MICROWAVE ovens provide an easy way to quickly heat food when hunger strikes. But does the convenience of microwave cooking come at a cost by zapping nutrients out of foods?

The answer may surprise you.

Any kind of cooking method will result in some nutrient losses, so a better way to look at the issue is to what degree nutrients are depleted, explained Scott A. Rankin, professor and chair of the Department of Food Science at the University of Wisconsin-Madison. “Typical microwave heating results in very minimal loss of valuable nutrients in food,” Rankin said.

The factors that affect nutrient losses in foods during cooking include time (the longer the food is cooked, the more nutrient loss); temperature (the more heat, the more losses); and the amount of liquid the food is cooked in (the more water, the more nutrients you will probably lose as they leach into the cooking liquid).

Microwave cooking emits wavelengths that are absorbed by water molecules in food, and the molecules generate heat as they resonate with those wavelengths in food, Rankin explained. But heating food in a microwave often requires very little or no liquid at all. Compare microwaving to cooking broccoli in a pot of boiling water: The water turns green when water-soluble nutrients like vitamin C leach from the broccoli into the water.

Additionally, in a conventional oven, hot air penetrates food from the outside in; thus the exterior of foods can be exposed to excessive heat by the time the food reaches its target temperature, and this increases the potential for nutrient loss. With microwave cooking, the temperature raises more uniformly throughout the food; thus the point at which all particles of the food have reached the desired temperature is achieved with little damage, Rankin said.

Steaming in the microwave is preferable to submerging foods in water, which can result in a loss of nutrients. “You can use a microwave steaming tray with water in the bottom, or simply add your vegetables and a small amount of water to a microwave-safe bowl and cover with microwave-safe plastic wrap, leaving one corner open to allow air to escape,” said Whitney Linsenmeyer, a registered dietitian and spokeswoman for the Academy of Nutrition and Dietetics.

Whether you choose microwaving or conventional cooking methods, keep your cooking times low when possible. It’s also best to use methods that require minimal added liquid, Linsenmeyer said.

(SD-Agencies)