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Allium sativum L., commonly known as garlic, is a species in the onion family Alliaceae. Its close relatives include the onion, shallot, and leek. Garlic has been used throughout recorded history for both culinary and medicinal purposes. It has a characteristic pungent, 'hot', flavour that mellows and sweetens considerably with cooking.[1] A 'head' of garlic, the most commonly used plant part, comprises numerous discrete 'cloves'. The leaves and stems are sometimes eaten, particularly while immature and tender.
The ancestry of cultivated garlic, according to Zohary and Hopf, is not definitely established: "a difficulty in the identification of its wild progenitor is the sterility of the cultivars."[2]
Allium sativum grows in the wild in areas where it has become naturalised; it probably descended from the species Allium longicuspis, which grows wild in south-western Asia.[3] The 'wild garlic', 'crow garlic' and 'field garlic' of Britain are the species Allium ursinum, Allium vineale and Aleum oleraceum, respectively. In North America, Allium vineale, known as 'wild-' or 'crow garlic', and Allium candadensis, known as 'meadow-' or 'wild garlic', are common weeds in fields.[4]
Garlic is widely used around the world for its pungent flavour, as a seasoning or condiment or to enhance other flavours. Depending on the form of cooking and the desired result, the flavor is either mellow or intense. It is often paired with onion, tomato, and/or ginger. It is very widely used in Lebanese cuisine: many Lebanese salads contain a garlic sauce. The parchment-like skin is relatively inedible, much like the skin of an onion. The skin is typically removed before cooking, though sometimes alternative approaches are used, such as slice garlic head crosswise, coat in olive oil, roast until the garlic is well cooked, and then the roasted garlic separates quite easily from the skins (by pulling it out, shaking it out, and/or squeezing it out). The term 'clove' is sometimes misinterpreted to mean the whole garlic bulb (head).
Garlic is commonly stored in cooking oil with herbs to yield an oil infused with flavour. Garlic-infused oils are widely available. Care must be taken preparing such, as there is a risk of botulism developing in the oxygen-free oil if the product is not stored properly. To reduce the risk of botulism, the oil containing the garlic must be refrigerated and used within one week. (see Caution below). Commercial producers use a combination of salts and/or acids to eliminate the risk of botulism in their products.[5] In Chinese cuisine, the young bulbs are pickled for 3–6 weeks in a mixture of sugar, salt and spices. Pickled garlic is available at supermarkets. The shoots are often pickled in Russia and states of the Caucasus and eaten as an appetizer.
Immature scapes are tender and edible. They are also known as 'garlic spears', 'stems', or 'tops'. Scapes generally have a milder taste than cloves. They are often used in stir frying or prepared like asparagus. Garlic leaves are a popular vegetable in many parts of Asia, particularly Chinese, Vietnamese, and Cambodian. The leaves are cut, cleaned and then stir-fried with eggs, meat or vegetables.
From the earliest times garlic has been used as a food. It formed part of the food of the Israelites in Egypt (Numbers 11:5) and of the labourers employed by Khufu in constructing the pyramid. Garlic is still grown in Egypt, but the Syrian variety is the kind most esteemed now (see Rawlinson's Herodotus, 2.125).
It was consumed by the ancient Greek and Roman soldiers, sailors and rural classes (Virgil, Ecologues ii. 11), and, according to Pliny the Elder (Natural History xix. 32), by the African peasantry. Galen eulogizes it as the "rustic's theriac" (cure-all) (see F Adams's Paulus Aegineta, p. 99), and Alexander Neckam, a writer of the 12th century (see Wright's edition of his works, p. 473, 1863), recommends it as a palliative of the heat of the sun in field labor.
In his Natural History Pliny gives an exceedingly long list of scenarios in which it was considered beneficial (N.H. xx. 23). Dr. T. Sydenham valued it as an application in confluent smallpox, and, says Cullen (Mat. Med. ii. p. 174, 1789), found some dropsies cured by it alone. Early in the 20th century, it was sometimes used in the treatment of pulmonary tuberculosis or phthisis.
Garlic was rare in traditional English cuisine (though it is said to have been grown in England before 1548), and has been a much more common ingredient in Mediterranean Europe. Garlic was placed by the ancient Greeks on the piles of stones at cross-roads, as a supper for Hecate (Theophrastus, Characters, The Superstitious Man); and according to Pliny, garlic and onions were invoked as deities by the Egyptians at the taking of oaths. The inhabitants of Pelusium in lower Egypt, who worshipped the onion, are said to have had an aversion to both onions and garlic as food.
To prevent the plant from running to leaf, Pliny (N.H. xix. 34) advised bending the stalk downward and covering with earth; seeding, he observes, may be prevented by twisting the stalk (by "seeding", he most likely means the development of small, less potent bulbs).
