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What Is It?

Along with its well-earned reputation for discouraging friends and repelling potential lovers, this powerful herb has a storied culinary and medical history. Egyptian pyramid builders took it for strength and endurance. Medieval healers recommended it as protection against supernatural forces–vampires in particular. The French scientist Louis Pasteur investigated its antibacterial properties, and doctors in the two World Wars treated battle wounds with garlic juice when other drugs were unavailable. Most recently, garlic has been touted for heart health as well.

A member of the family that also includes onions and scallions, garlic (Allium sativum) imparts a distinctive flavor and aroma when used in cooking. Its healing powers are concentrated in the most odiferous part of the plant and the one that is also used in the kitchen–the bulb.

Health Benefits

When the raw garlic bulb is crushed or chewed, one of its more than 100 therapeutic sulfur compounds–alliin–is converted into allicin, the chemical largely held responsible for garlic’s odor and healing powers. The same conversion from alliin to allicin can occur with supplements specifically designed to dissolve in the small intestine.

Garlic’s healing powers are broad and varied. Researchers are excited about the prospect that garlic may help to protect against certain cancers, for example. That’s because it contains cancer-fighting chemicals called allyl sulfides. In addition, allicin’s antioxidant properties in allicin may inactivate cell-damaging free radicals and assist the immune system in destroying early cancer cells. Specifically, studies have found that garlic is potentially beneficial in preventing digestive cancers, and it may possibly act against breast and prostate cancers as well.

When taken orally, garlic may lessen stomach upset, and when it’s applied topically in the form of an oil, garlic may help heal insect bites and even shrink unsightly but harmless common warts. (When treating warts you can also try taping a piece of fresh garlic onto the area for several nights.)

Specifically, garlic may help to:

Keep the heart healthy. Garlic benefits the heart in numerous ways. By making blood platelets less likely to clump and stick to artery walls, it lessens the risk of atherosclerosis (hardening of the arteries) and a subsequent heart attack. The latest findings indicate that the clot-busting compound ajoene, a derivative of allicin, discourages the development of artery-hardening plaque. A mounting body of research indicates that garlic also works to lower high cholesterol by interfering with its metabolism in the liver, the organ that releases cholesterol into the bloodstream. Cholesterol levels may fall as a result. Various trials have found that garlic supplements can lower LDL (“bad”) cholesterol and triglyceride levels while raising the level of HDL (“good”) cholesterol. While not all trials report such positive results, it may be worth trying garlic along with other cholesterol-lowering supplements.

In addition, garlic may promote heart health by maintaining the flexibility of the aorta, the major artery that carries blood from the heart to the rest of the body and one that tends to stiffen with age. In a small, placebo-controlled study involving 70-year-olds, those who took garlic for two years ended up with much more flexible aortas than those who were given a placebo. In addition, by widening blood vessels so the blood can circulate more freely, garlic may slightly lower blood pressure.

Fight colds, flu, sore throat, and other types of infections. Garlic’s antiseptic and antibacterial abilities were actually recognized centuries ago. Modern research confirms that, at least in the laboratory, the herb fights the germs responsible for causing the common cold, flu, sore throat, sinusitis, and bronchitis. Findings indicate that one of garlic’s therapeutic constituents, allicin, blocks key enzymes that aid bacteria and viruses in their effort to invade and damage tissues.

Treat vaginal yeast infections. Garlic extract reportedly counters Candida albicans; when given the chance to proliferate, this naturally present organism is responsible for causing most yeast infections. Research suggests that the genital itching, inflammation, and thick discharge associated with vaginal yeast infections may abate with garlic treatment.

Control athlete’s foot, swimmer’s ear (otomycosis), and other fungal skin infections. Laboratory studies indicate that compounds in garlic–probably allicin or closely related chemicals–can inhibit unwanted fungi. It’s unclear whether taking garlic orally will fight these types of infections, but garlic oil applied directly to the area is worth a try. Note: Garlic has also been found to be useful for a number of other disorders. For information on these additional ailments, see our Dosage Recommendations Chart for Garlic.


fresh herb

Dosage Information

Special tip: When purchasing pills, look for those that supply 10 mg of alliin, with a total allicin potential of 4,000 mcg; this is approximately the same amount found in one clove of fresh garlic.

For general health: take 400 to 600 mg of garlic once a day.

For colds, sore throat, and flu: take 400 to 600 mg of garlic four times a day until symptoms clear up.

For high cholesterol, high blood pressure, and heart disease prevention: take 400 to 600 mg of garlic once or twice a day. Be sure to check out our Dosage Recommendations Chart for Garlic, which lists therapeutic dosages for specific ailments at a glance.

Guidelines for Use

It’s a good idea to take garlic with food to buffer its strong odor and aftertaste.

Because heating garlic can destroy many of its therapeutic compounds, it’s best to rely on supplements when treating a specific disorder. Studies indicate, however, that letting crushed raw garlic rest for 10 minutes before heating does increase levels of allicin and other beneficial compounds.

