nutritional
avenues should be explored first.
Cholestyramine
Anti-cholesterol drug which works by binding bile acids.
Can cause depletion of folic acid.
Adapted from the Nutritional Health Bible by Linda Lazarides
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