Alium sativum is a perennial plant native to Turkestan and eastern Russia, but cultivated for thousands of years in China and the eastern Mediterranean, and for some time now worldwide. Some varieties were known to Hippocrates, Theophrastus and Dioscorides, who called garlic a polyfarmakon, or a multidrug, a name fully justified from the findings of modern research. The bulb’s active constituents are a volatile oil composed of sulfur containing compounds like allicin, diallyl disulfide, diallyl trisulfide, etc, considered to be the main active ingredients. Other constituents of garlic are alliin or S-allyl-L-cysteine sulfoxide, S-methyl-L-cysteine sulfoxide, ajoene, vinyl dithiins, gamma-glutamylcysteines and thiosulfinates, protein, a high concentration of minerals and trace elements like calcium, copper, germanium, iron, magnesium, potassium, zinc, and especially selenium, vitamins A, B and C, glucosinolates, and the enzymes alliinase, myrosinage and peroxidase.
- Anti-catarrhal. The high concentration of sulfur compounds and mustard oils in garlic amount to a powerful capacity for reducing mucous congestion. Together with its anti-inflammatory, anti-microbial and anti-viral properties, garlic has a deservedly great reputation in the treatment of respiratory infections
- Anti-inflammatory. Among other properties, garlic’s sulfur compounds have been shown to inhibit the release of inflammatory compounds.
- Anti-fungal. Garlic has clinically demonstrated significant anti-fungal properties in many in vitro and in vivo studies. Against Candida albicans, garlic was shown to be more potent than several other well known fungicides, including nystatin, gentian violet, and six other reputed anti-fungal agents. Garlic was even used effectively in a study of a major Chinese hospital, against cryptococcal meningitis, one of the most serious fungal infections.
- Anti-microbial. Garlic has been shown to exert a broad-spectrum anti-microbial activity against a very large variety of pathogenic organisms. Findings that support the traditional use of garlic in the treatment of a variety of infectious conditions like dysentery and others. Both garlic juice and allicin are known to inhibit Cytrobacter species, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Salmonella enteritidis, Staphylococcus aureus, alpha and beta hemolytic Streptococcus, and various mycobecteria. The studies showed that garlic was effective against bacteria which were resistant to antibiotics like penicillin, streptomycin, chloramphenicol, erythromycin and tetracyclins.
- Anti-viral. Fresh garlic, allicin, and other sulfur compounds of garlic, have in vitro killed herpes simplex virus 1 and 2, parainfluenza virus type 3, vaccinia virus, vesicular stomatitis virus, and human rhinovirus type 2. Fresh garlic extract killed all viruses tested, but the potency of commercial products depended on how they were prepared. These with the highest content of allicin and other thiosulfinates proved to be most potent.
- Blood sugar modifier. Allicin was shown to have a considerable effect in lowering blood glucose and thus be of benefit to diabetes. There may be a number of actions involved, such as increased hepatic metabolism, increased insulin release, and an insulin sparing effect. The last mechanism may be a major factor, since allicin and other sulfhydryl compounds found in garlic and onions compete with insulin (also a disulfide protein) for insulin inactivating compounds. The result is that some insulin is spared, which increases the amount of insulin available for reducing blood glucose.
- Cardiovascular tonic. Garlic excels as a cardiovascular tonic, an effect due mostly to sulfur compounds like allicin and its derivatives like ajoene, etc. Numerous double blind studies show that garlic supplementation can reduce total serum cholesterol and at the same time lower LDL (bad) cholesterol and boost HDL (good) cholesterol. This effect may be enhanced by eating more garlic and onions. In addition, garlic has also been shown to decrease both systolic and diastolic blood pressure, through processes related to its sulfur content and lipid reducing qualities. Other studies show that garlic inhibits platelet aggregation, but increases fibrinolytic activity, that is the breakdown of fibrin, which may be more directly associated with cardiovascular disease than cholesterol. The combination of these varied effects makes garlic an absolutely first class heart and vascular tonic.
- Immune booster. Garlic appears to possess important immune-boosting properties and anti-cancer effects, known mostly from population studies in China. Comparison of cancer rates between different regions of the country, showed that cancer rates are lowest where garlic consumption is greatest. Studies show that several garlic constituents have significant immune-enhancing and anti-cancer properties. Animal studies show allicin to possess powerful anti-tumor properties. Human studies show that garlic inhibits the formation of nitrosamines, potent carcinogenic agents formed in the body upon digestion of preserved meats, where nitrites and nitrates have been used to protect the consumer from botulism.
- Nutritive. It is not surprising to learn that garlic is a highly nutritious food, considering that it contains 33 sulfur compounds, 17 amino acids, 16 percent protein, and the vitamins and minerals already listed at the beginning of this section.
Caution. At normal dosages no toxicity has been encountered. Regular consumption of large amounts of fresh garlic may be irritating to the digestive system of some people. Large doses are not recommended for people on prescribed anticoagulants like warfarin.