Onion Nutrition Facts

If tears come to your eyes whenever you slice an onion, you'll be glad to know that your tears are not shed in vain. The very compounds that give onions their pungency, taste and smell have been identified as substances that may fight cancer.

Scientists believe that onions and other members of the allium family, such as garlic, leeks, chives and shallots, may be a significant dietary factor by protecting us from certain forms of cancer. The onion first attracted the attention of the scientific community in 1989 when a study was published in the Journal of the National Cancer Institute finding that people who ate the largest amount of vegetables in the onion and garlic family were less likely to develop stomach cancer than those who did not.

Onions contain as many as 150 phytochemicals. The flavonoid quercetin, an antioxidant (phytochemical) found in onions, helps eliminate free radicals in the body, inhibits low-density lipoprotein oxidation, protects and regenerates vitamin E, and helps to circumvent the harmful effects of heavy metal ions. Other sources of quercetin are tea and apples, but research shows that absorption of quercetin from onions is twice that from tea and more than three times that from apples.

Onions may also have a beneficial effect on cholesterol levels, according to some studies. Researchers found that people who eat an onion a day can raise their “good” (HDL) cholesterol, says Dr. Barry Sears in his book The Top 100 Zone Foods. Onions may also prevent the biochemical chain of events that leads to asthma and inflammatory reactions.