Garlic
(Allium sativum)

What is Garlic?
A nice review by students from the University of North Carolina School of Pharmacy

Garlic: 4 Varieties for Health
Nutrition Science News (March 2000)
Garlic contains many substances that studies show act together to prevent disease and age-related conditions. Sulfur-containing compounds are responsible for most of the health benefits of garlic and its preparations. [2, 3] Nonsulfur compounds in garlic include proteins, carbohydrates, saponins, flavonoids (notably allixin) and selenium. [4]

Enlist Garlic
2005 Garlic Symposium in Washington, DC
Papers presented at the 2005 Garlic Symposium in Washington, DC, held April 9 to 11, report the current scientific research into the effects of garlic on heart health and cancer prevention. Many of the studies presented reported the benefits of aged-garlic extract, an odourless supplement made from organically grown garlic.

Supplementation with Aged Garlic Extract Improves Both NK and γδ-T Cell
Function and Reduces the Severity of Cold and Flu Symptoms: A
Randomized, Double-blind, Placebo-controlled Nutrition Intervention
Clin Nutr. 2012 (Jun);   31 (3):   337–344
This trial showed that garlic supplementation reduced symptoms of colds or flu by 21%, and reduced the incidence by 58%, reduced the duration by 61%, and finally reduced days of lost school or work by a whopping 58%

Heat Stable Antimicrobial Activity of Allium ascalonicum
Against Bacteria and Fungi
Indian J Exp Biol 2005 (Aug); 43 (8): 751–754
To study antimicrobial activity of shallot in comparison with that of garlic and onion against 23 strains of fungi and bacteria, water extracts of garlic, shallot and onion bulbs were prepared. Each extract was studied in different forms for their antimicrobial activity viz., fresh extract, dry extract and autoclaved extract. Minimal inhibitory concentration and minimal lethal concentrations of these extracts were determined against all organisms by broth dilution susceptibility test. Fresh extract of garlic showed greater antimicrobial activity as compared to similar extracts of onion and shallot. However, dried and autoclaved extracts of shallot showed more activity than similar extracts of onion and garlic.

Helicobacter Pylori - In Vitro Susceptibility to
Garlic (Allium Sativum) Extract
Nutrition and Cancer 1997; 27(2): 118–121
In an in vitro model, an aqueous extract of garlic cloves was standardized for its thiosulfinate concentration and tested for its antimicrobial activity on Helicobacter pylori. The minimum inhibitory concentration of garlic was 40 g thiosulfinate per ml when it was tested on a chocolate agar plate with Helicobacter pylori.

Garlic (Allium sativum)--A Potent Medicinal Plant
Fortschr Med 1995 (Jul 20); 113 (20-21): 311–315
A good deal of evidence suggests beneficial effects of the regular dietary intake of garlic on mild hypertension and hyperlipidemia. Garlic seems to have anti-microbial and immunostimulating properties, enhance fibrinolytic activity, and exert favorable effects on platelet aggregation and adhesion. Standardised preparations guarantee exact dosing and minimize the problem of the strong odour of raw garlic. Thus, a traditional folk remedy has established its usefulness for many patients with less severe forms of cardiovascular disease as a medical drug with very few side effects. The available evidence gives rise to the hope that the list of indications may even be considerably extended in the future.

Antioxidant Activity of Allicin, an Active Principle in Garlic
Molecular and Cellular Biochemistry 1995 (Jul 19); 148 (2): 183–189
Garlic has been claimed to be effective against diseases, in the pathophysiology of which oxygen free radicals (OFRs) have been implicated. Effectiveness of garlic could be due to its ability to scavenge OFRs. However, its antioxidant activity is not know. We investigated the ability of allicin (active ingredient of garlic) contained in the commercial preparation Garlicin to scavenge hydroxyl radicals (-OH) using high pressure liquid chromatographic (HPLC) method.

A Quantitative Assessment of the Anti-Microbial Activity of Garlic
World Journal of Microbiology and Biotechnology 1993; 9: 303v307
An aqueous extract of freeze-dried garlic (Allium sativum), when incorporated into growth media, inhibited many representative bacteria, yeasts, fungi and a virus.

