Garlic (Allium sativum L.)

Mayo Clinic Health Manager

Get free personalized health guidance for you and your family.

Get Started

Free

E-Newsletter

Subscribe to receive the latest updates on health topics. About our newsletters

  • Housecall
  • Alzheimer's caregiving
  • Living with cancer

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

High cholesterol
Multiple studies in humans have reported small reductions in total blood cholesterol and low-density lipoproteins ("bad cholesterol") over short periods of time (4 to 12 weeks). It is not clear if there are benefits after this amount of time. Effects on high-density lipoproteins ("good cholesterol") are not clear. This remains an area of controversy. Well-designed and longer studies are needed in this area. 		B
Anti-fungal (applied to the skin)
Several studies describe the application of garlic to the skin to treat fungal infections, including yeast infections. Take caution as garlic can cause severe burns and rash when applied to the skin of sensitive individuals. 		C
Anti-platelet effects (blood thinning)
The effects of garlic on platelet aggregation have been assessed in several human trials. Because garlic has been associated with several cases of bleeding, therapy should be applied with caution (particularly in patients using other agents that may precipitate bleeding). 		C
Atherosclerosis ("hardening" of the arteries)
Preliminary research in humans suggests that deposits of cholesterol in blood vessels may not grow as quickly in people who take garlic. It is not clear if this is due to the ability of garlic to lower cholesterol levels, or to other effects of garlic. 		C
Cancer
Preliminary human studies suggest that regular consumption of garlic (particularly unprocessed garlic) may reduce the risk of developing several types of cancer including gastric and colorectal malignancies. Some studies use multi-ingredient products so it is difficult to determine if garlic alone may play a beneficial role. Further well designed human clinical trials are needed to conclude whether eating garlic or taking garlic supplements may prevent or treat cancer. 		C
Cryptococcal meningitis
Preliminary study documented potential benefits of oral plus intravenous garlic in the management of cryptococcal meningitis. Further research is needed before recommending for or against the use of garlic in the treatment of this potentially serious condition, for which other treatments are available. 		C
Familial hypercholesterolemia
Familial hypercholesterolemia is a genetic disorder in which very high cholesterol levels run in families. Research in children with an inherited form of high cholesterol suggests that garlic does not have a large effect in lowering cholesterol levels in these patients. 		C
Heart attack prevention in patients with known heart disease
It is not clear if garlic prevents future heart attacks in people who have already had a heart attack. The effects of garlic on cholesterol levels may be beneficial in such patients. 		C
High blood pressure
Numerous human studies report that garlic can lower blood pressure by a small amount, but larger, well-designed studies are needed to confirm this possible effect. 		C
Peripheral vascular disease (blocked arteries in the legs)
Some human studies suggest that garlic may improve circulation in the legs by a small amount, but this issue remains unclear. Better-designed studies are needed. 		C
Tick repellant
In early study, self-reports of tick bites were significantly less in people receiving garlic over a placebo "sugar" pill. Further well designed study is needed to confirm these results. 		C
Upper respiratory tract infection
Preliminary reports suggest that garlic may reduce the severity of upper respiratory tract infections. However, this has not been demonstrated in well-designed human studies. 		C
Diabetes
Animal studies suggest that garlic may lower blood sugar and increase the release of insulin, but studies in humans do not confirm this effect. 		D
Stomach ulcers caused by Helicobacter pylori bacteria
Early studies in humans show no effect of garlic on gastric or duodenal ulcers. 		D

Key to grades
A Strong scientific evidence for this use
B Good scientific evidence for this use
C Unclear scientific evidence for this use
D Fair scientific evidence against this use (it may not work)
F Strong scientific evidence against this use (it likely does not work)

Grading rationale

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Abortion, age-related memory problems, AIDS, allergies, amoeba infections, anti-bacterial, antioxidant, antitoxin, anti-viral, aphrodisiac, atrophic gastritis, arthritis, ascaridiasis (worms in the gut or liver), asthma, athlete's foot, benign breast disease, bile secretion problems, bladder cancer, bloody urine, breast fibromatosis, bronchitis, cholera, claudication (leg pain due to poor blood flow), colds, cough, cytomegalovirus infection, dental pain, digestive aid, diphtheria, diuretic (water pill), dysentery, dysmenorrhea (painful menstruation), earache, fatigue, fever, gallstones, hair growth, headache, heart rhythm disorders, hemorrhoids, hepatopulmonary syndrome, HIV, hormonal effects, immune system stimulation, improved digestion, induction of vomiting, inflammation, inflammatory bowel disease, influenza, kidney problems, kidney damage from antibiotics, leukemia, liver health, liver tumors, malaria, mucous thinning, muscle spasms, nephrotic syndrome, obesity, parasites and worms, perspiration, pneumonia, premenstrual syndrome (PMS), psoriasis, Raynaud's disease, ringworm ( Tinea corpori , Tinea cruris ), sedative, sinus decongestant, snake venom protection, spermicide, stomach ache, stomach acid reduction, stomach lining protection, stress (anxiety), stroke, thrush, toothache, traveler's diarrhea, tuberculosis, urinary tract infections, vaginal trichomoniasis, typhus, urinary tract infections, vaginal irritation, warts, well-being, whooping cough.

Dosing Synonyms

NS_patient-garlic

Portions of this document last updated:

Sept. 1, 2009

THIS EVIDENCE-BASED MONOGRAPH WAS PREPARED BY
THE NATURAL STANDARD RESEARCH COLLABORATION
(www.naturalstandard.com)


Text Size: smaller largerlarger