Garlic is a member of the same group of plants as the Onion. The bulb is the part used for consuming or as medicine. Epidemiological as well as laboratory studies have shown that garlic and onion consumption reduces certain cancer incidences in the stomach, colon, mammary, cervical, etc.
In an analysis of eight studies from Italy and Switzerland, researchers found that older adults with the highest onion and garlic intakes had the lowest risks of a number of cancers -- including colon, ovarian and throat cancers.
Garlic has been shown to metabolized into N-aceryl-S-allyl cysteine, allyl mercaptan, diallyl disulfide, diallyl sulfide, diallyl sulfoxide, diallyl sulfone, and allyl methyl sulfide. Garlic has been thought to bring about its anticarcinogenic effect through a number of mechanisms, such as the scavenging of radicals, increasing gluathione levels, increasing the activities of enzymes such as glutathione S-transferase, catalase, inhibition of cytochrome p4502E1, DNA repair mechanisms, prevention of chromosomal damage etc.
Health Benefit of Garlic
It appears that garlic may lower the risk of atherosclerosis (hardening of the arteries), but not necessarily through lowering cholesterol levels. Garlic may have anti-platelet activity and also lower blood pressure.
Garlic anti-microbial activity in the mouth.
Eating just one clove of raw or cooked garlic daily may help protect against stomach, esophagela, and colon cancer. That's the conclusion reached by a researcher at the
Garlic can combat intestinal parasites, perhaps fungal infections such as athlete's foot and perhaps vaginal yeast infections.
Garlic and Allicin
An ingredient in garlic appears to prevent a potentially deadly type of high blood pressure affecting the lungs, at least in rats. The garlic ingredient, called allicin, seems to ward off pulmonary hypertension, or high blood pressure in the arteries that bring blood to the lungs. In humans, pulmonary hypertension can lead to potentially fatal complications in the heart and blood vessels. Humans would need to eat two cloves of garlic every day to equal the rats' dose of allicin.
Garlic pills are sold in various extracts, including aged garlic and garlic extract with 2% Allicin. I prefer to eat a fresh garlic clove rather than to take a garlic supplement, but each person has a different preference. Each garlic clove is about 2 to 5 grams.
Garlic side effects or caution
Besides the obvious garlic bad breath, it may be a good idea to not consume high doses of garlic if you plan to have surgery because of the possible blood thinning properties of garlic. Very high intake of garlic may cause easy bruising.
Consider the use of mint, parsley, or fennel seeds to partially counteract garlic breath.
Garlic and cholesterol
Three forms of garlic -- including raw garlic and two types of commercial garlic supplements -- did not significantly reduce LDL cholesterol during a six-month trial. Crushing garlic triggers the formation of a compound known as allicin, which has been shown to prevent the formation of cholesterol in the laboratory. However, clinical trials on garlic as a cholesterol-lowering agent in humans have been inconsistent. Christopher D. Gardner, PhD, Stanford University Medical School, and colleagues enrolled 192 adults age 30 to 65 who had moderately high LDL levels (130 to 190 milligrams per deciliter) beginning in November 2002. Forty-nine participants were randomly assigned to receive raw garlic, 47 to take a powdered garlic supplement, 48 to take an aged garlic supplement and 48 to take placebo. The amount of garlic consumed in the three garlic groups was the equivalent of an average-sized garlic clove each day, six days per week. Fasting blood cholesterol levels were assessed monthly, and the chemical composition of the supplements was checked regularly. There were no statistically significant effects of the three forms of garlic on LDL cholesterol concentrations. Levels of other types of cholesterol -- including HDL, triglycerides and total cholesterol–high density lipoprotein cholesterol ratio -- also remained the same. No serious adverse events occurred, although bad body and breath odor were reported to occur often or almost always 57% in the raw garlic group.