Allicin, a Naturally Occurring Antibiotic From Garlic, Specifically
Inhibits Acetyl-CoA Synthetase
FEBS Lett 1990 (Feb 12); 261 (1): 106–108
Allicin is shown to be a specific inhibitor of the acetyl-CoA synthetases from plants, yeast and mammals. The bacterial acetyl- CoA-forming system, consisting of acetate kinase and phosphotransacetylase, was inhibited too.

The Antimicrobial Activity of Garlic and Onion Extracts
Pharmazie 1983 (Nov); 38 (11): 747–8
Aqueous extracts of garlic (Allium sativum) and onion (Allium cepa) were tested for activity against Gram-positive organisms, Gram-negative organisms and fungi. A significant growth inhibition was shown by most of the organisms, tested at random. A quantitative assessment of the activity was carried out by determining the minimum bacteriostatic and bactericidal concentrations of the extracts against Gram-positive and Gram-negative organisms. Garlic extract showed greater activity as compared to the extract of onion.

Allium Sativum (Garlic) Treatment for Murine
Transitional Cell Carcinoma
Cancer 1997 (May); 79: 1987–1994
The significant antitumor efficacy of subcutaneous and oral AS warrants further investigation and suggests that Allium Sativum may provide a new and effective form of therapy for transitional cell carcinoma of the bladder.

Helicobacter Pylori - In Vitro Susceptibility to
Garlic (Allium Sativum) Extract
Nutrition and Cancer 1997; 27 (2): 118–121
In an in vitro model, an aqueous extract of garlic cloves was standardized for its thiosulfinate concentration and tested for its antimicrobial activity on Helicobacter pylori. The minimum inhibitory concentration of garlic was 40 g thiosulfinate per ml when it was tested on a chocolate agar plate with Helicobacter pylori. This is the first report of Helicobacter pylori susceptibility to garlic extract of known thiosulfate concentration. This may be a new, low-cost intervention strategy with few side effects in populations at high risk for stomach cancer.

Allium sativum (Garlic) and Cancer Prevention
Nutrition Research 1990; 10: 937–948
Epidemiological studies reveal an inverse relationship between garlic consumption and death rate for gastric cancer in populations in China. These reports suggest a role for garlic in the prevention of human cancer. Garlic has been shown to inhibit the growth of transplantable tumors and to reduce the incidence of certain spontaneously-occurring tumors.

An Evaluation of Garlic and Onion as Antithrombotic Agents
Prostaglandins Leukot Essent Fatty Acids 1996 (Mar); 54 (3): 183–6
Aqueous extracts of garlic (Allium sativum) and onion (Allium cepa) were given orally or intraperitoneally to rats for a period of 4 weeks. Thromboxane B2 levels were significantly inhibited at 50 mg/kg of aqueous garlic extract, which is a low dose. At 500 mg/kg of garlic and onion, there was a further reduction in thromboxane B2 levels in the serum of rats.

Consumption of a Garlic Clove a Day Could be Beneficial
in Preventing Thrombosis
Prostaglandins Leukot Essent Fatty Acids 1995 (Sep); 53 (3): 211–2
The effect of the consumption of a fresh clove of garlic on platelet thromboxane production was examined. A group of male volunteers in the age range 40-50 years participated in the study. Each volunteer consumed one clove (approximately 3 g) of fresh garlic daily for a period of 16 weeks. Each participant served as his own control. Thromboxane B2 (TXB2, a stable metabolite of thromboxane A2), cholesterol and glucose were determined in serum obtained after blood clotting. After 26 weeks of garlic consumption, there was an approximately 20% reduction of serum cholesterol and about 80% reduction in serum thromboxane.

Effects of Garlic Extract on Platelet Aggregation: A Randomized
Placebo-Controlled Double-Blind Study
Clin Exp Pharmacol Physiol 1995 (Nov); 22 (11): 888–9
Studies of the effects of garlic on platelet aggregation have produced inconsistent results possibly related to variations in study design and in the garlic preparations used. The present study examined the effects on platelet aggregation and serum thromboxane and lyso-platelet activating factor, of feeding garlic extract to healthy men using a placebo-controlled, double-blind design. The effects of the same garlic preparation on platelet aggregation in vitro were also investigated.

