Go Ask Alice!: Fruits and vegetables that can protect against cancer and more

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Nutrients

Fruits and vegetables that can protect against cancer and more

Originally Published: June 28, 2002 ~ Last Updated / Reviewed on: June 27, 2007

Dear Alice,

As a cancer survivor, I am looking for ways to keep my body healthy. What fruits and vegetables are high in antioxidants?

—Jill

Dear Jill,

Antioxidants are substances that are believed to protect cells from "free radicals," which are harmful oxygen molecules. Free radicals may cause damage to cells, possibly resulting in cancer. Formed from normal body functioning, their production is increased by smoking, air pollution, infection, and excessive sunlight. Test-tube and animal research in laboratories strongly suggest that antioxidants may be a helpful tool in preventing cancer and other diseases. They may help prevent the formation of carcinogens (cancer causing substances), block the actions of carcinogens, and/or suppress cancer development. Most of these actions have yet to be proven in humans; however, the foods they are found in (mostly plants) contain many healthy components.

Substances in plants could help improve health or protect against disease. Some are vitamins or minerals, but more diverse are plant chemicals (a.k.a. phytochemicals). These substances impart distinct flavors, aromas, and pigments to foods. For example, one enormous class of antioxidants, flavonoids, includes a group of antioxidants named allyl sulfides, which are found in garlic, onions, and shallots. All of these contain a distinctive taste and smell. It's believed that allyl sulfides may help in the production of a detoxification enzyme that protects against carcinogens. Other antioxidants are detectable by their colors — and vividly colored fruits and veggies are rich sources of beneficial plant chemicals. Anthocyanins are antioxidants that impart the deep red, blue, and purple colors to raspberries, blueberries, eggplant, and red cabbage, among others.

All fruits and vegetables contain healthful substances — the following table lists various classes of antioxidants and other phytochemicals, some of their rich food sources, and how they are believed to work:

Substance	Food Sources	Possible Action(s)
Vitamin C	citrus fruits, tomatoes, peppers, broccoli, leafy vegetables, strawberries, potatoes	Inhibits nitrosamine formation, a potentially dangerous carcinogen
Carotenoids	apricots, papaya, sweet potatoes, tomatoes, mangoes, carrots, pumpkin, red peppers, spinach, corn, cantaloupe	Numerous anti-cancer functions
D-limonene	citrus fruits	May detoxify cancer promoters
Lycopene	cooked tomato products, watermelon, pink grapefruit	A class of carotenoids that's protective against prostate and possibly other cancers
Anthocyanins	blueberries, strawberries, raspberries, blackberries, grapes, cherries, red peppers, eggplant, red cabbage	Antioxidant cell protection; may help prevent binding of carcinogens to DNA
Allyl sulfides	garlic, onions, shallots, leeks, chives, scallions	Various anti-carcinogen functions
Monoterpenes	parsley, carrots, broccoli, cabbage, cucumbers, squash, eggplant, peppers, mint, basil, citrus fruits	Aid protective enzyme activity
Flavonoids	parsley, carrots, citrus fruits, broccoli, cabbage, cucumbers, squash, tomatoes, eggplant, peppers, soybeans, berries	Block receptor sites for hormones that promote cancer
Indoles	cabbage, Brussels sprouts, kale	Stimulate production of enzymes that break down cancer causing agents
Phenolic acids	parsley, carrots, broccoli, cabbage, tomatoes, eggplant, peppers, citrus fruits, whole grains, berries	Antioxidant properties; inhibit nitrosamine formation and help form protective enzymes
Catechins	green tea, berries	Antioxidants linked to lower rates of gastrointestinal cancer

As you can see, a wide variety of fruits and veggies fall into one or more of the categories named above. The benefit is in eating the food, not in taking any pill or supplement. Fruits and veggies contain a variety of phytochemicals, vitamins, and minerals, as well as fiber — these cannot be replicated in a pill form. In addition, excessive amounts found in some supplements have the potential to cause harm.

Include at least five servings of fruits and veggies a day. If you're already doing this, aim for even more. Researchers have found that 5 - 9 servings per day are most beneficial. Set your sights on variety, too. To obtain the benefits of the myriad substances in nature, try to vary your selections from day to day, and from week to week. Include something red, yellow, green, orange, blue, purple, brown, white. This may help you to achieve a more diverse, inclusive, and colorful (plus healthful) eating plan!

For more tips on how to pack plenty of fruits and vegetables into your diet, try these resources from the FDA: