Garlic is a plant food used all over the world. In many ancient and modern cultures, garlic has been considered a potent medicinal herb, effective in combating heart disease, infections, and cancer. Recent studies support these traditional uses for garlic, making its medicinal properties better recognized and accepted in the United States. However, because garlic contains many active ingredients-including potassium, phosphorus, vitamins B and C, diallyl disulfide, amino acids, germanium, and selenium researchers are not sure which ingredient does what at this point, or if garlic’s components are working alone or in combination.


Cardiovascular Disease

Studies have shown that garlic protects against heart disease and, in some cases, treats existing cardiovascular problems in a number of ways. For instance, garlic prevents platelets, the blood cells needed for clotting, from sticking to one another and to artery walls. By preventing excess clotting, garlic may protect against strokes and coronary thrombosis (blood clots within a coronary artery). It may also deter the development of atherosclerosis by reducing the chance that blood clots will adhere to artery walls. Perhaps it is no coincidence that in countries such as Italy and Spain, where garlic is an important part of the cuisine, arterial disease is much less common than it is in the United States.

In addition, there’s strong evidence that garlic protects the body from heart disease by changing the proportions of the various fats in the blood. In numerous animal and human studies, components of garlic have been shown to lower blood levels of the harmful fats and raise levels of the beneficial high-density lipoproteins (HDLs). Studies have also demonstrated the antioxidant benefits of garlic, which include the protection of LDLs from oxidation, a function that prevents LDLs from sticking to artery walls. A recent “meta-analysis”, a review of previous studies that appeared in the Journal of the American Medical Association, concluded that garlic significantly lowers cholesterol. In one study conducted by researchers at Loma Linda University, subjects were given either garlic or a placebo for six months. At the end of the study, 73 percent of the garlic group showed a 12- to 31-percent drop in cholesterol levels. Interestingly, these researchers reported that about half of those in the garlic group who regularly ate meat showed no significant improvement; in several, cholesterol actually rose. It appears that it is the individual on a vegetarian or high-carbohydrate diet who benefits most from garlic supplementation.

Many medical authorities feel that garlic can also reduce high blood pressure, perhaps by acting as a vasodilator-an agent that causes a widening of the blood vessels. Practitioners in several countries, including Japan and Austria, recognize the value of garlic in the treatment of this condition.

Infection and Immunity

Garlic’s efficacy as a treatment for infection was noted long ago in ancient Egypt, Greece, and Rome. Garlic eaters seemed to have more resistance to disease and fewer deaths in times of plague. During both World Wars, garlic was used to treat troops suffering from typhus, dysentery, and battle wounds. In the former Soviet Union, garlic is still known as “Russian penicillin”.

It has been discovered that garlic does contain substances, such as sulfur-containing compounds, that act against bacteria. In addition, garlic has proven effective against viruses, fungi, and parasites. Both in human studies and in the laboratory, garlic has been effective, for example, against Candida albicans, a fungus responsible for many common infections; Cryptococcal meningitis, a fungal infection of the brain; and two groups of bacteria, Streptococcus and Staphylococcus.


Animal and human studies suggest that garlic may prove to be a potent weapon against cancer. A National Cancer Institute study found that people whose diets are rich in garlic and its relatives, such as onions, have a lower incidence of stomach cancer than do people who consume less garlic. Other researchers have found that garlic inhibits the growth of bladder cancer in mice, both by acting on cancer cells directly and by enhancing the effectiveness of immune cells. In one study in which animals were exposed to a carcinogen that induces breast cancer, raw garlic powder and garlic extract reduced the incidence of breast cancer by 40 to 64 percent. Add to this the fact that garlic does not have the adverse side effects of other forms of cancer therapy, and it’s clear that this food could have implications for a safe, side effect-free treatment for not just stomach, bladder, and breast cancers, but other forms of cancer, as well. This therapy might be particularly useful as an adjunct to conventional cancer treatment.

Liver Disorders

Garlic also appears to defend the body from certain toxins. In laboratory and animal studies, garlic extract was able to protect the cells in the liver from the damaging effects of potent chemicals like carbon tetrachloride. The researchers pointed out that each day, we come in contact with a variety of harmful chemicals and microorganisms, and that, as a result, the incidence of liver disorders seems to be rising. In the ongoing search for substances that prevent or cure liver conditions, perhaps garlic will provide at least part of the answer.

New Recommendations

Garlic’s properties are so extraordinary and so wide ranging that in 1990, a special World Congress was held in Washington, D.C., during which over fifty leading garlic researchers representing fifteen countries presented their most recent research, and discussed the significance of their findings with two hundred participating physicians and scientists. These experts concluded that garlic in various forms can provide great health benefits, including the reduction of cardiovascular and cancer risks in people exposed to the stresses of modern industrialized life, such as the modern processed diet. Increased garlic intake may also help reduce the free-radical damage often associated with pollution and nuclear radiation. Interestingly, the researchers agreed that to provide health benefits, garlic products do not have to contain allicin-one of garlic’s active ingredients-nor do they have to have a garlic odor.

Based on the data then available, the researchers urged the public to increase its consumption of garlic and/or garlic products, suggesting a daily intake of at least one gram.

Food Sources: The consumption of fresh garlic is the least costly means of benefiting from this nutrient. Many studies either used fresh raw garlic, or examined diets that were rich in garlic and related vegetables, such as onions, leeks, and green onions. Although cooking seems to reduce garlic’s effectiveness, most people prefer cooked garlic to raw, and eating cooked garlic is certainly preferable to eating no garlic at all. If, however, you want to avoid garlic’s taste and odor, you can choose supplements, instead.


Garlic preparations are available as liquid extracts, oil-filled capsules, and tablets. The supplements generally contain 100 to 300 milligrams in each pill. Many of these forms are deodorized or specially coated. Fortunately, deodorized garlic seems to be just as effective as the fresh aromatic form. Many studies-such as those showing garlic’s effectiveness in reducing cholesterol and protecting the liver-used Garlic Plus, an odor-modified garlic extract.


There is no Optimum Daily Intake for garlic, but we generally recommend 200 to 1,200 milligrams per day, about 1 to 4 ounces of fresh garlic, or two to three tablets of 500mg each.


There doesn’t appear to be any adverse effect from supplementation with six capsules per day. In some people, fats in the blood may initially rise during garlic supplementation, and then begin to drop. No adverse effects have been noted as a result of this transient rise, even among heart disease patients. Higher doses could cause a sudden drop in blood pressure, and so should be taken under professional supervision only. Some people may experience skin eruptions with higher doses, but this side effect subsides when supplementation is reduced or stopped.