Garlic has been used as both food and medicine in many cultures for thousands of years, dating back to when the Egyptian pyramids were built. In early 18th -century France, gravediggers drank a concoction of crushed garlic in wine they believed would protect them from the plague that killed many people in Europe. More recently, during both World Wars I and II, soldiers were given garlic to prevent gangrene. Today garlic is used to help prevent heart disease, including atherosclerosis (plaque buildup in the arteries that can block the flow of blood and possibly lead to heart attack or stroke), high cholesterol, high blood pressure, and to improve the immune system. Garlic may also protect against cancer.
While the science is not conclusive, research shows promise for garlic in the areas of cancer protection and heart-related risk factors for patients.
Garlic is rich in antioxidants, which help destroy free radicals -- particles that can damage cell membranes, interact with genetic material, and possibly contribute to the aging process as well as the development of a number of conditions, including heart disease and cancer. Free radicals occur naturally in the body, but environmental toxins (including ultraviolet light, radiation, cigarette smoke, and air pollution) can also increase the number of these damaging particles. Antioxidants neutralize free radicals and may reduce or even help prevent some of the damage they cause over time.
There are several types of garlic preparations. Most clinical studies have been performed on aged garlic extract (AGE) or enteric coated, dried garlic tablets. The conditions for which garlic is showing the most promise include:
Studies report that garlic consumption may decrease the progression of cardiovascular disease. Cardiovascular disease is associated with several factors, including raised serum total cholesterol, raised low density lipoprotein (LDL), and increased LDL oxidation (free radical damage), increased platelet aggregation (clumping), hypertension, and smoking. Garlic may help decrease LDL and total cholesterol levels while raising good cholesterols (high density lipoprotein, or HDL), decreasing platelet aggregation (helps the blood flow more easily), and decreasing blood pressure. Recently, garlic was also found to decrease two other markers of cardiovascular disease, homocysteine and C-reactive protein.
Garlic may also reduce blood pressure. Numerous studies have reported that oral garlic is associated with reduced systolic and diastolic blood pressure.
A well-designed study of nearly 150 people found that garlic helps prevent and treat the common cold. In this study, people received either garlic supplements or placebo for 12 weeks during "cold season" (between the months of November and February). Those who received garlic had significantly fewer colds than those who received placebo. Plus, when faced with a cold, the symptoms dissipated more quickly among those receiving garlic compared to those receiving placebo.
Garlic may strengthen the immune system, helping the body fight diseases such as cancer. Laboratory studies suggest that garlic may have anti-cancer activity. Studies that follow groups of people over time suggest that people who have more raw or cooked garlic in their diet are less likely to develop certain types of cancer, particularly colon and stomach cancers. In fact, a review of 7 studies researchers found a 30% reduction in risk of colorectal cancer among people who had a high intake of raw or cooked garlic. Dietary garlic may also protect against the development of breast, prostate, and laryngeal (throat) cancers.
- A large-scale study, called the Iowa Women's Health Study, looked at the garlic, fruit, and vegetable consumption in 41,000 middle-aged women. Results showed that women who regularly consumed garlic, fruits, and vegetables had a 35% lower risk of developing colon cancer.
- Garlic may help the immune system function more effectively during times of need such as in cancer. In a study of 50 patients with inoperable colorectal, liver, or pancreatic cancer, immune activity improved after they were given aged garlic extract for 6 months.
- Studies also suggest that aged garlic supplementation may reduce the side effects of chemotherapy, including fatigue and anorexia (lack of appetite). Further, results found that aged garlic decreased heart and intestinal damage commonly seen with certain chemotherapy agents.
While these results are promising, more research is needed to better understand whether dietary intake of garlic and other plants in the same family (such as onions, leeks, scallions, chives, and shallots) truly help protect against cancer.
- Laboratory studies suggest that large quantities of fresh, raw garlic may have antiparasitic properties against the roundworm, Ascaris lumbricoides, which is the most common type of intestinal parasite. Garlic for this purpose, however, has not been tested in people.
- Fresh garlic contains allicin, which is reported to have antibacterial, antiviral, and antifungal properties. Some studies have reported that garlic consumption may kill bacteria known to cause ulcers, but there are also studies that report no effect on this bacteria. Several studies report that topical application of garlic may help treat fungal skin conditions, such as Tinea cruris and Tinea corporis.
- Preliminary studies show that garlic may help combat fatigue. More research is needed.
