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LE Magazine September 2002
Two JAMA
Studies Reveal That Antioxidants
Reduce Alzheimer's Risk
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In the June 26, 2002 issue of the Journal of The American Medical
Association (JAMA),
two studies show that antioxidants can dramatically lower the
risk of Alzheimer’s disease. The first study involved
5,385 participants who at baseline were at least 55 years old
and were free of dementia. The investigators looked at the
dietary intake of beta-carotene, flavonoids, vitamins C and E.
After adjustments for other risk factors, the researchers
found that the higher the intake of vitamins C and E, the
lower the incidence of Alzheimer’s disease. For each
single-digit increase in vitamin C and E consumption, there
was a corresponding 18% decrease in Alzheimer’s disease
incidence. When antioxidant intake of cigarette smokers was
evaluated, Alzheimer’s risk was reduced by 35% with
vitamin C, 42% with vitamin E, 46% with flavonoids and 51%
with beta-carotene. The conclusion of the researchers was that
“high dietary intake of vitamin C and vitamin E may lower
the risk of Alzheimer disease.”
In the second JAMA study,
researchers sought to ascertain if the intake of antioxidant
nutrients, vitamin E, vitamin C and beta-carotene is
associated with incident Alzheimer’s disease. The
investigators examined 815 people 65 years of age and older
who were free of dementia. The results showed a consistent
reduction in Alzheimer’s risk with increasing intake of
dietary vitamin E. Those with the highest intake of dietary
vitamin E showed a remarkable 70% reduction in
Alzheimer’s disease incidence. Interestingly, intake of
vitamin E, C and beta-carotene supplements was not
significantly associated with Alzheimer’s disease risk in
this study. Dietary vitamin E is rich in the gamma tocopherol
fraction of vitamin E, whereas vitamin E supplements consist
primarily of alpha tocopherol. It is the gamma tocopherol
fraction of vitamin E that has been shown to be the critical
factor in suppressing free radicals. The brain is especially
vulnerable to the toxic effects of free radicals because of
its high-energy output. Notably, in this study, only those
with a genetic predisposition for contracting Alzheimer’s
disease (those whose genetic structure was without the APOE
epsilon 4 allele) showed the remarkable protective benefit
from dietary vitamin E.
In response to these studies, a leading nutritionist stated
that Americans don’t meet their requirements for vitamin
E. Jeffrey Blumberg, professor of nutrition at Tufts
University, was quoted in The Washington Post as saying,
“antioxidant nutrients provide a defense network against
disease” and “it makes sense that antioxidants like
vitamin E and C over the long term help to reduce the
risk.”
In the previous week’s issue of JAMA (June 19, 2002), two studies
were published that endorsed the use of dietary supplements by
healthy people as a way of reducing the risk of cancer,
cardiovascular disease and osteoporosis. This was the first
time that the American Medical Association officially
recognized the benefits of dietary supplements in preventing
disease.
Long-term
consumption of folate prevents
colorectal cancer
Colorectal cancer is the third-leading cause of cancer
death in adults in the U.S. In 2002, approximately 150,000
Americans will be diagnosed with colorectal cancer, over
56,000 will die from it. Despite medical advances,
improvements in survival rates for patients with advanced
stages of colorectal cancer have been minimal. Hence,
researchers are focusing their attention on prevention. One
promising preventive is the long-term consumption of
folate.
A new study, led by Paul Terry, Ph.D. of Albert Einstein
College of Medicine in New York and reported in the International Journal of Cancer
[2002;Vol. 97;864-867], showed that women with diets high in
folate reduced their risk of developing colorectal cancer. The
long-term study evaluated the dietary habits of 57,000 women.
After an average of 10 years, 389 of the participants
developed colorectal cancer. Those subjects whose diets were
higher in folate developed colorectal cancer at a lower
rate.
In Terry’s study, most participants consumed large
amounts of folate through their diet. But another long-term
study found an even greater reduction in colorectal cancer
risk in women taking folic acid supplements.
In the famous Nurses’ Health Study, reported in the
April 2001 issue of Harvard
Women’s Health Watch, women who took folic
acid-containing multivitamins for at least 15 years were 75%
less likely to develop colon cancer than those who did not.
Key to the findings was the length during which participants
took the supplements: only those who took folic
acid-containing supplements for a minimum of 15 years lowered
their risk of colorectal cancer.
Although the exact mechanisms by which folate helps protect
against colorectal cancer are not clear, research points to
its vital role in normal cell division and the repair of DNA
damage.
Researchers Eichholzer and associates at the University of
Zurich, evaluating studies on folate’s effects on the
risk of colon cancer, report that folate appears most
effective when taken through long-term supplementation.
Research reviews by Molloy and associates at Trinity College
in Dublin, Ireland concur with these findings.
—Elizabeth Heubeck
Antioxidants:
a possible preventative against
age-related macular degeneration
Age-related macular degeneration (AMD), which affects
central vision and the ability to see detail, is a common
condition among people over the age of 60. As life
expectancies continue to rise, so too will the risk for
developing macular degeneration. In the advanced stage of
macular degeneration, cells within the macula begin to
deteriorate, resulting in lost vision that cannot be regained.
