Garlic (Allium sativum)

Medical Uses

Garlic is used for high blood pressure, high cholesterol, infections, and cancer prevention.

Historical Uses

Called the “stinking rose,” garlic has been used by the Egyptians, Chinese, Greeks, Romans, and native North Americans to heal many ailments. In the early 1900s, Dr. W Minuchin, a physician who was interested in the effects of garlic, performed clinical trials that showed its usefulness in treating tuberculosis, lupus, diphtheria, and infections.


Plant garlic cloves in the spring, about 2 inches deep and 6 inches apart, in well-drained soil. Planting garlic around vegetable plants helps to repel insects; planting it around fruit and nut trees helps to repel moles. Harvest the garlic when the top of the plant dies.

Garlic: Part used

• Bulb

Major Chemical Compounds

  • • Allicin
  • • Ajoene
  • • Selenium
  • • Saponins
  • • Fructans
  • • Potassium
  • • Thiamine
  • • Calcium
  • • Magnesium
  • • Iron
  • • Phosphorus
  • • Zinc

Garlic: Clinical Uses

Garlic is used for hypertension, hypercholesterolemia, infection, and cancer prevention. It is approved by the German Commission E and the World Health Organization for hyperlipidemia and atherosclerotic vascular changes. It maybe useful in mild hypertension (WHO, 1999).

Mechanism of Action

Allicin is a natural antibiotic and antiviral. Ajoene is a platelet aggregation inhibitor. Selenium is a cancer-fighting compound. Saponins lower blood pressure. Fructans stimulate the immune system.

The antibacterial effects of allicin may result from its reducing bacterial conversion of nitrate to nitrite in the stomach, which in turn decreases the formation of carcinogenic nitrosamines. The antibacterial activity and nitrate-scavenging effects of compounds in garlic have been documented in at least 20 studies worldwide, which lends support to the idea of using garlic for infection and cancer prevention. Other studies cite the effectiveness of garlic in hypertension and hypercholesterolemia.

Garlic: Dosage

Capsules: 600 to 900 mg daily (using a commercial product called Kwai, as was used in the study by Koscielny et al. described under Summary of Studies.).

Fresh garlic: About 4 grams a day.

Allicin is released when garlic is chewed. Its effects are most pronounced when garlic is consumed raw, although it tends to cause halitosis. Also, heat and stomach acid destroy its activity. Enteric-coated tablets are available that release allicin in the small intestine, where it combines with cysteine and is absorbed without causing breath odor.

Side Effects

Side effects are rare at the recommended dosage. Some gastrointestinal upset has been reported. Essential oil of garlic and garlic applied directly to the skin can be irritating. Garlic may increase blood clotting time and elevate international normalized ratios.


• Garlic is contraindicated in patients who are allergic to it.

• Breast-feeding patients should not use garlic.

• Patients should not take large amounts of garlic before undergoing surgery (WHO, 1999).

Herb-Drug Interactions

Garlic should be used cautiously if the patient takes an anticoagulant.

Pregnancy and Breast-Feeding

Garlic is not recommended for pregnant women, breast-feeding mothers, infants of breast-feeding mothers, or small children. Other sources suggest and traditional use states that garlic is safe when consumed in small amounts during pregnancy.

Summary of Studies

Koscielny et al. (1999). This randomized, double-blind, placebo-controlled study included 152 subjects and lasted more than 4 years. The subjects had arterial plaque and a risk factor for heart disease; they consumed either a placebo or Kwai 900 mg. Results: Those who took Kwai had a 2.6 percent reduction in plaque, whereas the placebo group had a 15.6 percent increase in plaque. More benefit was noted in women.

Ernst (1997). This article reviewed 20 epidemiological studies worldwide from 1966 to 1996, 8 studies on garlic, and other studies on onion. Results: A strong association was noted between the consumption of vegetables containing allium and protection against cancer, especially of the gastrointestinal tract.

Silagy & Neil (1994). This meta-analysis included 415 subjects in eight randomized, controlled trials over 4 weeks. Results: Garlic powder preparation of Kwai 600 mg to 900 mg/day may be of some clinical use in patients with mild hypertension. Of seven trials that compared garlic to placebo, three showed a significant reduction in systolic blood pressure and four showed a significant reduction in diastolic blood pressure. The authors felt that more studies were needed.

