Low Antioxidants in Colon Tissues May Increase Risk of Cancer

BACKGROUND: A low intake of antioxidant carotenoids is associated with an increased risk of developing colorectal cancer. It may be possible to increase levels of these carotenoids in precancerous colon polyps, thereby reducing the likelihood of the polyps becoming cancerous. This small study was performed at the Center of Internal Medicine, University of Hohenheim, in Stuttgart, Germany, and published February, 2003 in Clinical Nutrition.

RESEARCH: Researchers analyzed levels of several carotenoids in intestinal biopsy samples from seven men and women with colon polyps and five people without polyps. The carotenoids included alpha-carotene, beta-carotene, lutein, Lycopene, zeaxanthin, and beta-cryptoxanthin. However, for technical reasons, alpha-carotene levels could not be reliably measured.

RESULTS: Biopsies showed that patients with polyps had significantly lower levels of all of the carotenoids compared with patients without polyps. In addition, carotenoid levels were lower in polyps compared with nearby unaffected tissues.

beta-carotene: 0.37 vs 0.19
Lycopene: 0.34 vs 0.21
beta-cryptoxanthin: 0.14 vs 0.09
zeaxanthin: 0.18 vs 0.09
Lutein: 0.18 vs 0.13

IMPLICATIONS: In discussing the results of their study, the researchers wrote that they assume that the lower levels of carotenoids in polyps were the result of "local carotenoid depletion," possibly caused by increased free-radical stresses. The researchers also recommended a clinical study in which subjects would receive supplementation of a number of carotenoids to determine whether these antioxidants, as a group, might help prevent colorectal cancer.

Source:

Muhlhofer A, Buhler-Ritter B, Frank J, et al, "Carotenoids are decreased in biopsies from colorectal adenomas," Clinical Nutrition, 2003;22:65-70.

Key concepts: antioxidant carotenoids, beta-carotene, lycopene, beta-cryptoxanthin, zeaxanthin, lutein, polyps, colon cancer