Effect of Garlic and Fish-oil Supplementation on Serum Lipid and
Lipoprotein Concentrations in Hypercholesterolemic Men
Am J Clin Nutr 1997 (Feb); 65 (2): 445–50
The combination of garlic and fish oil reversed the moderate fish-oil-induced rise in LDL-C. Coadministration of garlic with fish oil was well-tolerated and had a beneficial effect on serum lipid and lipoprotein concentrations by providing a combined lowering of total cholesterol, LDL-C, and triacylglycerol concentrations as well as the ratios of total cholesterol to HDL-C and LDL-C to HDL-C.

A Double-Blind Crossover Study in Moderately Hypercholesterolemic Men
That Compared the Effect of Aged Garlic Extract and Placebo
Administration on Blood Lipids
Am J Clin Nutr 1996 (Dec); 64 (6): 866–70
A double-blind crossover study comparing the effect of aged garlic extract with a placebo on blood lipids was performed in a group of 41 moderately hypercholesterolemic men {cholesterol concentrations 5.7-7.5 mmol/L (220-290 mg/dL)}. After a 4-wk baseline period, during which the subjects were advised to adhere to a National Cholesterol Education Program Step I diet, they were started on 7.2 g aged garlic extract per day or an equivalent amount of placebo as a dietary supplement for a period of 6 mo., then switched to the other supplement for an additional 4 mo. Blood lipids, blood counts, thyroid and liver function measures, body weight, and blood pressure were followed over the entire study period.

Garlic Powder Tablets Reduce Atherogenicity of Low Density
Lipoprotein. A Placebo-Controlled Double-Blind Study
Nutrition and Metabolism and Cardiovascular Disease 1996; 6: 21–31
In a placebo-controlled double-blind trial of 23 subjects with coronary artery disease who had 1 to 3 major coronary arteries that were 72% blocked or higher, 300 mg of garlic powder from 1 Kwai tablet, 2 and 4 hours after a single dose, showed the atherogenicity of the patients sera to be markedly decreased.

Garlic as a Lipid Lowering Agent-A Meta-Analysis
Journal of the Royal College of Physicians of London 1994; 28(1):
Garlic supplements may have an important role to play in the treatment of hypercholesterolaemia. To determine the effect of garlic on serum lipids and lipoproteins relative to placebo and other lipid lowering agents, a systematic review, including meta- analysis, was undertaken of published and unpublished randomized controlled trials of garlic preparations of at least four weeks duration.

Effect of Garlic on Total Serum Cholesterol
Ann Intern Med 1993 (Oct 1); 119 (7 Pt 1): 599–605
Meta-analysis of the controlled trials of garlic to reduce hypercholesterolemia showed a significant reduction in total cholesterol levels. The best available evidence suggests that garlic, in an amount approximating one half to one clove per day, decreased total serum cholesterol levels by about 9% in the groups of patients studies.

Garlic Supplementation and Lipoprotein Oxidation Susceptibility
Lipids 1993 (May); 28 (5): 475–7
Because garlic has been reported to beneficially affect serum lipid levels, platelet function, fibrinolysis and blood pressure, this additional effect of retarding lipoprotein oxidation may contribute to the potential antiatherosclerotic effect of garlic.

Can Garlic Reduce Levels of Serum Lipids? A Controlled Clinical Study
The American Journal of Medicine 1993 (Jun); 94: 632–635
Treatment with standardized garlic 900 mg/d produced a significantly greater reduction in serum TC and LDL-C than placebo. The garlic formulation was well tolerated without any odor problems.

A Meta-Analysis of the Effect of Garlic on Blood Pressure
Journal of Hypertension 1994 (Apr); 12 (4): 463–468
The results suggest that this garlic powder preparation may be of some clinical use in subjects with mild hypertension. However, there is still insufficient evidence to recommend it as a routine clinical therapy for the treatment of hypertensive subjects. More-rigorously designed and analyzed trials are needed.

Can Garlic Lower Blood Pressure? A Pilot Study
Pharmacotherapy 1993 (Jul); 13 (4): 406–7
Our results indicate that this garlic preparation can reduce blood pressure. Further controlled studies are needed, particularly with more conventional doses (e.g., < or = 900 mg/day), in patients with mild to moderate hypertension and under placebo-controlled, double-blind conditions.