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Vegetable Debate: Fresh, Frozen, or Canned?

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Vegetable Debate:
Fresh, Frozen, or Canned?

Vegetables are an essential part of a healthy, well-balanced diet and are the body’s last defense mechanism against diseases and illnesses. They are low in fat and calories, cholesterol free, and excellent sources of vitamins, minerals, and dietary fiber. Furthermore, they are rich in antioxidants or disease-fighting plant substances that protect against many health conditions, including cancer. But which type of vegetables is best? Do fresh, frozen, or canned vegetables contain more vitamins?

Garden fresh vegetables
People assume that fresh vegetables are the healthiest choice, because they are not processed. Think again. This is true if you are buying produce from a local farmers’ market or picking vegetables directly out of the garden, but maybe not the case if you buy vegetables from a grocery store or purchase produce grown in another state or country.

The nutritional content of fresh vegetables depends on various factors, including seasonality and availability in the region. Many vegetables travel long distances to end up in the produce section of the local grocery store. When vegetables are shipped across several states, they are exposed to extreme light, heat, and temperature conditions, which can cause a loss of important nutrients, such as thiamine and vitamins A and C. Many fresh vegetables that travel many miles by truck or boat are harvested before they reach peak ripeness, so vitamins and nutrients have not had the time to reach complete potency. The produce still may show outward signs of ripening, but the vegetables will never have the same nutritional composition as fully developed plants.

From farm to fork
It is estimated that much of the food consumed in the United States travels an average of 1500 miles from the farm to your kitchen table. This is an economic and environmental concern; at this rate, depletion of fuel and local agricultural resources could occur in the near future.

One step you can take is to get a seasonal guide to local fresh produce, which is available from your state’s Department of Agriculture. However, from late October until early April, the only local fresh produce available in the northern regions of North America and in the northern latitudes of the world comes from the root vegetable, cabbage, onion, or squash families. If you want other types of fresh produce at this time of year, you can freeze or can your own when vegetables are at peak flavor and in season. In order to do so, you need canning and freezing equipment, as well as knowledge of storage methods and food safety.

Here is a better, easier alternative. The simple act of pushing your grocery cart through the frozen and canned vegetable section of your food market can help save the earth and improve your nutrition and health! Frozen produce is sent directly from the fields and orchards where it is grown to a processor near the field. After produce is frozen or canned, it is preserved and stored at the processor before distribution in a large bulk shipment. Perishable fresh produce, on the other hand, needs to get to its destination rapidly and is shipped in smaller quantities and great distances, especially during the off-season. As previously noted, this is a very uneconomical process. 

Fresh produce is shipped fast enough to prevent damage and spoilage, but its nutritional value may suffer. In fact, loss of vitamins and minerals in fresh vegetables is perhaps more significant than originally thought, according to study findings by Joy Rickman and colleagues published in the Journal of the Science of Food and Agriculture. The longer vegetables are in transition, the more nutrients are oxidized into the air. The average time frame from farm to your fork is about 10–14 days. In contrast, produce that is frozen and canned sits only a couple of hours before its freshness and nutrients are sealed in by the freezing or canning methods.   

In order to ensure that you receive the full spectrum of vitamins and minerals from your fresh produce choices, choose produce directly from your garden or local farmers’ markets during the summer and fall harvest. But what if the shelves in the produce aisle are bare in the late fall and winter? What if you cannot always purchase the fresh selection, whether because of cost, season availability, spoilage risk, or taste preferences? Should you head to the freezer case to buy bags of frozen vegetables? Absolutely! Many scientific studies indicate that frozen vegetables are just as healthy, if not better in some instances, than the fresh selection. 

The freezer section
In 1998, the US Food and Drug Administration confirmed that frozen produce provides the same essential nutrients and health benefits to the body as its fresh counterpart. Frozen produce is nothing more than fresh produce that is blanched (cooked for a short time in boiling water or steamed) and then frozen within hours after the harvesting time. In addition, frozen vegetables are processed at their peak in terms of freshness and nutrition. 

