Onions, garlic linked to lower cancer risks

By Amy Norton
Reuters Health
Dec. 02, 2006

NEW YORK (Reuters Health) - People who flavor their diets with plenty of onions and garlic might have lower odds of several types of cancer, a new study suggests.

In an analysis of eight studies from Italy and Switzerland, researchers found that older adults with the highest onion and garlic intakes had the lowest risks of a number of cancers -- including colon, ovarian and throat cancers.

The findings, which appear in the American Journal of Clinical Nutrition, are in line with some past research. But those studies were mainly conducted in China, and it is unclear if the results are different in Western countries.

Dietary habits are substantially different in China, with garlic intake, in particular, being far higher, Dr. Carlotta Galeone, the lead author of the new study, told Reuters Health.

These latest findings suggest the anti-cancer benefit of these vegetables extend to Western populations, according to Galeone, a researcher at the Mario Negri Institute of Pharmacologic Research in Milan, Italy.

It's still not certain that onions and garlic have a direct effect on cancer risk. It's possible, for instance, that onion and garlic lovers also have an overall diet that protects against cancer, according to Galeone and her colleagues.

On the other hand, they note, animal studies and lab experiments with cancer cells have found that certain compounds in onions and garlic may inhibit the growth of tumors. Sulfur compounds found in garlic and antioxidant flavonoids in onions are among the potentially protective substances.

The current findings are based on results from eight studies conducted in Italy and Switzerland. Each study compared healthy older adults to patients with a particular form of cancer, asking participants for detailed information on their diets, physical activity and other lifestyle habits.

When it came to colon cancer, Galeone's team found that men and women who ate seven or more servings of onions per week had less than half the risk of those who shunned the vegetable. Similarly, garlic lovers were a quarter less likely to develop the disease than people who maintained garlic-free diets.

The vegetables were also linked to lower risks of cancers of the mouth, throat, kidneys and ovaries.

Given what's known about the biological activity of some onion and garlic compounds, it wouldn't be a bad idea to spice up your diet with the vegetables, according to Galeone.

It's probably wise to mix them with plenty of other vegetables, however.

Some research has found that garlic and tomatoes may have "synergistic" cancer-fighting effects, Galeone and her colleagues note. And, in general, experts recommend that people eat a variety of fruits and vegetables every day for overall health.

SOURCE: American Journal of Clinical Nutrition, November 2006.