Definition
Atherosclerosis, or hardening of the arteries, is the leading cause of death
in men over age 35 and all people over 45. Most heart attacks and strokes are
due to atherosclerosis. Although the origin of this condition is not completely
understood, we know that it is accelerated by factors such as high blood
pressure (hypertension), high cholesterol, diabetes, mildly impaired glucose
tolerance, smoking, and physical inactivity.
Current theories suggest that atherosclerosis begins with injury to the lining
of the arteries. High blood pressure physically stresses this lining, while
circulating substances, such as low-density lipoprotein (LDL) cholesterol,
homocysteine, free radicals, and nicotine, chemically damage it. White blood
cells then attach to the damaged wall and take up residence. Then, for reasons
that are not entirely clear, they begin to accumulate cholesterol and other
fats. Platelets also latch on, releasing substances that cause the formation of
fibrous tissue. The overall effect is a thickening of the artery wall called a
fibrous plaque.
Over time, the thickening increases, narrowing the bore of the artery. When
blockage reaches 75 to 90%, the person begins to notice angina symptoms,
specifically heart pain. In the lower legs, blockage of the blood flow leads to
leg pain with exercise, a condition called intermittent claudication.
Blood clots can develop on the irregular surfaces of the artery and may become
detached and block downstream blood flow. Fragments of plaque can also detach.
Heart attacks are generally caused by such blood clots, whereas strokes are more
often caused by plaque fragments or gradual obstruction. Furthermore,
atherosclerotic blood vessels are weak and can burst.
With a disease as serious and progressive as atherosclerosis, the best treatment
is prevention. Conventional medical approaches focus on lifestyle changes, such
as increasing aerobic exercise, reducing the consumption of saturated fats, and
quitting smoking. The regular use of aspirin also appears to be quite helpful by
preventing platelet attachment and blood clot formation. If necessary, drugs may
be used to lower cholesterol levels or blood pressure.
Recently, conventional medicine has also begun to suggest keeping levels of
homocysteine low by adding supplemental folate to the diet, and making sure to
get enough vitamin B6 and B12. Consult with your physician for up-to-date
information regarding the ideal dose of these supplements. At the time of this
writing, recommendations suggest that 800 mcg of folate daily (a dose higher
than the standard recommended intake) may be necessary to achieve full
benefits.1 However, a physicians supervision is essential before taking this
much folate, due to the risk of covering up B12 deficiency. For other dosage and
safety issues, see the full folate, vitamin B6, and vitamin B12 articles.
Treatment
Principal Proposed Treatments:
In the field of preventing atherosclerosis, conventional and alternative
approaches overlap. Natural medicine supports (indeed, it first championed) many
of the lifestyle changes now encouraged by conventional medicine, and treatments
such as vitamin B6 and folate are now widely recommended by physicians. Many
other "alternative" approaches for preventing atherosclerosis are on the verge
of acceptance into conventional medicine.
Numerous studies have been performed to determine precisely which nutrients are
most helpful in preventing atherosclerosis. However, it is tricky to interpret
the results of this research.
The most common and potentially most confusing type of study is the
observational study. This type of study follows large groups of people for years
and keeps track of a great deal of information about them, including diet.
Researchers then examine the data closely and try to identify which dietary
factors are associated with better health and longer life.
However, the results can be misleading. For example, if an observational study
finds that people who take vitamin supplements live longer, it is not
necessarily the vitamins that deserve the credit. Vitamin users also tend to
exercise more and to eat more healthful foods, habits that may play a more
important role than the vitamins. It is hard to tell.
A more reliable kind of study is the intervention trial. In these studies, some
people are given a certain vitamin and then compared to others who are given a
placebo (or sometimes no treatment at all). The best intervention trials use a
double-blind design. The results of intervention trials are far more conclusive
than those of observational studies. Unfortunately, they are very expensive to
perform, and relatively few have been completed.
This section details the evidence that is available to date. Because this is
such a rapidly changing field, new evidence will likely have been found by the
time you read this article. Consult a health-care professional for the latest
information.
(For other natural treatments that may reduce two important risk factors for
atherosclerosis, see the articles on cholesterol and hypertension.)
Garlic: May Prevent Atherosclerosis Through a Combination of Effects
Garlic produces several effects that together may reduce atherosclerosis risk.
