Garlic Extract May Lower Colon Cancer Risk

Healthnotes Newswire (April 20, 2006)—In people known to have colon polyps, an aged garlic extract can prevent new polyps and reduce the number and size of existing polyps, according to the Journal of Nutrition (2006;136:821S–6S).

Colon polyps, abnormal growths that occur inside the large intestine, have the potential to become cancer. Colon cancer is the second most common cancer in Western societies. People with family members who have had colon cancer, and people with inflammatory bowel disease, such as Crohn’s disease and ulcerative colitis, are at high risk for colon cancer. Familial polyposis, an inherited condition characterized by frequent formation of colon polyps, also increases the risk.

Garlic is a bulb vegetable that has been regarded as a powerful medicinal for centuries. It is rich in selenium, a trace mineral and antioxidant known to have antiviral and anticancer effects, and contains a number of other beneficial compounds. Garlic lowers cholesterol levels; has demonstrated antibacterial, antiviral, and antifungal effects; and has anticancer properties. Lower rates of gastric and colon cancers have been noted in people who eat lots of garlic.

Aged garlic extract (AGE) is a processed garlic product that has some of garlic’s most important constituents in forms that are more stable than those that occur in fresh garlic. Studies in test tubes and animals suggest that AGE might be useful in preventing cancer.

The 37 people in the current study were between 40 and 79 years old and had been diagnosed with colon polyps. Polyps of a size greater than 5 millimeters were surgically removed before beginning treatment. After surgery, the people were randomly assigned to take either three capsules two times per day of a high-dose AGE, providing 2.4 milliliters of AGE per day, or the same number of capsules of a low-dose AGE, providing 0.16 milliliters of AGE per day (an amount expected to have no effect).

Compared with the number and size of polyps present at the beginning of the study, there was an increase in polyps at both the 6-month and 12-month exams in people taking the low-dose AGE; however, people taking the high-dose AGE had a significant decrease in number and size of polyps after 12 months.

The results of this study suggest that AGE might prevent colon cancer in people with high risk by reducing the number and size of precancerous colon polyps. These findings need to be replicated in a larger study. Whether fresh garlic and extracts of fresh garlic might have similar preventive effects is a subject for future research.

A number of dietary factors might contribute to colon cancer risk. A diet that is rich in vegetables appears to be the most protective. In contrast, frequently eating fried or darkly browned meat more than doubles risk, apparently because of the formation of cancer-causing chemicals during high-temperature cooking. Some studies have found that increasing dietary fiber can reduce risk, but other studies have failed to confirm those reports.