May 23 2022

Medicinal uses of common garlic (Allium Sativum))

Introduction     

Common garlic(<em>Allium Sativum</em>)

The popular Garlic is a plant belonging to the lily family, originary of Central Asia, from where its cultivation spreads worldwide. Garlic is one of the most important medicinal plants, especially appreciated in the Far East[1-3]. Also in USA is one of the most used medicinal plants[4].

Knowledge and use of garlic as a medicinal remedy is very old. Already in the Ebers Papyrus (1550 BC) were attributed antitumoral effects to this plant[5-6].

At the time of Dioscorides its use as therapeutic resource was widespread. According to the claims of this author, garlic can expel flatulences, causes disturbing belly, is desiccant of the stomach, generator of thirst and produces superficial ulcerations. Its therapeutic usefulness included elimination of intestinal parasites and ectoparasites such as lice and nits, snake bites and rabid dogs, provoking diuresis and sedation of cough, besides several other applications.

The first scientific observations of garlic start with Louis Pasteur, who was the first author to describe the antibacterial effect of garlic and onion[7]. Later have been happening experimental and clinical investigations that have left us at the gates of a lot of potential future applications based on scientific evidence.

Synonymy     

Scientific names:

- Allium controversum
- Allium ophioscorodon
- Allium sativum subespecie ophioscorodon
- Allium sativum variedad ophioscorodon

Composition     

Garlic exert its effects through more than 200 substances. This edible vegetable contains sulfur-containing compounds such as allicin, alliin and ajoene, volatile oils, enzymes (alliinase, peroxidase and miracinase), carbohydrates (sucrose and glucose), minerals (selenium), amino acids such as cysteine, glutamine, isoleucine and methionine, that help to protect cells from free radicals, bioflavonoids like quercetin and cyanidin, alistatin I and II and vitamins C, E and A to help protect people from oxidation and free radicals, as well as other vitamins like niacin, vitamins B1 and B2 and beta-carotene[1].

As just indicated, the components of garlic include enzymes as alliinase and amino acids containing sulphides, including alliin, an odorless and tasteless substance, devoid of therapeutic effects, derived from other(allicin) by effect of enzymes from the plant, when released by chew, crush or cut garlic[8]. Allicin can subsequently be transformed into other compounds with different biological properties, such as ajoene, vinilditine, diallyl disulfide or diallyl trisulfide.

Garlic has the particularity to have different properties depending on whether raw or cooked. If you cut or crushed a clove of garlic, alliin is released, which is converted by effects of alliinase in allicin. This transformation does not take place if previously garlic is cooked, releasing substances other as ajoene, which have different effects.

Allicin (diallyil thiosulfide) is the main biologically active component of garlic oil and is produced by the interaction between alliin and alliinase [9]. Allitridine is one of main active compounds of garlic [10]. The S-allyl-cysteine mercapto is an organosulfur derived from garlic, present in the alcoholic extract[11]. In addition to allicin and ajoene, already mentioned, can be detected other as allyl metyl thiosulphide, metyl allyl thiosulphide, alliin, deoxialliin, diallyl disulfide and diallyl trisulfide[12].

Allicin contains hydrogen sulfide as main compound, which, in theory, facilitates relaxation of vascular cells, reducing blood pressure, promoting circulation passage and transport of oxygen through the blood.

Although garlic contains over 20 sulfur compounds from a few amino acids, the function of each of them looks different from the other. For example, allicin, metyl allyl trisulphide and diallyl trisulphide have antibacterial, anti-thrombotic and anticancer activity respectively[13].

Diallyl trisulfide final compound is stable and proceed from degradation of allicin[14], that was first synthesized in China in 1981 and is used to treat infections causes by bacteria, fungi and other pathogens.

Immunomodulatory proteins present in garlic are ASA I and ASA II lectins. These substances, when are of nutritional origin, are very stable and with high immunogenic influence[15-16].

Ajoene (4,5,9-trithiadodeca-1,6,11-triene-9-oxide) is a derivative of garlic that has greater stability than allicin [6] .

