Carotenoids, substances found in many fruits and vegetables, have biological properties which have proven their chemoprotective role in cancer. Slattery and colleagues, in a study published in The American Journal of Clinical Nutrition, narrowed their scope to particular types and stages of colon cancer and how they are affected by carotenoids. The researchers found that lutein has the greatest role in modulating colon cancer, especially in younger people.
The dietary carotenoids a-carotene, b-carotene, lycopene, lutein, zeaxanthin, and b-cryptoxanthin were evaluated. The study population consisted of 1993 subjects ranging in age from 30 to 79 years who had been diagnosed with colon cancer, and a control group of 2410 patients without cancer. Participants were asked to report what foods they had eaten during a specific time period two years before, or two years prior to their diagnosis for the cancer patients. Of all the carotenoids investigated, only lutein and zeaxanthin showed a protective effect against colon cancer, with an enhanced effect in younger people. The main sources of lutein consumed by the study participants were spinach, broccoli, lettuce, tomatoes, carrots, oranges and orange juice, celery, greens and eggs. In explaining the apparently potent antioxidant effect of lutein and zeaxanthin, the authors point to their biochemical effectiveness as scavengers of oxygen radical species, as well as their reaction with cell membranes which are susceptible to carcinogenesis in the colon.