In medical laboratories, garlic
is coming up roses
By Judy Foreman
02/19/96
Garlic, the "stinking rose" beloved by gourmets
and health gurus for nearly 4,000 years now, is finally getting
respect from the mainstream medical establishment.
First mentioned in 1550 B.C. in an Egyptian
medical papyrus, then given a whiff of credibility in 1858, when
Louis Pasteur discovered that its juice kills bacteria, garlic is
now one of the hottest phytochemicals - plant compounds - in medical
research.
In cancer centers, government labs and dietary
supplement factories, garlic in all its many forms - raw and
raunchy, stewed and sweet, deodorized and dandified - is being
hungrily studied, not to mention munched, by eager scientists.
But the more they tease apart the 60-to-100
compounds in garlic's crescent-shaped cloves, the more complicated
its chemistry turns out to be.
In fact, the chemistry is so ridiculously
complicated - you definitely don't want the details - that garlic
supplement manufacturers could almost, but not quite, be forgiven
for all their glaring omissions, spurious claims and misleading ads.
Such sins aside - for the moment - there's no
question that garlic research has become mainstream and that
scientists are starting to understand how garlic may help fight
cancer, heart disease and other ills, just as old wives' tales have
long said. Several
months ago, for instance, the National Cancer Institute, long
interested in the potential of some foods and herbs to prevent or
treat cancer, threw its weight behind a study of 3,600 people in
Shandong province in China. In 1988 and 1989, epidemiological
studies of thousands of people in Shandong had shown that the risk
of stomach cancer was lowest among people who ate the most garlic.
To find out if garlic can actually prevent cancer
in high-risk people, NCI epidemiologist Linda Morris Brown and
others have begun a randomized clinical trial in which Shandong
residents will get supplements of aged garlic extract and others, a
look-alike placebo.
While it might have been better in some ways to
let some people simply eat more garlic than others, says Brown,
supplements were necessary to ensure that the trial subjects didn't
know who was getting the extra garlic and who was not, lest those
expectations - the placebo effect - influence the results.
And that's just one sliver of a growing body of
research, some of it paid for by supplement manufacturers, on
garlic's medicinal potential.
Several months ago, Pennsylvania State University
researchers found in a randomized, double-blind study of men with
high cholesterol that aged garlic extract has a "mild
cholesterol-lowering effect."
Brown University researchers found much the same
thing in 1994. Nine 700-mg capsules of aged garlic extract a day
lowers cholesterol by a modest 8 percent, says Robert I-San Lin, a
co-author of the study. Lin is also director of nutrition at the
Nutrition International Co. in Irvine, Calif., which sells vitamins
and meal supplements and helped support the study.
At a garlic conference in Berlin last fall,
British and Australian researchers pooled data from 16 studies on
cholesterol and found that garlic has a small beneficial effect.
In similar work involving eight pooled studies on
blood pressure, they found that garlic lowered systolic blood
pressure (the top number) by about eight points and diastolic
pressure (the bottom number), by 5 points.
Garlic may also fight cardiovascular disease in
yet another way - by reducing the tendency of platelets in the blood
to clot and stick to artery walls.
And emerging data suggest garlic can fight cancer
as well.
Dr. Manfred Steiner, a hematologist at East
Carolina Medical School in Greenville, N.C., has found that SAMC
(S-allyl mercaptocysteine, a consituent of aged garlic extract) can
stop the process by which cells divide and grow in both normal and
cancerous cells, at least in the test tube.
"You add these compounds and you can watch what
happens," he says. "Cell growth slows and cells die off."
Like Steiner, John Pinto, a biochemist at
Memorial Sloan-Kettering Cancer Center in New York, has documented
the ability of garlic to slow cell growth and says it may help fight
cancer in other ways as well.
SAMC, for instance, may keep cancer from getting
started by protecting the genetic molecule DNA against damage from
free radicals, the destructive forms of oxygen that are formed as
food is burned. In test tube experiments, Pinto has found that SAMC
protects against this damage by boosting glutathione, a natural free
radical fighter.
