- Nutrition -

Fresh, Frozen or Canned

While fresh produce is generally best, with a little nutritional know-how, you can eat healthy from your market’s freezer case and canned-foods aisle, too.

The refrain has been around as long as moms have been feeding their young: Eat your fruits and veggies. And just in case the message didn’t sink in (and current stats suggest, sadly, that it didn’t), the government is trying to drive the lesson home. According to the U.S. Department of Agriculture’s Dietary Guidelines for Americans in 2005, we should consume 2 cups of fruit and 21/2 cups of veggies each day (based on the intake of 2,000 calories a day). That’s equivalent to the five to nine daily servings recommended by the National Cancer Institute.

Why so many servings? Fruits and veggies are loaded with essential vitamins, minerals, fiber and disease-fighting phytochemicals that help lower your risk for many illnesses, including heart disease, stroke, high blood pressure, type 2 diabetes, vision loss from macular degeneration or cataracts, and certain cancers.

The trouble is, 75 percent of Americans still fail to meet the minimum five-a-day recommendation. Women average about four servings daily; men, about three and a half. Clearly, we need more broccoli, bananas – and, yes, maybe even Brussels sprouts – in our diets. But our busy lives can make it tough to shop for fresh fruits and vegetables, and harder still to prepare and eat them while they’re fresh enough to deliver their full nutritional benefits.

That’s why stocking frozen and canned produce can be a smart alternative. First, it’s better to eat lightly processed fruits and veggies than not eat them at all. And second, as Patricia Kendall, PhD, a professor of food science and human nutrition at Colorado State University in Fort Collins, points out, “A food that’s frozen or canned at peak quality is often better for you than the fresh version that has sat in your refrigerator for two weeks.”

When Fresh Is Best

If you want to eat fruits and vegetables at their nutritional peak, consider growing some of your own so you can cook them right after plucking them. Ideally, you’d harvest in the morning, when nutrient levels are highest. For those of us without gardens, however, buying produce fresh at the local farmers’ market is the best option. When shopping there, strive to buy from a local grower, rather than from a national distributor whose produce may be shipped from thousands of miles away.

“When fruits and vegetables are picked, they are still, in a sense, living organisms,” says Barbara Klein, PhD, professor emeritus of food science and human nutrition at the University of Illinois at Urbana-Champaign. “But once you take them off the vine, they immediately go into senescence, which is a decay process.” The cell membranes begin to break down, releasing enzymes that cause vitamins and phytochemicals to degrade. The process is irreversible. So although you can sometimes rehydrate tired-looking produce, such as spinach, by soaking it in cold water, you can’t recover lost nutrients.

Vegetables tend to lose their nutrients faster than fruits. (Strawberries, raspberries and blueberries, interestingly, may continue to gain a cancer-preventing phytochemical, anthocyanin, after they’re picked.) Nutrient loss is also accelerated in any produce that’s been cut, chopped or undergone tissue trauma (such as bruising).

But time itself is your biggest nutritional enemy. Researchers at Pennsylvania State University recently discovered that after eight days of storage at typical refrigerator temperature (about 40 degrees F.), fresh spinach loses almost half its folate, a vitamin-B compound essential for healthy blood and cells and, during pregnancy, for preventing birth defects.

The problem, of course, is that it can take up to three weeks, particularly in winter, for spinach and other fresh produce to travel from the field to your table. That’s where canned and frozen goods come to the rescue.

The Goods on Processing

The canning process (which includes bottling in glass jars) was invented in 1809 by a French chef. Except for feeding armies, however, tinned food didn’t catch on in a big way until World War I. Frozen foods made their debut in 1930, when grocery stores began stocking the new invention by Clarence Birdseye, an American naturalist, taxidermist and wannabe chef.

Convenience, rather than appearance or taste, drove the early sales of these foods. “Years ago, canned foods in particular weren’t so attractively packaged, and the food that came out of the cans didn’t look all that great,” says Susan Moores, a registered dietitian in St. Paul, Minn., and a spokesperson for the American Dietetic Association. But today’s canned and frozen foods are better-looking than those of past generations, and they also hold more nutrients.

Modern-day processing of canned and frozen produce usually occurs within a few miles – and, most important, hours – of harvest. The food is blanched (heated for a short time in hot water or steam, then immediately cooled in ice water) before being sealed in its packaging. This speed helps stabilize many of the nutrients.

Some water-soluble and heat-sensitive nutrients are lost during processing, but a sizable number are retained, and in some cases, select nutrients are gained.

