Strong onions show anti-cancer promise

October 27, 2004

J Agric Food Chem 2004; Early online publication

Eating strong-flavored onions may protect against cancer, claim US scientists who found that extracts of the vegetables inhibited the growth of colon and liver cancer cells.

"No one yet knows 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 than the mild ones," Rui Hai Liu (Cornell University, New York) said.

Noting that onions are a major source of phenolics and flavonoids - antioxidant phytochemicals associated with several health benefits including a reduced risk of cancer - Liu and fellow investigators assessed the content of these compounds in shallots and 10 onion varieties commonly available in the US.

They found that shallots and the onion varieties with the strongest flavor - Western Yellow, New York Bold, and Northern Red - had the highest phenolic and flavonoid content. Moreover, laboratory tests revealed that these vegetables also had the highest antioxidant activity.

The onions with the mildest flavor had the lowest phytochemical content and antioxidant activity, the researchers note.

Liu et al then investigated the effect of extracts of the vegetables on colon and liver cancer cells in vitro, and found that exposure to the shallots, Western Yellow, New York Bold and Northern Red extracts all inhibited proliferation. Interestingly, these antiproliferative effects were stronger in the colon cancer cells than the liver cells.

"These results may influence consumers toward purchasing onion varieties exhibiting greater potential health benefits, and may significantly affect future breeding efforts to enhance onion nutritional qualities," Lui and colleagues conclude in the Journal of Agricultural and Food Chemistry.