The Claim: Microwave Ovens Kill Nutrients in Food

THE FACTS They are a staple in kitchens everywhere, but for about as long as microwave ovens have been around, people have suspected that the radiation they emit can destroy nutrients in food and vegetables.

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Leif Parsons

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Forum: Fitness and Nutrition

According to most studies, however, the reality is quite the opposite. Every cooking method can destroy vitamins and other nutrients in food. The factors that determine the extent are how long the food is cooked, how much liquid is used and the cooking temperature.

Since microwave ovens often use less heat than conventional methods and involve shorter cooking times, they generally have the least destructive effects. The most heat-sensitive nutrients are water-soluble vitamins, like folic acid and vitamins B and C, which are common in vegetables.

In studies at Cornell University, scientists looked at the effects of cooking on water-soluble vitamins in vegetables and found that spinach retained nearly all its folate when cooked in a microwave, but lost about 77 percent when cooked on a stove. They also found that bacon cooked by microwave has significantly lower levels of cancer-causing nitrosamines than conventionally cooked bacon.

When it comes to vegetables, adding water can greatly accelerate the loss of nutrients. One study published in The Journal of the Science of Food and Agriculture in 2003 found that broccoli cooked by microwave — and immersed in water — loses about 74 percent to 97 percent of its antioxidants. When steamed or cooked without water, the broccoli retained most of its nutrients.

THE BOTTOM LINE Microwave ovens generally do not destroy nutrients in food.

scitimes@nytimes.com

¶ Wednesday, October 18, 2006