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A clove a day?

A Clove a Day?

"But for its odour," wrote Charak, the father of Hindu medicine, it "would be costlier than gold."

Hippocrates used it to treat people for pneumonia and infected wounds.

In 1858, Louis Pasteur announced that it killed bacteria.

During World War I it was rubbed on wounds to prevent gangrene. During World War II it was called "Russian penicillin."

Today, it's used by millions of people to prevent or treat everything from baldness to athlete's foot.

But just tell your doctor you want to eat garlic to help keep your heart healthy or protect you from cancer, and you'll get either a shrug or a stern lecture about the folly of folk medicine.

Your doctor may be right. But that could change. Research is beginning to show that Charak and the others may have known whereof they spoke.


Is garlic good for our hearts?

It's too early to tell for sure, but preliminary studies in animals and humans hint that garlic may lower levels of artery-clogging fats like LDL ("bad") cholesterol, and raise HDL ("good") cholesterol.

Garlic may help prevent heart disease in other ways, too. It appears to lengthen the time it takes blood to clot, and may actually help dissolve clots. (Most heart attacks and strokes occur when blood clots get stuck in narrowed arteries.)

Scientists have a clearer picture of garlic's effect on animals than on humans. When they fed raw garlic or garlic oil to rabbits and rats, LDL cholesterol dropped and HDL rose. But the amounts were equivalent to 14 to 230 cloves per day for a human.

Garlic also seemed to prevent--and even reverse--the early stages of atherosclerosis.

When researchers fed rabbits a cholesterol-raising diet for three months, fatty plaque deposited in their arteries. Nine months later, animals that were given 1 to 1 1/2 mg of garlic oil in their daily chow had fewer than half as many deposits as rabbits that received no garlic.(1)


Most studies in which people were fed large quantities of garlic show the same results: decreases in total cholesterol and LDL cholesterol, and increases in HDL cholesterol.

But many of these studies suffered from poor design. * Some had no control (untreated) groups, so researchers had nothing to compare their results against. * In others, participants or researchers may have known who was eating garlic and who was in the control group, and that may have biased the results. (In most garlic studies, it quickly becomes apparent who's getting the garlic.) * Many failed to ask the participants what they were eating before--or even during--the experiments. That makes it difficult to tell what caused the improvements: dietary changes, garlic, or both.

In one of the better studies, Benjamin Lau and his colleagues at California's Loma Linda University fed four capsules per day of Kyolic extract, an odor-free garlic supplement, to 15 volunteers with high cholesterol.(2) (The company says it isn't possible to translate that dose into a specific number of cloves per day.)

The researchers fed indistinguishable (but garlic-free) "placebo" pills to the control group--12 volunteers with equally high cholesterol. Lau cautioned all the volunteers not to change their diets.

After six months, 11 of the 15 volunteers who were given garlic had lowered their cholesterol by more than ten percent; only two of the 12 volunteers in the control group had lowered theirs at all.

While these numbers are encouraging, keep in mind that Lau only looked at 27 people for six months. Also, each person got either garlic or a placebo. A better test would have compared each person's cholesterol after being switched from a "placebo" to garlic or vice versa.


Lowering cholesterol is not the only way garlic could help prevent heart disease. It may also increase the blood's ability to dissolve clots.

Arun Bordia, of the Bombay Hospital Research Centre in India, fed garlic oil (equal to close to 11 cloves of raw garlic per day for a 150-pound person) to healthy people, people who had a history of heart attack, and people who had recently suffered a heart attack.(3)

After three months, all groups showed improved fibrinolytic activity (a rough measure of the blood's clot-dissolving capability). The improvement was greatest in the healthy people, but changes also were apparent in those with old or recent heart attacks.

Other studies are looking at whether garlic can make blood less "sticky," which would prevent clots from forming in the first place.

Eric Block, head of the Department of Chemistry at the State University of New York at Albany, has discovered (and patented) ajoene, a component of garlic that seems to make blood platelets less sticky, which helps slow down clotting. At least that's what it does in test tubes.

Block cautions that it's a big jump from the laboratory to the human body. "It's difficult to determine how much value is retained after it [the ajoene] has been cooked, ingested, digested, and absorbed," he says.

