Waiting to Eat Fresh Vegetables Means Loss of Nutrients
The research also underscores the importance of keeping fresh vegetables cold -- experts recommend a refrigerator temperature between 36 and 40 degrees Fahrenheit -- and eating them as soon as possible.
Eight days. And that count started from within 12 hours of the time the spinach was packaged. Commercial spinach must be transported from the field -- somewhere in the Southwest at this time of year -- to the processing plant and to the store.
Then it must sit on store shelves until it is purchased. This takes a few days at least, and the clock is ticking.
LaBorde said while fresh fruits and vegetables are becoming popular, not a lot is known about their nutrient loss because much of the early research was done on canned and frozen vegetables. "We've got the fresh vegetables that are so popular right now," he said. "When you have a fresh vegetable, it slowly dies. And as it dies, the enzymes take over and slowly degrade it."
He said the fruits and vegetables most at risk of nutrient loss are those that are crushed or cut. Apples, he said, are not going to change much because they are designed to fall off the tree.
Spinach and most greens are a different story, though. "In this case you're ripping it off the plant," LaBorde said. "(Loss) would be even higher with chopped spinach." Broccoli, another cut vegetable, loses about half its total carotenoids after six days at 41 degrees, previous research shows. The culprits are degrading enzymes that are normally contained inside intact cells but are released and free to cause damage when veggies are wounded. Chopped or peeled versions of fruits or vegetables also are vulnerable to nutrient loss during refrigerator storage.
LaBorde and Suzy Pelican of the University of Wyoming Cooperative Extension agree that fresh veggies are part of a good diet, but a combination of fresh, canned and frozen is the best way to go. "Don't assume fresh is best and frozen or canned are not," Pelican added. Canned or frozen fruits and vegetables are relatively stable and impervious to nutrient loss. Frozen vegetables are made that way very soon after harvest, preserving almost all of the nutrients. And in canning, the enzymes that break down vitamins in fresh vegetables are inactivated.
"If eating fresh vegetables soon is a problem, buy canned or frozen," LaBorde added. Canned vegetables are cheaper too. "Those bagged spinach things are pretty expensive -- you're paying for that cold temperature chain and all that," LaBorde said. He also said to avoid buying greens on sale and not to buy them if they're in the middle of an aisle and not refrigerated. "Take them from the coldest part of the refrigerated section," he said.
But since spinach is such a rich source of folate, losing some isn't the end of the world, Pelican said. Not all nutrients are prone to degradation either, she added. Vitamins and minerals are two different animals, she said. Vitamins like folate and carotenoids are large molecules that are easily degraded. Minerals, on the other hand, are elements like iron that aren't prone to break down. Fiber and minerals remain in spinach at their initial levels long after vitamins have degraded, she said.
Planning also can be a good way to avoid nutrient losses. That way, vegetables get used quickly. It can be something as simple as "We're going to buy the bag of spinach and use it the next night and not next Sunday," she said.
Farmer's markets have sprung up in the state, Pelican said, and they are another alternative. "In the months they're open, that's going to be a good way to get fresh vegetables that haven't been transported far," she said.
Eating a variety of fruits and vegetables is a great hedge too, Pelican said. "Variety is important because then you're not putting all your eggs in one basket," she added.
HOLDING ON TO VITAMINS
Tips for avoiding nutrient loss in vegetables from Suzy Pelican, a nutritionist at the University of Wyoming:
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