According to the research team, red onions contained significantly high concentrations of the flavonoid quercetin. The experts also noted that red onions were rich in anthocyanin, a compound that fortified quercetin's scavenging properties. The study also revealed that red onions were equally potent in eliminating breast cancer cells.
"Anthocyanin is instrumental in providing colour to fruits and vegetables so it makes sense that the red onions, which are darkest in colour, would have the most cancer-fighting power. We found onions are excellent at killing cancer cells. Onions activate pathways that encourage cancer cells to undergo cell death. They promote an unfavourable environment for cancer cells and they disrupt communication between cancer cells, which inhibits growth. The next step will be to test the vegetable's cancer-fighting powers in human trials," lead author Abdulmonem Murayyan said in ScienceDaily.com.
However, outside expert Dr. Justine Alford was wary of the results. Dr. Alford currently serves as senior science information officer for Cancer Research U.K.
"The researchers found that extracts from certain types of onions could kill bowel cancer cells in a lab, but that doesn’t mean the same would happen in a person’s body which is much more complex. If scientists can tease out which molecules in onions have these apparently beneficial effects, then perhaps they could be investigated as a potential drug in the future," Dr. Alford told DailyMail.co.uk.
The recent findings were reflective of a 2004 study carried out by researchers at the Cornell University. As part of the study, the research team took extracts from 10 onion varieties and shallots and used them against colon cancer cells. The scientists found that the pungent yellow and Western Yellow onion varieties provided the strongest protection against colon cancer cell proliferation. The study also revealed that shallots, the pungent yellow, and Western Yellow onion varieties also offered the greatest protection versus liver cancer cell proliferation.
According to researchers, onions and shallots are excellent sources of phytochemicals called phenolics and flavonoids. The phytochemicals stave off cancer onset by eliminating free radicals and inhibiting the production of reactive compounds that may damage otherwise normal cells. In addition, the research team noted that onions and shallots contain varying levels of these phytochemicals. (Related: Follow more news on anti-cancer compounds at Anticancer.news.)
According to the team, shallots had six times higher phenolic content compared Vidalia onions. On the other hand, Western Yellow onions contain 11 times more flavonoids than Western White varieties.
"Our study of 10 onion varieties and shallots clearly shows that onions and shallots have potent antioxidant and antiproliferation activities and that the more total phenolic and flavonoid content an onion has, the stronger its antioxidant activity and protective effect," lead author Dr. Rui Hai Liu told the Cornell Chronicle.