Garlic and Cancer Prevention

Garlic (Allium sativum)

A native to Central Asia, Garlic (Allium sativum) of the family Liliaceae has historically been prized for both culinary and medicinal use. It has the strongest flavor of all the alliums. A hardy perennial, garlic grows as bulbs, which are made up of cloves. Garlic is unique because of its high sulphur content.

In addition to this, garlic contains arginine, oligosaccharides, flavonoids and selenium, all of which are said to be beneficial to health. The characteristic odour and flavor of are garlic comes from sulphur compounds formed from allicin. The latter is the major precursor of garlic’s bioactive compounds, formed when garlic bulbs are chopped, crushed, or damaged. 

Several studies show an association between increased intake of garlic and reduced risk of certain cancers, including cancers of the stomach, colon, oesophagus, pancreas and breast. An analysis of data from various studiesshowed that the higher the amount of raw and cooked garlic consumed, the lower the risk of stomach and colorectal cancer.

Several compounds are involved in garlic's possible anticancer effects. Garlic contains allyl sulphur and other compounds that slow or prevent the growth of tumor cells. Allyl sulfur compounds, which occur naturally in garlic and onions, make cells vulnerable to the stress created by products of cell division. Because cancer cells divide very quickly, they generate more stressors than most normal cells. Thus, cancer cells are damaged by the presence of allyl sulphur compounds to a much greater extent than normal cells.

Garlic cloves

Protective effects from garlic may also arise from its antibacterial properties or from its ability to block the formation of cancer-causing substances, halt the activation of cancer-causing substances, enhance DNA repair, reduce cell proliferation, or induce cell death.

Although garlic has been used safely in cooking, excessive consumption can cause some side effects, in addition to strong breath and body odour. Ingestion of fresh garlic bulbs, extracts or oil on an empty stomach may occasionally cause heartburn, nausea, vomiting and diarrhea. Some studies suggest that garlic can lower blood sugar levels and can occasionally cause allergies.

Sources

• National Cancer Institute: http://www.cancer.gov/
• Milner JA. Garlic: Its anticarcinogenic and antitumorigenic properties. Nutrition Reviews 1996; 54:S82–S86
• Fleischauer AT, Arab L. Garlic and cancer: A critical review of the epidemiologic literature. Journal of Nutrition 2001; 131(3s):1032S–1040S. 
• Milner JA. Mechanisms by which garlic and allyl sulfur compounds suppress carcinogen bioactivation. Garlic and carcinogenesis. Advances in Experimental Medicine and Biology2001; 492:69–81.
• Boon H, Wong J. Botanical medicine and cancer: A review of the safety and efficacy. Expert Opinion on Pharmacotherapy 2004; 5(12):2485–2501.