The antibiotic effect is attributed to allicin, as the hypoglycemic effect, to which also contribute disulfide allyl propyl and S-allylcysteine sulfoxide compounds, while the anticancer effect would be related to diallyl mono sulphide. The inhibition of platelet aggregation would be due triallyl and diallyl sulfide compounds. Ajoene inactivates gastric lipase, closely related to digestion and absorption of fats. Tetra, hexa and hepta diallyl sulfides compounds are potentially antioxidants.

Medicinal properties of garlic are related to organosulfur compounds mainly alliin derivatives [5].

Properties and traditional applications     

Garlic has been traditionally used to treat a wide variety of ailments, including bacterial and fungal infections [17-18], intestinal worm infestations, wounds, diarrhea, rheumatism, diabetes mellitus, cardiovascular diseases (thrombosis, hypertension, hyperlipidemia), metabolic disorders and others. Today, this plant is included in traditional medicine in most cultures[19]. Garlic, available in various formulations for medicinal purposes has also been used to relieve symptoms caused by cancer and benign prostatic hypertrophy[20]. However, in all the applications listed, clinical evidence in support of these uses is very weak or is absent.

Popularly is also used or has been used in the past as mosquito repellent, anti-catarrhal, for hoarseness and as a sedative for cough. Topical application of garlic is used traditionally to treat skin warts.

Some organizations such as German Commission E, recommended garlic as an aid to dietary measures in patients with elevated blood lipid levels and as a preventive measure of vascular changes associated with aging. The British Herbal Pharmacopoeia attributed to garlic antibacterial properties, considering that is effective for respiratory infections and catarrhal conditions (The British Herbal Compendium). The indian Ayurveda Pharmacopoeia recommends the use of garlic as a brain tonic, appropriate in mental disorders and epilepsy.

In some parts of the Arab world stems inhalation of garlic is recommended to treat tuberculosis. In that cultural sphere is believed that eating garlic daily is good for preventing colic, diarrhea, abdominal pain, diabetes mellitus and inflammations. It is also recommended to boil peeled garlic cloves, accompanied by cow's milk, sen, laurel and pepper to treat colds, nephrosis and improve memory performance.

The ash of burnt garlic cloves would be used in that same culture to treat eye infections.

In general, garlic is one of the most widely used botanical therapeutic resources in the Arab world [21-22]. A study shows that over 10% of Jordanians with diabetes mellitus have taken garlic as a remedy for their illness[23]. In Palestine is recommended to treat cancer and prostate hypertrophy[24]. In the eastern area of Morocco, garlic is widely used as antihypertensive[25].

In traditional Bolivian culture is believed that eating garlic is good for atherosclerosis (three cloves of garlic and honey in a cup of milk), stroke, hypertension, gastric and respiratory problems, while soup of garlic would be recommended for circulatory problems and kidney.

Also is recommended a glass of water with 20 drops of tincture of garlic to treat bleeding, hypertension, palpitations and varicose veins.

In the Dominican Republic is considered appropriate to rub garlic on joints with rheumatic diseases. On the other side of the island, Haitians eat decoction of garlic bulbs, juices or infusions of the plant to treat dermatitis, bloating, itching, bronchitis, pneumonia and other bronchopulmonary diseases. Also eat the bulbs for treating high blood pressure or intestinal infestations.

In some areas of Mexico, it's recommended to take three cloves of garlic in a glass of milk every morning to prevent malaria and tuberculosis. Also is recommended as emmenagogue.

In Peru, garlic cloves are eaten to treat arrhythmias, arteriosclerosis, various other cardiovascular diseases (hypertension, thrombosis, stroke, etc.), diabetes mellitus, catarrhal states, malaria, menopause and smokers withdrawal syndrome . They also like to rub garlic on painful joints with rheumatism, skin warts, vitiligo, itchy areas, etc.

In rural areas of Guatemala, garlic is used as, often associated with conventional drugs[26].

