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LE Magazine November 2000
In The News
 Soy isoflavones help
prevent urological cancer
There's been some debate over whether the chemopreventive
benefits of soy bean foods lie in their isoflavone content as
a whole, or if individual compounds are to be credited. A new
study shows that isoflavones, such as genistein and daidzein,
work synergistically to inhibit cancer growth and induce
apoptosis (Clin Cancer Res 2000 Jan;6[1]: 230-6). After
analyzing the effects of soy on several bladder cancer cell
lines, researchers at the National Cheung Kung University
suggested the potential use of soybean foods as a means of
chemoprevention for urinary tract cancer. The investigators
administered isoflavones individually in various doses or in a
mixed regimen to mice. Inhibition of cancer cell growth was
observable with each independent type of isoflavone in all
cancer cell lines that were tested. Overall, though, genistein
was the most potent in its preventive action, and the combined
regimen of all three forms of isoflavones had the greatest
inhibitory effect than any of the single compounds exerted.
Soy and its isoflavone constituents in general have already
been shown to be chemopreventive in previous research.
For example, a meta-analysis of peer reviewed studies and
reports from 1966-1998 by researchers at the West Virginia
University School of Medicine revealed that a number of
epidemiological studies support the use of dietary agents to
protect against various urological forms of cancer, including
the bladder, prostate and kidney (J Urol 1999
Jun;161[6]:1748-60). Among the reviewed findings, strong
evidence surfaced about the preventive effect of soy protein
consumption-in addition to reduced fat intake, vitamin E and
selenium-against prostate cancer. When Ohio State University
researchers compared the effects of diets containing soy
protein isolate (whole soy protein with low isoflavone
content) and soy phytochemical concentrate (isoflavone-rich
soy extract with 85 times the amount found in soy protein),
they found a dose-dependent benefit with regards to higher
isoflavone consumption (J Nutr 1999;129:1628-35). While mice
on a soy protein diet had tumors that were 11% smaller than
control mice consuming milk protein, those that received a
combined diet of soy protein and the phytochemical concentrate
had tumors that were 40% smaller than the controls. In
particular, genistein (the main isoflavone in soy) is believed
to be chemopreventive because of its anti-estrogenic activity.
Moreover, it inhibits carcinogenic enzymes, including
tyrosine-specific protein kinases, as well as DNA
topoisomerases. It also inhibits angiogenesis, the growth of
blood vessels, which cancer cells require to fuel their
growth, as well as promoting apoptosis in cancer cells. In
fact, two thirds of research that examined the effects of
genistein on in vitro and in vivo cancer models suggests that
it significantly reduced the risk of cancer (J Nutr 1995
Mar;125[3 Suppl]:777S-783S). One animal study reported that a
genistein diet significantly increases antioxidant activity in
various organs, such as catalase in the small intestine, liver
and kidney, the activity of superoxide dismutase and
glutathione peroxidase in skin, and glutathione reductase in
skin and the small intestine (Nutr Cancer 1996;25[1]:1-7).
These results followed a 30-day diet of the soybean isoflavone
genistein.
Just as no single dietary means serves a magic bullet for any
disease, though, the Chinese study authors suggest that soy
consumption could be considered part of a whole preventive
dietary approach. They comment that, "Taken together with the
fact that diets high in vegetables and fruits are the most
effective means of preventing bladder cancer, dietary change
can be considered a practical strategy in confronting urinary
tract cancer." -Angela Pirisi
Growth hormone may help treat Crohn's
disease
The cause of Crohn's disease, a chronic inflammatory
disorder of the bowel, remains still largely unexplained,
which is what makes it difficult to treat. Theories suggest
that Crohn's may be the result of an infection or toxin that
alters the permeability of the gut, while others believe that
a genetic defect may predispose certain individuals to the
chronic inflammation. So far, a number of treatments exist but
with variable results. These have included immunosuppressive
drugs, anti-inflammatory drugs, antibiotics, narcotics, a
high-protein diet and regulatory peptides such as growth
hormone. A recent study published in the New England Journal
of Medicine (2000;342:1633-7) suggests that administering
growth hormone (GH) to patients with Crohn's disease may help
to resolve many of the symptoms associated with the
disorder.
