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Garlic: Health Benefits and Medicinal Uses

Garlic (Allium sativum) produces a strong-smelling bulb used as a cooking ingredient that also has medicinal benefits. Though native to Asia, it has been cultivated throughout the world for thousands of years. Today, garlic and its products are used mainly to lower cholesterol levels and reduce the risk of cardiovascular disease such as angina and heart attacks. Some experts suggest that garlic could also work on cancer. If taken sensibly, garlic is entirely safe.

Potential Health Effects of Garlic

Garlic is best known for its antibacterial, antiviral and antifungal properties. Other suggested beneficial effects of garlic include lowering blood pressure and blood sugar (glucose) levels, thinning the blood and reducing the tendency of blood to clump together and block blood vessels (antithrombotic effects) and reducing changes (mutations) in the genetic material of the body’s cells (antioxidant).

Garlic is full of a derivative of the amino acid cysteine called alliin that is rapidly converted to allicin when garlic is chopped or crushed. Allicin is garlic’s main active ingredient that gives it its typical aroma as well as its health benefits. Garlic also contains other active ingredients like ajoene that is found in much lower concentration than allicin. Ajoene has many of the same medicinal properties that are also attributed to garlic such as antioxidant, antithrombotic, antibacterial, antiviral, antifungal and cancer-inhibiting effects.

Moreover, garlic is a good dietary source of vitamins B6 and C and many vital minerals including calcium, copper, iron, manganese, phosphorus, potassium and selenium.

Potential Health Risks of Garlic

Like most other plants used as food, garlic is very safe. The only adverse effects are unpleasant body odour, allergic reactions (usually a skin rash) in sensitive individuals, nausea (usually only at excessively high doses) and heartburn and flatulence (especially with high doses). However, pregnant and breastfeeding women should not take garlic supplements because there is not enough evidence that they are absolutely risk-free for the baby (but, garlic as food is safe).

People who have bleeding abnormalities, or are on blood-thinning drugs (anticoagulants such as warfarin) should only take garlic supplements if recommended by their doctor. This is because garlic also thins the blood and the combined effect could cause bleeding problems. For the same reason, it is recommended to stop taking garlic supplements well before major surgery. Other drugs and herbs that may interact with garlic include the antibiotic isoniazid, the immunosuppressant cyclosporine, the antiretroviral drug saquinavir, ginkgo biloba, ginseng and birth control pills.

Medical Conditions Treated with Garlic

Garlic has long been used in food and as a medicinal plant throughout the world. It is interesting to see some of its traditional medicinal uses in different parts of the world. They include bringing on abortion, expelling worms, fighting inflammation, increasing sexual desire (aphrodisiac) as well as urine output (diuretic), promoting hair growth and menstruation, reducing fever, sedating, and treating asthma, diarrhea, skin infections and the absence of periods (amenorrhea). In addition, in Fiji and Malaysia garlic was given to mothers after childbirth while in Mexico it was given to new-born infants. These traditional uses of garlic give clues about where modern science should focus its research efforts when looking for possible therapeutic uses of garlic.

Probably the best-researched health effect of garlic is its ability to lower cholesterol levels in the blood. It may do this by reducing the liver’s capacity to produce cholesterol. However, the latest research suggests that this effect is only short-term and small, certainly less than that of conventional medications.

Studies also show that the blood pressure-lowering effects of garlic as food are small and less powerful than that of conventional blood pressure-lowering drugs. For more significant reduction in blood pressure it would be necessary to take large doses of garlic supplements.

However, there is some promising evidence that garlic could have anti-cancer effects. Research suggests that regularly taking garlic in food gives some protection against certain types of cancer, particularly the stomach and colorectal cancers. But, there is no evidence to suggest that garlic might cure cancer once it has been diagnosed.

Other uses of garlic in complementary and herbal medicine today include treating allergies, asthma, atherosclerosis, athlete’s foot, benign prostatic hyperplasia, bronchitis, cancers (e.g., breast, colon, lung, prostate, rectal and stomach cancer), chronic fatigue syndrome, cystic fibrosis, diabetes, diarrhea, ear infections, gastritis, H. pylori infection, headache, hemorrhoids, hepatitis, jock itch, menstrual problems, muscle soreness, ringworm, scleroderma, shortness of breath, sinusitis, stomach ulcers, osteoarthritis, vaginitis and yeast infections. In addition, garlic is often used for detoxifying the liver. However, at the moment there is no definite proof that garlic may help with any of these conditions.

Garlic Supplements

Many garlic preparations are available including standardized products. They are either based on powdered dried garlic bulbs or oil extracts from fresh garlic bulbs and are taken by mouth. However, odour-free garlic products do not really work: no smell, no benefit. A standardised extract gives a guaranteed amount of ingredients (i.e., it is standardized to 1.3% alliin or 0.6% allicin content). That is, each tablet contains the same amount of active ingredients so that the patient knows how much is needed to achieve desired effect. For fungal skin infections, topical products derived from garlic, such as ajoene cream and gel, can be used.