In the Trinidad island, the decoction of garlic is used for hypertension, dyspepsia and stomach pain. It is customary in certain areas of the island rubbing the mother's abdomen with garlic to facilitate delivery.

The Yucatan people use garlic bulbs in milk or tomato juice to treat diabetes, rheumatism and malaria. It is keeping for 5 days in alcohol and is used in the form of drops for treating asthma, atherosclerosis and hypertension.

In India, the garlic is popularly used for the treatment of diabetes[27-28]. In Samahni Valley (Pakistan) is used the juice of garlic bulbs as anticancer medicine, birth control and antihypertension[29]. In the Sikh community living in the UK, garlic is one of the most used alternative medicines[30].

Also medicinal use in Europe has many followers. Thus, in Bulgaria is widely used for various diseases[31]. In the central regions of Italy, one study concludes that garlic is one of the most used plants, especially as anthelmintic[32-33].

In veterinary medicine, garlic is still used in British Columbia to treat parasitic fleas of pets (dogs, cats). It is also used to treat endoparasites and ear ailments in animals[34-35].

How it is applied

Garlic supports various forms of administration, such as ingestion of raw bulbs and leaves, tincture (20%, in 45% ethanol), as essential oil, syrup, solution and fresh juice.

Clinical Studies     

In general:

A systematic review and meta-analysis identifies six review on clinical efficacy of garlic. The evidence based on controlled clinical trials does not seem to be convincing from the viewpoint of the authors of the research. In the case of cholesterol, the effect size was considered small and probably with very little relevance. For hypertension, were available few studies and the effect was too small to be considered clinically significant. For other indications, no data were available to make any kind of clinical recommendation[36].

Cardiovascular/lipids effects

Some authors argue that garlic has therapeutic utility in patients with ischemic heart disease associated with diabetes[37]. A clinical trial of 12 weeks duration including 70 diabetic patients with elevated blood fats, showed a significant reduction in total cholesterol and LDL-cholesterol and elevation of HDL-cholesterol regarding starting values, which was not observed in the group of patients treated with placebo. According to the authors, the results suggest a beneficial effect of short-term garlic in diabetic patients with alteration of blood fats[38].

Using 12 months of a garlic preparation (Allicor) appeared to reduce the 10-year cardiovascular risk significantly in a clinical trial with 79 patients[39].

A systematic review of good methodological quality estimates that there is no scientific evidence beyond a reasonable doubt on the effectiveness of this vegetable in patients with peripheral artery disease[40].

A trial of six weeks duration in 30 patients with coronary disease showed a decrease in heart rate and overhead as well as improved exercise tolerance compared with baseline[41].

A clinical trial, double-blind, placebo-controlled and 12-week duration in 75 healthy volunteers, showed no significant difference between garlic and placebo with respect to pressure and arterial stiffness or blood lipid levels[42]. Other authors by contrast, observed a lipid-lowering effect with a garlic based product (Kwai]; they concluded that the degree of blood lipids decrease was related to prior level of blood lipids :the higher the starting level, the higher the fall of this[43].

The vast majority of published placebo controlled trials conclude that there is not support for a possible effect of garlic on lipid-lowering therapy. The scientific evidence about the effect of the plant on hypertension is notoriously inadequate in humans[44].

Other authors show their conviccción that garlic can normalize blood lipids, stimulate fibrinolytic activity, inhibit platelet aggregation, reduce roughness and arterial thickening, improving the structural alterations of the vessels associated with aging and atherosclerosis that lead to lower blood pressure[3].

One study concludes that continued treatment of tablets with high doses of garlic powder significantly reduced the increase in arteriosclerotic plaque between 5 and 18% during the 48 months of observation[45]. Other experts believe that there is some evidence suggesting that using certain formulations of garlic and/or onion is accompanied by an improvement of risk factors in normal subjects and patients with atherosclerosis[46]. Similarly, a review including numerous studies claims that garlic can normalize plasma lipids, stimulate fibrinolytic activity, inhibit platelet aggregation and reduce glucose and blood pressure, so the authors concluded that garlic has a remarkable potential in the prevention and control cardiovascular diseases[19].