Garlic has been used as both food and medicine in many cultures for thousands of years, dating as far back as the time that the Egyptian pyramids were built. Garlic is claimed to help prevent heart disease, including atherosclerosis, high cholesterol, high blood pressure, and to improve the immune system. Garlic may also protect against cancer.[6]
However a rigorous, NIH-funded clinical trial published by the "Archives of Internal Medicine", on 26 February 2007, found that consumption of garlic, in any form, did not reduce cholesterol levels in patients with moderately high levels.[7][8]
With regard to this clinical trial, Heart.org reports, "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 website says, "The findings underscore the hazards of meta-analyses made up of small, flawed studies and the value of rigorously studying popular herbal remedies".[9] However, while garlic may not lower cholesterol levels in the bloodstream, this study does not contradict studies that show that garlic protects arteries from that cholesterol. For example, a Czech study found garlic supplementation reduced accumulation of cholesterol on vascular walls of animals.[10] Another study had similar results, with garlic supplementation significantly reducing the placque in the aorta's of cholesterol-fed rabbits.[11] Another study showed that supplementation with garlic extract inhibited vascular calcification in human patients with high blood cholesterol.[12]
In 2007 a BBC news story reported that Allium sativum may have beneficial properties, such as preventing and fighting the common cold.[13] This assertion has the backing of long tradition. Traditional British herbalism used garlic for hoarseness and coughs, both as a syrup and in a salve made of garlic and lard, which was rubbed on the chest and back.[14] The Cherokee also used it as an expectorant for coughs and croup.[15]
Allium sativum has been found to reduce platelet aggregation and hyperlipidemia.[16][17]
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 shown to prevent some complications of diabetes mellitus.[18][19] People taking insulin should not consume medicinal amounts of garlic without consulting a physician. In such applications, garlic must be fresh and uncooked, or the allicin will be lost.
Allium sativum may also possess cancer-fighting properties due to the presence of allylic sulfur compounds such as diallyl disulfide (DADs), believed to be an anticarcinogen.[20]
Decocted garlic extracts that are left to set overnight are very effective in healing wounds. In 1858, Louis Pasteur observed garlic's antibacterial activity, and it was used as an antiseptic to prevent gangrene during World War I and World War II.[21] 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.[22]
In modern naturopathy, garlic is used as a treatment for intestinal worms and other intestinal parasites, both orally and as an anal suppository. Garlic cloves are used as a remedy for infections (especially chest problems), digestive disorders, and fungal infections such as thrush.
Garlic supplementation in rats along with a high protein diet has been shown to boost testosterone levels.[23]
Dietary supplements in an "odourless" pill form, as are commonly available, claim to possess the medicinal benefits of garlic, without (in the words of one manufacturer) "the unsocial qualities associated with fresh garlic cloves". However independent validation (e.g. not sponsored by the pill manufacturers) through rigorously conducted clinical trials of the benefits, if any, of these pills is lacking or has been found to be negative, e.g. showing no beneficial effects.
When crushed, Allium sativum yields allicin, a powerful antibiotic and anti-fungal compound (phytoncide). It also contains alliin, ajoene, enzymes, vitamin B, minerals, and flavonoids.
The percentage composition of the bulbs is given by E. Solly (Trans. Hon. Soc. Loud., new ser., iii. p. 60) as water 84.09%, organic matter 13.38%, and inorganic matter 1.53% - that of the leaves being water 87.14%, organic matter 11.27% and inorganic matter 1.59%.
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 cell vacuoles trigger the breakdown of several sulfur-containing compounds stored in the cell fluids. 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 evolve 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 onions, shallots, or leeks.[24] Although people have come to enjoy the taste of garlic, these compounds are believed to have evolved as a defensive mechanism, deterring animals like birds, insects, and worms from eating the plant.[25]
A large number of sulfur compounds contribute to the smell and taste of garlic. Diallyl disulfide is believed to be an important odour component. Allicin has been found to be the compound most responsible for the spiciness of raw garlic. This chemical opens thermoTRP (transient 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.[26]
When eaten in quantity, garlic may be strongly evident in the diner's sweat and 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.
This well-known phenomenon of "garlic breath" is alleged to be alleviated by eating fresh parsley. The herb is, therefore, included in many garlic recipes, such as Pistou and Persillade. However, since the odour 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. Due to its strong odor, garlic is sometimes called the "stinking rose".
Garlic has been regarded as a force for both good and evil. A Christian myth considers that after Satan left the Garden of Eden, garlic arose in his left footprint, and onion in the right.[27] In Europe, many cultures have used garlic for protection or white magic, perhaps owing to its reputation as a potent preventative medicine.[28] Central European folk beliefs considered garlic a powerful ward against demons, werewolves, and vampires.[28] To ward off vampires, garlic could be worn, hung in windows or rubbed on chimneys and keyholes.[29]
The association of garlic to evil spirits, may be based on the antibacterial, antiparasitic value of garlic, which could prevent infections that lead to delusions, and other related mental illness symptoms.[30][31]
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