Are microwave ovens bad for you? True, false or utterly absurd? Myth: Microwaves do not make food radioactive. Photo: Natalie Boog To those of us who have little time and even less inclination to cook, the microwave oven has become a stalwart kitchen companion. Fast, reliable, efficient - it embodies everything I am not in the kitchen. But as I warmed my packet lunch at work earlier this week, a colleague made a passing comment about the dangers of my beloved, time-saving appliance. Many claims about the health hazards of microwaves have been made throughout the years - the radiation emitted can zap the nutrients out of food, some say. Others warn that standing too close to a microwave in use can nuke your own cells and lead to cancer. There have even been suggestions microwaves can interfere with pacemakers. But more than 40 years since the device first appeared in kitchens around the world, is there any evidence to show they are bad for us? Microwave ovens work by emitting microwaves, a form of electromagnetic radiation, that is reflected around the oven walls and absorbed by moisture inside the food. Because the food absorbs this energy at a greater rate than it loses it, your meal heats up. But once a microwave door is opened, the source of the radio waves, the magnetron, is switched off and microwaves disappear. Although microwaves are a form of radiation, they do not remain in the food and do not make it radioactive. While cooking some vegetables can reduce their vitamin content, particularly vitamin C, heating can improve the nutritional value of other foodstuffs. Cooked tomatoes, carrot, celery, green beans and zucchini give the body a greater supply of antioxidants than eating them raw. The CSIRO says leaching effects aside, studies have found little difference in the nutrient retention between food cooked by microwaves or by conventional ovens, provided cooking time and temperature guidelines are followed. As human tissue contains moisture just like plant and animal products, exposure to sufficiently high levels of microwaves can cause burns. According to Australia's radiation and nuclear safety agency (ARPANSA), which evaluates the radiation risk of consumer products, ovens are manufactured with two safety switches that stop microwaves being generated as soon as the oven door opens. A small amount of microwaves can leak around the oven door, but these would be well below levels that cause heating. While leakage is unlikely to interfere with pacemakers, even when very close, the agency recommends wearers should seek advice from manufacturers or the national health agency. And with extensive research, no substantiated evidence has shown microwave exposure, at any level, causes or promotes cancer, ARPANSA says.