SAMC and its chemical cousins may also act as
chemical pumps, Pinto adds, pushing into overdrive a complex family
of enzymes that detoxifies carcinogens and drugs, the so-called
cytochrome P-450 system.
By activing these enzymes, garlic seems to help
keep carcinogens away from DNA and then, using other molecules, to
escort the carcinogens out of cells, Pinto says.
Microbiologist Michael Wargovich at the M.D.
Anderson Cancer Center in Houston, who is also studying garlic's
effects on the P-450 system, agrees. In fact, his latest project,
presumably awaited with bated breath by backyard chefs, is to find
out whether garlic can detoxify the carcinogens created when
hamburgers are burned.
And other recent studies, including two supported
in part by Wakunaga of America Co., the world's leading manufacturer
of garlic supplements, have shown that garlic constituents may
retard bladder and breast cancers in rodents.
All of which, of course, is music to
manufacturers' ears.
The public is so ga-ga about garlic, in fact,
that the world market for supplements is now $ 250 million a year,
says William Sterling, director of sales and marketing for Wakunaga,
which has the lion's share, $ 200 million a year.
But the mere fact that sales are booming does not
mean that supplements are any better than natural garlic. And you
certainly won't find much enlightenment on the labels.
Many labels don't even say which compounds are in
the product, much less how they may help or harm you, because
supplements are not tightly regulated by the US Food and Drug
Administration, as drugs are.
And labels often make little sense, like some
touting a garlic component called allicin. Some products may not
even contain active allicin because allicin breaks down so easily,
says biophysicist Lin of California.
And even those with allicin "potential," which
are supposed to creat allicin in the body when mixed with water, may
not do so because stomach acids block allicin formation, he adds.
Besides, even if you could get lots of allicin
into your system, it might not be a good idea because allicin can
irritate the digestive tract, just as raw garlic can. In fact, the
nutritionists who run the Garlic Information Center in New York say
supplements without allicin may be safer than raw garlic.
The real problem, though, is not that supplement
makers are making a bundle on our garlic gullibility, but that
researchers, despite recent progress, still don't have the answers.
"We still don't know precisely which constituents
of garlic work best or whether it's better to eat real garlic or
take supplements," says Dr. Richard Rivlin, program director of the
clinical nutrition research unit at Sloan-Kettering.
Nor does anybody know how much garlic we should
consume, though Lin of California, is willing to offer his best
guess.
He recommends a daily dose of 10 grams (or three
cloves) of natural garlic, which is equivalent to 4 grams of garlic
powder or 40 milligrams of garlic oil, though cloves, powders and
oils all have different constituent chemicals.
(There's no way to translate natural garlic into
aged extract equivalents because some compounds in the extracts are
not in raw garlic.)
However you take it, the bottom line, as Pinto of
Sloan-Kettering puts it, is that "some garlic is better than none."
A garlic chemistry
primer
The main component in raw garlic is alliin. But
as soon as you crush or cut a clove of garlic, an enzyme called
alliinase is released, converting alliin into allicin.
Allicin, which gives garlic its odor, is a strong
oxidant, that is, a chemical that creates free radicals, which in
excess, can be dangerous. Allicin can cause stomach irritation and,
in rare cases, hemolytic anemia, destruction of red blood cells. If
if placed directly on the skin, allicin can cause blistering.
During cooking, allicin produces ajoene, DADS (diallyl
disulfide) and other compounds that may help keep blood from
clotting.
During aging, alliin and allicin are converted to
water-soluble compounds such as S-allyl cysteine and S-allyl
mercaptocystine, which have little odor, are stable and survive
cooking. These are among the ingredients in "aged garlic extract"
supplements and may help combat cancer and protect against heart
disease.
Garlic also contains oil-soluble compounds like
DAS (diallyl sulfide) and DADS which may have beneficial effects on
blood pressure, lipids and clotting and may help prevent cancer.
Where to call
For more information on garlic, you may call:
·
The Garlic
Information Center hotline, 1-800-330-5922, The line was set up last
year by researchers at Cornell University Medical College.
