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.