Garlic is an herb that is grown around the world. It is related to onion, leeks, and chives. It is thought that garlic is native to Siberia, but spread to other parts of the world over 5000 years ago.
Garlic is used for many conditions related to the heart and blood system. These conditions include high blood pressure, low blood pressure, high cholesterol, inherited high cholesterol, coronary heart disease, heart attack, reduced blood flow due to narrowed arteries, and “hardening of the arteries” (atherosclerosis).
Some people use garlic to prevent colon cancer, rectal cancer, stomach cancer, breast cancer, prostate cancer, multiple myeloma, and lung cancer. It is also used to treat prostate cancer and bladder cancer.
Garlic has been tried for treating an enlarged prostate (benign prostatic hyperplasia; BPH), cystic fibrosis, diabetes, metabolic syndrome, osteoarthritis, hayfever (allergic rhinitis), traveler’s diarrhea, high blood pressure late in pregnancy (pre-eclampsia), yeast infection, flu, and swine flu. It is also used to prevent tick bites, as a mosquito repellant, and for preventing the common cold, and treating and preventing bacterial and fungal infections.
Garlic is also used for earaches, chronic fatigue syndrome, menstrual disorders, abnormal cholesterol levels caused by HIV drugs, hepatitis, shortness of breath related to liver disease, stomach ulcers caused by H. pylori infection, exercise performance, exercise-induced muscle soreness, a condition that causes lumps in the breast tissue called fibrocystic breast disease, a skin condition called scleroderma, and lead toxicity.
Other uses include treatment of fever, coughs, headache, stomach ache, sinus congestion, gout, joint pain, hemorrhoids, asthma, bronchitis, shortness of breath, low blood sugar, snakebites, diarrhea and bloody diarrhea, tuberculosis, bloody urine, a serious nose and throat infection called diphtheria, whooping cough, tooth sensitivity, stomach inflammation (gastritis), scalp ringworm, and a sexually transmitted disease called vaginal trichomoniasis. It is also used for fighting stress and fatigue.
Some people apply garlic oil to their skin or nails to treat fungal infections, warts, and corns. It is also applied to the skin for hair loss and thrush.
Garlic is used in the vagina for yeast infections.
Garlic is injected into the body for chest pain.
In foods and beverages, fresh garlic, garlic powder, and garlic oil are used to add flavor.
How does it work?
Garlic produces a chemical called allicin. This is what seems to make garlic work for certain conditions. Allicin also makes garlic smell. Some products are made “odorless” by aging the garlic, but this process can also make the garlic less effective. It’s a good idea to look for supplements that are coated (enteric coating) so they will dissolve in the intestine and not in the stomach.
Uses & Effectiveness
Possibly Effective for
- Hardening of the arteries (atherosclerosis). As people age, their arteries tend to lose their ability to stretch and flex. Garlic seems to reduce this effect. Taking a specific garlic powder supplement (Allicor, INAT-Farma) twice daily for 24 months seems to reduce how much hardening of the arteries progresses. Higher doses of this product seem to provide more benefits in women than men when taken over a four-year period. Research with other products containing garlic along with other ingredients (Kyolic, Total Heart Health, Formula 108, Wakunaga) have also shown benefits.
- Diabetes. Garlic seems to modestly reduce pre-meal blood sugar levels in people with or without diabetes. It seems to work best in people with diabetes, especially if it is taken for at least 3 months. It’s not known if garlic reduces post-meal blood sugar levels or HbA1c levels.
- High cholesterol. While not all research agrees, the most reliable evidence suggests that taking garlic can reduce total cholesterol and low-density lipoprotein (LDL, “bad” cholesterol) by a small amount in people with high cholesterol levels. Garlic appears to work best if taken daily for more than 8 weeks. However, taking garlic doesn’t help increase high-density lipoprotein (HDL, “good” cholesterol) or lower levels of other blood fats called triglycerides.
- High blood pressure. Taking garlic by mouth seems to reduce systolic blood pressure (the top number) by about 7-9 mmHg and diastolic blood pressure (the bottom number) by about 4-6 mmHg in people with high blood pressure.
- Tick bites. People who consume high amounts of garlic over about an 8-week period seem to have a reduced number of tick bites. But it’s not clear how garlic compares to commercially available tick repellants.
- Ringworm. Applying a gel containing 0.6% ajoene, a chemical in garlic, twice daily for one week seems to be as effective as antifungal medication for treating ringworm.
- Jock itch. Applying a gel containing 0.6% ajoene, a chemical in garlic, twice daily for one week seems to be as effective as antifungal medication for treating jock itch.