Produce for freezing is picked off the vine at its peak ripeness, quickly frozen to a temperature that maximally locks in its vitamins, minerals, antioxidants, and flavor, and kept frozen on its way to your local grocery store. This is why it is recommended that if you cannot access fresh foods you should purchase frozen foods instead of canned. The sooner produce is frozen after picking, the more antioxidants, vitamins, and minerals it will retain. While some early nutrient loss does occur with the first steps in the process used for freezing vegetables—washing, peeling, and heat-based blanching—the low temperature of freezing keeps the produce at optimal quality for approximately 1 year. Once you thaw and eat, you get most of the vegetable’s original nutritional value. Depending on what cooking method you choose or how you prepare the vegetable, it also may taste very similar to the fresh variety.

In an article in Eating Well magazine, Gene Lester, PhD, a plant physiologist at the US Dept of Agriculture’s Agricultural Research Center, Weslaco, TX, notes that while canned vegetables tend to lose many nutrients during the preservation process, frozen vegetables may be even more healthful than some of the fresh produce sold in grocery stores.

So, fresh vs frozen? The answer is frozen if the produce is traveling a long distance during off season and also if you do not plan on eating the vegetables quickly after buying them.

Straight out of the can
The method used for canning produce is somewhat different than frozen, and in some instances, this can affect the nutritional content. Canned vegetables tend to lose some of their vitamin C in the high-heat temperature ranges used for canning. Similar to the frozen process, in the canning technique, the vegetables are picked at peak ripeness, blanched (this time for longer duration and with somewhat increased nutrient loss for heat-sensitive compounds, compared to the frozen method), and then canned. Salt is added to many canned vegetables to preserve flavor and prevent spoilage on the shelves in the stores and your homes. These additions can take a very healthy vegetable and make it less desirable than its fresh or frozen variety. 

However, when they are handled and canned quickly without added salt and preservatives, most of the nutrients are sealed in and retained. Therefore, some canned vegetables are similar in nutritional value to fresh vegetables, and the concentrations of the vitamins and minerals remain the same even after 1–2 years of sitting on your shelf as a result of the oxygen-free environment.  Miranda Hitti reports that the American Dietetic Association noted in a statement released in January 2006 that “canned …vegetables are good substitutes for fresh produce and sometimes maybe healthier.” The statement further indicated that canned tomatoes, corn, and carrots provide higher amounts of antioxidants than the fresh variety as a result of the canning process. 

But if you see dented or bulging cans, throw them out!

Nutrition Facts labels
Check the sodium content on the Nutrition Facts labels, and buy vegetables with the key terms “no added salt” or “low sodium” printed on the label. Buy vegetables that do not contain added butter or cream sauce. When you buy canned vegetables, rinse them to get rid of some of the salt. When choosing frozen vegetables, make sure the only ingredients listed are the type of vegetables you intend to purchase. Boiling vegetables also releases nutrients, so boil them only for a very short time.     

Nutritional comparison between fresh, frozen, and canned vegetables
By the time the produce is eaten, fresh, frozen, and canned vegetables may have few differences in nutritional value, depending on the handling and processing methods used after harvest. Each has the same carbohydrate, fat, and protein content as the product prior to picking the crop. While loss in water- and fat-soluble vitamins does vary depending on the processing method used after harvest, you can rest assured that the majority of frozen and canned (without preservatives) fruits and vegetables are just as healthy for your family as the fresh variety. In fact, you might try choosing a mix of fresh, frozen, and canned produce in order to help your family more easily, inexpensively, and creatively enjoy the nine or more servings per day of fruits and vegetables recommended by the Center for Disease Control and Prevention without sacrificing nutrition. 

Vitamin C: This water-soluble vitamin is very sensitive to heat, light, and oxygen. If fresh vegetables are stored at the proper temperature and eaten within a few days, then they are the best source of vitamin C. However, during prolonged storage and the long shipping process, vitamin C degrades very fast. Depending on the harvesting method, loss of as much as 77% of the vitamin (as is the case with green beans) might occur in 7 days storage at 39° Fahrenheit. Vitamin C also escapes out of the vegetable when frozen vegetables are blanched. A large percentage of vitamin C (10%–90%) is lost with the first steps of the canning process as well. However, the vitamin remains stable during canned goods storage and little is lost during the short reheating time. 