It appears to mildly lower cholesterol and blood pressure levels, as well as
protect against free radicals and reduce the tendency of the blood to coagulate.
Garlic preparations have been shown to slow the development of atherosclerosis
in rats, rabbits, and human blood vessels, reducing the size of plaque deposits
by nearly 50%. Furthermore, in a double-blind, placebo-controlled study that
followed 152 individuals for 4 years, standardized garlic powder at a dosage of
900 mg per day significantly slowed the development of atherosclerosis as
measured by ultrasound. While this study suffered from some statistical
problems, it nonetheless provides preliminary evidence that garlic can protect
against hardening of the arteries.
In addition, an observational study of 200 individuals suggests that garlic
protects the arteries in other ways as well. The study measured the flexibility
of the aorta, the main artery exiting the heart. Participants who took garlic
showed less evidence of damage to their arteries.
Finally, in another study 432 individuals who had suffered a heart attack were
given either garlic oil extract or no treatment over a period of 3 years. The
results showed a significant reduction of second heart attacks and an
approximately 50% reduction in death rate among those taking garlic.
For more information, including dosage and safety issues, see the full garlic
article.
Antioxidants: Widely Recommended, but Do They Really Work?
The body is engaged in a constant battle against damaging chemicals called free
radicals, or pro-oxidants. These highly reactive substances are believed to play
a major role in atherosclerosis, cancer, and aging in general.
To counter the harmful effects of free radicals, the body manufactures
antioxidants to chemically neutralize them. However, the natural antioxidant
system may not always be equal to the task. Sources of free radicals, such as
cigarette smoke and smoked meat, may overwhelm this defense mechanism. In the
not-too-distant future, tests of "antioxidant status" may join cholesterol and
blood pressure as standard components of preventive medicine screening.
Certain dietary nutrients augment the bodys natural antioxidants and may be
able to help out when the primary system is under stress. Vitamins E and C and
beta-carotene are the best known, but many other substances found in fruits and
vegetables are also strong antioxidants. For years weve been thinking that
individual antioxidant supplements might offer considerable protection against
heart disease, especially vitamin E. However, current evidence appears to dampen
these high expectations.
Vitamin E: Not the Magic Bullet We Thought
Most but not all observational studies have found associations between high
intake of vitamin E and reduced risk of cardiovascular disease. However, as
noted above, observational studies alone cannot be relied upon to identify
useful treatments. Intervention trials, which provide much more convincing
evidence of effectiveness, have generally failed to find vitamin E supplements
effective.
The Heart Outcomes Prevention Evaluation (HOPE) trial found that natural vitamin
E (d-alpha-tocopherol) at a dose of 400 IU daily did not reduce the number of
heart attacks, strokes, or deaths from heart disease any more than placebo. The
details of this well-designed, double-blind trial were published in the January
20, 2000, issue of The New England Journal of Medicine. The trial followed over
9,000 men and women who had existing heart disease or were at high risk for it.
In addition, a large, open trial compared the effectiveness of aspirin and
vitamin E for the prevention of heart attacks, strokes, and other diseases
related to atherosclerosis. While aspirin treatment proved dramatically helpful,
vitamin E produced little-to-no benefit.
Negative results have been seen in other large trials as well.
The Cambridge Heart Antioxidant Study (CHAOS) trial, published in 1996, really
raised researchers hopes. In that trial, people with existing heart disease who
took natural vitamin E (400 IU or 800 IU daily) had substantially fewer nonfatal
heart attacks compared to the placebo group after about 1.5 years. Even so,
heart-related deaths were not reduced in the vitamin E group. Furthermore, it
has been suggested that possible flaws in the design of this trial might make
its findings questionable.
It has been suggested that another form of vitamin E (gamma-tocopherol) might be
more helpful than the vitamin E used in these trials (alpha-tocopherol). Gamma-tocopherol
is present in the diet much more abundantly than alpha-tocopherol, and it could
be that the studies showing benefits with dietary vitamin E actually tracked the
influence of gamma-tocopherol. However, an observational study specifically
looking to see if gamma-tocopherol levels were associated with risk of heart
attack found no relationship between the two. Nonetheless, intervention trials
of gamma-tocopherol are currently underway.
For more information, including dosage and safety issues, see the full vitamin E
article.
