Waiting to Eat Fresh Vegetables Means Loss of Nutrients

Knight Ridder/Tribune Business News

Mar. 27–CHEYENNE — That bag of spinach that has been sitting in the fridge for a week looks OK. Not too many wilted pieces. Tastes fine too. But guess what? It's missing a lot of the nutrients it had when picked.

According to research from Pennsylvania State University, a bag of spinach that has been stored at 39 degrees Fahrenheit for eight days has lost half of its folate and carotenoids, compounds known for their importance in preventing birth defects, fighting heart disease and preventing blindness and cancer. And at higher temperatures, the breakdown was even faster. At 50 degrees it took only six days to reach about half of initial levels; at 68 degrees it took four. What's a consumer to do?

"People should just eat (spinach) fast and not let it sit in their drawers," said Luke LaBorde, associate professor of food science at Pennsylvania State. "You have to accept the reality that it's a living plant, and you should eat it while it's fresh."

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.

Tips for avoiding nutrient loss in vegetables from Suzy Pelican, a nutritionist at the University of Wyoming:
–Include frozen and canned vegetables as part of your meal options, but when buying canned, select no-salt varieties.
–Plan meals in advance so fresh veggies are used quickly.
–Make sure your refrigerator is as cold as you think it is. It should be below 40 degrees Fahrenheit and above freezing. Keep an inexpensive thermometer inside to keep tabs.
–For food safety as well as nutrients, make sure food gets from grocery store to fridge as soon as possible.
–Shop at farmers' markets when available.
–Steam vegetables in the smallest amount of water possible for as short a time as possible unless using a steamer — or microwave them.
–Follow the purchase and "use by" dates on bagged greens


NOTE from Rhio: The recommendation to eat canned or frozen over fresh (by LaBorde) doesn't make any sense, since you would still get better nutrition from 1 week old veggies than from canned or frozen ones. The minerals and fiber would still be there as Pelican points out. It would be interesting to know if the amino acids degrade (it wasn't mentioned in the article). And as far as fresh vegetables being expensive… certainly they are not as expensive as getting treatment would be, when you experience the results of inadequate nutrition.

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