Garlic, Allium sativum, is known for its pungent smell and unique flavor. In the same family as onions, leeks and chives, garlic grows in head-like clusters containing individual pods surrounded by a durable, fibrous peel. When crushed or cut, a compound known as allicin is released and gives rise to the peculiar odor of garlic. Ancient societies of China, Egypt, and Greece utilized garlic for a multitude of medicinal properties. In fact, recent epidemiologic studies have suggested that garlic appears to possess cancer-fighting and cardiovascular protective properties.
The pungent odor and anti-cancer properties of garlic result from sulfur-containing chemicals such as diallyl sulfide, disulfides, trisulfides, allyl mercaptan, and allyl methyl sulfide. These, and many other compounds found in garlic, may inhibit cancer cell growth by mechanisms such as induction of cell death (apoptosis), disrupting cancer cell metabolism, decreasing cell growth and proliferation, decreasing tumor vessel growth (angiogenesis), and scavenging free radicals—oxygen-containing chemicals that damage DNA. Carcinogens, chemicals that are acquired through the environment, cause a variety of cancers in a laboratory tests, have been shown to be inhibited by garlic extracts. Garlic has also been shown to prevent DNA damage, as well as aid in DNA repair. Specifically, allyl compounds can decrease tumor proliferation in experimental models of lymphoma, skin, esophagus, breast, prostate, and lung cancer. Garlic may also enhance function of immune cells known as lymphocytes, natural killer cells, and macrophages, which destroy cancer cells.
Population-based studies provide evidence that certain human malignancies may be prevented by regular garlic ingestion. A study of 42,000 women in Iowa, aged 55-69, demonstrated that garlic consumption was associated with a decreased risk of cancer overall and a 50% lower risk of colon cancer compared to women who did not consume garlic. Studies in Northern China where garlic production is high reveal a decreased incidence of stomach cancer compared to the rest of the country.
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