Beta-Carotene: Best in Food, Not As a Supplement
The study results involving beta-carotene are interesting. Beta-carotene is one
member of a large category of substances in foods known as carotenes, which are
found in high levels in yellow, orange, and dark green vegetables.
Many studies suggest that eating foods high in carotenes can prevent
atherosclerosis. However, isolated beta-carotene in supplement form may not
help, and could actually increase your risk, especially if you consume too much
alcohol.
A huge, double-blind, intervention trial involving 29,133 Finnish male smokers
found 11% more deaths from heart disease and 15 to 20% more strokes in those
participants taking beta-carotene supplements. This certainly does not encourage
one to take it.
Similar poor results with beta-carotene were seen in another large, double-blind
study in smokers. Furthermore, beta-carotene supplementation was also found to
increase the incidence of angina in smokers.
What is happening here? Clearly, smoking presents a challenge to antioxidants.
However, the question remains: Why should beta-carotene not only fail to help
but actually worsen the situation?
One possible explanation is that beta-carotene in the diet always comes along
with other naturally occurring carotenes. It is quite likely that other
carotenoids in the diet are equally or more important than beta-carotene alone.
Taking beta-carotene supplements may actually promote deficiencies of other
natural carotenes, and overall that may hurt more than it helps.
The moral of the story is that you should eat your vegetables but maybe not take
beta-carotene supplements.
Other Antioxidants: May Be Helpful, but Little Direct Evidence
A high intake of vitamin C from fruits and vegetables appears to reduce the risk
of heart disease. However, there is little evidence that vitamin C supplements
provide the same benefits. Foods containing vitamin C also contain many other
healthful ingredients (such as bioflavonoids and carotenes), so its not clear
that pills containing only vitamin C work just as well.
Many other antioxidant vitamins, supplements, and herbs have been suggested as
preventive treatments for atherosclerosis. Selenium, OPCs from grape seed or
pine bark, lipoic acid, turmeric, resveratrol from red wine and grape skins, and
coenzyme Q10 are commonly mentioned. However, although a number of interesting
studies have suggested that these substances may be beneficial, the state of the
evidence is still too preliminary to draw any conclusions.
Combined Antioxidants
It has been suggested that the best approach is to use a combination of
antioxidants. This makes sense theoretically because, for example, vitamin E
fights free radicals that dissolve in fats while vitamin C fights those that
dissolve in water. However, evidence for benefit with such combinations comes
only from observational studies. A 3-year, double-blind, placebo-controlled
study of 160 individuals found no benefit with combined antioxidant treatment,
providing vitamin E (800 IU), vitamin C (1,000 mg), beta-carotene (25 mg), and
selenium (100 mcg).
Lifestyle Approaches
This fact cannot be emphasized enough: The most important way to prevent
atherosclerosis involves lifestyle changes such as quitting smoking, increasing
exercise, and adopting a diet high in whole grains, fruits, and vegetables and
low in animal products. Olive oil and canola oil are probably among the most
healthful of vegetable oils. Heating oils to high temperatures (as in fried
foods) can oxidize them and make them less healthful.
The moderate use of alcohol, and specifically red wine, appears to help prevent
atherosclerosis, although this is controversial as well. Contrary to some
reports, coffee drinking does not appear to increase risk of heart disease.
although unfiltered coffee may be harmful.
Other Proposed Treatments:
Although the following treatments are widely recommended for atherosclerosis,
they cannot be considered scientifically proven at this time.
Omega-3 Fatty Acids
Study results on fish or fish oil for cardiovascular disease have yielded
contradictory results. However, a review (technically a meta-analysis) of many
studies on the subject suggests that when all the evidence is put together, it
appears that fish or fish oil can reduce overall mortality, heart disease
mortality, and sudden cardiac death (e.g., heart stoppage due to arrhythmia).
Fish oil is believed to exert its primary benefit in cardiovascular disease by
reducing serum triglycerides, although not all studies have found this effect.
The most important omega-3 fatty acids found in fish oil are called EPA (eicosapentaenoic
acid) and DHA (docosahexaenoic acid). DHA and EPA may have different effects on
triglycerides, but again study results are not consistent; some studies found
EPA more effective, while others did not. Like cholesterol, triglycerides are a
type of fat in the blood that tends to damage the arteries, leading to heart
disease. Reducing triglyceride levels should help prevent heart disease to some
extent. However, the standard drug gemfibrozil appears to be more effective than
fish oil for this purpose. Fish oil has been specifically studied for reducing
triglyceride levels in people with diabetes, and it appears to do so safely and
effectively.
