Garlic
From Wikipedia, the free encyclopedia
For other uses, see Garlic (disambiguation).
| Garlic | |
|---|---|
| Allium sativum, known as garlic, from William Woodville, Medical Botany, 1793. | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Order: | Asparagales |
| Family: | Amaryllidaceae |
| Subfamily: | Allioideae |
| Genus: | Allium |
| Species: | A. sativum |
| Binomial name | |
| Allium sativum L. | |
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive,[1] andrakkyo.[2] With a history of human use of over 7,000 years, garlic is native to central Asia,[3] and has long been a staple in the Mediterranean region, as well as a frequent seasoning in Asia, Africa, and Europe. It was known to Ancient Egyptians, and has been used for both culinary and medicinalpurposes.[4]
Medicinal use and health benefits
| Nutritional value per 100 g (3.5 oz) | |
|---|---|
| Energy | 623 kJ (149 kcal) |
| Carbohydrates | 33.06 g |
| - Sugars | 1 g |
| - Dietary fiber | 2.1 g |
| Fat | 0.5 g |
| Protein | 6.36 g |
| Thiamine (vit. B1) | 0.2 mg (17%) |
| Riboflavin (vit. B2) | 0.11 mg (9%) |
| Niacin (vit. B3) | 0.7 mg (5%) |
| Pantothenic acid (B5) | 0.596 mg (12%) |
| Vitamin B6 | 1.235 mg (95%) |
| Folate (vit. B9) | 3 μg (1%) |
| Vitamin C | 31.2 mg (38%) |
| Calcium | 181 mg (18%) |
| Iron | 1.7 mg (13%) |
| Magnesium | 25 mg (7%) |
| Manganese | 1.672 mg (80%) |
| Phosphorus | 153 mg (22%) |
| Potassium | 401 mg (9%) |
| Sodium | 17 mg (1%) |
| Zinc | 1.16 mg (12%) |
| Selenium | 14.2 μg |
| Link to USDA Database entry Percentages are relative to US recommendations for adults. Source: USDA Nutrient Database | |
Garlic is claimed to help prevent heart disease (including atherosclerosis, high cholesterol, and high blood pressure) and cancer.[1][30] Animal studies, and some early research studies in humans, have suggested possible cardiovascular benefits of garlic. A Czech study found garlic supplementation reduced accumulation of cholesterol on the vascular walls of animals.[31] Another study had similar results, with garlic supplementation significantly reducing aortic plaque deposits of cholesterol-fed rabbits.[32] Another study showed supplementation with garlic extract inhibited vascular calcification in human patients with high blood cholesterol.[33] The known vasodilative effect of garlic is possibly caused by catabolism of garlic-derived polysulfides to hydrogen sulfide in red blood cells (RBCs), a reaction that is dependent on reduced thiols in or on the RBC membrane. Hydrogen sulfide is an endogenous cardioprotective vascular cell-signaling molecule.[34]
A randomized clinical trial funded by the National Institutes of Health (NIH) in the United States and published in the Archives of Internal Medicine in 2007 found the consumption of garlic in any form did not reduce blood cholesterol levels in patients with moderately high baseline cholesterol levels.[35][36] According to Heart.org, "despite decades of research suggesting that garlic can improve cholesterol profiles, a new NIH-funded trial found absolutely no effects of raw garlic or garlic supplements on LDL, HDL, or triglycerides... The findings underscore the hazards of meta-analyses made up of small, flawed studies and the value of rigorously studying popular herbal remedies". In an editorial regarding the initial report's findings, two physicians from Weill Cornell Medical College of Cornell University, pointed out that there may "be effects of garlic on atherosclerosis specifically that were not picked up in the study".[37]
However, a 2012 meta-analysis of randomized, double-blind, placebo-controlled trials looking at the effects of garlic on serum lipid profiles, found garlic was superior to placebo in reducing serum total cholesterol and triglyceride levels. Compared with the placebo groups, serum total cholesterol and triglyceride levels in the garlic groups was reduced by 0.28 (95% CI, -0.45, -0.11) mmol L⁻¹ (P = 0.001) and 0.13 (95% CI, -0.20, -0.06) mmol L⁻¹ (P < 0.001), respectively.[38]
Allium sativum has been found to reduce platelet aggregation[39][40][41][42] and hyperlipidemia.[42][43][44]
