(WebMD) An apple a day plus a veggie-intensive diet are the stars of new cancer prevention studies.

The findings are being presented at the annual Frontiers in Cancer Prevention Research conference in Seattle.

A chemical in apples helped prevent colon cancer in laboratory and animal studies, reports lead researcher Francis Raul, PhD, research director of the French National Institute for Health and Medical Research in Strasbourg, France.

Three or more servings of vegetables a day -- potatoes not included -- reduced risk of non-Hodgkin’s lymphoma by 40%, says lead researcher Linda Kelemen, RD, ScD, with the Mayo Clinic College of Medicine. Non-Hodgkin’s lymphoma occurs when cells in the lymph nodes -- small organs that help fight off infection -- divide and grow out of control.

"It’s been estimated that up to one-third of cancers are related to food we eat. ... That’s a lot of preventable cancers," Kelemen said in a news teleconference held today. Antioxidants in fruits and vegetables protect the body from damaging free radicals "like rust-proofing your car."

Apples and Cancer Prevention

In the apple studies, Raul first exposed cancer cells to various antioxidants found in apples. They found that one type of antioxidant, called procyanidins, triggered a series of cell signals that resulted in cancer cell death.

In an experiment with laboratory rats, the rats were exposed to colon cancer-causing substances and then fed a mixture of water and apple procyanidins. Rats getting "apple water" for six weeks had half the number of precancerous lesions in their colons compared with rats eating the regular diet.

The finding "suggests that eating the whole apple, including the skin, might offer some [cancer prevention] benefits," says Raul.

Cyanidins are also found in abundance in red wine and cocoa.

Cancer Prevention and Veggies

In their study, Kelemen and her colleagues identified 450 men and women between ages 20 and 74 diagnosed with non-Hodgkin’s lymphoma. Each provided diet information in a survey. She compared the cancer patients’ diets with a group of people without cancer.

Those who ate both green leafy and cruciferous vegetables got "particularly strong" cancer prevention protection, she reports. Cruciferous vegetables include broccoli, cabbage, cauliflower, and Brussels sprouts.

The daily diet of the cancer-free people included:

One serving (one cup) daily of greens like spinach

One-half cup of broccoli, cabbage, cauliflower, or Brussels sprouts

Also getting good marks in cancer prevention: Whole fruits, yellow-orange-red vegetables, and processed tomato products like tomato sauce and juice. However, the cancer risk reduction was not significant, says Kelemen.

As for specific nutrients and vitamins:

Selenium and zinc have some cancer prevention effects.

Individual vitamins like A, C, E, individual carotenoids (like beta-carotene) and retinol (promoted as a vitamin A booster) did not lower cancer risk.

"If more people ate at least three servings of vegetables per day, there would be substantial reduction of cancer rate," Kelemen added.

"Why wait until you get cancer to change your eating habits? Do it now, when you’re healthy, so you can stay healthy. Set a good example for your children. Grocery stores and supermarkets offer pre-washed, ready-to-eat vegetables. Some have salad bars with already prepared fruits and vegetables. They are just as costly as buying fast food and a lot healthier."

SOURCES: American Association for Cancer Research Third Annual International Conference on Frontiers in Cancer Prevention Research, Seattle, Oct. 16-20, 2004. News release, American Association for Cancer Research. WebMD Medical Reference from Healthwise: "Non-Hodgkin’s Lymphoma."