Similarly, some but not all studies also suggest that fish, fish oil, or EPA or
DHA separately can modestly raise levels of HDL ("good") cholesterol.
Additionally, fish oil may help the heart by "thinning" the blood and by
reducing blood levels of homocysteine. Blood clots play a major role in heart
attacks, and homocysteine is an amino acid that appears to raise the risk of
heart disease. One study directly indicates that fish oil may be able to prevent
blood clots from blocking the synthetic grafts inserted in people undergoing
kidney dialysis.
Studies contradict one another on whether fish oil can lower blood pressure. A
6-week, double-blind, placebo-controlled study of 59 overweight men suggests
that the DHA in fish oil, but not the EPA, can reduce blood pressure.
For more information, including dosage and safety issues, see the full fish oil
article.
Flaxseed oil has been suggested as an alternative to fish oil. While fish oil is
much better studied, there is some evidence, including two double-blind studies,
that flaxseed oil or whole flaxseed may reduce LDL ("bad") cholesterol, perhaps
slightly reduce hypertension, and slow down atherosclerosis.
Mesoglycan
Mesoglycan is a substance obtained from the intestines of pigs.
In one study, 200 mg per day of mesoglycan significantly slowed the rate of
thickening of arteries. After 18 months of treatment, the additional layering of
the inside vessel lining was 7.5 times less in the group receiving mesoglycan
than in the group that did not receive any treatment. However, because this was
not a double-blind, placebo-controlled trial, the results cant be taken as
truly reliable. Preliminary evidence suggests that this supplement may work in
several ways: supplying material for repair of arteries, "thinning" the blood,
and improving cholesterol levels.
For more information, including dosage and safety issues, see the full
mesoglycan article.
Magnesium
A double-blind, placebo-controlled trial of 50 individuals with coronary artery
disease found that supplementation with magnesium at 730 mg daily significantly
improved exercise tolerance. There is also some evidence that magnesium may
reduce the atherosclerosis risk caused by hydrogenated oils, margarine-like fats
found in many "junk" foods.
In addition, a double-blind study of 42 individuals with heart disease found
that magnesium supplements reduced the tendency of the body to form blood clots.
For more information, including dosage and safety issues, see the full magnesium
article.
Chromium
Mildly impaired responsiveness to insulin (insulin resistance) is a fairly
common condition that appears to increase the risk of heart disease. Chromium
supplementation might restore normal insulin responsiveness, as well as aid in
weight loss and possibly improve cholesterol levels. The net result might be
decreased risk of heart disease.
In support of this theory, an observational trial found associations between
higher chromium intake and reduced risk of heart attack.
Other Herbs and Supplements
Some but not all observational studies suggest that green tea might help prevent
heart disease.
Many herbs appear to decrease platelet stickiness, including bilberry, feverfew,
ginger, ginkgo, and hawthorn. Whether this translates into an actual benefit for
preventing atherosclerosis remains unknown.
Indirect evidence suggests that DHEA might help prevent heart disease however,
it seems likely to be more beneficial for men than for women.
Frequent consumption of nuts may reduce the risk of heart disease, probably
because the monounsaturated fats in nuts reduce cholesterol levels.
Weak evidence suggests genistein may be helpful for preventing heart disease by
reducing cholesterol and keeping it from depositing on cell walls.
Other treatments sometimes mentioned for atherosclerosis include astragalus,
copper, GLA, grass pollen, lutein, bilberry leaf, and TMG, although there is
little evidence as yet that they are helpful.
Chelation therapy, a technique that involves intravenous administration of the
substance EDTA, is widely promoted in some alternative medicine circles as a
treatment for atherosclerosis. However, there no is meaningful evidence that it
works, and growing evidence that it does not work.
For other natural substances that may help prevent atherosclerosis by lowering
its major risk factors, see the articles on cholesterol and hypertension.
Finally, accumulating evidence hints that trans-fatty acids, a type of fatty
acid found in margarine and other hydrogenated oils, increase risk of
cardiovascular disease. In July 2002, the US Institute of Medicine concluded
that there is no safe intake level of trans-fatty acids, and overall consumption
should be kept as low as possible.