A placebo-controlled clinical trial involving 60 patients with coronary disease, showed a significant reduction in total cholesterol and triglycerides, increasing HDL cholesterol and fibrinolytic activity[47].

A trial, including 24 healthy volunteers treated for six weeks with 900 mg of garlic powder, showed a decrease in postprandial triglycerides in analytical controls[48].

A review detects a decrease from 5 to 20% of cholesterol and triglycerides level in 7 out 8 trials, including more than 500 patients, using a daily dose of 0.6-0.9 grams garlic powder. The metabolic mechanisms of this reduction are unknown[49].

Effects on the common cold

A systematic review of the Cochrane Collaboration states that there is insufficient evidence of possible effects of garlic in preventing and treating the common cold, although several individual trials could support the opposite[50].

Cancer risk

There is not a credible evidence to support any effect of garlic on cancer and/or a reduction of cancer risk of stomach, breast, endometrial and lung. However, there is very limited evidence for a reduced risk of colon, prostate, esophagus, larynx, mouth, ovary and kidney cancers[51]. Overall, though the antitumor capacity of garlic has been evaluated in animal models, it has not been well established in humans[52].

An observational study seems to show an inverse association between consumption of garlic or other similar vegetables and the risk of several common cancers[53]. However, it is not possible to infer a cause-effect relationship from this kind of studies.

Arterial hypertension

Although some studies seem to show a positive effect on hypertension there are insufficient data about its efficacy in this disease[4].

A systematic review using MEDLINE, CINAHL and the Cochrane Central Register of Controlled Trials selected 10 papers that met the required criteria for methodological quality and concluded that the therapeutic use of garlic was associated with a reduction in systolic blood pressure in patients in whom this parameter was previously high, although no changes in diastolic blood pressure were recorded[54].

An observational case-control study showed that patients whose blood pressure was low was associated with a greater likelihood of consuming more garlic in their diet. The study recorded significantly lower values only for systolic pressure[55].

Carbohydrates/diabetes

There is insufficient scientific evidence, based on clinical trials of good methodological quality, regarding this subject, so it can not be recommended the use of garlic for this purpose[56]. There is not general consensus on the use of garlic as antidiabetic agent, due not only to lack of consistent scientific evidence but also the controversial data from animal experiments[57].

Platelet function

A study in 18 healthy volunteers suggests that garlic, at dietary doses, does not alter the parameters related to the function of platelets and, therefore, does not increase the risk of bleeding in surgical interventions, although it has been shown experimentally inhibition of platelet aggregation by the plant[58-59].

Sickle cell anemia

A clinical trial in five patients with this type of anemia, undergoing treatment with a formulation of garlic, recorded a decline of Heinz bodies after 4 weeks of therapy, which, in the opinion of the authors, would show an antioxidant effect of red blood cells in these patients[60-61].

Antibacterial effects

Some studies indicate that garlic has a broad spectrum antibacterial activity[62].

The argued arguments for this purpose include:

1. Garlic juice was effective against the majority of intestinal pathogens responsible for gastroenteritis in humans and animals.
2. Garlic is effective even in the case of antibiotic-resistant strains.
3. Garlic combination with antibiotics resulting in total or partial synergy between the two components.
4. It has been repeatedly observed a complete lack of resistance of germs to garlic.
5. Garlic can even prevent the formation of toxins by microorganisms [7].

Hepatopulmonary syndrome

It has been published a case of a patient who suffered a severe hepatopulmonary syndrome in which had failed treatment with somatostatin and rejected liver transplant. By his own account, the patient ingested daily large amounts of garlic powder. After 18 months of following this regimen, experienced a partial improvement of symptoms[63].

A preliminary study of 6 months in 15 patients with HPS treated with encapsulated garlic powder appeared to improve arterial oxygenation and symptoms in six of the fifteen patients undergoing treatment[64].

