Title : Atherosclerosis
link : Atherosclerosis
Atherosclerosis
Atherosclerosis is hardening of
the arteries, a common disease of the major blood vessels characterized by
fatty streaks along the vessel walls and by deposits of cholesterol and
calcium.
Atherosclerosis of arteries
supplying the heart is called coronary artery disease. It can restrict the flow
of blood to the heart, which often triggers heart attacks—the leading cause of
death in Americans and Europeans. Atherosclerosis of arteries supplying the legs
causes a condition called intermittent claudication, which is characterized by
pain in the legs after walking short distances.
People with elevated cholesterol
levels are much more likely to have atherosclerosis than people with low
cholesterol levels. Many important nutritional approaches to protecting against
atherosclerosis are aimed at lowering serum cholesterol levels. People with
diabetes are also at very high risk for atherosclerosis, as are people with elevated
triglycerides and high homocysteine.
What are the symptoms of
atherosclerosis?
Atherosclerosis is typically a
silent disease until one of the many late-stage vascular manifestations
intervenes. Some people with atherosclerosis may experience angina (chest pain)
or intermittent claudication (leg cramps and pain) on exertion. Symptoms such
as these develop gradually as the disease progresses.
Dietary changes that may be
helpful
The most important dietary
changes in protecting arteries from atherosclerosis include avoiding meat and
dairy fat and avoiding foods that contain trans fatty acids (margarine, some
vegetable oils, and many processed foods containing vegetable oils). Increasingly,
the importance of avoiding trans fatty acids is being accepted by the
scientific community. Leading researchers have recently begun to view the
evidence linking trans fatty acids to markers for heart disease as
“unequivocal.”
People who eat diets high in
alpha-linolenic acid (ALA), which is found in canola and flaxseed oils, have
higher blood levels of omega-3 fatty acids than those consuming lower amounts,
which may confer some protection against atherosclerosis. In 1994, researchers
conducted a study in people with a history of heart disease, using what they called
the “Mediterranean” diet. The diet differed significantly from what people from
Mediterranean countries actually eat, in that it contained little olive oil.
Instead, the diet included a special margarine high in ALA.
Those people assigned to the
Mediterranean diet had a remarkable 70% reduced risk of dying from heart
disease compared with the control group during the first 27 months. Similar
results were also confirmed after almost four years. The diet was high in beans
and peas, fish, fruit, vegetables, bread, and cereals, and low in meat, dairy
fat, and eggs. Although the authors believe that the high ALA content of the
diet was partly responsible for the surprising outcome, other aspects of the
diet may have been partly or even totally responsible for decreased death
rates. Therefore, the success of the Mediterranean diet does not prove that ALA
protects against heart disease.
A systematic review of 20 years
of research evaluated the association between dietary fibre and coronary heart
disease.The meta-analysis portion of this review showed that regular whole
grain foods are associated with a coronary heart disease risk reduction of about
26%. In general, the fibres most linked to the reduction of cholesterol levels
are found in oats, psyllium seeds, fruit (pectin) and beans (guar gum).
An analysis of many soluble fibre
trials proves that a cholesterol lowering effect exists, but the amount the cholesterol
falls is quite modest. For unknown reasons, however, diets higher in insoluble
fibre (found in whole grains and vegetables and mostly unrelated to cholesterol
levels) have been reported to correlate better with protection against heart
disease in both men and women. Some trials have used 20 grams of additional
fibre per day for several months to successfully lower cholesterol.
Independent of their action on
serum cholesterol, foods that contain high amounts of cholesterol—mostly egg
yolks—can induce atherosclerosis. It makes sense to reduce the intake of egg
yolks. However, eating eggs does not increase serum cholesterol as much as
eating saturated fat, and eggs may not increase serum cholesterol at all if the
overall diet is low in fat. A decrease in atherosclerosis resulting from a pure
vegetarian diet (no meat, poultry, dairy or eggs), combined with exercise and
stress reduction, and has been proven by controlled medical research.
Preliminary evidence has
suggested that excessive salt consumption is a risk factor for heart disease
and death from heart disease in overweight people. Controlled trials are needed
to confirm these observations. Eating a diet high in refined carbohydrates
(e.g., white flour, white rice, simple sugars) appears to increase the risk of
coronary heart disease, and thus of heart attacks, especially in overweight
women. However, controlled
trials of reducing refined carbohydrate intake to prevent heart disease have
not been attempted to confirm these preliminary findings.
Lifestyle changes that may be
helpful
Virtually all doctors acknowledge
the abundant evidence that smoking is directly linked to atherosclerosis and
heart disease. Quitting smoking protects many people from atherosclerosis and
heart disease, and is a critical step in the process of disease prevention.
Obesity, type A behaviour (time
conscious, impatient, and aggressive), stress, and sedentary lifestyle are all
associated with an increased risk of atherosclerosis; interventions designed to
change these risk factors are linked to protection from this condition.
Aggressive verbal or physical
responses when angry have been consistently related to coronary atherosclerosis
in numerous preliminary studies. A low level of social support, especially when
combined with a high level of outwardly expressed anger has also been associated
with accelerated progression of coronary atherosclerosis.
Nutritional supplements that
may be helpful
Tocotrienols may offer protection
against atherosclerosis by preventing oxidative damage to LDL cholesterol. In a
double-blind trial in people with severe atherosclerosis of the carotid
artery—the main artery supplying blood to the head—tocotrienol administration
(200 mg per day) reduced the level of lipid peroxides in the blood.
