[665] in Vegetarian_Support_Group
On the Chemopreventive Power of Garlic
daemon@ATHENA.MIT.EDU (arthurl@tiac.net)
Wed Sep 20 08:54:54 1995
Date: Wed, 20 Sep 1995 08:53:07 -0400
From: "arthurl@tiac.net" <arthurl@zork.tiac.net>
To: vsg@MIT.EDU
I came across this article today via Lycos.
Arthur Lobo
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> [M. D. ANDERSON ONCOLOG]
>
> Researcher Studies the Chemopreventive Power of Garlic
>
> Garlic may contain compounds that prevent esophageal and colon tumors
>
> By Sunita Patterson
>
> "Our apothecary's shop is our garden full of pot-herbs, and our doctor
> is a clove of garlic," an anonymous author wrote in 1615. Modern
> science tends to dismiss such folk remedies as superstition, but in
> the case of garlic, this Renaissance writer's beliefs may have a solid
> scientific foundation. Recent studies have suggested that garlic might
> be helpful in curing various skin diseases, in lowering blood
> pressure, and in inhibiting platelet aggregation, possibly reducing
> the risk of heart attack. To the centuries-old lore of the power of
> garlic as an antibiotic, Michael J. Wargovich, Ph.D., associate
> professor of medicine at M. D. Anderson Cancer Center, has added data
> showing garlic's effectiveness in preventing the development of
> esophageal and colon cancer in rodents. Other laboratories have shown
> garlic to be active against mammary cancer, skin cancer, and lung
> cancer in rats.
>
> Because of these results in animals, and because it is a natural,
> edible substance, garlic is promising for cancer prevention in humans,
> said Wargovich, whose laboratory is one of the National Cancer
> Institute's primary screening laboratories for potential colon cancer
> chemopreventives. The search for compounds that prevent cancer has
> intensified with the mounting evidence that many types of cancer are
> caused or triggered by factors relating to lifestyle and environment.
> One of two basic scientists who work alongside clinicians in the
> Department of Gastrointestinal Medical Oncology and Digestive
> Diseases, Wargovich is working on several projects with the hope of
> showing that chemopreventive agents are available on a grocery shelf.
>
> Garlic Extract Prevents Esophageal and Colon Tumors in Rodents
>
> Wargovich encountered garlic's chemopreventive properties almost 10
> years ago, during a postdoctoral fellowship at the Ludwig Institute in
> Toronto, where he developed an assay system for determining whether
> various compounds could suppress the DNA- damaging effects of
> carcinogenic agents. When researchers at New York University later
> found that garlic and onion oils inhibited tumor formation in a skin
> carcinogenesis assay, Wargovich tried the garlic oil in his system and
> was intrigued to find minor suppression of damage to mouse nuclei.
>
> He set out to discover which of the 60 to 100 chemicals in garlic had
> led to the inhibition and found that most of the preliminary work had
> already been done. Since garlic has been used for centuries as a
> flavoring agent, the food industry already had isolated 20 to 40 of
> its chemical components. Wargovich's laboratory bought samples of 13
> of them and began systematically testing them in the colon carcinogen
> assay.
>
> "Right away, we came up with an extremely active substance that to
> this day is one of the most powerful anticarcinogens around,"
> Wargovich said. The compound was diallyl sulfide (DAS), "notorious for
> its odor," he said; "it smells pretty awful in the laboratory."
> Wargovich demonstrated that DAS inhibits the formation of
> 1,2-dimethylhydrazine (DMH)-induced colon tumors in mice. He continued
> his experiments after coming to M. D. Anderson in 1984 and found that
> the amount of tumor inhibition correlates linearly with the dose of
> DAS administered. "I began thinking that DAS might be helpful in other
> sites along the digestive tract," Wargovich said. He undertook a study
> of nitrosomethylbenzylamine (NMBA)-induced esophageal tumors in the
> rat and found that DAS completely inhibited the tumors from
> developing.
>
> Will these results in mice and rats translate into prevention of
> cancers in man? Wargovich is optimistic. He noted that the types of
> tumors induced by DMH and NMBA in rodents are similar to colon tumors
> and squamous cell esophageal cancers seen in humans. However, several
> challenges remain in developing DAS for use by man, he said. First,
> little is known about DAS's distribution around the body. Second,
> because of DAS's distinctive odor and taste, it would be difficult to
> do a blind clinical trial; however, one solution to that problem would
> be to give control subjects lower, noneffective doses of the compound.
>
> A third drawback of DAS is that because it is lipid soluble, it breaks
> down when heated. "If you smell garlic cooking in your kitchen, you've
> destroyed a lot of the compounds that we think are cancer preventive,"
> Wargovich said. Because people are hesitant to eat a lot of raw
> garlic, his laboratory is investigating some of its water-soluble
> components, which persist during limited heating and are far less
> smelly. "We're trying to find a potential chemopreventive agent that's
> palatable," he said. One water- soluble compound that he has found
> effective in inhibiting DMH- induced colon tumors in mice is
> S-allyl-cysteine (SAC). Although larger doses of SAC than of DAS are
> required for inhibition, SAC seems to be less toxic.