Losers and Gainers

In 2005, a group of Dutch researchers reported that the processing of fruits and vegetables reduces levels of glucosinolates, the phytochemicals that studies suggest may protect against cancer and memory loss. Glucosinolates are found primarily in cruciferous vegetables, such as broccoli, cabbage and collards.

Processing has also been found to lower levels of vitamin C, which degrades quickly when exposed to heat. Fresh blackberries, for example, contain four times more vitamin C than canned varieties.

By contrast, frozen peaches have 21 times more vitamin C than their fresh counterparts, as the result of the addition of ascorbic acid (vitamin C) during processing to help the fruit maintain its color.

Processing also in- creases levels of lyco-pene, a phytochemical found primarily in tomatoes and associated with a reduced risk of prostate cancer and heart disease. A medium-sized fresh tomato contains about 3.7 milligrams of lycopene compared to the 11.8 milligrams found in a half-cup of canned tomatoes. (Note that you can increase lycopene absorption by cooking fresh tomatoes with a little olive oil.)

Then there’s canned pumpkin, which contains up to 30 times more vitamin A than raw pumpkin, and 20 times more than the fresh-cooked version because more water is cooked out of the canned varieties.

As a rule, though, marked gains in a single nutrient won’t entirely compensate for the other nutritional losses associated with processing. So when should you buy canned or frozen instead of fresh? Just about any time that having those fruits and veggies on hand – in any form – means you’ll be more likely to get them into your body. “For me, the real question is, ‘What is it going to take to get you to eat them?'” Kendall says. “That’s the bottom line.”

So if you don’t like the mess associated with peeling and cooking fresh beets – buy them canned, even if they do contain only half as much folate and potassium. Don’t like the taste of canned asparagus? Keep buying fresh stalks throughout the winter months, even though they may contain slightly less vitamin A. The crucial thing is to get five to nine servings a day of whatever fruits and vegetables appeal to you, in whatever way you can work them into your meals and snacks.

Wise Choices

Another way to get the most nutritional value from canned and frozen produce is to read product labels carefully. “When you’re picking frozen or canned fruits and vegetables, watch the company they keep,” Moores advises. “Look closely at the label and choose products that have as few companions as possible on the ingredient list.” That means avoiding fruits packaged in heavy syrups and vegetables processed with salt (sodium) or in fatty sauces.

Fortunately, canning and freezing don’t require chemical additives. So you shouldn’t see long lists of impossible-to-pronounce ingredients on processed fruits and veggies. The not-so-bad ingredients that you can expect to see on processed produce include ascorbic acid and citric acid (found naturally in fruits such as lemons and limes), which are sometimes added to canned fruit to preserve its color. And manufacturers occasionally use calcium chloride (another additive considered safe) to help processed fruits and vegetables maintain their crispness and firmness.

Age-Old Advice

Fresh, frozen or canned? Making that decision in the supermarket isn’t as important as choosing, five to nine times a day, to pull the produce off your pantry shelf or out of your refrigerator and put it onto your kitchen table. So make a list of your favorite fruits and veggies, squeeze that shopping trip into your schedule, and load up on produce that you can eat on your timeline. Your body will be the better for it, and moms everywhere can delight in serving up a satisfying “I told you so.”

WEB EXTRA!

Making the Grade

The taste, texture and appearance of processed fruits and vegetables vary. To give consumers a better idea about what’s inside that package of processed food, the U.S. Department of Agriculture has established an inspection and grading system for canned and frozen produce.

The system is entirely voluntary, and not all manufacturers opt in. When available, however, the grades (found on labels) can help you decide which product might be best suited for the cooking use you have in mind.

U.S. Grade A (Fancy): These fruits and vegetables are the very best. They are properly ripe and tender; are the most succulent and flavorful; have few or no blemishes; are of uniform size, weight and shape; and have an excellent color. They also tend to be the most expensive. They’re great for really visible uses — as stand-alone side dishes or desserts, for example.

U.S. Grade B (Extra Standard): Although still of good quality, these fruits and vegetables are not quite as tasty, tender or attractive as Grade A. They’re usually slightly riper than Grade A but still have many uses, including in side dishes and gelatin salads.

U.S. Grade C (Standard): These fruits and vegetables have the least flavor and uniformity of color. They may contain some broken and uneven pieces. Grade C produce is a good choice when you want to save money and when appearance is not too important, such as in casseroles, sauces, soups, cobblers, smoothies or puddings.

Susan Perry, author of Taking Charge of High Blood Pressure: Start-Today Strategies for Combating the Silent Killer (Reader's Digest, 2003), writes about health and science.

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