In 2007, the BBC reported Allium sativum may have other beneficial properties, such as preventing and fighting the common cold.[45] This assertion has the backing of long tradition in herbal medicine, which has used garlic for hoarseness and coughs.[46] The Cherokee also used it as anexpectorant for coughs and croup.[47] However, in contrast to these earlier claims concerning the cold-preventing properties of garlic, a 2012 report in the Cochrane Database of Systematic Reviews concludes that "there is insufficient clinical trial evidence regarding the effects of garlic in preventing or treating the common cold. A single trial suggested that garlic may prevent occurrences of the common cold but more studies are needed to validate this finding. Claims of effectiveness appear to rely largely on poor-quality evidence."[48]
Garlic is also alleged to help regulate blood sugar levels. Regular and prolonged use of therapeutic amounts of aged garlic extracts lower blood homocysteine levels and has been shown to prevent some complications of diabetes mellitus.[49][50] People taking insulin should not consume medicinal amounts of garlic without consulting a physician.
Garlic was used as an antiseptic to prevent gangrene during World War I and World War II.[51] More recently, it has been found from a clinical trial that a mouthwash containing 2.5% fresh garlic shows good antimicrobial activity, although the majority of the participants reported an unpleasant taste and halitosis.[52]
Garlic cloves are used as a remedy for infections (especially chest problems), digestive disorders, and fungal infections such as thrush.[53][54] Garlic can be used as a disinfectant because of its bacteriostatic and bacteriocidal properties.[4][unreliable source?]
Garlic has been found to enhance thiamin absorption, and therefore reduces the likelihood for developing the thiamin deficiency beriberi.[55]
In 1924, it was found to be an effective way to prevent scurvy, because of its high vitamin C content.[55]
Garlic has been used reasonably successfully in AIDS patients to treat Cryptosporidium in an uncontrolled study in China.[56] It has also been used by at least one AIDS patient to treattoxoplasmosis, another protozoal disease.[57]
Garlic supplementation has been shown to boost testosterone levels in rats fed a high protein diet.[58]
A 2010 double-blind, parallel, randomised, placebo-controlled trial, involving 50 patients whose routine clinical records in general practice documented treated but uncontrolled hypertension, concluded, "Our trial suggests that aged garlic extract is superior to placebo in lowering systolic blood pressure similarly to current first line medications in patients with treated but uncontrolled hypertension."[59]
[edit]Other uses
The sticky juice within the bulb cloves is used as an adhesive in mending glass and porcelain.[2] An environmentally benign garlic-derived polysulfide product is approved for use in the European Union (under Annex 1 of 91/414) and the UK as a nematicide and insecticide, including for use for control of cabbage root fly and red mite in poultry.[60]
[edit]Adverse effects and toxicology
Garlic is known for causing bad breath (halitosis), as well as causing sweat to have a pungent "garlicky" smell, which is caused by allyl methyl sulfide (AMS). AMS is a volatile liquid which is absorbed into the blood during the metabolism of garlic-derived sulfur compounds; from the blood it travels to the lungs[1] (and from there to the mouth, causing bad breath; see garlic breath) and skin, where it is exuded through skin pores. Washing the skin with soap is only a partial and imperfect solution to the smell. Studies have shown sipping milk at the same time as consuming garlic can significantly neutralize bad breath.[61] Mixing garlic with milk in the mouth before swallowing reduced the odor better than drinking milk afterward.[61] Plain water, mushrooms and basil may also reduce the odor; the mix of fat and water found in milk, however, was the most effective.[61]
The green, dry "folds" in the center of the garlic clove are especially pungent. The sulfur compound allicin, produced by crushing or chewing fresh garlic, produces other sulfur compounds: ajoene, allyl polysulfides, and vinyldithiins.[1] Aged garlic lacks allicin, but may have some activity due to the presence of S-allylcysteine.