Garlic and blood pressure
A combination of garlic supplements and vitamin C reduced blood pressure back to normal levels in people with mildly elevated levels. Garlic ingredients or garlic extract alone increases endothelial cell nitric oxide production, an effect that was shown to be enhanced by the combination with antioxidant vitamins. Drs. Mousa and Mousa recruited six subjects with marginally elevated blood pressure (140/90 mmHg) and assigned them to take placebo for 10 days; followed by one-week washout, then vitamin C (2000 mg) for 10 days, a further week of wash-out period, then garlic tablets (650 mg of bulb powder) for 10 days. Finally, after the last washout, garlic and vitamin C were given together for 10 days. They report that the daily vitamin C alone did not have any effect on blood pressure, while garlic alone resulted in a significant decrease in systolic but not diastolic blood pressure. When the supplements were given together mean systolic and diastolic blood pressures reduced to reference values of 110-120 and 75-80 mmHg, respectively. Blood pressure increased when the combined supplement was stopped. Measurements of nitric oxide levels after garlic administration showed a two-fold increase, relative to placebo, while administration of both garlic and vitamin C resulted in a three-fold increase, relative to the control. Nutrition Research, Volume 27, Issue 2, Pages 119-123. "Cellular effects of garlic supplements and antioxidant vitamins in lowering marginally high blood pressure in humans: pilot study" Authors: A.S. Mousa and S.A. Mousa
Garlic Research Update
Comparison of the Bioactive Compounds and Antioxidant Potentials of Fresh and Cooked Polish, Ukrainian, and Israeli Garlic.
J Agric Food Chem. 2005 Apr 6;53(7):2726-2732.
Garlic (Allium sativum L.) is an essential part of Polish, Ukrainian, and Israeli cuisine. The aim of this investigation was to compare the changes in bioactive compounds, proteins, and antioxidant potentials in fresh Polish, Ukrainian, and Israeli garlic samples after subjection to cooking temperature. Dietary fiber and essential trace elements were comparable. The antioxidant potentials were determined by four scavenging methods using beta-carotene, 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide (NO), and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS(*)(+)) radical cation with K(2)S(2)O(8) or MnO(2) assays. Polyphenols, tocopherols, proteins, and antioxidant potentials were higher in Polish garlic, but not significantly (P > 0.05). The SDS- and native-PAGE electrophoretic patterns of all three fresh garlic samples were without significant differences. Most of the proteins were in the molecular mass range of 24-97 kDa, and the more intensive major bands were concentrated at 50 and 12 kDa. The 50 kDa protein nearly disappears and the intensity of the 12 kDa lectin bands slightly decreases during cooking. It was observed that the bioactive compounds, antioxidant potential, and proteins in garlic decrease significantly after 20 min of cooking at 100 degrees C. In conclusion, (a) the bioactive compounds, electrophoretic patterns, and antioxidant potential of fresh Polish, Ukrainian, and Israeli garlic samples are comparable; (b) garlic samples subjected to 100 degrees C during 20 min preserve their bioactive compounds, antioxidant potential, and protein profile and are comparable with fresh garlic; and (c) fresh garlic should be added to dishes cooked at 100 degrees C in the last 20 min of the cooking process.
The efficacy of cholesterol-lowering action and side effects of garlic enteric coated tablets in man.
J Med Assoc
The present study aimed at investigating the cholesterol-lowering and side effects of garlic enteric coated tablets in comparison with placebo tablets. The study is a randomized double-blinded crossover design involving 116 volunteers. However, 16 of them did not complete the study. The remaining 100 volunteers were divided into two groups: 45 were in the trial group and the remaining 55 in the control group. The volunteers in the trial group were asked to take garlic tablets in the first three months, placebo in the second three months and discontinue all tablets in the last three months, while the volunteers in the control group started with three months of placebo followed by three months of garlic tablets and ended up with three months of tablets discontinuity. The results showed that there were no significant differences in the total serum cholesterol levels between the two groups at the end of three months or six months of the study. Side effects included headache, itching and complaints of garlic smell. No serious side effects relating to liver, kidney functions or hematologic side effects were detected.
Effect of garlic (Allium sativum) powder tablets on serum lipids, blood pressure and arterial stiffness in normo-lipidaemic volunteers: a randomised, double-blind, placebo-controlled trial.
Br J Nutr. 2004 Oct;92(4):701-6.
Recent studies have cast doubt on the proposed lipid-lowering and blood pressure-lowering effects of garlic. We tested the effect of dried garlic (Allium sativum) powder on blood lipids, blood pressure and arterial stiffness in a 12-week randomised, double-blind, placebo-controlled trial. Seventy-five healthy, normo-lipidaemic volunteers (men and women aged 40-60 years) were assigned to dried garlic powder tablets (10.8 mg alliin (3-(2-propenylsulfinyl)-L-alanine)/d, corresponding to about three garlic cloves) or placebo. Sixty-two subjects were eligible for the per-protocol analysis. The primary outcome measure was serum total cholesterol concentration. Secondary outcome measures were LDL-cholesterol, HDL-cholesterol and triacylglycerol concentrations, blood pressure and arterial stiffness (assessed by pulse wave velocity). No significant differences between the garlic and placebo groups were detected for any of the outcome measures. However, garlic powder was associated with a near-significant decrease (12 %) in triacylglycerol concentration (P=0.07). In conclusion, garlic powder tablets have no clinically relevant lipid-lowering and blood pressure-lowering effects in middle-aged, normo-lipidaemic individuals. The putative anti-atherosclerotic effect of garlic may be linked to risk markers other than blood lipids.