- Athlete’s foot. Applying a gel containing 1% ajoene, a chemical in garlic, seems to be effective for treating athlete’s foot. Also, applying a garlic gel with 1% ajoene seems to be about as effective as the medicine Lamisil for treating athlete’s foot.
Possibly Ineffective for
- Cystic fibrosis. Research suggests that taking garlic oil macerate daily for 8 weeks does not improve lung function, symptoms, or the need for antibiotics in children with cystic fibrosis and lung infection.
- Inherited high cholesterol (familial hypercholesterolemia). In children with high levels of low-density lipoprotein (LDL or “bad”) cholesterol, taking garlic powdered extract by mouth does not seem to improve cholesterol levels or blood pressure.
- Ulcers caused by a bacterium called Helicobacter pylori (H. pylori). Taking garlic by mouth for H. pylori infection used to look promising due to laboratory evidence showing potential activity against H. pylori. However, when garlic cloves, powder, or oil is used in humans, it does not seem to help treat people infected with H. pylori.
- Mosquito repellent. Taking garlic by mouth does not seem to repel mosquitos.
- Leg pain associated with poor blood flow (peripheral arterial disease). Taking garlic by mouth for 12 weeks does not seem to reduce leg pain when walking due to poor circulation in the legs.
- High blood pressure during pregnancy (pre-eclampsia). Early evidence suggests that taking a specific garlic extract (Garlet) daily during the third trimester of pregnancy does not reduce the risk of developing high blood pressure in women who are at high risk or pregnant for the first time.
Insufficient Evidence for
- Hair loss (alopecia areata). Early evidence suggests that applying a garlic 5% gel along with a topical steroid for 3 months increases hair growth in people with hair loss.
- Chest pain (angina). Early research suggests that administering garlic intravenously (by IV) for 10 days reduces chest pain compared to intravenous nitroglycerin.
- Enlarged prostate (benign prostatic hyperplasia or BPH). Early research suggests that taking a liquid garlic extract daily for one month reduces prostate mass and urinary frequency. But the quality of this research is questionable.
- Common cold. Early research suggests that garlic might reduce the frequency and number of colds when taken for prevention.
- Corns. Early research suggests that applying certain garlic extracts to corns on the feet twice daily improves corns. One particular garlic extract that dissolves in fat seems to work after 10-20 days of treatment.
- Heart disease. Some early research suggests that taking a specific garlic product (Allicor, INAT-Farma) for 12 months reduces the risk of sudden death and heart attack in people at risk for developing clogged arteries. Other early research suggests that taking a supplement containing aged garlic (Kyolic, Total Heart Health, Formula 108, Wakunaga) might prevent clogged arteries from worsening.
- Muscle soreness after exercise. Early evidence suggests that taking allicin, a chemical in garlic, daily for 14 days can reduce muscle soreness after exercise in athletes.
- Exercise performance. Early research suggests that taking a single 900 mg dose of garlic before exercise can increase endurance in young athletes.
- Lumpy breast tissue (fibrocystic breast disease). Early research suggests that taking a specific combination product (Karinat, INAT-Farma) containing garlic, beta-carotene, vitamin E, and vitamin C twice daily for 6 months reduces the severity of breast pain, premenstrual syndrome, and lumpy breast tissue in people with fibrocystic breast disease.
- Stomach inflammation (gastritis). Early research suggests that taking a specific combination product containing garlic (Karinat, INAT-Farma) twice daily for 6 months improves digestion, stops the growth of certain bacteria (H. pylori), and reduces the risk of stomach cancer in people with stomach inflammation. However, the effect of garlic alone has not been determined.
- Liver disease (hepatitis). Early research suggests that taking garlic oil together with diphenyl-dimethyl-dicarboxylate improves liver function in people with hepatitis. However, the effects of garlic alone are not clear.
- Shortness of breath and low oxygen levels associated with liver disease (hepatopulmonary syndrome). Early research suggests that taking garlic oil for 9-18 months might improve oxygen levels in people with hepatopulmonary syndrome.
- Lead poisoning. Early research suggests that taking garlic three times daily for 4 weeks can reduce blood lead concentrations in people with lead poisoning. But it does not seem to be more effective than D-penicillamine.
- Metabolic syndrome. Early research shows that taking raw, crushed garlic twice daily for 4 weeks can reduce waist circumference, blood pressure, and blood sugar levels in people with metabolic syndrome. It also seems to improve high-density lipoprotein (HDL, “good” cholesterol) levels.
- Inflamed mouth sores (oral mucositis). Early research suggests that using a garlic mouthwash three times daily for 4 weeks improves redness in people with mouth sores. People seem to be more satisfied with garlic than the drug nystatin, but it is less effective.