>
> Garlic Targets Enzyme Systems in the Liver
>
> The key to garlic's effectiveness in these experiments may not lie in
> its direct effects on the colon and esophagus, but rather in
> preliminary biochemical reactions in the liver. Evidence suggests that
> garlic affects two liver enzyme systems that could be responsible for
> the anticarcinogenic effects, Wargovich said. The first involves a
> form of cytochrome P450 that, in metabolizing DMH and NMBA, activates
> these carcinogens. DAS has been shown to inhibit this enzyme system.
> The second enzyme system involves the liver's detoxification pathway.
> Wargovich has shown that DAS boosts the activity of glutathione
> S-transferase, which joins foreign substances (such as DMH and NMBA)
> with glutathione, forming complexes that are excreted from the liver
> in bile.
>
> Last year, Wargovich and his colleagues found that carcinogenesis in
> the rat esophagus is inhibited if DAS is administered before, but not
> after, NMBA. This result further supported the idea that DAS modifies
> the metabolic activation of NMBA or increases detoxification activity.
> In this study, Wargovich also noted that DAS does not itself promote
> the production of esophageal tumors. This observation was encouraging
> because a number of promising agents that block the early phases of
> carcinogenesis in one organ have been found after chronic testing to
> promote tumorigenesis in another organ and thus cannot be used in man.
>
> Most data suggest that the detoxification pathway is responsible for
> the preventive effects Wargovich has observed, he said. "That's good
> in that we are exposed daily through breathing and food to an array of
> environmental carcinogens," he said. However, if garlic increases the
> detoxification activity in the liver, other medications and analgesics
> are probably excreted along with the carcinogens. The liver doesn't
> recognize the difference between a drug and a poison; both types of
> chemicals are treated the same way, Wargovich said.
>
> Wargovich has been collaborating on this research with Wakunaga
> Pharmaceutical Company, which sells over-the-counter garlic
> preparations in Japan. Whereas Asians have been using garlic
> medicinally for centuries, Wargovich noted, "in this country, we're a
> little behind in using foods and herbs for medication."
>
> Wargovich and Wakunaga researchers have proposed the first clinical
> trial of these garlic derivatives. Since they are beginning to
> understand how DAS and SAC work, they plan to target people who would
> benefit most from them--those who are exposed to high levels of
> carcinogens in their lifestyle. Levels of glutathione S-transferase
> are lower in Japanese smokers than in nonsmokers; the trial would
> reveal whether garlic compounds can boost the levels of this enzyme in
> smokers, thereby restoring the protective detoxifying function of the
> liver. Successful results from this and other trials could lead to new
> chemoprevention regimens for people at high risk of developing cancer.
>
> Anticarcinogenic "Designer Foods" Are a Possibility
>
> Wargovich is often asked whether his results mean people should start
> eating lots of garlic. "My answer is, sure, eat more garlic," he said.
> "But don't go overboard, because it can have toxic effects." Since
> garlic is a good antibiotic, too much can wreak havoc on the
> gastrointestinal system. Wargovich also noted that researchers haven't
> pinpointed a single food that will prevent cancer. "It is likely that
> a mixed diet with a lot of different chemopreventive agents (e.g.,
> fresh fruits and vegetables) will be most effective," he said. (Other
> potential chemopreventive compounds Wargovich is studying are aspirin
> and calcium.) Only limited experimentation has been done with
> combinations of chemopreventive agents (e.g., garlic and citrus
> fruits), but in almost every case, he said, the combination has been
> more effective in inhibiting carcinogenesis than has any single agent.
>
> A project that Wargovich is working on with Dr. Leonard Pike, head of
> the Vegetable Improvement Center at Texas A&M, aims to create a
> "designer food" that is enriched in chemopreventive agents and is
> palatable. This idea combines 1990s technology with an old approach.
> "The major diseases in this country were conquered by
> supplementation--putting vitamins in bread, iodine in salt," Wargovich
> noted. However, one question that is raised by such supplementation is
> where the Food and Drug Administration draws the line between a food
> and a drug.
>
> Pike spent 10 years breeding the sulfur compounds out of onions,
> resulting in the Texas 1015 supersweet onion, which has been very
> popular. Using traditional breeding methods, just as the 19th- century
> botanist Gregor Mendel did, Pike will try to develop a
> garlicky-tasting onion that is rich in the chemopreventive agents
> Wargovich has been studying. "Plant geneticists have long bred crops
> for color, size, and marketability," Wargovich said. "Now they are
> breeding crops for health benefits."
>
> -----
> Physicians who desire additional information may write Dr. Wargovich,
> Department of Gastrointestinal Medical Oncology and Digestive
> Diseases, Box 78, The University of Texas M. D. Anderson Cancer
> Center, 1515 Holcombe Boulevard, Houston, Texas 77030, or call (713)
> 792-7493.
>
> ------------------------------------------------------------------------
>
>
> Next story in the January-March 1994 issue of Oncolog
> Main menu for Oncolog
>
> ------------------------------------------------------------------------
>
> M. D. ANDERSON ONCOLOG
> Volume 39, Number 1 (January-March 1994)
> Copyright 1994 The University of Texas M. D. Anderson Cancer Center,
> Houston, Texas
>
