The ancient Egyptians were onto something when they paid their pyramid-building crews with onions, and placed onions in the tombs of their pharaohs. In the Biblical account of the Exodus, onions are among the Egyptian foods the children of Israel miss. In ancient Greece, Olympians prepared for the games by drinking onion juice and rubbing their bodies with onions.
Today, of course, science better understands onions health benefits. Onions are a good source of vitamin C, potassium and dietary fiber, says Diane L. McKay, PhD, an assistant professor at Tufts Friedman School. Onions are also among the richest sources of quercetin, a flavonoid with antioxidant and anti-inflammatory benefits.
Dutch researchers have found that the absorption of quercetin from onions is twice that from tea and three times that from apples-two of the other major dietary sources. In addition to helping combat free oxygen radicals in the body, quercetin inhibits the dangerous oxidation of LDL cholesterol particles.
GARLICS COUSIN: An allium vegetable, onions are related to garlic, which has been more extensively studied for health benefits in humans. As in garlic, organic sulfur compounds in onions are released by cutting or crushing; in garlic, these compounds have been associated with cancer protection, improved cholesterol levels and decreased stiffness in blood vessels. It may be that letting onions sit for a few minutes after cutting, prior to cooking, helps preserve these beneficial compounds, as has been demonstrated in garlic.
Research at the University of Wisconsin has shown that the more pungent onions-highest in sulfur compounds-exhibit anti-platelet activity. So eating onions might improve blood thinning and prevent platelet aggregation, which contributes to atherosclerosis, stroke and heart attacks.
Those sulfur compounds, as well as quercetin, may be responsible for onions apparent cancer-protective effects. Moderate onion consumption has been associated with lower risk of colorectal, laryngeal and ovarian cancer, with daily onion intake linked to reduced incidence of esophageal and oral cancers.
GUT AND BONES: Other properties of onions seem to improve the health of your gastrointestinal tract. In particular, onions may combat Heliobacter pylori, the microorganism that contributes to ulcer formation. (Its true, however, that if you suffer from heartburn, onions may aggravate the condition.)
Onions are a healthy choice for those worried about diabetes, too. Besides quercetin and sulfur compounds, which promote insulin production, onions are a good source of chromium, which appears to have a beneficial role in the regulation of insulin action.
Onions may even help protect your bones as you age. In animal studies, Swiss researchers reported that onion consumption increased the mineral content of bones. In humans, a 2009 study of women age 50 and older found that those who consumed onions most frequently were at 20% lower risk of hip fracture versus those who seldom ate them.
As in the hip-fracture study, most research on onions suggests that you need to eat them as often as daily to experience the fullest benefits. You dont need to rub them on your body or drink onion juice as ancient Olympians did, but adding extra onion to savory dishes of all sorts is a simple way to boost nutrition and health.