Opinions Vary on Fruits and Vegetables
When one thinks of the fresh versus frozen versus canned debate, it is usually fruit and vegetables that spring to mind and the fresher the better. And so it is surprising to hear New York City dietitian Hillary Baron say that frozen and canned fruits and vegetables can be nutritionally reasonable alternatives to fresh produce. In fact, they often contain as much and sometimes more of certain nutrients. Freezing and canning can occur immediately after harvesting when nutrient content is greatest. The nutrients are preserved until the package is opened. Fresh produce, on the other hand, must travel from the farmer to the store to your dinner table, which could take weeks or months and which will result in a loss of nutrients. Incorrect handling can compound these losses. For example, the temperature might not be cool enough or the fruits and vegetables could become bruised.
Registered dietician Allegra Burton maintains that fresh is usually better. She suggests that locally grown produce is likely to be fresher and thus more nutritious and better tasting than foods shipped hundreds or thousands of miles. Nutrients will vary from one batch of produce to another, depending on climate, handling and other factors, but a balanced diet will make up for this over the long-term.
Canning is in general thought to diminish the nutritional value of food. This is because the heating process destroys between one-third and one-half of vitamins A, E, thiamin and riboflavin, says Burton. Once canned, losses of between 5 percent and 20 percent of these vitamins may occur in one year. However, a recent study conducted by the National Food Processors Association for the U.S. Department of Agriculture found that there was virtually no difference in the nutritional values of fresh, frozen and canned foods when they are prepared for the table. In fact, the comparison of fresh, frozen and canned carrots showed that the canned carrots contained more of certain nutrients than the frozen or even the fresh carrots.
Ms. Baron says that vitamin C tends to increase during canning and a recent study showed that canned tomatoes had a higher concentration and more readily absorbable form of lycopene, a chemical found in tomatoes that has cancer-fighting properties. The key is in the preparation of the food.
The nutritional value of fresh produce does decrease with time, Burton says. Up to one half of some vitamins may be lost within a few days of harvesting unless fresh produce is quickly cooled or preserved. Even if you refrigerate it produce will continue to lose half or more of some of its vitamins within one to two weeks. Ms. Burton adds that frozen is the next best thing to fresh.
How to Minimize Nutrient Loss
The most important thing to remember is to cook vegetables with very little water and for just a short time, says Ms. Burton. She suggests the following:
- To minimize nutrient loss during heating, microwave your vegetables and cooked fruits very briefly.
- Steam vegetables with a small amount of water rather than boiling them. Boiling vegetables in lots of water is a poor choice as many of the vitamins and minerals are released into the water and unless you drink that water – which is not a bad idea – much of the nutritional value is lost.
- Keep the peels on as this also helps to preserve nutrients
What About Meats?
Fruit and vegetables are not the only types of food that come in fresh, frozen and canned varieties. Choosing the right option for meat is equally important. Fresh or frozen meat is good, but canned meat can pose a problem because of its high sodium content. Sodium is added to preserve the meat.Why is sodium bad? In large amounts, salt, which is made up of sodium, causes your body to retain water in order to maintain the right blood and body fluid chemistry. If there is too much salt in your body, the body must hold more water in order to dilute blood and body fluids, says Ms. Burton. This, she warns, may contribute to and exacerbate high blood pressure. Canned meats may also contain preservatives such as nitrates and nitrites, which may contribute to stomach cancer, according to Ms. Burton.
As far as canned meats go, choose those canned in water with little or no salt. Ms. Burton feels that frozen meat and poultry are equally as good as fresh and may be better if the fresh meat has been on the shelves for a while.
Regardless of whether you choose fresh, frozen or canned foods, there is one thing you must do: Read the label of all foods you buy so that you can determine their comparative nutritional value. And remember that the way you prepare food, be it fresh, frozen or canned, impacts on its nutritional content.