Steinmetz et al. (1994). This prospective cohort study used the Iowa Women’s Health Study of 41,387 women ages 55 to 69. Over the 5-year period in which subjects recorded dietary habits, 212 developed colon cancer. Results: Garlic was the strongest inverse association with risk for colon cancer. No other vegetables containing allium were included in the study.

Orekov et al. (1994). In this in vivo study, blood serum was taken 2 hours after oral administration of a 300-mg garlic powder tablet. Results: Substantially less cholesterol in vivo.

Warshafsky (1993). This meta-analysis of five clinical trials with 365 subjects included four double-blind and all placebo-controlled studies of 8 to 24 weeks. Results: Garlic supplementation of an amount equivalent to one clove a day led to a 9 percent decrease in total serum cholesterol level.

Bordia (1981). This study used two groups with hyperlipidema. Group A had 20 healthy subjects; they were fed 25 mg/kg/day of garlic oil over a 6-month period, followed by 2 months without garlic. Group B had 62 subjects with coronary heart disease and elevated serum cholesterol. Subjects in subgroup Bl received garlic for 10 months. Subjects in subgroup B2 made up the control group. Results: In Group A, garlic significantly lowered serum cholesterol and triglyceride levels (17 and 20 percent) and raised high-density lipoprotein levels (by 29.3 to 41.2 mg/dL). In Group B, garlic decreased serum cholesterol (18 percent), triglyceride, and low-density lipoprotein levels while increasing high-density lipoprotein levels. Conclusion: Essential oil of garlic showed hypolipidemic action in both healthy people and those with coronary artery disease. These changes were not maintained after 2 months without garlic oil.

Amer et al. (1979). In vitro and in vivo animal studies showed topical treatment of fungal infections with garlic produced complete healing in 14 to 17 days following twice-daily application of the extract for 1 week.

Sarrell et al. (2001). In a randomized controlled trial of 103 children aged 6 to 18 years with the diagnosis of otalgia, Otikon, an ear drop containing Allium sativum and other herbs, was as effective as anesthetic ear drops.

Kannar et al. (2001). In a double-blind randomized, placebo-controlled study of 46 subjects with hypercholesterolemia, 9.6 mg of an allicin-releasing, enteric-coated garlic supplement over a 12-week period showed a cholesterol-lowering effect.

Lawson et al. (2001). From 1989 to 1997 there were many positive studies of the use of garlic to reduce serum cholesterol, but lately these studies have been negated. Lawson et al. reiterate the importance of using a high-quality allicin-releasing garlic supplement as determined under the standardized drug release conditions of U. S. Pharmacopeia Method 724A.

Garlic: Warnings

• Side effects are rare at the recommended dosage. Some gastrointestinal upset has been reported.

• Garlic may increase the risk of bleeding. Don’t take large amounts of before surgery.

• Use garlic cautiously if you take a blood-thinning medication.

• Avoid garlic use in pregnancy. (Some sources and traditional use state that garlic is safe during pregnancy when consumed in small amounts in food.)

• Essential oil of garlic and garlic applied directly to the skin can be irritating.

• Don’t take garlic if you are allergic to it.

• Don’t use garlic while breast-feeding.

• Garlic is not recommended for breast-feeding infants and small children.


Herb and Garlic Linguine

  • 1 box light cream cheese
  • 3 tablespoons extra virgin olive oil
  • 1 tablespoon fresh parsley
  • 1 box linguine
  • ¼ cup hot water
  • 1 tablespoon fresh basil
  • ½ tablespoon oregano
  • 4 cloves garlic

Chop garlic cloves into large pieces and simmer in olive oil until warm. At the same time, heat the cream cheese and, when softened, add hot water and whisk. Add the herbs to the cream cheese mixture. Cook the linguine. Strain the garlic out of the oil and add the oil to the linguine. Next, add the cream cheese mixture in the desired amount on top of each plate of linguine. Makes 4 servings.

Heart-Healthy Garlic Spaghetti

Using this recipe, I can quickly prepare a healthy meal for my husband and teenage boys even after a long day.

  • 1 box angel hair spaghetti
  • 1 cup olive oil
  • 4-6 cloves garlic
  • Parmesan cheese

Start boiling the water for the angel hair spaghetti. As it heats, peel and chop the garlic into big chunks. Warm the olive oil and add the garlic. Cook the angel hair, drain, and mix with the garlic oil. Sprinkle with grated parmesan cheese. Enjoy!