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updated 6/11/2004 12:42:04 PM ET 2004-06-11T16:42:04

Americans need to eat more vegetables and fruits. Although all produce is good for us, "powerhouse" vegetables and fruits are best and should be eaten more often, according to a new report.

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These vegetables deserve more emphasis because they are concentrated sources of nutrients that have been linked to a reduced risk of cancer, heart disease and other serious health problems.

Other experts disagree and say it would be better to simply maximize the variety and amount of produce we eat. All produce contains phytochemicals that play unique roles in promoting good health. Which is best: a variety or powerhouse ones?

Powerhouse vegetables and fruits fall into one of four groups: dark green leafy vegetables, yellow/orange vegetables and fruits, cruciferous vegetables and citrus fruit. The green leafy vegetables, like spinach and kale, provide folate, vitamin C, beta-carotene and other carotenoids.

Go for 5 a day
These substances seem to protect against heart disease, stroke, several types of cancer and cataract formation. Yellow and orange vegetables, like carrots and winter squash, are the other main source of beta-carotene. Cruciferous vegetables, including cauliflower, broccoli, and bok choy, contain phytochemicals that seem to inhibit colon and other cancers. Citrus fruits are full of vitamin C, an antioxidant that helps fight age-related health problems.

The reason powerhouse produce seems attractive is that current advice about vegetables and fruits - eat more and a variety - may be inadequate to give people optimal health benefits. For example, a person could eat a standard-size serving of iceberg lettuce, potatoes, corn, apple and banana to meet the minimum goal of five servings of vegetables and fruits a day. Those servings offer only 0.132 milligrams of beta-carotene.

Find out how dietary advice has changedThat amount is significantly below the three to six milligrams recommended by the National Academy of Sciences. If a person eats at least one serving from the powerhouse yellow/orange or dark green group, the dietary recommendation is met.

Another way to get enough health-protective nutrients and phytochemicals may be to choose differently colored vegetables and fruits. The 5 A Day for Better Health program (www.5aday.org), partially sponsored by the National Cancer Institute, encourages consumers to select produce from the complete color spectrum every day.

The program categorizes virtually all vegetables and fruits into one of five color groups: blue/purple, green, white, yellow/orange and red. Because each group tends to provide a distinct nutritional benefit, eating one from all five groups gathers a wide range of benefits.

The color-coded system, however, is not foolproof. A person could still choose iceberg lettuce from the green group and corn from the yellow/orange group and fail to meet the beta-carotene recommendation.

Long-term diet matters
The shortfall could be remedied over several days, as long as different vegetables and fruits were consumed. Eating carrots, sweet potatoes, or spinach salad on another day would supply enough beta-carotene to meet the recommendation for four days. Good nutrition does not depend on a single day. Our diet over several days and longer periods matters much more.

Although eating more powerhouse produce is a good nutritional idea, focusing only on them overlooks equally healthy foods. Apples, onions, berries, mushrooms, tomatoes and watermelon all offer important phytochemicals, yet these foods don't fit in any powerhouse category. Powerhouse produce isn't the only source of vitamins and minerals, either. For example, red peppers, kiwi and strawberries are excellent sources of vitamin C in the absence of a citrus fruit or green leafy vegetable.

Perhaps, the best vegetable or fruit for you is the one you haven't had in a while.

Nutrition Notes is provided by the American Institute for Cancer Research in Washington, D.C.

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