The four-month study examined 37 adults with moderate to
severe Crohn's disease, 19 of which were put on a regimen of
daily self-injections of GH (5 mg/day for first week, then 1.5
mg/day), while the remaining 18 received placebo. In addition,
the test group was instructed to raise their protein intake to
2 grams per kilogram of body weight. Results were then
measured using a self-report disease activity scale of 0-600,
whereby a higher number means more disease activity. While
side effects associated with taking GH included edema in 10
patients, and headaches in five, they dissipated within two to
three weeks of being on a maintenance dose. Results showed
that the GH group experienced a marked improvement in symptoms
within the first month of the self-administered treatment, and
an increasing benefit over the next three months. Disease
activity scores revealed that 14 of the 19 GH patients had a
decrease of over 90 points, eight of whom had a score reduced
by 150 points, and four of whom showed a drop of over 300
points. More specifically, the GH group showed significant
improvement in three areas of disease activity by the end of
the study, which included the number of liquid or very soft
stools per day, the severity of abdominal pain and well-being.
In addition, half of the patients in the GH group who were on
medication were able to reduce their dose. Contrarily, the
placebo group showed no significant improvement in disease
activity, and 11% of them required more medication. While the
authors aren't sure of how GH may benefit Crohn's disease,
they do note its positive effect on gut growth and function in
conditions such as Crohn's. "Growth hormone" they write,
"enhances the uptake of amino acids and electrolytes by the
intestines, decreases intestinal permeability and increases
intestinal protein synthesis in animals." Meanwhile,
supplemental protein intake, add the researchers, "has been
shown to enhance the synthesis of protein by muscles and
overall. The beneficial effect of supplemental prote in on the
intestinal tract is further enhanced when growth hormone is
administered."
This authors hope that growth hormone may prove effective for
Crohn's disease patients, while boasting less severe side
effects than other therapies. A large multicenter study, state
the researchers, would help confirm their findings and
determine the most appropriate GH dosage, rate of
administration and length of treatment to maximize benefits.
-AP
Folic acid from fortified cereals
and supplements best at lowering homocysteine levels and heart
disease risk
 For the longest while,
extolling the virtues of folic acid have followed along the
lines of its ability to reduce the risk of birth defects, such
as spina bifida. Besides being an essential nutrient in
pregnancy, folic acid has also been recommended as an
effective tool in the war against heart disease. The link in
both preventive instances has been that this powerful B
vitamin-found in green, leafy vegetables, orange juice, beans
and fortified grains-works by activating an enzyme called
methylenetetrahydrofolate reductase (MTHFR) that regulates
blood levels of the amino acid homocycteine (tHcy).
Previous research, such as findings presented at the 20th
Congress of the European Society of Cardiology in Vienna by
Greek researchers, report that low levels of folic acid were
closely linked to the incidence of acute heart attacks.
Another study from the University of Michigan announced that
about 10% to 50% of heart patients have high blood levels of
tHcy. While it is known that tHcy levels correlate inversely
to folic acid levels, the question of how much folate is
enough to prevent cardiovascular disease and what are the best
sources are still pending. While multivitamins typically
include 400 mcg of folate, an amount that's known to reduce
tHcy concentrations, most U.S. adults don't achieve this level
through their dietary intake. Moreover, a new study published
in the American Journal of Clinical Nutrition
(2000;71:1448-54) suggests that folic acid-rich foods don't
seem to reduce tHcy levels nearly as effectively as a
supplement or folic-acid enriched breakfast cereals do.
This study, led by researchers at the University of Otago, in
Denedin, New Zealand, compared three approaches for increasing
dietary folate to a target intake of about 600 mcg per day
with a view to reducing tHcy levels. Enrolled were 65
subjects, aged 36-71, with high tHcy levels and a baseline
folic acid intake of about 250 mcg. The researchers examined
the relative effects of folic acid supplementation,
consumption of folic acid-fortified breakfast cereals and a
higher intake of folate-enriched foods over a 12-week period.
Compared to a control group, results showed that taking a
daily supplement reduced tHcy levels by 21% and folic
acid-fortified breakfast cereals decreased levels by 24%,
while folate-enriched foods brought tHcy down by only 9%. This
was despite the fact that all three folic acid sources raised
blood folate levels. The reason for the disparity among these
figures, suggest the researchers, may boil down to the
bioavailability of folate from various sources. Apparently, as
little as 50% of folate is actually available from food-based
sources that make up a mixed diet. The study authors conclude
that, "Daily consumption of folic acid-fortified breakfast
cereals and the use of folic acid supplements appear to be the
most effective means of reducing tHcy concentrations." -AP
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