Antiparasitic effect

A research conducted to evaluate the clinical usefulness of garlic in the treatment of ascariasis, to confirm the popular belief of its efficacy in this infestation, it has not been shown to have a conclusive effect[65].

Antifungal effect

After ingestion of 25 ml of garlic extract, a significant antifungal activity was detected in the serum at 30 and 60 minutes but not in the urine, so the trial authors consider that garlic would be of limited value in antifungal therapy[66].

Pharmacology and toxicology     

Garlic, in moderate doses, appears to be quite safe and usually does not cause adverse reactions, except for possible allergic reactions in some people that can be particularly severe, such as contact dermatitis and severe asthma attacks[8]. However it should be noted the possible acute or chronic toxicity from ingesting large amounts of this plant or its extracts[46].

The compounds contained in garlic can inhibit certain enzymes, so should be used only in limited quantities[67]

Some garlic derived substances containing thiol groups (sulfur-bearing) can cause acantholysis in vitro (Brenner et al. 1995) and, possibly, pemphigus in vivo.

More than five cloves of garlic a day induces flatulence and gastroesophageal heartburn (Castleman et al. 1996) in addition to antiplatelet effect. The maximum tolerated dose has been established in 25 ml of garlic extract. Higher levels can cause an intense feeling of esophageal or gastric burning and vomiting[66]. Even at lesser than maximum recommended doses, garlic can result in nausea, vomiting and diarrhea. The sulfide groups are local irritants and can cause digestive disorders and skin disorders if applied locally.

Garlic is contraindicated in patients with hyperthyroidism. The Commission E refers rare gastrointestinal symptoms with the medicinal use of garlic, allergic reactions, disorders in skin and halitosis. Local application of garlic or its essential oil may cause irritation at the site of application.

Raw garlic is estimated especially dangerous in children, very susceptible to the irritating effects of this plant.

Although there are no published cases of serious drug interactions, theoretically are possible by concurrent use of garlic with anticoagulants, anti-inflammatory and other drugs with an intense hepatic metabolism (antiretrovirals, quinolones, macrolides, calcium channel blockers, antidepressants, imidazole antifungals, theophylline, antipsychotics, etc.).

Some data suggest that S-allyl cysteine mercapto exert its protective action by inhibiting the activity of CYP2E1[11].

Experimental studies     

Please note:

The findings of experimental studies are not directly or indirectly applicable to humans. It is dangerous to infer from the findings of these studies alleged properties of this plant for the treatment of ailments in people.

Antiplatelet effect

Several studies have shown beneficial effect from garlic in the prevention of thromboembolic events[47][68-71].

Antibacterial and antifungal effects

Several studies show activity against Staphylococcus, Streptococcus Mutans and Streptococcus Pneumoniae,[4][72-79]. Garlic extract inhibits the development of Helicobacter pylori at minimum concentrations 2-5 mg/ml[80].

Other studies have also shown activity against bacteria and fungi as well as protozoa and other endoparasites including Giardia lamblia, Entamoeba histolytica and Trypanosoma spp[14][81-95].

The essential oil of garlic has shown marked growth inhibition in vitro of Trichophyton rubrum, Trichophyton erinacei and Trichophyton soudanense as well as a synergistic effect with ketoconazole[96]. Other species: such as Candida and Malassezia have also been sensitive to garlic derivatives[97]. A study seems to show that diallyl trisulfide has an antifungal activity in vitro against Cryptococcus species, that potentiates the effect of amphotericin B[98]. Other experimental studies also show antifungal effects against several microorganisms, including cytomegalovirus and leishmania[10][12][99-105].

Antitoxíc effects:

In laboratory animals, treatment with garlic, S-allyl cysteine mercapto, volatile oil or allicin counteracts the toxic effect of paracetamol, cadmium, lead, carbon tetrachloride, arsenic, galactosamine-lipopolysaccharide, mercury compounds and hypoxia[9][11][106-114].

Neurological effects

An experimental observation concludes that garlic can improve in laboratory animals physical performance and learning ability[115].

