Colorectal Cancer News:

Study: Stronger Flavored Onions Provide More Protection Against Colorectal Cancer

Researchers at Cornell University have found that the stronger the onion, the more potent it is in helping to protect against colorectal cancer, according to a study reported in the November 3 of the Journal of Agricultural and Food Chemistry.

Researchers have known for some time that onions may help fight cancer, but this study is believed to be the first to compare cancer-fighting abilities among commonly consumed onion varieties.

Onions are rich in quercetin, a potent antioxidant that has been linked to protection against cataracts and heart disease as well as cancer, according to the researchers.

“No one knows yet how many daily servings of onions you’d have to eat to maximize protection against cancer, but our study suggests that people who are more health-conscious might want to go with the stronger onions rather than the mild ones,” said study leader Rui Hai Liu, MD, a Cornell University chemist.

Liu and his colleagues analyzed 10 common onion varieties and shallots for total antioxidant activity and their ability to fight the growth of cancer in human cell lines. Although shallots resemble onions, they are actually a separate, distinctive species. Fresh, uncooked samples were used, with extracts taken from the bulbs with the outer skin removed.

According to Liu, shallots and onion varieties with the strongest flavor -- such as Western Yellow, New York Bold and Northern Red -- had the highest total antioxidant activity.

This indicates that they may have a stronger ability to destroy charged molecules called free radicals, an excess of which are thought to increase the risk of disease, particularly cancer.

Onion varieties with the mildest flavor -- Empire Sweet, Western White, Peruvian Sweet, Mexico, Texas 1015, Imperial Valley Sweet and Vidalia -- had the lowest total antioxidant activity, he added.

In tests against liver and colon cancer cells, onions were significantly better at inhibiting the growth of colon cancer cells than liver cancer cells, an indication that they are potentially better at fighting colon cancer, Liu explained.

Green onions and cocktail onions were not tested in this study, nor did the researcher test whether cooking made a difference in cancer-fighting ability. Liu cautioned that human studies are needed before any definitive links between onion consumption and cancer-prevention can be established.

Source:Medical Week staff, October 23, 2004