It's Your Health
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Many Canadians use microwave ovens as a convenient way to thaw, cook and reheat food. A number of people have concerns, however, about the effect of microwaves on their health and on the health and safety of their foods.
Many people who use microwave ovens say they are going to "nuke" their food. This reference to nuclear energy is incorrect and misleading. Microwaves are a form of radiofrequency electromagnetic energy. They are generated electronically. They do not come from radioactive sources and they do not cause food or the oven itself to become radioactive.
When microwaves penetrate food, they cause water molecules in the food to rotate. The rotation causes friction between the molecules and the result is a rapid rise in temperature. This is why the cooking time with microwave ovens is shorter than with conventional ovens. When you shut the microwave oven off, the microwaves disappear.
Some microwave energy may leak from your oven while you are using it, but this would pose no known health risks, as long as the oven is properly maintained. The Need More Info? section below refers to an It's Your Health article called Radiation Safety of Microwave Ovens. The article features safety tips to minimize your exposure to microwave energy when using a microwave oven.
Microwaves do not change the chemical components of in food and so the formation of new compounds, like carcinogens, is not expected. Some studies have been conducted to investigate any possible negative health effects of microwaving foods. These studies, which have been reviewed by Health Canada scientists, have found no evidence of toxicity or carcinogenicity.
In general, the health and safety concerns associated with microwave cooking are similar to the issues involved with other cooking methods, such as conventional ovens, stove-top cooking and grilling. For example, all cooking methods have some effect on the nutrients in food. The effect is worse if you over-cook the food. Microwave cooking tends to be less harsh on nutrients than conventional cooking methods, because the cooking times are shorter and less water is used. To help preserve nutrients when microwaving food, use techniques that promote the even distribution of heat. This will help prevent the formation of "hot spots" where portions of the food could be over-cooked. Steps to promote even heating are outlined in the Minimizing Your Risk section below.
There is no simple answer to questions about which cooking method is best for retaining nutrients. Research into the subject is ongoing. From a health perspective, there is no reason to use any one cooking method exclusively.
Other concerns associated with all methods of cooking, including microwave cooking, are foodborne illness and burns.
Raw food of animal origin, such as meats, seafood, poultry and eggs (including juices and drippings) may carry disease-causing bacteria. No matter which cooking method you use, the risk that bacteria will multiply and cause foodborne illness increases when foods are allowed to sit at temperatures in the "danger zone" between 4o C and 60o C (40o F to 140o F) for more than 2 hours. To minimize the risk of foodborne illness:
It is always important to be careful when handling or eating hot food. With conventional cooking methods, there are often warning signs that you are dealing with high temperatures. However, your microwave oven is enclosed and you cannot see the source of heat, so you may get a false sense of how hot the food and containers may be.
Therefore, with microwave ovens, there are specific concerns about potential burns related to:
To minimize these risks when using the microwave oven:
Some foods come wrapped in materials (e.g., styrofoam) that may not be suitable for use in the microwave. These materials could leach chemicals into your food or cause burns if they melt during microwave cooking. To minimize risks when using your microwave oven:
As a general safety precaution, always supervise young children when they use the microwave oven (or any other cooking appliance). Finally, read and follow the manufacturer's directions for using the oven, and keep the oven in good working order.
Health Canada carries out many different activities to minimize risks related to the use of microwave ovens. For example, Health Canada has established a regulation under the Radiation Emitting Devices Act to govern the design, construction and functioning of microwave ovens that are imported, sold or leased in Canada. This regulation specifies limits for microwave leakage from ovens.
In addition, Health Canada assesses risks, sets standards and monitors the safety record of such products as microwave cooking containers and food packaging materials, and establishes policies on the safety and nutritional value of food. As a founding member of the Canadian Partnership for Consumer Food Safety Education, Health Canada also participates in public awareness campaigns about safe food practices. One example is CanFight BAC™, a program that encourages Canadian consumers to think of food safety at every step of the food handling process, from shopping for groceries to reheating leftovers.
For more information on microwave radiation safety, contact:
For additional information, visit the following Health Canada Web sites:
Additional information can also be located at:
For additional articles on other issues go to the It's Your Health Web site.
You can also call (613) 957-2991.
Original: July 2005
© Her Majesty the Queen in Right of Canada,
represented by the Minister of Health, 2005L