- Thrush (oral candidiasis). Early research suggests that applying garlic paste to affected areas in the mouth can increase the healing rate in people with oral thrush.
- Osteoarthritis. Early research shows that taking garlic tablets twice daily for 12 weeks can reduce pain in overweight women with osteoarthritis in the knee.
- Hardened skin (scleroderma). Research suggests that taking garlic daily for 7 days does not benefit people with scleroderma.
- Vaginal yeast infections. Some early research suggests that applying a vaginal cream containing garlic and thyme nightly for 7 nights is as effective as clotrimazole vaginal cream for treating yeast infections. But other early research suggests that taking garlic (Garlicin, Nature’s Way) twice daily for 14 days does not improve symptoms.
- Warts. Early evidence suggests that applying a specific fat-soluble garlic extract to warts on the hands twice daily removes warts within 1-2 weeks. Also, a water-soluble garlic extract seems to provide modest improvement, but only after 30-40 days of treatment.
- Weight loss. Early research suggests that taking a combination product (Prograde Metabolism) containing many different extracts including garlic root extract twice daily for 8 weeks reduces body weight, fat mass, and waist and hip circumference when used together with diet and exercise.
- Side Effects & Safety
- Garlic is LIKELY SAFEfor most people when taken by mouth appropriately. Garlic has been used safely in research for up to 7 years. When taken by mouth, garlic can cause bad breath, a burning sensation in the mouth or stomach, heartburn, gas, nausea, vomiting, body odor, and diarrhea. These side effects are often worse with raw garlic. Garlic may also increase the risk of bleeding. There have been reports of bleeding after surgery in people who have taken garlic. Asthma has been reported in people working with garlic, and other allergic reactions are possible.Garlic products are POSSIBLY SAFE when applied to the skin. Gels, pastes, and mouthwashes containing garlic have been used for up to 3 months. However, when applied to the skin, garlic might cause skin damage that is similar to a burn.RAW garlic is POSSIBLY UNSAFE when applied to the skin. Raw garlic might cause severe skin irritation when it is applied to the skin.
- Special Precautions & Warnings:
- Pregnancy and breast-feeding: Garlic is LIKELY SAFEto use during pregnancy when taken in the amounts normally found in food. Garlic is POSSIBLY UNSAFE when used in medicinal amounts during pregnancy and when breast-feeding. There is not enough reliable information about the safety of applying garlic to the skin if you are pregnant or breast feeding. Stay on the safe side and avoid use.Children: Garlic is POSSIBLY SAFE when taken by mouth and appropriately for a short-term in children. However, garlic is POSSIBLY UNSAFE when taken by mouth in large doses. Some sources suggest that high doses of garlic could be dangerous or even fatal to children. The reason for this warning is not known. There are no case reports available of significant adverse events or mortality in children associated with taking garlic by mouth. When applied to the skin, garlic might cause damage to the skin that is similar to a burn.Bleeding disorder: Garlic, especially fresh garlic, might increase the risk of bleeding.Diabetes: Garlic can lower blood sugar. In theory, taking garlic might make blood sugar too low in people with diabetes.
Do not take this combination
- Isoniazid (Nydrazid, INH) interacts with GARLIC
Garlic might reduce how much isoniazid (Nydrazid, INH) the body absorbs. This might decrease how well isoniazid (Nydrazid, INH) works. Don’t take garlic if you take isoniazid (Nydrazid, INH).
- Saquinavir (Fortovase, Invirase) interacts with GARLIC
The body breaks down saquinavir (Fortovase, Invirase) to get rid of it. Garlic might increase how quickly the body breaks down saquinavir. Taking garlic along with saquinavir (Fortovase, Invirase) might decrease the effectiveness of saquinavir (Fortovase, Invirase).
Be cautious with this combination
- Birth control pills (Contraceptive drugs) interacts with GARLIC
Some birth control pills contain estrogen. The body breaks down the estrogen in birth control pills to get rid of it. Garlic might increase the breakdown of estrogen. Taking garlic along with birth control pills might decrease the effectiveness of birth control pills. If you take birth control pills along with garlic, use an additional form of birth control such as a condom.<br /> Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.
- Cyclosporine (Neoral, Sandimmune) interacts with GARLIC
The body breaks down cyclosporine (Neoral, Sandimmune) to get rid of it. Garlic might increase how quickly the body breaks down cyclosporine (Neoral, Sandimmune). Taking garlic along with cyclosporine (Neoral, Sandimmune) might decrease the effectiveness of cyclosporine (Neoral, Sandimmune). Do not take garlic if you are taking cyclosporine (Neoral, Sandimmune).
