Garlic has been used as both food and medicine for thousands of years, dating back to when the Egyptian pyramids were built. In early 18th century France, gravediggers drank crushed garlic in wine believing it would protect them from the plague. During both World War I and II, soldiers were given garlic to prevent gangrene. It was also used as an antiseptic and applied to wounds to prevent infection.
Today garlic is used to help prevent heart disease, including atherosclerosis or hardening of the arteries (plaque buildup in the arteries that can block the flow of blood and may lead to heart attack or stroke), high cholesterol, high blood pressure, and to boost the immune system. Eating garlic regularly may also help protect against cancer.
Garlic is rich in antioxidants. In your body, harmful particles called free radicals build up as you age and may contribute to heart disease, cancer, and Alzheimer disease. Antioxidants like those found in garlic fight off free radicals, and may reduce or even help prevent some of the damage they cause over time.
The conditions for which garlic is showing the most promise include the following:
Garlic is most often mentioned as an herb for heart disease and atherosclerosis (hardening of the arteries). But evidence is mixed. Some studies suggest that garlic may help prevent heart disease. It may slow down atherosclerosis and lower blood pressure a little, between 5% and 8%. Most of the studies on high blood pressure use a specific formulation called Kwai. One study that lasted 4 years found that people who took 900 mg daily of standardized garlic powder slowed the development of atherosclerosis. Garlic also seems to act as a blood thinner, which may help prevent heart attacks and strokes.
Earlier studies found that garlic lowered high cholesterol. But almost all recent studies that are high quality have found that garlic didn't lower cholesterol.
Early evidence suggests garlic may help prevent colds. In one study, people took either garlic supplements or placebo for 12 weeks during cold season, between November and February. Those who took garlic had fewer colds than those who took placebo. And when they did get a cold, the people taking garlic saw their symptoms go away faster than those who took placebo.
Garlic may strengthen the immune system, helping the body fight diseases such as cancer. In test tubes, garlic seems to kill cancer cells. And population studies, ones that follow groups of people over time, suggest that people who eat more raw or cooked garlic are less likely to get colon and stomach cancers and cancer of the esophagus. In fact, researchers who reviewed 7 studies found a 30% reduction in risk of colorectal cancer among people who ate a lot of raw or cooked garlic. Garlic supplements do not seem to have the same effect.
A large-scale study, called the Iowa Women's Health Study, looked at how much garlic, fruit, and vegetables were in the diets of 41,000 middle-aged women. Results showed that women who regularly ate garlic, fruits, and vegetables had a 35% lower risk of developing colon cancer.
Garlic may help the immune system function better during times of need such as in cancer. In a study of 50 people with inoperable colorectal, liver, or pancreatic cancer, immune activity improved after they took aged garlic extract for 6 months.
In test tubes, garlic killed roundworms, Ascaris lumbricoides, the most common type of intestinal parasite. But it has not been tested in humans, so researchers do not know if it works in people.
One study found that men with benign prostatic hyperplasia (enlarged prostate) had fewer urinary symptoms when they took garlic, compared to men who took placebo. The garlic also reduced prostate size. More research is needed to see if garlic really helps men with enlarged prostate.
Several studies report that a garlic gel applied to the skin may treat ringworm, jock itch, and athlete's foot.