In a rat study allicin was found to be an activator of TRPA1. The neurons released neurotransmitters in the spinal cord to generate pain signals and released neuropeptides at the site of sensory nerve activation, resulting in vasodilation, as well as inflammation.[62] Allicin is released only by crushing or chewing raw garlic and cannot be formed from cooked garlic.
Some people suffer from allergies to garlic and other plants in the allium genus.[1] Symptoms can include irritable bowel, diarrhea, mouth and throat ulcerations, nausea, breathing difficulties, and, in rare cases, anaphylaxis. Garlic-sensitive patients show positive tests to diallyl disulfide, allylpropyldisulfide, allylmercaptan and allicin, all of which are present in garlic. People who suffer from garlic allergies will often be sensitive to many plants, including onions, garlic, chives, leeks, shallots, garden lilies, ginger, and bananas.
Garlic reduces platelet aggregation (as does aspirin);[63] this had caused very high quantities of garlic and garlic supplements to be linked with an increased risk of bleeding, particularly duringpregnancy and after surgery and childbirth,[64][65] although culinary quantities are safe for consumption.
Several reports of serious burns resulting from garlic being applied topically for various purposes, including naturopathic uses and acne treatment, indicate care must be taken for these uses, usually testing a small area of skin using a very low concentration of garlic.[66] On the basis of numerous reports of such burns, including burns to children, topical use of raw garlic, as well as insertion of raw garlic into body cavities, is discouraged. In particular, topical application of raw garlic to young children is not advisable.[67] The side effects of long-term garlic supplementation, if any exist, are largely unknown, and no FDA-approved study has been performed. Possible side effects include gastrointestinal discomfort, sweating, dizziness, allergic reactions, bleeding, and menstrual irregularities.[65] The safety of garlic supplements has not been determined for children;[68] some breastfeeding mothers have found their babies slow to feed and have noted a garlic odour coming from their baby when they have consumed garlic.[64][69]
Garlic may interact with warfarin, antiplatelets, saquinavir, antihypertensives, calcium channel blockers, quinolone family of antibiotics such as Cipro,and hypoglycemic drugs, as well as other medications.[64] Members of the alium family might be toxic to cats or dogs.[70] Some degree of liver toxicity has been demonstrated in rats, particularly in extremely large quantities exceeding those that a rat would consume under normal situations.[71]
[edit]Spiritual and religious uses
Garlic has been regarded as a force for both good and evil. According to Cassell's Dictionary of Superstitions, there is an Islamic myth that considers that after Satan left the Garden of Eden, garlic arose in his left footprint and onion in the right.[72] In Europe, many cultures have used garlic for protection or white magic, perhaps owing to its reputation as a potent preventative medicine.[73] Central European folk beliefs considered garlic a powerful ward against demons, werewolves, and vampires.[73] To ward off vampires, garlic could be worn, hung in windows, or rubbed on chimneys and keyholes.[74]
In both Hinduism and Jainism, garlic is considered to stimulate and warm the body and to increase one's desires. Some devout Hindus generally avoid using garlic and the related onion in the preparation of foods for religious festivities and events. Followers of the Jain religion avoid eating garlic and onion on a daily basis.
A belief among some Hindus is that when Devas and Asuras fought for nectar during churning of the ocean of milk (Samudramathan) in the other world, two Asuras were able to get access to nectar and had some quantity in their mouths in stealthy ways. Knowing the Asuras' foul play the God cuffed the heads of those Asuras before they could swallow it and as a result nectar fell down on the earth from their mouths in drops which later grew as garlic; that is why the vegetable has such wonderful medicinal properties.