It was observed a significant improvement in memory function in the passive avoidance test. Elevated brain levels of 5-HT was associated with improved cognitive performance. These results seem to demonstrate that stimulation of memory is associated with an increase of this substance in rats[116].

Garlic extract showed a significant antidepressant effect, probably by inhibiting MAO A and B[117].

Anti-osteoporosis effect

A food supplement with garlic oil extract can counteract osteoporosis in ovariectomized rats, normalizing biochemical markers of disease[118]. The results of an study suggest that garlic may prevent bone loss due to ovarian failure, possibly increasing the transfer of calcium through intestine[119].

Hormonal/sexual effects

Aqueous extract of garlic has spermicide activity[120]. It has also been proven effective in animal models to treat thyroxine induced hyperglycemia[121].

In laboratory animals, consumption of raw garlic for a month reduced testosterone secretion and alter spermatogenesis in a dose-dependent manner[122].

The administration of aqueous extract of garlic for three months increased the weight of the seminal vesicles and epididymis in male animals and also sperm count[123].

Antioxidant effect

Some observations of Allium species show a strong antioxidant effect, due to its high concentration of flavonoids, carotenoids and chlorophyll derivatives[124-125]. According to the results of an in vitro study, garlic contain substances with remarkable free antiradical capacity[126].

It has been observed that old garlic extracts have free-radical activity, which is not the case of fresh extracts. The compounds S-allylcysteine and S-allyl cysteine mercapto are the most active agents[2].

Some studies indicate that the essential oil of garlic is an effective antioxidant in tissue damage produced by nicotine[127].

Antitumor effects

Allium sativum and some of its components can inhibit or delay the growth of various experimental tumors[2][128-140].Other studies indicate it may potentiate the effect of fludarabine and cytarabine[6] or could prevent the effect of certain carcinogens[141].

The authors of a study conclude that the compound S-allyl cysteine mercapto has significant antiproliferative action[142]. Previously, the same research group had shown that this substance inhibits cancer cell growth and causes apoptosis (cell death) in tissues of human colon cancer (Shirin et al, Cancer Res, 61:725-731, 2001). Diallyl sulfide significantly induces cell death[143-144] and activity of N-acetyltransferase[145]. Diallyl sulfide in vivo inhibits leukemic cell line WEHI-3[146].

Results of an observational study in animals indicate that ingestion of garlic inhibits the formation of intestinal cancer by N-Ethyl-N'-nitro-N-nitrosoguanidine[147]. Allicin inhibits cell growth and induces apoptosis in gastric epithelial cells[148]. The diallyl sulfur inhibits almost 3 out of 4 colorectal cancers induced by hydralazine dimethyl compound[149]. Diallyl sulfide inhibits N-acetyltransferase activity and gene expression in human colon cancer cells[150].

Cardiovascular effects

The dialysate of garlic has significant antiarrhythmic effect in both supraventricular and ventricular arrhythmias[151]. Studies on an experimental model suggest that garlic has beneficial effects on the strength of contraction and heart rate[152].

Allicin may influence atherosclerosis as an antioxidant and also through lipoproteins, modifying and inhibiting LDL cholesterol[153]. In any case, the influence of garlic and its derivatives on blood fats is higher the more higher the administered dose[154].

Both proteins and essential garlic oil show a significant lowering effect on blood fat[155]. The beneficial effect of garlic of blood fat is, at least in part, due to inhibition exerted on transaminases, alkaline phosphatase, HMG CoA reductase and other enzymes[156].

Allicin reduces the formation of atherosclerotic plaques in mice fed with a high cholesterol diet[157]. Garlic extract prevent the rise in blood fats caused by an atherogenic diet[158].

The addition of 2-3% of garlic powder to an atherogenic diet lowered total cholesterol concentrations in experimental rats. Paradoxically, were reduced more in animals receiving 2% of garlic than in those receiving 3%[159].