Effect of garlic on lipid profile and psychopathologic parameters in people with mild to moderate hypercholesterolemia.
Isr Med Assoc J. 2003 Sep;5(9):637-40.
The beneficial effect of 3-hydroxy-3-methylglutyaryl co-enzyme A reductase inhibitors on cardiovascular risk reduction has been clearly established. Concerns have been raised that lowering blood cholesterol by other hypolipidemic drugs or by a non-pharmacologic approach may have deleterious effects on psychopathologic parameters. Garlic is one of the most commonly used herbal remedies and is considered to have hypocholesterolemic as well as other cardioprotective properties. Its effect on psychopathologic parameters has never been reported. OBJECTIVE: To evaluate the effect of garlic on lipid parameters and depression, impulsivity, hostility and temperament in patients with primary type 2 hyperlipidemia. METHODS: In a 16 week prospective double-blind placebo-controlled study, 33 patients with primary hypercholesterolemia and no evidence of cardiovascular disease were randomly assigned to receive either garlic or placebo. Garlic in the form of alliin 22.4 mg/day was given to 13 patients, and placebo to 20. Both groups received individual dietary counseling. The changes in lipid profile and the various psychopathologic parameters were determined at the beginning and end of the trial. The differences in lipid parameters were evaluated by Student's t-test. The psychological data were analyzed by one-way analysis of variance (ANOVA) with repeated measures and Neuman-Keuls test. RESULTS: No significant changes were observed in levels of total cholesterol, low density lipoprotein-cholesterol, high density lipoprotein-cholesterol and triglycerides, or in the psychopathologic parameters evaluated. CONCLUSION: Short-term garlic therapy in adults with mild to moderate hypercholesterolemia does not affect either lipid levels or various psychopathologic parameters.
No effect of garlic extract supplement on serum lipid levels in hypercholesterolemic subjects.
J Med Assoc
The authors assessed the effects of an enteric-coated Thai garlic extract tablet standardized for allicin-releasing potential on serum lipid levels in hypercholesterolemic subjects. SUBJECTS AND METHOD: The authors performed a randomized, double-blind, placebo-controlled trial in 136 hypercholesterolemic subjects (cholesterol concentrations > or = 5.2 mmol/L; mean age +/- SD: 47.0 +/- 6.6 yr). All subjects were given dietary advice to lower fat intake within 4 weeks and were advised to eat normally during the study period. The subjects were randomly assigned to receive an enteric-coated Thai garlic extract tablet once daily (standardized to 1.12% allicin or 5.6 mg/tablet), or placebo after the evening meal for 12 weeks. Seventy subjects (32.9% male; mean age +/- SD and BMI of 47.0 +/- 6.6 yr and 24.6 +/- 3.3 kg/m2) received the garlic extract treatment while 66 subjects (37.9% male, mean age +/- SD and BMI of 47.0 +/- 6.0 yr and 24.3 +/- 3.4 kg/m2) received placebo. RESULTS: There were no statistically significant changes in serum total cholesterol, triglycerides, low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol after the 12-week treatment as analyzed on repeated measures by analysis of variance. In addition, no changes in plasma glucose, liver and renal functions were found. CONCLUSIONS: Treatment with an enteric garlic-coated Thai garlic extract and dietary advice did not produce any significant changes in lipid levels in subjects with hypercholesterolemia.
Antimicrobial activity of garlic, tea tree oil, and chlorhexidine against oral micro-organisms.
Int Dent J. 2002 Dec;52(6):433-7.