- Medications changed by the liver (Cytochrome P450 2E1 (CYP2E1) substrates) interacts with GARLIC
Some medications are changed and broken down by the liver.<br /> Garlic oil might decrease how quickly the liver breaks down some medications. Taking garlic oil along with some medications that are changed by the liver can increase the effects and side effects of your medication. Before taking garlic oil talk to your healthcare provider if you take any medications that are changed by the liver.<br /> Some medications that are changed by the liver include acetaminophen, chlorzoxazone (Parafon Forte), ethanol, theophylline, and drugs used for anesthesia during surgery such as enflurane (Ethrane), halothane (Fluothane), isoflurane (Forane), and methoxyflurane (Penthrane).
- Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates) interacts with GARLIC
Some medications are changed and broken down by the liver.<br /> Garlic might increase how quickly the liver breaks down some medications. Taking garlic along with some medications that are broken down by the liver can decrease the effectiveness of some medications. Before taking garlic talk to your healthcare provider if you are taking any medications that are changed by the liver.<br /> Some medications changed by this liver include lovastatin (Mevacor), ketoconazole (Nizoral), itraconazole (Sporanox), fexofenadine (Allegra), triazolam (Halcion), and many others.
- Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs) interacts with GARLIC
Garlic might slow blood clotting. Taking garlic along with medications that also slow clotting might increase the chances of bruising and bleeding.<br /> Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, warfarin (Coumadin), and others.
- Warfarin (Coumadin) interacts with GARLIC
Warfarin (Coumadin) is used to slow blood clotting. Garlic might increase the effectiveness of warfarin (Coumadin). Taking garlic along with warfarin (Coumadin) might increase the chances of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
The following doses have been studied in scientific research:
- For hardening of the arteries: A 300 mg garlic powder tablet (Kwai, Lichtwer Pharma), taken as a single dose or three times daily for up to 4 years, has been used. Also, 150 mg of a specific garlic supplement (Allicor, INAT-Farma) twice daily for 24 months has been used. Combination products containing garlic have also been used. A specific aged garlic extract supplement (Kyolic, Total Heart Health, Formula 108, Wakunga) containing 250 mg of aged garlic extract taken daily for 12 months, has been used. Also, a combination product containing 300 mg aged garlic extract, taken at a dose of four tablets daily for one year, has been used.
- For diabetes: Garlic powder 600-1500 mg daily has been used for at least 12 weeks. A 300 mg garlic tablet (Allicor, INAT-Farma) taken two to three times daily with medications called metformin or sulfonylurea, for 4 to 24 weeks has been used.
- For high cholesterol: A dose of 1000-7200 mg of a specific aged garlic extract (Kyolic, Wakanuga) has been used daily in divided doses for 4-6 months. A dose of 600-900 mg of a specific garlic powder tablet (Kwai, Lichtwer Pharma) has been taken daily in two or more divided doses for 6-16 weeks. Also, 300 mg of another specific garlic powder product (Garlex, Bosch Pharmaceuticals) taken twice daily for 12 weeks has been used. Also, 1,200 mg of garlic powder plus 3 grams of fish oil daily for 4 weeks, or 500 mg of garlic oil plus 600 mg of fish oil daily for 60 days, has been used.
- For high blood pressure: 300-1500 mg of garlic tablets taken in divided doses daily for 24 weeks has been used. 2400 mg of a specific garlic powder tablet (Kwai, Lichtwer Pharma) taken as a single dose or 600 mg daily for 12 weeks has been used. Capsules containing 960-7200 mg of aged garlic extract, taken daily in up to three divided doses for up to 6 months, have been used. Specific products containing aged garlic extract include Kyolic (Garlic High Potency Everyday Formula 112, Wakunga/Wagner). 500 mg of garlic oil plus 600 mg of fish oil daily for 60 days has been used.
- For tick bites: Capsules containing 1200 mg of garlic taken daily for 8 weeks have been used.
APPLIED TO THE SKIN:
- For fungal skin infections (ringworm, jock itch, athlete’s foot): Garlic ingredient ajoene as a 0.4% cream, 0.6% gel, and 1% gel applied twice daily for one week has been used.
Stomach or digestion problems: Garlic can irritate the gastrointestinal (GI) tract. Use with caution if you have stomach or digestion problems.
Low blood pressure: Garlic can lower blood pressure. In theory, taking garlic might make blood pressure become too low in people with low blood pressure.
Surgery: Garlic might prolong bleeding and interfere with blood pressure. Garlic might also lower blood sugar levels. Stop taking garlic at least two weeks before a scheduled surgery.