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Garlic (Allium sativum)

Posted on Dec. 30, 2005, 8:01 p.m. in Botanical Agents


Garlic has been renowned for its medicinal properties throughout history. It is referred to in both the Bible and the Talmud, and Hippocrates, Galen, and Dioscorides all mention the use of garlic for many conditions, including parasites, respiratory problems, poor digestion, and low energy. By 1500 BC, the Egyptians had identified 22 different uses for garlic ranging from headaches to general physical weakness. Today, the herb figures in a seemingly endless array of remedies for everything from insect bites and fever to intestinal ailments. The main active ingredient of garlic is the sulfur compound allicin, produced by crushing or chewing fresh garlic, which in turn produces other sulfur compounds, including ajoene, allyl sulfides,  and vinyldithiins.


Garlic contains amino acids, various vitamins and trace minerals, flavonoids, enzymes, and at least 200 additional compounds. Researchers have documented garlic’s potential to  reduce heart attacks by lowering the levels of blood fats, including triglycerides and LDL ("bad") cholesterol, and raising "good" HDL cholesterol levels. In one recent study, Russian researchers determined that garlic’s beneficial effects on cardiovascular health could be attributed to both direct actions on the walls of heart arteries and to indirect preventive actions at the cellular level. In other words, garlic is a doublebarrelled weapon against heart disease. Numerous studies also indicate that garlic can boost immunity, balance blood sugar, and  prevent digestive ailments (it may also help the liver to neutralize toxins). Among the most active medicinal compounds are dozens of sulfur compounds found in few other plants; these are thought to be responsible for garlic’s documented antibacterial (Louis Pasteur confirmed the antibacterial action of the bulb in 1858), antiviral, antifungal, and other healthful  roperties. Research published in 2001 suggests that allicin, the main active ingredient of garlic, could be useful in the fight against potentially fatal hospital acquired infections. Researchers found that that topical creams containing just 32 parts per million (ppm) of allicin inhibited the growth of 30 different samples of the antibiotic-resistant bacterium  methicillinresistant Staphylococcus aureus (MRSA), and that concentrations of 256 ppm were enough to kill the bacteria. Meanwhile results of another study revealed that people who took a daily allicin-containing garlic supplement were more than 50% less likely to catch a cold. Furthermore, those taking the supplement whom were unlucky enough to catch a cold tended to recover much more quickly and were significantly less likely to become re-infected with the disease. Epidemiological studies have shown that eating garlic regularly can reduce the risk of developing esophageal, stomach, and colon cancers. This is partly attributable to garlic’s ability to prevent the formation of carcinogenic compounds. Animal and in vitro studies have also demonstrated that the sulfur compounds found in garlic can inhibit the growth of different types of cancer, in particular breast and skin tumors.


Garlic is available fresh or juiced, as well as in tablets, capsules, and tinctures. Odor-controlled powders, concentrates, and capsules are popular forms, as are enteric-coated tablets (which have a coating that prevents the destruction of active compounds by stomach acids). Supplement manufacturers are increasingly standardizing their products for desirable garlic compounds (principally one called allicin, but also total sulfur, allin, and S-allyl cysteine), but debate rages on as to which of these compounds are most important and which  ormulations are most effective. The potency of garlic products may be described in terms of fresh or whole garlic equivalent; an average dose is 1,500 to 1,800mg of fresh garlic equivalent, approximately equal to eating one-half clove of fresh garlic. To fight infection, 3 or 4 chopped, crushed or chewed cloves should be consumed per day or, in supplement form (1.3% allicin), 600-900 mg divided into 2-3 doses/day. Read labels.

MAXIMUM SAFE LEVEL: Not established


Garlic is extremely safe but taking very large daily doses (more than 10g) of some products may cause flatulence, stomach irritation, or indigestion. Because of garlic’s anti-clotting properties, persons taking anticoagulant drugs, such as Warfarin and Ticlopidine, should check with their doctor before taking garlic. In addition, people scheduled for surgery should inform their surgeon if they are taking garlic supplements Women should avoid taking garlic supplements during pregnancy as laboratory studies suggest that they may cause irregular uterine contractions.

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