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Article Dated: 6/1/2009 |
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Most experts agree that if fruit protects your health, fresh or frozen is better than juice. Why?
To shield their seeds from predators and the environment, "plants put a lot of potent natural compounds into the outermost layer of their fruit," says medicinal plants expert Navindra Seeram of the University of Rhode Island. So when the skins and peels are removed in processing, out go those protectors.
"Juices generally retain less than 50 percent of the bioactive compounds found in the whole fruit," says Luke Howard, who studies fruit processing at the University of Arkansas. In some studies, it's as little as 20 percent.
"Once you start to process a fruit, losses are inevitable," Howard explains. Oxygen can destroy some of the phytochemicals, and enzymes are released that can convert compounds into larger or smaller molecules that the body can't absorb or metabolize.
That's especially true of tropical fruits. "With some, like acai, as soon as you pick them, if they're not handled properly they start to completely disintegrate on the spot, and in 24 hours they're just mush and have very little bioactivity left," says Rutgers University berry expert Amy Howell. "What you buy may have nothing left of the antioxidant activity that was there when they picked the fruit."
More phytochemicals are lost when the skin, seeds and pulp are removed or filtered out. "For example, only about 20 to 25 percent of the proanthocyanidins in the whole blueberry survive in the juice," says Howard. Blueberry purees do better, he notes. They retain about 40 percent and canned blueberries hold on to 65 to 80 percent of their proanthocyandins. The losses continue during storage. "That's really a big killer of bioactivity," says Howell. For example, "after six months of storage at room temperature, only about 10 percent of the proanthocyanidins remain in blueberry juice." If the fruit is quickly frozen or freeze-dried, though, fewer compounds are lost, she adds. There are other reasons to stick to fresh or frozen fruit. An 8 oz. glass of most juices packs 100 to 140 calories. And the calories from liquids don't curb your appetite like the calories from solid foods do, so you won't compensate by eating less later. If you're not careful, the calories and the pounds can quickly pile up.
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