Natural Standard Monograph, Copyright © 2014 (www.naturalstandard.com). Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified health care professional before making decisions about therapies and/or health conditions.
Uses based on scientific 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 professional.
High blood pressure
Numerous human studies report that garlic may lower blood pressure, particularly systolic blood pressure. It is unclear if effects are more pronounced in people with high blood pressure vs. normal blood pressure.
Multiple studies in humans have reported small reductions in total blood cholesterol and low-density lipoproteins (LDL or "bad" cholesterol) over short periods of time. Garlic lacks effects on high-density lipoproteins (HDL or "good" cholesterol).
Heart disease (risk)
Several studies have concluded that garlic may have a positive impact on heart disease risk. Evidence suggests that garlic may reduce the incidence of heart attack or cardiac death.
Preliminary evidence suggests that garlic may be beneficial against oral microorganisms like Streptococci and may be an alternative to the antiseptic chlorhexidine. Further research is needed before a conclusion can be made.
Several studies describe garlic applied to the skin to treat fungal infections, including yeast infections. Additional research is needed before a conclusion can be drawn.
Atherosclerosis ("hardening" of the arteries)
Research suggests modest short-term reductions in total cholesterol and low-density lipoprotein (LDL or "bad" cholesterol) levels with garlic supplements. Insufficient evidence exists on the effects of garlic on arthrosclerosis prevention or treatment. Further research is warranted in this area.
Based on preliminary study, allicin (the major biologically active component of garlic) supplementation may reduce exercise induced muscle damage. The mechanism may be associated with allicin's antioxidant effects. Further studies are needed to confirm these findings.
A single dose of garlic has increased endurance performance. Long-term use of garlic for this purpose should be investigated.
Benign breast diseases
Preliminary research suggests a garlic combination supplement may improve symptoms of benign breast disease. Additional study is needed using garlic alone.
Preliminary human studies suggest that regular consumption of garlic (particularly unprocessed garlic) may reduce the risk of several cancer types, including gastric and colorectal cancer. Further well-designed studies are needed in this area.
Chest pain (angina)
Preliminary evidence suggests that garlic reduces chest pain by relieving spasm of the heart vessels and preventing blood clots. Additional studies are needed before a conclusion can be made.
Chronic venous ulcers (ulcers from poor circulation)
A study has reported benefits from a combination garlic therapy on venous ulcers. Further research is warranted on this topic.
Garlic supplementation has increased calf blood flow in healthy people. Further research is needed before conclusions can be made.
Common cold / upper respiratory tract infection
Preliminary reports suggest that garlic may reduce the severity of upper respiratory tract infections. In non-human studies, garlic has displayed anti-bacterial and anti-viral properties. Additional research is needed in this area.
Garlic has been studied in combination with other therapies for cystic fibrosis. Further research is warranted.
The dental effects of garlic have been studied. Further research is needed before firm conclusions may be made.
Familial hypercholesterolemia (inherited high cholesterol)
Familial hypercholesterolemia is a genetic disorder in which very high cholesterol levels are inherited. The effect of garlic on familial hyperlipidemia is unclear. Further research in this area is needed to draw a conclusion.
Gastric cancer prevention
Garlic has been studied for its use in gastric lesions. Further research is needed before firm conclusions may be made.
Gastritis (inflammation of stomach)
Preliminary evidence suggests that a combination product with garlic (Karinat®) may be beneficial for manging chronic atrophic gastritis, a precursor of stomach cancer. Additional evidence is needed before a conclusion can be made.
Application of garlic gel on the skin may be beneficial for treating hair loss. Additional study is needed on this topic.
Heart disease prevention (secondary)
Research suggests modest short-term reductions in total cholesterol and low-density lipoprotein levels (LDL or "bad" cholesterol) with oral garlic supplements. Long-term effects on lipids and atherosclerosis are unclear. There is limited evidence regarding the effects of garlic on heart attack, cardiac morbidity and mortality.
Heavy metal/lead toxicity
Garlic's role in improving clinical manifestations of lead poisoning has been studied. Further research is warranted.
Helicobacter pylori infection
In non-human studies, garlic has shown activity against bacteria and viruses. Several human case studies have examined the effects of garlic on H. pylori infection and found mixed results. Further research is needed to clarify these findings.
The effect of a hepatitis medication plus garlic oil has been studied. Further research of garlic alone is warranted.