In some Buddhist traditions, garlic - along with the other five "pungent spices" - is understood to stimulate sexual and aggressive drives to the detriment of meditation practice.[75]
[edit]Properties
When crushed, Allium sativum yields allicin, an antibiotic[76] and antifungal compound (phytoncide) discovered by Chester J. Cavallito and colleagues in 1944. Fresh or crushed garlic also affords the sulfur-containing compounds alliin, ajoene, diallyl polysulfides, vinyldithiins, S-allylcysteine, and enzymes, B vitamins, proteins, minerals, saponins, flavonoids, and Maillard reaction products, which are not sulfur-containing compounds. Furthermore, a phytoalexin (allixin) was found, a nonsulfur compound with a γ-pyrone skeleton structure with antioxidant effects, antimicrobial effects,[77] antitumor promoting effects,[78] inhibition of aflatoxin B2 DNA binding,[78] and neurotrophic effects. Allixin showed an antitumor promoting effect in vivo, inhibiting skin tumor formation by TPA and DMBA initiated mice.[78] Analogs of this compound have exhibited antitumor promoting effects in in vitro experimental conditions. Herein, allixin and/or its analogs may be expected useful compounds for cancer prevention or chemotherapy agents for other diseases.
The composition of the bulbs is approximately 84.09% water, 13.38% organic matter, and 1.53% inorganic matter, while the leaves are 87.14% water, 11.27% organic matter, and 1.59% inorganic matter.[79][80]
The phytochemicals responsible for the sharp flavor of garlic are produced when the plant's cells are damaged. When a cell is broken by chopping, chewing, or crushing, enzymes stored in cellvacuoles trigger the breakdown of several sulfur-containing compounds stored in the cell fluids (cytosol). The resultant compounds are responsible for the sharp or hot taste and strong smell of garlic. Some of the compounds are unstable and continue to react over time. Among the members of the onion family, garlic has by far the highest concentrations of initial reaction products, making garlic much more potent than onion, shallot, or leeks.[81] Although many humans enjoy the taste of garlic, these compounds are believed to have evolved as a defensive mechanism, deterring animals such as birds, insects, and worms from eating the plant.[82]
A large number of sulfur compounds contribute to the smell and taste of garlic. Allicin has been found to be the compound most responsible for the "hot" sensation of raw garlic. This chemical opens thermotransient receptor potential channels that are responsible for the burning sense of heat in foods. The process of cooking garlic removes allicin, thus mellowing its spiciness.[83]Allicin, along with its decomposition products diallyl disulfide and diallyl trisulfide, are major contributors to the characteristic odor of garlic, while other allicin-derived compounds, such asvinyldithiins and ajoene show beneficial in vitro biological activity.[1] Because of its strong odor, garlic is sometimes called the "stinking rose". When eaten in quantity, garlic may be strongly evident in the diner's sweat and garlic breath the following day. This is because garlic's strong-smelling sulfur compounds are metabolized, forming allyl methyl sulfide. Allyl methyl sulfide (AMS) cannot be digested and is passed into the blood. It is carried to the lungs and the skin, where it is excreted. Since digestion takes several hours, and release of AMS several hours more, the effect of eating garlic may be present for a long time.[1]
This well-known phenomenon of "garlic breath" is alleged to be alleviated by eating fresh parsley.[84] The herb is, therefore, included in many garlic recipes, such as pistou, persillade, and the garlic butter spread used in garlic bread. However, since the odor results mainly from digestive processes placing compounds such as AMS in the blood, and AMS is then released through the lungs over the course of many hours, eating parsley provides only a temporary masking. One way of accelerating the release of AMS from the body is the use of a sauna.[citation needed]
Because of the AMS in the bloodstream, it is believed by some to act as a mosquito repellent, but no clinically reported evidence suggests it is actually effective.[85]
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