Preserving Vitamin Content in Foods

ByMelinda T. Willis

April 11, 2002 -- Many of us know that fresh fruits, vegetables and juices are among the best sources of vitamins. But when it comes to taking advantage of these health-boosting properties, experts say it's a race against the clock.

An example is orange juice. A new study published in the April issue of the Journal of the American Dietetic Association reports that if not consumed quickly enough, O.J. can lose its vitamin C content by as much as 100 percent.

Frozen O.J. lost up to 50 percent of its vitamin C within four weeks of opening the package, scientists found, and some ready-to-drink preparations lost all of it within that time frame.

Experts say this is not an issue of "bad" orange juice — it's just that some nutrients found in food are naturally pretty finicky and can break down over time. That's especially true with vitamin C. Thus the researchers recommend purchasing O.J. at least three to four weeks before the expiration date and consuming what you buy within one week.

"One of the things that people need to remember is that vitamins and minerals are sensitive ... so we need to handle them with some care," says Connie Diekman, director of university nutrition at Washington University in St. Louis.

Vanquishing Vitamin Loss

It's sound advice for much more than just orange juice, experts say. Everything from fresh lettuce to peaches can be robbed of some nutrients over time — particularly those sensitive vitamins. But there are ways to preserve them and maybe slow some of that loss.

The three main culprits that strip vitamins from foods — especially produce — are heat, light and air. Too much exposure to any one or all three of these can accelerate vitamin loss over time.

"Even before you open your mouth to enjoy [fresh produce], you can start losing those nutrients," says Jackie Newgent, a chef and registered dietitian and culinary instructor at the Institute of Culinary Education in New York City.

But there are small steps that can be taken to help maximize the vitamins found in produce when shopping for, preparing and storing it.

While it seems laughable to many Americans with their jam-packed schedules, experts say the ideal way to shop for produce is every day or every other day. If daily shopping is not possible, they suggest limiting the amount of broccoli, apples or orange juice that you buy to what you or your family will consume in three to four days.

And if shopping that frequently is even too much to handle, heading to the freezer section is an option.

"If you're not going to use the fresh [produce] within a three- to four-day period of time, your best bet really is to buy frozen," says Diekman.

That's because frozen fruits and veggies get their nutrients "locked" in at the time they are prepared — giving you more time to consume them at their peak nutrition.

Prepping Produce

When it comes to preparing fresh produce, experts advise limited contact with water, as it can whisk away water-soluble vitamins like vitamin C and the B vitamins.

"It's important from a food safety standpoint to wash fruits and vegetables thoroughly — but soaking vegetables or cooking and exposing the water-soluble vitamins to fluids for extended periods of time reduces the nutritional value of those foods," says Lisa Tartamella, a registered dietitian at Yale New Haven Hospital in New Haven, Conn.

That's why steaming veggies is preferred to boiling them. But if you do choose to boil, experts recommend reusing that nutrient-rich water in soups and sauces.

Just because the vitamin content of fresh foods can easily be depleted, it doesn't mean that there is no value to that week-old tomato on the counter, or that you should toss out orange juice after it has been open two weeks. These foods still contribute to the recommended daily amount — just not as much as they would have a week earlier.

"All those little steps that you can take along the way to help retain those nutrients are really going to make a big difference," says Newgent.

Perhaps more than anything, experts feel the new study highlights the importance of eating a variety of foods and meeting the recommended intake of five servings of fruits and vegetables a day, instead of relying on one particular food for one particular vitamin. There might not be as much in that one food as you think.

"There is no one true super-food that takes the place of every other," adds Tartamella. "Different fruits and vegetables receive the spotlight, but ... it doesn't make them perfect or complete."