Moreover, people receiving
tocotrienols for 12 months had significantly more protection against
atherosclerosis progression and in some cases reductions in the size of their atherosclerotic
plaques, compared with those taking a placebo.
Supplementation with fish oil,
rich in omega-3 fatty acids, has been associated with favourable changes in
various risk factors for atherosclerosis and heart disease in some, but not
all, studies. A double-blind trial showed that people with atherosclerosis who
took fish oil (6 grams per day for 3 months and then 3 grams a day for 21
months) hadsignificant regression of atherosclerotic plaques and a decrease in
cardiovascular events (e.g., heart attack and stroke) compared with those who
did not take fish oil. These results contradict the findings of an earlier controlled
trial in which fish oil supplementation for two years (6 grams per day) did not
promote major favourable changes in the diameter of atherosclerotic coronary
arteries.
In some studies, people who
consumed more selenium in their diet had a lower risk of heart disease. In one
double-blind report, people who had already had one heart attack were given 100
mcg of selenium per day or placebo for six months. At the end of the trial,
there were four deaths from heart disease in the placebo group but none in the selenium
group; however, the number of people was too small for this difference to be statistically
significant. Some doctors recommend that people with atherosclerosis supplement
with 100–200 mcg of selenium per day.
Experimentally increasing
homocysteine levels in humans has led to temporary dysfunction of the cells
lining blood vessels. Researchers are concerned this dysfunction may be linked
to atherosclerosis and heart disease. Vitamin C has been reported in one controlled
study to reverse the dysfunction caused by increases in homocysteine.
Herbs that may be helpful
Many actions associated with
herbal supplements may help prevent or potentiallyalleviate atherosclerosis.
Herbs such as garlic and ginkgo appear to directly affect the hardened arteries
by multiple mechanisms. Herbs such as psyllium, guggul, and fenugreek reduce
cholesterol and other lipid levels in the blood—known risk factors for hardened
arteries. A related group are herbs, including green tea, prevents the
oxidation of cholesterol, an important step in protecting against atherosclerosis.
Finally, there are herbs such as ginger and turmeric that reduce excessive stickiness
of platelets, thereby reducing atherosclerosis.
Garlic has been shown to prevent
atherosclerosis in a four-year double-blind trial. The preparation used,
standardized for 0.6% allicin content, provided 900 mg of standardized garlic
powder per day. The people in this trial were 50 to 80 years old, and the
benefits were most notable in women. This trial points to the long-term
benefits of garlic to both prevent and possibly slow the progression of
atherosclerosis in people at risk.
Garlic has also lowered
cholesterol levels in double-blind research, though more recently, some
double-blind trials have not found garlic to be effective. Some of the negative
trials have flaws in their design. Nonetheless, the relationship between garlic
and cholesterol-lowering is somewhat unclear.
Garlic has also been shown to
prevent excessive platelet adhesion in humans. Allicin, often considered the
main active component of garlic, is not alone in this action. The constituent
known as ajoene has also shown beneficial effects on platelets. Aged garlic extract,
but not raw garlic, has been shown, to prevent oxidation of LDL cholesterol in humans,
an event believed to be a significant factor in the development of atherosclerosis.
Ginkgo may reduce the risk of
atherosclerosis by interfering with a chemical the body sometimes makes in
excess, called platelet activating factor (PAF). PAF stimulates platelets to stick
together too much; ginkgo stops this from happening. Ginkgo also increases
blood circulation to the brain, arms, and legs.
Garlic and ginkgo also decrease
excessive blood coagulation. Both have been shown in double-blind and other
controlled trials to decrease the overactive coagulation of blood that may
contribute to atherosclerosis.
Guggul has been less extensively
studied, but double-blind evidence suggests it can significantly improve
cholesterol and triglyceride levels in people. Numerous medicinal plants and
plant compounds have demonstrated an ability to protect LDL cholesterol from
being damaged by free radicals. Garlic, ginkgo, and guggul are of particular
note in this regard. Garlic and ginkgo have been most convincingly shown to
protect LDL cholesterol in humans.
Several other herbs have been
shown in research to lower lipid levels. Of these, psyllium has the most
consistent backing from multiple double-blind trials showing lower cholesterol
and triglyceride levels. The evidence supporting the ability of fenugreek to lower
lipid levels is not as convincing, coming from preliminary studies only.
Since oxidation of LDL
cholesterol is thought to be important in causing or accelerating atherosclerosis,
and green tea protects against oxidation, this herb may have a role in preventing
atherosclerosis. However, while some studies show that green tea is an antioxidant
in humans, others have not been able to confirm that it protects LDL cholesterol
from damage. Much of the research documenting the health benefits of green tea
is based on the amount of green tea typically drunk in Asian countries—about three
cups per day (providing 240–320 mg of polyphenols).
The research on ginger’s ability
to reduce platelet stickiness indicates that 10 grams (approximately 1 heaping
teaspoon) per day is the minimum necessary amount to be effective. Lower
amounts of dry ginger, as well as various levels of fresh ginger, have not been
shown to affect platelets.
Turmeric’s active compound
curcumin has shown potent anti-platelet activity in animal studies. It has also
demonstrated this effect in preliminary human studies. In a similar vein,
bilberry has been shown to prevent platelet aggregation as has peony. However, none
of these three herbs has been documented to help atherosclerosis in human
trials.
Butcher’s broom and rosemary are
not well studied as being circulatory stimulants but are traditionally reputed
to have such an action that might impact atherosclerosis. While butcher’s broom
is useful for various diseases of veins, it also exerts effects that are protective
for arteries.
That is Atherosclerosis
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