Garlic is a perennial that originally came from central Asia, and is now cultivated throughout the world. It can grow 2 feet high or more. The most important part of this plant for medicinal purposes is the compound bulb. Each bulb is made up of 4 - 20 cloves, and each clove weighs about 1 gram. Garlic supplements can either be made from fresh, dried, aged, or garlic oil, and each may have different effects on the body.
What's It Made Of?
There are several important components of garlic that have been identified, and many more that have not. Alliin is an odorless sulfur-containing chemical derived from the amino acid cysteine. When garlic bulbs are crushed, alliin is converted into another compound called allicin. Allicin appears to be one of the primary active compounds that gives garlic its characteristic odor and many of its healing benefits. However, allicin is not absorbed effectively by the human body.
To combat this problem, aged garlic is fermented to break allicin down to usable compounds. These compounds are water-soluble sulfur compounds (S-allyl cysteine and others) and a small amount of oil-soluble sulfur compounds. The sulfur containing compounds in aged garlic give the supplement its reported benefits in cholesterol levels, heart disease, and cancer.
Garlic supplements are made from whole fresh garlic, dried, or freeze-dried garlic, garlic oil, and aged garlic extracts.
Not all garlic contains the same amount of active ingredients. There is a wide variation in the amount of important components in both fresh garlic and commercial supplements. The amount of healthy compounds present depends on where the garlic is grown as well as how the product is prepared. Some experts believe that the wide variation in the quantity of active ingredients in garlic preparations explains why there is some variability in how well the substances lower cholesterol, improve blood pressure, and fight infection in different people.
Aged garlic products are made by fermenting garlic. Several clinical studies support the use of aged garlic for cardiovascular disease prevention. Aged garlic is high in sulfur compounds that are easily absorbed and have beneficial effects on heart disease and health.
It is important to read the label on all garlic products carefully. To get the most beneift, use standardized garlic products. Also, follow the directions of a qualified health care provider with knowledge and experience in herbal medicine.
How to Take It
An appropriate medicinal dose for children has not been established. For this reason, use of garlic for health-related reasons in children should be directed by a qualified health care provider who has experience treating children with herbal remedies.
Whole garlic clove (as a food supplement): 2 - 4 grams per day of fresh, minced garlic clove (each clove is approximately 1 gram)
Aged garlic extract: 600 - 1,200 mg, daily in divided doses
Tablets of freeze-dried garlic: 200 mg, 2 tablets 3 times daily, standardized to 1.3% alliin or 0.6% allicin. Products may also be found standardized to contain 10 - 12 mg/Gm alliin and 4,000 mcg of total allicin potential (TAP).
Fluid extract (1:1 w/v): 4 mL, daily
Tincture (1:5 w/v): 20 mL, daily
Oil: 0.03 - 0.12 mL, 3 times daily
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain components that can trigger side effects and that can interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider qualified in the field of botanical medicine.
Garlic is considered to have very low toxicity and is listed as Generally Recognized as Safe (GRAS) by the U.S. Food and Drug Administration.
Side effects from garlic include upset stomach, bloating, bad breath, body odor, and a stinging sensation on the skin from handling too much fresh or dried garlic. Handling garlic may also cause skin lesions. Other, more rare side effects that have been reported by those taking garlic supplements include headache, fatigue, loss of appetite, muscle aches, dizziness described as vertigo (dizziness), and allergies such as an asthmatic reaction or contact dermatitis (skin rash).
Garlic has blood-thinning properties. This is also important to know if you are going to have surgery or deliver a baby. Too much garlic can increase your risk for bleeding during or after those procedures.
Garlic may alter the function of certain prescription medications. If you are being treated with any of the following medications, you should not use garlic supplements without first talking to your health care provider.
Antiplatelet medications -- Garlic may exaggerate the activity of medications that inhibit the action of platelets in the body. Examples of such medications include indomethacin, dipyridamole, Plavix, and aspirin.
Blood-thinning medications -- There have been reports of a possible interaction between garlic and warfarin that could increase the risk of bleeding in people taking this blood-thinning medication. Therefore, when taking medications that may thin the blood, such as aspirin and warfarin, you should not use garlic supplements unless you are under the supervision of a doctor.
Protease inhibitors -- Garlic may reduce blood levels of protease inhibitors, a medication used to treat people with the human immunodeficiency virus (HIV). Protease inhibitors inclue indinavir, ritinavir, and saquinavir.