Veggies Lose Nutrients in the Microwave

An article from the Oct. 16, 2003 issue of the "HealthDayNews" reports on new research that shows different ways of preparing, storing and processing vegetables can affect how good they are for you. The data for this article came from two studies that appeared in the November issue of the Journal of the Science of Food and Agriculture. The studies report that several different processing procedures and cooking can reduce antioxidants, which are cancer-fighting compounds, normally found in vegetables.

Antioxidants are plentiful in vegetables and work to eliminate free radicals, which can damage cell DNA and contribute to various diseases. That's why eating fiber, fruits, and vegetables, all of which contain antioxidants, can help prevent cancer and cardiovascular disease.

One of the studies showed that broccoli, for instance, lost 97 percent of flavonoids, 74 percent of sinapics and 87 percent of caffeoyl-quinic derivatives (three different types of antioxidants) when it is zapped in the microwave. When boiled the conventional way (i.e., not in a pressure-cooker), broccoli lost 66 percent of its flavonoids; when tossed in a pressure cooker, it lost 47 percent of its caffeoyl-quinic acid derivatives. Steamed broccoli, on the other hand, lost only 11 percent, 0 percent and 8 percent, respectively, of flavonoids, sinapics, and caffeoyl-quinic derivatives.

Cristina Garcia-Viguera, lead author of the research paper noted that the advantage of steaming vs. conventional boiling is that you're "Not using water directly in contact with the vegetable. The nutritional compounds don't go into the water. Once the compounds are in the water, the temperature destroys them much easier." The damage from a microwave occurs because it heats the inside of the vegetable. That, combined with the fact that you normally use water when microwaving, can cause the destruction of the valuable nutrients.

Vegetables that are blanched before freezing (a common processing technique) can lose up to one third of their antioxidants. Frozen storage can also cause losses, though these losses are much smaller.

Samantha Heller, a senior clinical nutritionist at New York University Medical Center in New York City states that not all of the healthy properties of vegetables are being eliminated. "You're still getting plenty of healthy compounds as well as fiber, so there's absolutely no reason not to eat vegetables -- although, of course, the fresher the better." She goes on to say, "If people are willing to have vegetables anyway, shape or form, even if they are going to nuke then, I'd rather have them do that."