The AICR also recommends crunchy "cruciferous" vegetables, such as broccoli and cabbage, which are packed with vitamins, minerals and antioxidants to protect against several cancers; fruits to protect against mouth, neck, lung and stomach cancers; and red-orange fruits and vegetables — cantaloupe, sweet potatoes — for protection against mouth cancers.
While researchers debate the overall benefits of fruits and veggies, there is mounting evidence that a diet rich in fiber from whole grains helps protect against cancer. Yikyung Park, a National Cancer Institute researcher working with the NIH-AARP study, reported on the benefits in a 2011 paper.
"Men and women who consumed the highest amount of dietary fiber were less likely to die from any cause," Park says. That research also found a link between fiber and a reduced risk of cancer death in men. And Park says fiber from whole grains was more protective than fiber from fruits and vegetables.
Foods, experts stress, are the best way to get most nutrients. Studies have found that high levels of vitamins in pill form can sometimes increase cancer risk rather than reduce it. For example, while beta-carotene — found in carrots and sweet potatoes — is thought to help protect against cancer, two studies unexpectedly linked high doses of beta-carotene supplements given to smokers to an increased risk of lung cancer. Another study found high doses of vitamin E supplements actually increased the risk of prostate cancer.
"Our bottom line message on supplements is that there's not enough evidence that they reduce cancer risk," says Colleen Doyle, director of nutrition and physical activity for the American Cancer Society.
The effects of coffee and alcohol
Coffee appears to lower the risk of endometrial cancer. And when researchers looked at the coffee habits of those in the NIH-AARP study, they found that men and women who drank four or more cups a day had a lower risk of colon cancer compared with non-coffee drinkers. Sinha, of the National Cancer Institute, theorizes that coffee — both regular and decaf — may help protect against colon cancer because it reduces "transit times." The less time food waste spends in the colon, the lower the risk of colon cancer. But the answer is likely more complex, she says: "There are about 1,000 compounds in coffee … We have only begun to skim the surface with these compounds."
When it comes to alcohol, "any level of alcohol increases risk for breast cancer," says Bender.
But high alcohol consumption also increases the risk of several other cancers for both women and men, including colon and liver cancers.
The American Cancer Society recommends that people who drink alcohol limit themselves to no more than two drinks a day for men, one drink a day for women.
Finally, remember to look at the big picture and consider your total diet. The easiest way to do this is to think colors. Your plate of food should have a rainbow of them — deep-coral baked salmon with a mix of dark green lettuces studded with ruby-red cranberries and a scoop of orange mashed sweet potatoes. The more colors, the more nutrients.
AARP has distilled the findings of the NIH-AARP study into a new diet book by John Whyte, M.D. AARP New American Diet is designed to help Americans age 50 and older lose weight and keep it off — with foods that also help reduce the risk of cancer, heart disease and diabetes.