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Quinn on Nutrition: Canned produce

January 13, 2014


This question comes from a friend: "I know someone who is moving to the sticks for an extended period, and will probably go into town once a week for groceries. However, refrigeration is very, very limited. How can he make sure he gets his leafy greens and such with no refrigerator to keep things cool?"

I’d advise your friend to eat his leafy greens on the days he goes to town … when they are as fresh as possible. Fresh produce loses valuable nutrients during days of storage, even with refrigeration.

In fact, a comprehensive study on this topic by the University of California at Davis found that — by the time they are consumed — fresh, frozen, or canned vegetables and fruit may contain similar amounts of nutrients. 

Canned fruits and vegetables are packed at their peak of freshness and retain most of their original nutrients since the canning process shields the food from oxygen. The heating process of canning primarily lowers the vitamin C content of canned food, the researchers said. 

Some nutrients may be more concentrated in canned foods. One-half cup of canned tomatoes, for example, contains almost 12 grams of lycopene — an antioxidant that may help reduce the risk for heart disease and some cancers such as prostate cancer. A medium fresh (uncooked) tomato contains less than 4 grams of lycopene. 

Canned pumpkin, according to data from the United States Department of Agriculture, contains more than three times the vitamin A as fresh cooked pumpkin. Lutein — an antioxidant in corn known to protect the eyes from cataracts and macular degeneration — was found by researchers at Cornell University to more bioavailable in canned corn than fresh. 

Heat treatment also kills dangerous bacteria. And in the case of canned carrots, tomatoes, and spinach, it also enhances the body’s absorption of carotene, an antioxidant that converts to vitamin A in the body. And Oregon State University scientists found that canned blueberries have some enhanced antioxidant benefits over fresh blueberries.

Have your friend stock up on citrus fruits like oranges and grapefruit that don’t require refrigeration and are rich sources of the vitamin C he needs. Keep his leafy greens as cool as possible and eat them within 1 or 2 days. 

Tell him to ditch the salt shaker, since canned foods are notoriously high in sodium. Or look for lower sodium versions. 

Remember too, that canned food is cooked food. A canned pear is a poached pear. Canned tuna has been filleted and steamed. Canned beans have been soaked and simmered. This might save him some energy costs. 

Experts say the canning process helps a food maintain its quality and nutrient content for about two years. And it remains safe to eat as long as the container is not bulging or leaking, according to the Canned Food Alliance. 

Bottom line. Fresh, frozen, or canned, your friend in the sticks needs a variety of foods from each nutrient group: fruit, vegetables, grains, protein, and calcium sources. A study at the University of Massachusetts concluded that "it’s the ingredients you choose, not the form of the ingredients, that really determine a recipe’s nutrient content."

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McClatchy-Tribune Information Services