If you're interested in using food to lower your risk of cancer, remember to eat lots of onions. Research shows that people with the highest consumption of onions (as well as other allium vegetables) have a lower risk of several types of cancer, including:^1,2,3,4

• Liver, colon⁵ and renal cell (kidney)
• Esophageal and laryngeal
• Prostate⁶ and colorectal
• Breast⁷
• Ovarian and endometrial

Onions contain several anti-cancer compounds, including quercetin, anthocyanins, organosulfur compounds such as diallyl disulfide (DDS), S-allylcysteine (SAC) and S-methylcysteine (SMC) and onionin A (ONA).

Onion Compound Suppresses Ovarian Cancer

Starting with the latter, ONA was recently found to offer protection against epithelial ovarian cancer (EOC),⁸ the most common type of ovarian cancer. As noted by Medical News Today:⁹

"With a [five]-year survival rate of approximately 40 percent, effective treatments for the illness are needed.

Although new cases of EOC ranks 10th among female malignancies, the team says the number of deaths due to this type of ovarian cancer ranks fifth in the United States.

About 80 percent of patients with EOC have a relapse after initial chemotherapy treatment."

ONA, it turns out, slowed growth of EOC. The compound also inhibited other cancerous activities, and enhanced the effects of anti-cancer drugs. Mice fed ONA also lived longer. According to the authors:

"We found that ONA reduced the extent of ovarian cancer cell proliferation induced by co-culture with human macrophages. In addition, we found that ONA directly suppressed cancer cell proliferation.

Thus, ONA is considered useful for the additional treatment of patients with ovarian cancer owing to its suppression of the pro-tumor activation of [tumor-associated macrophages] and direct cytotoxicity against cancer cells."

The Stronger an Onion's Flavor, the More Effective Its Anti-Cancer Effects

Previous research has revealed that the stronger the flavor of the onion, the better its cancer-fighting potential. A 2004 study, in which food scientists analyzed 10 different varieties of onion, the following were found to be particularly effective against liver and colon cancer:^10,11

• Liver cancer: shallots, Western yellow onion and pungent yellow onion
• Colon cancer: pungent yellow onion, Western yellow onion

Northern red onions were also found to be high in anti-cancer chemicals, just not quite as potent as the others listed.

Mild-flavored onions, such as Empire Sweet, Western white, Peruvian sweet and Vidalia had the lowest antioxidant activity, making them less potent in terms of anti-cancer benefits. According to lead author, Dr. Rui Hai Liu, an associate professor of food science:

"Onions are one of the richest sources of flavonoids in the human diet, and flavonoid consumption has been associated with a reduced risk of cancer, heart disease and diabetes.

Flavonoids are not only anti-cancer but also are known to be anti-bacterial, anti-viral, anti-allergenic and anti-inflammatory …

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."