Onions (excerpt from the best-selling book, “The 150 Healthiest Foods on Earth“)
There’s no two ways about it: onions are a cancer-fighting food.
In a number of impressive published studies, the consumption of onions (and other members of the allium vegetable family) demonstrated protective effects against stomach cancer. And in one study published in the journal of the National Cancer Institute, eating onions (as well as other members of its family like garlic, scallions, chives and leeks) significantly lowered the risk for prostate cancer.
Onions (and its close relatives) have also been shown to have the same effect against esophageal cancer. In Vidalia, Georgia, where the Vidalia onion comes from and where onions are consumed in large quantities, the death rate from stomach cancer is 50% lower than the national mortality rate from stomach cancer. One theory is that onions contain diallyl sulfide which has the effect of increasing the body’s production of an important cancer fighting enzyme, glutathione-S-transferase.
At least two important studies show that onions help build strong bones. In one, published in the prestigious journal Nature, male rats fed a small amount of dried onion daily had a 17% increase in calcium; female rats that had had their ovaries removed (which would rapidly induce bone loss and osteoporosis) had stronger bones when fed onions.
And in another study, published in the Journal of Agriculture and Food Chemistry, a compound in onions inhibited the activity of the cells (osteoclasts) that break down bones. The popular drug Fosamax works in a similar way, but onions have no side effects unless you count the need to chew gum before making out.
Onions belong to the allium family, which also includes leeks, garlic and shallots. They contain a whole pharmacy of compounds with health benefits, including thiosulfinates, sulfides, sulfoxides and other smelly sulfur compounds.
But those same smelly compounds offer a lot of nutrition bang for the relatively small price of a little eye-watering. In a study in the European Journal of Clinical Nutrition, onions are one of a very select group of foods the combination of which was found to reduce mortality from coronary heart disease by an impressive 20% (the others included broccoli, tea and apples).
Onions contain powerful antioxidants and are anti-inflammatory, antibiotic and antiviral. They are a great source of quercetin, one of my favorite anti-inflammatory compounds, and one which itself is associated with beneficial effects on chronic diseases like cancer and heart disease.
The class of chemicals that quercetin belongs to- flavanoids- have anti-allergic properties as well, and quercetin in particular is frequently used by nutritionists as part of their arsenal for treating allergies with natural substances. Quercetin can help relieve asthma and hay fever by blocking some of the inflammatory responses in the airways.
Our bodies absorb quercetin from onions very easily, though you’ll probably need quercitin supplements if your main interest is using it therapeutically as an anti-inflammatory. Onions also contain a number of sulfides very similar to those in garlic, which may lower blood lipids and blood pressure.
The type of onion affects the content of the health promoting chemicals, and the stronger tasting ones probably have superior properties.