Many experts contend that supplements made from pure garlic powder are the most effective.

So-called “deodorized capsules” may effectively remove odor, but manufacturing processes may deplete the garlic’s therapeutic effects.

In fact, if strong “garlic” breath normally discourages you from taking this herb, try enteric-coated supplements. By passing undigested through the stomach and into the intestines, these pills dramatically reduce the risk for bad breath. They also promote full absorption of the allicin.

Garlic supplements can be taken indefinitely.

General Interaction

Because medicinal amounts of garlic may intensify the effects of medications designed to prevent blood clots (anticoagulants or aspirin) or to reduce high blood pressure (antihypertensives), consult your doctor before combining garlic and these drugs.

Garlic may interfere with the action of drugs that lower blood sugar; consult your doctor before taking both at the same time. Note: For information on interactions with specific generic drugs, see our WholeHealth Chicago Drug/Nutrient Interactions Chart.

Possible Side Effects

Some people have trouble digesting garlic, which can irritate the stomach lining and cause nausea or intestinal gas. Large doses in particular can cause heartburn and diarrhea.

Large quantities of garlic can cause body odor and bad breath. This is particularly problematic for people who lack the liver processing system for detoxifying allicin.


Avoid garlic supplements before surgery because the herb’s anticlotting actions may prolong bleeding from a surgical wound.

If you plan to take garlic for cholesterol problems, have your doctor check your cholesterol levels after three months to see if they have changed; if they haven’t, talk with your doctor about other options.

Avoid taking garlic supplements or consuming medicinal amounts of garlic during pregnancy; although no problems have been reported, lab tests suggest that irregular uterine contractions may develop.


Athlete’s Foot Apply to affected areas twice a day.
Colds 400-700 mg 3 times a day for five days. Dose can be reduced to once a day for maintenance purposes after this.
Earache Place a few drops oil in the ear twice a day.
Flu 400-700 mg 3 times a day for five days. Dose can be reduced to once a day for maintenance purposes after this.
High Blood Pressure 600 mg twice a day
High Cholesterol 400-600 mg a day
Sore Throat 400-600 mg 4 times a day with food.
Yeast Infection (Vaginal) 250-350 mg (providing 4,000-5,000 mcg allicin) twice a day

Doctor Recommendations
David Edelberg, M.D.

Probably more research has been done (and more articles written) about garlic than any single herb you’ll find at the health-food store. The array of garlic products is vast, claims for it spectacular, and information about it very confusing. Worldwide, research is ongoing about the role that garlic plays in lowering blood cholesterol, protecting against artherosclerosis, reducing blood pressure, and even preventing cancer and stimulating the immune system. Every once in a while, an article finds that garlic doesn’t really lower your cholesterol or protect your heart. Understand, this is simply a small negative blip in the long and positive therapeutic saga of this astonishing herb.


Have you just had a close-packed elevator trip or a long plane ride with some sneezing, coughing people? Are the surrounding office cubicles filled with cold victims? Is your throat getting a little painful? Just remember when you’re fighting a cold, garlic (like your other standbys echinacea and vitamin C) is an excellent resource because it has both antiviral and immune-stimulating properties. Start early. Chewing a garlic clove twice a day at the first sign of cold symptoms is one approach. But if you have some issues about sporting breath that only a mother could love, get supplements and start taking a capsule four times a day. Three or four days later, depending how you feel, drop the dose to three times a day until you’re all better.


Garlic comes in a number of forms, starting with the fresh clove, and also including capsules, tablets, softgels, oil, powder, and liquid. Pure garlic powder seems to be the key ingredient in top-quality products; recent studies have shown this is the most effective form. Enteric-coated capsules help prevent garlic breath; they also pass through the stomach undigested, which actually helps with the formation of allicin, key to many of the therapeutic effects of this herb. Deodorized capsules are somewhat problematic. Although efficient at removing odor, various manufacturing processes may also deplete the garlic’s therapeutic effect. While supplement companies are working out the kinks, enteric-coated products are probably your best bet.


Allicin, the active ingredient in garlic, is formed within the body from another compound called alliin. For an effective dose of garlic, studies have shown that you need to get 10 mg of alliin, with a total allicin potential of 4,000 mcg. This is about the same as eating a clove of garlic (the allicin is released when you simply crush or chew a clove).


Taking garlic supplements with food will help to temper the potent aftertaste. A word about digesting garlic. Not everyone can tolerate this substance. It can irritate the lining of your stomach, and may produce queasiness and nausea. Or you may lack the liver processing systems for detoxifying the allicin, meaning the garlic gets excreted through your skin instead. (You’ve probably stood next to someone literally reeking of garlic: This person either has eaten too much garlic or has a detoxification problem.) So, if you can tolerate garlic, then enjoy! Take the enteric-coated tablets, but also think of new ways to use powdered or chopped raw garlic in your meals. Be imaginative. Perhaps the day will come when you’re actually excited when Ben & Jerry’s newest ice cream flavor is Garlic Crunch. And, except for its 12% butterfat, it might actually be good for you.

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