Garlic is a hardy, bulbous, rooted, perennial plant with narrow flat leaves and bears small white flowers and bulbils. The compound bulb consists of 6 to 34 bulblets called ‘cloves’ which are surrounded by a common, thin, white or pinkish papery sheet. Garlic has a strong flavour and taste.
ORIGIN AND DISTRIBUTION OF GARLIC:
Garlic is a native of West Asia and Mediterranean area. China, Korea, India, USA, Spain, Argentina and Egypt are the major garlic growing countries. Garlic prefers cool weather and grow in a well-drained, moderately clay loam at higher elevation (900 to 1200 mtrs).
Uses of Garlic:
Garlic is used for flavouring various dishes practically all over the world. In United States almost half of the produce is dehydrated for use in mayonnaise products, salad dressings and in several meat preparations. Raw garlic is used in the preparation of garlic powder, garlic salt, garlic vinegar, garlic cheese croutins, garlicked potato chips, garlic bread, garlicked bacon etc. Spray dried garlic products, liquid garlic preparations are other products. In India and other Asian and Middle East Countries, garlic is used in pickles, curry powders, curried vegetables, meat preparations etc. Oil of garlic is used as a flavouring agent in soups, canned foods, sauces etc. The other properties are anti-bacterial, fungicidal and insecticidal. In the area of medicine, it is used for various ailments of stomach, skin diseases. It has wider applications in indigenous medicines and is also considered as highly nutritive.
Health Benefits of Eating Raw garlic Cloves:
Garlic (Allium sativum L.) has acquired a reputation in different traditions as a prophylactic as well as therapeutic medicinal plant. Garlic has played important dietary and medicinal roles throughout the history. Some of the earliest references to this medicinal plant were found in Avesta, a collection of Zoroastrian holy writings that was probably compiled during the sixth century BC. Garlic has also played as an important medicine to Sumerian and the ancient Egyptians. There is some evidence that during the earliest Olympics in Greece, garlic was fed to the athletes for increasing stamina
Ancient Chinese and Indian medicine recommended garlic to aid respiration and digestion and to treat leprosy and parasitic infestation. Avicenna, in his well-known book, Al Qanoon Fil Tib (The Canon of Medicine), recommended garlic as a useful compound in treatment of arthritis, toothache, chronic cough, constipation, parasitic infestation, snake and insect bites, gynecologic diseases, as well as in infectious diseases (as antibiotic). Also read Origin and History of Spices.
These effects have been largely attributed to i) reduction of risk factors for cardiovascular diseases, ii) reduction of cancer risk, iii) antioxidant effect, iv) antimicrobial effect, and v) enhancement of detoxification foreign compound and hepatoprotection.
Benefits of garlic on cardiovascular diseases:
Garlic and its preparations have been widely recognized as agents for prevention and treatment of cardiovascular diseases. Scientific literature supports the proposal that garlic consumption have significant effects on lowering blood pressure, prevention of atherosclerosis, reduction of serum cholesterol and triglyceride, inhibition of platelet aggregation, and increasing fibrinolytic activity.
In one trial, investigation on 47 hypertensive patients showed that garlic significantly decreased the mean systolic blood pressure by 12 mmHg and the mean supine diastolic blood pressure by 9 mmHg versus placebo. The authors stated that garlic was free from side effects and no serious complication was reported.
Most of human studies on lipid lowering effects of garlic and garlic preparations described significant decrease in serum cholesterol and triglyceride. High-density lipoprotein cholesterol levels improved only slightly, and triglycerides were not influenced significantly. Garlic was highly tolerable in all trials and was associated with minimal side effects.
Furthermore, it was reported that garlic decreases the risk of peripheral arterial occlusive diseases, plasma viscosity, and unstable angina and increases elastic property of blood vessels and capillary perfusion.
Anti-tumour effect of garlic:
Garlic has been found to contain a large number of potent bioactive compounds with anticancer properties, largely allylsulfide derivatives. The growth rate of cancer cells is reduced by garlic, with cell cycle blockade.
In 1990, the U.S. National Cancer Institute initiated the Designer Food Program to determine which foods played an important role in cancer prevention. They concluded that garlic may be the most potent food having cancer preventive properties. Garlic has a variety of anti-tumour effects, including tumour cell growth inhibition and chemo-preventive effects.
Garlic components have been found to block covalent binding of carcinogens to DNA, enhance degradation of carcinogens, have anti-oxidative and free radical scavenging properties, and regulate cell proliferation, apoptosis, and immune responses. Ajoene, a garlic stable oil soluble sulphur rich compound and garlic-derived natural compound, have been shown to induce apoptosis in leukemic cells in addition to the other blood cells of leukemic patients.
Metformin and Garlic treatment in diabetic patients for 12 weeks reduced fasting blood glucose (FBG), but the percentage of change in FBG was more substantial with metformin supplemented with garlic than with metformin alone.