B vitamins: Most water-soluble B vitamins, such as thiamine and riboflavin, are sensitive to heat and light, which causes significant loss of these nutrients with blanching during the freezing and canning processes. Therefore, fresh produce tends to provide the best source in terms of the B vitamins. 

Polyphenolic compounds: Water-soluble polyphenolic substances, found primarily in the skins of fruits and vegetables, are lower in products that are frozen or canned without the skin compared to fresh. However, if you keep the skin on or if the juice is included, these nutrient levels are as high or higher in canned compared to fresh products. 

Fat-soluble vitamin A, carotenoids, and vitamin E: Very few fat-soluble vitamins, including vitamins A and E, disintegrate during the blanching process, so overall frozen and canned produce is just as healthy as fresh in terms of these nutrients. Vitamin losses depend on the specific vegetable. For example, fresh green beans have more beta-carotene, a precursor of vitamin A, than frozen or canned. But frozen green peas have more beta-carotene than both fresh and canned peas. Canned tomatoes have the highest levels of beta-carotene and lycopene, a carotenoid pigment that is protective against heart disease, prostate cancer, and other cancers, because of the heat-induced release of the antioxidants with the blanching method. 

Other levels: Mineral, fiber, carbohydrate, protein, and fat levels are similar in fresh, canned, and frozen produce.

The bottom line
Summer and early fall is the best time of year to visit local farmers’ markets or your own garden for fresh produce. However, during the rest of the year, it is important to continue eating vegetables, whether fresh, frozen, or canned. The average American eats only one third of the recommended daily intake of five to nine servings of vegetables per day.

Decide whether you want fresh, frozen, or canned vegetables—they will all provide you with the essential vitamins, minerals, and nutrients your body needs to function. Try to add vegetables into your meals daily to keep your body healthy and prevent diseases, whether you pick them straight from your backyard garden, get them at the farmers’ market or from your store’s produce section, grab them out of your freezer, or pull them off your kitchen shelf!

 

References and recommended readings
American Council on Exercise. How much difference is there in nutritional value between fresh and frozen fruits and vegetables? Available at: http://www.acefitness.org/blog/859/how-much-difference-is-there-in-nutritional-value. Accessed April 11, 2012. 

FitDay. Vitamins in veggies: fresh vs. canned vs. frozen. Available at: http://www.fitday.com/fitness-articles/nutrition/vitamins-minerals/vitamins-in-veggies-fresh-vs-canned-vs-frozen.html. Accessed April 11, 2012. 

Gorman RM. Fresh vs. frozen vegetables: are we giving up nutrition for convenience? Available at: http://www.eatingwell.com/nutrition_health/nutrition_news_information/fresh_vs_frozen_vegetables_are_we_giving_up_nutrition_fo. Accessed April 11, 2012.

Hitti M. Canned fruits, veggies healthy, too: some processed produce more nutritious than fresh.  Available at: http://www.webmd.com/food-recipes/news/20070316/canned-fruits-veggies-healthy-too. Accessed April 11, 2012.

Jones HK. Fresh vs. frozen: choosing your fruits and vegetables. Available at: http://www.healthcastle.com/veggies_fresh_frozen.shtml. Accessed April 11, 2012.

Levin M. Fresh versus frozen or canned: how to choose your fruit and vegetables. Available at: http://www.age-well.org/fresh-versus-frozen-fruit-vegetables.html. Accessed April 11, 2012.

Rickman JC, Barrett DM, Bruhn CM.  Executive summary: nutritional comparison of fresh, frozen, and canned fruits and vegetables. Available at: http://www.mealtime.org/uploadedFiles/Mealtime/Content/ucdavisstudyexecutivesummary.pdf. Accessed April 11, 2012.

Tufts Medical Center. How far has your food traveled? Available at:
http://www.tufts-nemc.org/apps/HealthGate/Article.aspx?chunkiid=13904. Accessed April 14, 2012.

 

Contributed by Melissa Springer, RD, LDN

Review Date 4/12
G-1790

 

 

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