To date, therefore, the best hope for avoiding declining
vision that accompanies macular degeneration lies in
prevention. Breakthrough research points to the power of
antioxidants as a possible preventative.
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In a multi-center study sponsored by the National Eye
Institute, researchers sought to determine if a long-term
regimen of antioxidants would reduce the risk of advanced
macular degeneration. Researchers followed subjects for an
average of 6.3 years and found that those at high risk of
developing advanced macular degeneration reduced their risk by
approximately 25% when treated with a combination of
antioxidants [Sackett CS et al, Insight 2002; Jan-Mar;27(1):5-7].
The following daily therapeutic dosages of nutrients were used
in the study: vitamin C, 500 mg; vitamin E, 400 IU; beta
carotene, 15 mg; and zinc, 80 mg.
In another study, researchers measured the level of serum
and/or plasma antioxidants (vitamins C, E and A, total and
individual carotenoids, and zinc) in subjects with advanced
and early age-related maculopathy (ARM). They found that
levels of vitamins C and E, and total carotenoids were lower
in subjects with advanced age-related maculopathy than in
those with early age-related maculopathy. Findings suggest
that a deficit of antioxidants is associated with age-related
maculopathy [Sionelli F et al, Clin
Chim Acta 2002 Ju;320(1-2):111-115].
“Now that we know antioxidants and zinc are helpful in
reducing the risk of severe disease, it is even more important
for older-age Americans to have regular eye exams. Intervening
in at-risk individuals could help reduce severe disease and
vision loss in millions of Americans,” states Dr. Paul
Sieving, Director of the National Eye Institute.
—EH
Tea protects
against stomach and
esophagus cancers
Logic would suggest a protective role for tea against
various gastrointestinal cancers. For example, UCLA scientists
found that tea decreases stomach inflammation, thus reducing
the risk of developing chronic gastritis, a condition that
causes pre-cancerous lesions and can lead to stomach cancer
over time [International Journal of
Cancer 2001 May;92:600-604]. Their study of over 600
Chinese men and women showed that green tea drinkers had a 48%
lower risk of stomach cancer than non-drinkers. An earlier
epidemiological study of 902 cancer patients and 1,552 healthy
controls showed that green tea reduced the risk of esophageal
cancer in women by 50%, and in non-smoking men and women by
60% [J Natl Cancer Inst 1994
Jun 1; 86(11):855-8]. Both studies found that risk decreased
as tea consumption increased.
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However, some scientists suspect that tea drinkers may also
have other healthier lifestyle factors that may help reduce
their disease risk and confound any tea benefit. A team of
U.S. and Chinese researchers, who presented new findings at
the 93rd annual meeting of the American Association for Cancer
Research (AACR), says it now has direct evidence of tea’s
cancer-fighting abilities. They compared levels of tea
polyphenols and several by-products (measured in urine) among
190 cases of gastric cancer, 42 cases of esophageal cancer and
772 healthy controls. The investigators found that tea
drinkers had half the risk of cancer as light- to
non-drinkers, even after factoring in other health behaviors,
such as smoking, drinking, dietary carotene intake and the
presence of H. pylori (the bacteria that causes stomach
ulcers).
—Angela
Pirisi
High
C-reactive protein points to Alzheimer's risk
There may be more to a key protein found in the body than
first meets the eye, when it comes to predicting disease.
C-reactive protein, whose presence has long been known as an
inflammatory marker and predictor of cardiovascular disease,
may also serve as a warning sign for the onset of certain
dementias like Alzheimer’s [Ital Heart J 2001 Nov;2(11):804-6;
Circulation 1998 Feb 10;97(5):425-8; Am J Clin Pathol 2001 Dec;116
Suppl:S108-15].
A prospective study found that high levels of C-reactive
protein may warn of an increased risk of dementia years ahead
of time because it indicates the presence of vascular
inflammation [Annals of
Neurology 2002 Aug].
The inflammation related to disease risk may simply be the
body’s way of responding to the disease itself, says Lon
White, M.D., senior neuroepidemiologist at Pacific Health
Research Institute in Honolulu, and a study co-author.
“As tissue in the brain is lost with dementia, the body
could respond to those losses with inflammatory
processes.”
Researchers compared serum levels of C-reactive protein to
risk of developing dementia in 1,050 men over a 25-year
period. Compared to men with the lowest levels of the protein,
those with the highest level had triple the risk of developing
dementias, even “long before clinical symptoms
appear,” the authors note.
Other studies have hinted at C-reactive protein’s
possible link to the risk of ischemic stroke and the more
subtle stroke-like disorder known as transient ischemic attack
[Stroke 2001
Nov;32(1):2575-9].
White says it’s another piece in a complex puzzle.
“We’re trying to. . . put together what the sequence
of events is that leads to heart disease, stroke,
neurodegenerative diseases—especially in late
life—so that we can begin to put together the most
intelligent approach to modify those pathogenic processes
early on. . . ” he says.
This study corroborates the need to protect against chronic
inflammation.
—John
Martin
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