The beneficial effect of garlic on diabetes mellitus is mainly attributed to the presence of volatile sulphur compounds, such as alliin, allicin, diallyl disulphide, diallyl trisulfide, diallyl sulphide, S-allyl cysteine, ajoene, and allyl mercaptan. Garlic extracts have been reported to be effective in reducing insulin resistance.
Chronic feeding of garlic extracts showed significant decrease in blood glucose level. However, some other studies showed no change of blood glucose level after that in human. Therefore, the role of garlic in diabetic patients needs to be further investigated.
Effect of garlic on chemically-induced hepatotoxicity:
Several studies showed that garlic can protect the liver cells from some toxic agents. Acetaminophen is a leading analgesic and antipyretic drug used in many countries. Overdose is known to cause hepatotoxicity and nephrotoxicity in humans and rodents. Although more than 90% of acetaminophen is converted into sulphate and glucuronide conjugates and excreted in the urine, a small portion is metabolized by different liver enzymes. This can arylate critical cell proteins and cause toxicity. It is demonstrated that garlic protects against acetaminophen-induced hepatotoxicity.
Anti-microbial effect of garlic:
Garlic has been used for centuries in various societies to combat infectious disease. The antibacterial activity of garlic is widely attributed to allicin. It is known that allicin has sulfhydryl modifying activity and is capable of inhibiting sulfhydryl enzymes. Cysteine and glutathione counteract the thiolation activity of allicin. Garlic extract and allicin have been shown to exert bacteriostatic effects on some vancomycin-resistant enterococci.
The cloves of garlic and rhizomes of ginger, extracted with 95% ethanol, suggested to have anti-bacterial activity against multi-drug clinical pathogens and can be used for prevention of drug resistant microbial diseases. Pseudomonas aeruginosa was the most sensitive germ to the mixture Garlic also suggested as a treatment for multi-drug resistant tuberculosis.
Several studies have shown that the extract was effective against a host of protozoa including Candida albicans, Scedosporium prolificans, tinea pedis, Opalina ranarum, Balantidium entozoon, Entamoeba histolytica, Trypanosomes, Leishmania, Leptomonas, and Crithidia.
Due to the occurrence of unpleasant side effects and increasing resistance to the synthetic pharmaceuticals, garlic was recommended for the treatment of giardiasis. Inhibitory activity of garlic on giardia was noted with crude extract at 25 pg/mlL and the lethal dosage was established as approximately 50 pg/mL. Encouraged by these results, a clinical trial was carried out on patients that had giardiasis. Garlic was established as an antigiardial, removing the symptoms from all patients within 24 hours and completely removing any indication of giardiasis from the stool within 72 h at a dosage of 1 mg/mL twice daily aqueous extract or 0.6 mg/mL commercially prepared garlic capsules. It was suggested that allicin, ajoene, and organosulfides from garlic are effective antinrotozoals compounds.
Many fungi are sensitive to garlic, including Candida, Torulopsis, Trichophyton, Cryptococcus, Aspergillus, Trichosporon, and Rhodotorula. Garlic extracts have been shown to decrease the oxygen uptake, reduce the growth of the organism, inhibit the synthesis of lipids, proteins, and nucleic acids and damage membranes.
It has been reported that garlic exhibited antifungal effects on two species, the air-borne pathogen Botrytis cinerea and Trichoderma harzianum. Greater satisfaction with the use of garlic rather than nystatin was reported by the patients with denture stomatitis.
Studies have reported that garlic extract showed in vitro activity against influenza. In the case of HIV, it is thought that ajoene acts by inhibiting the integrin dependent processes. Allyl alcohol and diallyl disulfide have also proven effective against HIV-infected cells. No activity has been observed with allicin or S-allyl cysteine. It appears that only allicin and allicin-derived substances are active. Taken together, the beneficial effects of garlic extract make it useful in medicine. There are insufficient clinical trials 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.
A word of caution:
The consumption of raw garlic can cause various side-effects, including anemia, growth retardation and the destruction of the gut microflora, and can also alter serum protein levels. Moreover, fresh garlic may cause indigestion and its pungent odour may linger on the breath, which may be a social barrier. To overcome these unwelcome effects, an alternative product from garlic that has less odour, but is rich in antioxidants has been produced and is known as aged garlic extract (AGE). AGE is an extract from garlic powder in a non-toxic solvent. It is derived from a prolonged extraction time at room temperature, generally >15 months. The aging process converts unstable compounds, such as allicin, to stable substances and several water-soluble organosulfur compounds, including the two major compounds, S-allylcysteine (SAC) and di-allyl-disulfide (DAD). AGE also contains other phytochemicals, such as ajoene, allixin, flavanoids, polyphenols and thiosulfinates. Aged garlic extract has a very potent antioxidant activity, as well as numerous bio-activities, conferring several health benefits to humans.