The alcoholic extract of garlic orally produced an antihypertensive effect in rats[160], while dialysate of garlic produced a fall of the minimum blood pressure and heart rate in a dose-dependent manner[161]. A single dose of garlic produces an antihypertensive effect in rats between 2 and 6 hours after administration, that could last up to more than 24 hours[162].

It has been shown in dogs a diuretic effect by intravenous administration of a purified fraction of garlic, which would reach the peak of action about three hours after administration[163]. Simultaneously a reduction in blood pressure is observed. High doses of garlic, above 15 mg/kg, cause bradycardia and ECG changes[164].

Antidiabetic effect

Some authors claim that the inclusion of garlic in the diet may help to lower glucose, cholesterol and triglycerides levels, based on experimental studies[165-167]. For other experts, garlic in the diet may reduce oxidative stress, but found no changes in cholesterol attributable to this plant[168].

In mice with experimental diabetes, garlic reduces polyphagia and polydipsia, but does not alter significantly hyperglycemia and hypoinsulinemia[169]. Other authors conclude that garlic would lower the postprandial hyperglycemic peak[170].

A study in rats with alloxan diabetes shows that S-allyl cysteine sulfoxide improves the disorder so nearly comparable to glibenclamide and insulin[171]. Administration of a dose of 200 mg/kg of S-allyl cysteine sulfoxide decreases blood concentration of fats, glucose and hepatic enzymatic activity[172].

Garlic administration decreases oxidative stress-induced hyperglycemia, thereby delaying the progression of lens opacification in diabetic rats[173].

Data from a study suggest that fresh garlic homogenate enhances nephropathy in mice with experimental streptozotocin diabetes[174].

Oral treatment of diabetic rats with Allium sativum and other plants, not only decreases the blood glucose level, but also reactivates antioxidant and other enzymes in the experimental model studied. According to these results, the effect would be comparable to glibenclamide. The authors conclude that garlic not only has a hypoglycemic effect but also decreases oxidative stress in experimental diabetes mellitus[175].

Another experimental study concludes that petroleum ether extract and raw garlic have some hypoglycemic effect, which is not observed in alcoholic extract[176].

Treatment of rats with alloxan induced diabetes with repeated administration of garlic can lead biochemical parameters to normal and may reduce liver and kidney damage induced by diabetes[177].

An experimental study on various medicinal plants showed that only garlic was able to reduce blood glucose significantly compared with the control group[178].

Compared with oral agents, antidiabetic effect of garlic was superior to glibenclamide[179].

ACE activity is higher in diabetic rats than in normals but animals treated with garlic show no enzyme elevation compared to controls. Study authors believe that garlic extract may have some value in preventing vascular complications of diabetes mellitus[180]..

Miscellany

A potential use of garlic derived from its action upon the production of cytokines, substances involved in inflammation, particularly inflammation of the small intestine[181].

Pretreatment with garlic suppresses chemically chromosomal aberrations induced in albino mice[182].

The garlic-derived S-allyl cysteine sulfoxide has shown a protective effect in the albino mouse against radiation induced by a cobalt-60 source, reducing the mortality caused by this agent. Moreover, the essential oil of garlic prevents fat elevation induced by radiocalcium[183].

immunostimulatory effect

Outcomes of a study supports a strong immunostimulatory effect by garlic, with an increase in cellular immunity parameters (percentage of phagocytic cells, granulocytes NBT positive and lysozyme level)[184]. Garlic orally can promote humoral response via cytokines[185] and can alter the phagocytic ability of blood cells[186].

The results of a study suggest that the two major proteins present in raw garlic, QR-2 and QR-1, contribute to the immunomodulatory activity of the plant, which would be very similar (if not identical) to the ASA I and II agglutinins[187].

Conclusions     

Common garlic, Allium sativum, is one of the best-studied medicinal plants, if not the most. Despite the many indications of its potential therapeutic value, has not been conclusively established nor its clinical applicability neither its safety of use. For this reasons, MEDIZZINE believes that can not be recommended the use of garlic as a medicinal remedy. Possible toxic effects of the plant and its contraindication in children should be considered.

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