To compare the antimicrobial activity of tea tree oil, garlic, and chlorhexidine solutions against oral microorganisms. METHOD: The five-week study consisted of thirty subjects. The first week was considered baseline. All subjects used a control solution (second week), and were randomly divided into the three groups (third week): G1-0.12% chlorhexidine; G2 - 2.5% garlic (Allium sativum, L.); and G3 - 0.2% tea tree oil (Melaleuca alternifolia). Dishes containing blood agar and Mitis Salivarius Bacitracin agar (MSB) were inoculated with the subjects' saliva (collected twice a week). Total microorganisms and mutans streptococci were counted in blood agar and MSB, respectively. RESULTS: Chlorhexidine and garlic groups showed antimicrobial activity against mutans streptococci, but not against other oral microorganisms. The tea tree oil group showed antimicrobial activity against mutans streptococci and other oral microorganisms. Maintenance of reduced levels of microorganisms was observed only for garlic and tea tree oil during the two consecutive weeks (fourth and fifth). Unpleasant taste (chlorhexidine 40%, tea tree oil 30%, garlic 100%), burning sensation (chlorhexidine 40%, tea tree oil 60%, garlic 100%), bad breath (chlorhexidine 40%, tea tree oil 20%, garlic 90%), and nausea (chlorhexidine 0%, tea tree oil 10%, garlic 30%) were reported. CONCLUSION: Garlic and tea tree oil might be an alternative to chlorhexidine.
Hypotensive effect of long-acting garlic tablets allicor (a double-blind placebo-controlled trial)]
Ter Arkh. 2002;74(3):76-8.
AIM: To evaluate a hypotensive action of long-acting garlic powder tablets allicor in patients with mild or moderate hypertension and to compare allicor effects with those of foreign analog--kwai garlic tablets. A double-blind, randomized and placebo-controlled study enrolled 85 patients with mild or moderate hypertension. The patients were divided into 4 groups: group 1 received allicor in a dose 600 mg/day, group 2--2400 mg/day, group 3--kwai in a dose 900 mg/day, group 4--placebo. RESULTS: Allicor produced reaction in both systolic and diastolic pressure. An increase of allicor daily dose to 2400 mg does not provide an additional hypotensive effect. Kwai results in only systolic but not diastolic arterial pressure lowering. CONCLUSION: Allicor is more effective than kwai in reduction of diastolic blood pressure. It can be recommended as a hypotensive treatment in mild and moderate arterial hypertension.
Anti-arrhythmic profile of a garlic dialysate assayed in dogs and isolated atrial preparations.
J Ethnopharmacol. 1994 Jun;43(1):1-8.
The effects of garlic (Allium sativum L., Liliaceae) dialysate were studied on arrhythmias induced in anaesthetized dogs and on isolated left rat atria. Garlic dialysate suppressed premature ventricular contractions (PVC) and ventricular tachycardia (VT) in ouabain-intoxicated dogs as well as the ectopic rhythms induced by isoprenaline (10(-6) M) and aconitine (10(-8) M) on electrically driven left rat atria. The effective refractory period (ERP) and the sinus node recovery time (SNRT) of isolated rat atria were prolonged in a dose-dependent manner by the administration of this extract. Garlic dialysate decreased the positive inotropic and chronotropic effects of isoprenaline in a concentration-dependent manner. These last effects were increased by propranolol. The results suggest that garlic dialysate has a significant antiarrhythmic effect in both ventricular and supraventricular arrhythmias.
Garlic clove -- garlic has diallyl sulfide which inhibits chemical carcinogens activated by CYP2E1. Garlic has hypolipidemic, hypoglycemic, antibacterial, antifungal, antioxidant and anticancer effects. Garlic odor or garlic breath is caused by conversion of alliin to volatile sulfur compounds. Heated, cooked, or roasted garlic is less healthy. Garlic bread is not a good way to get the benefit of garlic since there is little actual garlic and much of the ingestion is white bread with no nutritional value.
Garlic (Allium sativum L.) has been used as an herbal medicine, but there is no report on the health benefits of the skin or peel. The extract of garlic skins (peels) showed strong antioxidant activity, and some responsible constituents were isolated and identified. These compounds were phenylpropanoids, N-trans-Coumaroyloctopamine, N-trans-feruloyloctopamine, guaiacylglycerol-beta-ferulic acid ether, and guaiacylglycerol-beta-caffeic acid ether were identified as were trans-coumaric acid and trans-ferulic acid.
Garlic has long been used medicinally, most recently for its cardiovascular, antineoplastic, and antimicrobial properties. Sulfur compounds, including allicin, appear to be the active components in the root bulb of the garlic plant. Studies show significant but modest lipid-lowering effects and antiplatelet activity. Significant blood pressure reduction is not consistently noted. There is some evidence for antineoplastic activity and insufficient evidence for clinical antimicrobial activity. Side effects generally are mild and uncommon. Garlic appears to have no effect on drug metabolism, but patients taking anticoagulants should be cautious. It seems prudent to stop taking high dosages of garlic seven to 10 days before surgery because garlic can prolong bleeding time.