WHILE the producers of garlic supplements battle over whether consumers are likely to benefit more from a powder or an extract of the "stinking bulb," scientists are zeroing in on exactly what components of garlic might be medically helpful and how the substances work.
The good news is that whatever good garlic does, the effects do not depend upon its culinarily prized but socially scorned scent.
Allicin, the odoriferous chemical formed when a garlic clove is cut or bruised, "is not important at all," said Dr. Herbert Pierson, formerly of the National Cancer Institute who now heads Preventive Nutrition Consultants Inc., an international consulting company in Woodinville, Wash.
"Allicin is highly unstable and degrades instantly in processing, when exposed to heat, oxygen, light, proteins or changes in acidity," he explained. "It is not crucial to any of garlic's biological activities." That is a good thing, because allicin is a toxic substance that can kill cells indiscriminately.
You do not have to purchase supplements to derive garlic's benefits; just eating it in any form or using garlic powder sold as a condiment in grocery stores should do as much good. Furthermore, garlic is not the only member of the allium family that is likely to confer medicinal benefits: onions, scallions, shallots and chives contain many of the same substances and may be equally helpful.
At a recent meeting on so-called designer foods in Washington, organized by Dr. Pierson and Dr. Paul A. Lachance of Rutgers University in New Brunswick, N.J., scientists from research centers around the world used many eight-syllable words and described elaborate laboratory experiments to define scientifically what the Chinese have believed for more than 4,000 years: that garlic seems to have preventive and therapeutic actions on many fronts, from battling infections and neurological deterioration to helping prevent and treat heart disease and cancer.
But the researchers emphasized that garlic is no panacea, nor should it be relied upon as a primary treatment. No one questions that modern antibiotics, a heart-friendly diet and exercise regimen and established treatments for cancer are far more effective than any amount of garlic. Rather, garlic may serve as an adjunct that helps to enhance immune responses, curb coronary risk factors, block the action of carcinogens and perhaps even contain the spread of cancer. Good Things in Garlic
Garlic and its relatives are rich sources of sulfur-containing compounds that have a variety of pharmacological activities. Many of these compounds are formed when allicin breaks down. But just as the amounts of these substances can vary from one garlic bulb to another, depending on the variety or on growing conditions and storage after harvest, the composition of garlic supplements also varies depending upon the processing procedure used. Thus, an oil extract of garlic will contain only those compounds that are fat-soluble and a water-extract will contain only those that are water-soluble. Nonetheless, all forms of garlic -- raw, cooked, dried and powdered, and extracted in oil or water -- contain some sulfur compounds that tests indicate are beneficial to health.
"All garlic products have some efficacy, at least in animal systems," said Dr. John Milner, a nutrition researcher at Pennsylvania State University. "There's not 10 cents worth of difference between any of them."
The product that has undergone the most extensive testing is an odor-free, aged water-and-alcohol extract sold commercially in both liquid and dried forms as Kyolic, manufactured by the Wakunaga Pharmaceutical Company in Hiroshima, Japan. The product's main virtue is that it has been standardized to contain a specific amount of one of the pharmacologically active compounds in garlic, S-allylcysteine.
Some of garlic's constituents act on substances in the blood or directly on blood vessels to reduce the risk of a heart attack. For example, saponins, which are steroid-like compounds, inhibit an enzyme in the muscle cells of arteries, resulting in arterial dilation and a reduction in blood pressure. Other sulfur-containing compounds that act like the antihypertensive drugs known as ACE inhibitors also help to lower blood pressure "without causing side effects like impotence and headaches," Dr. Pierson said. Disease Prevention
Various garlic compounds with antioxidant properties help to lower cholesterol levels in the blood. In people with elevated cholesterol, garlic supplements taken daily for months, including the tablets sold as Kwai that are widely used in Europe, lowered cholesterol levels by an average of from 9 to 14 percent, which should translate into an 18-to-28-percent reduction in heart attack risk. Garlic can also lower levels of potentially harmful blood fats called triglycerides.
Probably more important is the ability of garlic components to reduce the blood's clotting tendency by lessening the stickiness of blood platelets and by promoting anticlotting activity. Scientists at the Washington meeting said garlic is much more potent than aspirin in this regard.
Following leads like the findings that garlic eaters in Iowa have a reduced risk of colon cancer and those in China have a lower rate of stomach cancer, Dr. Milner and others have identified several compounds in garlic that block the formation of potent carcinogens called nitrosamines as well as the gene-damaging effects of other carcinogens.
In animal studies, those treated with garlic and exposed to cancer-causing agents developed fewer cancers than animals that did not get any garlic. Dr. Milner has also studied five human tumors in laboratory cultures and has shown that one garlic compound, diallyl disulfide, is very effective in inhibiting tumor growth. Other studies suggest that garlic can help prevent metastasis, the spread of cancer from its original site to other parts of the body.
Dr. Pierson said that in healthy people, both the liquid and dried forms of aged garlic extract resulted in a rise of natural killer cells. These immune system cells help to block the spread of cancers.
French researchers at the Washington meeting described experiments in laboratory rats with a brain syndrome resembling Alzheimer's disease. They reported that aged garlic extract's antioxidant properties slowed the deterioration of the brain. Other neurological effects included a normalization of the brain's serotonin system, which can cause depression when it malfunctions. Garlic as Food Vs. Garlic Pills
Sales of garlic supplements in the United States are estimated at $100 million a year.
Fresh garlic, even at $2 a pound, is much less expensive than supplements, and garlic powder seasoning is even cheaper, selling for about $2 for four grams, as against $10 to $14 for a quarter teaspoon of active ingredients in a garlic powder supplement, says Dr. Herbert Pierson of Preventive Nutrition Consultants Inc.
Dr. John Milner of Pennsylvania State University reminds consumers that "eating is one of the pleasures of life, and people should be encouraged to eat garlic."
Garlic is least irritating to the body when cooked; when used in dressings, whole unpeeled cloves can be parboiled for a few minutes. For those concerned about garlic breath, Dr. Milner said, "a deodorized form is a viable option."
Anyone who has a bleeding disorder or ulcers or who is taking anticoagulants would be wise to avoid garlic supplement products, since they can promote bleeding. Those who take them should do so only with food or at regular meals and should not exceed the manufacturer's recommended dosage.