Ajoene may be inactivated by very high temperatures. "If you're cooking below the boiling point of water, ajoene won't be destroyed," says Block. "But if you're frying, particularly deep frying, it may start to be destroyed."


Though people have used garlic as a natural antibiotic for centuries, it's in the lab where garlic's anti-microbial properties have been most clearly observed.

It inhibits the growth of or kills two dozen kinds of bacteria (including Staphylococcus and Salmonella) and at least 60 types of fungi and yeast.

The hero appears to be allicin, the chemical that's responsible for garlic's smell. So if you destroy the aroma--by cooking or processing--garlic may lose its ability to battle microbes.

During the days before synthetic antibiotics, garlic was often used to fight tuberculosis. Recently, Edward Delaha and Vincent Garagusi, of Georgetown University Hospital, set out to confirm garlic's ability to kill tuberculosis and similar microbes, known as mycobacteria.(4)

They added an allicin-rich garlic extract to 30 strains of mycobacteria growing in test tubes. A month later, the garlic had done critical damage to all 30.

Garagusi says he has approached several pharmaceutical companies with his findings, but that he has been unable to drum up any interest in garlic "therapy."

The pure extract is very unstable, he explains, "so we would need to find methods to extract and stabilize it. And that's why the resources of a large pharmaceutical company would be important."


Garlic may protect against cancer--at least in laboratory animals.

In an experiment by Michael J. Wargovich, of Houston's M.D. Anderson Hospital, mice that were fed a component of garlic (diallyl sulfide) before being exposed to a cancer-causing chemical had 74 percent fewer colon cancer tumors than mice that received no garlic.(5)

Wargovich speculates that large quantities of diallyl sulfide could help the liver detoxify the carcinogen.

Other animal studies show that garlic's sulfide compounds can inhibit the development of cancer of the lung, large bowel, and esophagus.

There is no solid evidence that garlic can protect humans against cancer, even in enormous doses. That may be because it doesn't, or simply because few good human studies have been done.

At least not until now. "The National Cancer Institute is looking at ten compounds that are dynamite in preventing cancer in animal studies," says Wargovich.

If the NCI determines that the compounds are safe, the next step would be to study their effects in humans. And if those studies are positive, Wargovich says the food industry could fortify products with the compounds.

"You'd have designer foods that help prevent cancer," he says.


How much garlic do you need to get its presumed benefits? Not even the researchers agree.

In many of the studies designed to lower cholesterol, large quantities of specially prepared garlic extracts were used. But they were extracted, stored, and administered under laboratory conditions.

Most researchers don't report how much garlic it took to produce a day's worth of extract, so it's not possible to translate their doses into a cloves-per-day equivalent.

As for protection against infection or cancer, there's not enough experimental results to even guess at an effective dose.

And, until more commercial garlic supplements have been used in research studies, there's no way to tell how much (if anything) most of them are worth.


If you enjoy the taste of garlic, but aren't quite ready to take the 10-or-more-a-day plunge, you can always add a couple of crushed cloves to your favorite soup, stew, or chili. (Do it a minute or two before serving to preserve the active ingredients--and the strongest flavor.)

Or, you can rub the bottom of your salad bowl with a crushed clove or two before cutting up your greens (then mince the garlic and add it to the salad).

Look at it this way: Even if you don't get a "therapeutic" dose, and even if garlic has no magical properties, by using it instead of salt and fat, you'll have improved your diet.

And, you'll finally be able to figure out who your friends are.

(1)Artery 7: 428, 1980. (2)Nutr. Res. 7: 139, 1987. (3)Athero. 28: 155, 1977. (4)Antimicro. Agents Chemo. 27: 485, 1985. (5)Carcinogen. 8: 487, 1987.
COPYRIGHT 1989 Center for Science in the Public Interest
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Article Details
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Title Annotation:garlic
Author:Schmidt, Stephen
Publication:Nutrition Action Healthletter
Date:Dec 1, 1989
Previous Article:How's your diet? Take the CSPI nutrition quiz.
Next Article:Sorting out the soups.

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