Hepatopulmonary syndrome is shortness of breath in people with liver disease. Garlic has been studied in people with hepatopulmonary syndrome. Further research is needed before firm conclusions may be drawn.
A preliminary study lacked support regarding garlic consumption for repelling mosquitoes. Well-designed clinical trials are required before conclusions may be made.
Otitis media (middle ear infections)
Preliminary evidence suggests that a combination product containing garlic may be beneficial for ear pain caused by middle ear infections. Additional evidence is needed before a conclusion may be made.
Experts suggest that international travelers eat fresh garlic to prevent intestinal parasites. There are mixed results regarding the use of garlic in the treatment of parasitic infections. Further evidence is needed before a conclusion may be made.
Peripheral vascular disease (narrowed arteries in the legs)
Research suggests modest short-term reductions in total cholesterol and low-density lipoprotein levels (LDL or "bad" cholesterol) with oral garlic supplements. There is currently insufficient evidence demonstrating effects of garlic on peripheral vascular disease. Further research is warranted in this area.
Pre-eclampsia (high blood pressure in pregnancy)
In the available research, garlic administration lacked significant effects on the incidence of preeclampsia, systolic or diastolic blood pressure. Well-designed studies are still required.
Sickle cell anemia
Initial evidence suggests that aged garlic extract may reduce the number of damaged red blood cells in patients with sickle-cell anemia. Well-designed clinical trials are required before conclusions may be made.
Systemic sclerosis (thickening of skin)
Preliminary evidence suggests that dried garlic powder may benefit people with systemic sclerosis. Well-designed clinical trials are required before conclusions may be made.
Early research has reported fewer tick bites in people receiving garlic. However, there is a lack of sufficient data for or against the use of garlic as an insect repellent.
Type 2 diabetes
It is unclear if garlic may decrease glucose concentrations and increase insulin secretion. Additional research is needed in this area.
According to preliminary research, garlic extract applied to the skin may be beneficial in treating warts and corns. This effect may be due to garlic's antiviral, immune-stimulating, or blood clot prevention properties. Further research is needed.
*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).
For full grading rationale, click here.
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 health care professional
Abortion inducing, age-related memory disorders, aging skin, allergies, Alzheimer's disease, anthrax, antioxidant, antispasmodic (suppressing spasms), antitoxin, antiviral, anxiety, arrhythmia (abnormal heart rhythm), arsenic poisoning, arthritis, asbestos lung protection, asthma, bile flow stimulant, bladder disorders, blood clot prevention, bloody urine, bone and wound healing, bronchitis, chemotherapy toxicity, cholera, contraception, cough, cytomegalovirus (virus of the herpes family), dementia (prevention), diaphoretic (promote sweating), diarrhea (traveler's), digestive aid, diphtheria (bacterial infection), diuretic (increasing urination), doxorubicin cardiotoxicity (protection against heart damage), drug/toxin induced hepatotoxicity (acetaminophen), dysentery (bloody diarrhea), earache, emetic (causing vomiting), energy, expectorant (increasing mucus), fat burning, fatigue, fever, flu, gallstones, gastrointestinal hypermotility (overactive intestinal tract), gentamicin toxicity, glaucoma (increased eye pressure), hair growth, headache, heartburn, hemorrhoids, HIV/AIDS, hormonal effects, immune system stimulation, inflammation, inflammatory bowel disease, kidney disorders, kidney toxicity, leukemia, libido, lung disease, lymphangitis (inflammation of lymph nodes), malaria, menstrual flow stimulant, methicillin-resistant Staphylococcus aureus, methotrexate toxicity, muscle spasms, neuroprotection, obesity, osteoporosis, painful menstruation, peptic ulcer disease, pneumonia, premenstrual syndrome (PMS), psoriasis (skin disease), radioprotection, Raynaud's disease (blood vessel disorder), ringworm, sedative, sexual arousal, sinus congestion, snake venom protection, spermicide, stomachache, stress, stroke, toothache, tuberculosis, tumor (breast fibromatosis), typhus, urinary tract infections, vaginal trichomoniasis (sexually transmitted disease), vaginitis (vaginal inflammation), warts, well-being, whooping cough, wound healing.
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy. Consult a healthcare professional immediately if you experience side effects.
Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy.
Natural Standard developed the above evidence-based information based on a systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.
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