Cooking with Microwaves

A “microwave” is an electric oven that emits microwaves, a type of electromagnetic radiation, to heat your food. Inside the appliance, a magnetron emits radio waves of a wavelength of 12cm and a frequency of around 2.45 gigahertz through a channel called a waveguide into the cooking compartment. The microwave radiation causes the molecules in the food to rotate and produce thermal energy, which heats up the food. Microwaves excite the liquids in foods more energetically, so foods that contain higher liquid content will cook faster. But are microwaves safe?

Microwave and Power-frequency Radiation

The oven cables and motor give off high power-frequency electromagnetic fields (over one microtesla), which extend for about a meter. Microwave radiation also leaks in varying amounts from the seal around the door and through the glass of microwave ovens, and the water molecules in the body of someone standing close by could be agitated to some degree by the microwave radiation. Eyes are particularly vulnerable, as they contain large amounts of fluid and a lower blood supply to take away any heat. This is important to bear in mind about children whose height and curiosity could lead to them watching the changes in microwave cooking from too close a distance.

Current regulations require that a microwave oven leak no more than one milliwatt per square centimetre (1mW/cm2) when it leaves the factory, and five mW/cm2 after a period of use. It is not known whether these levels are safe, so microwave ovens should be used with caution. Since microwave emissions can change with regular use, ovens should be checked regularly for signs of damage. Even when a microwave oven is working correctly, the microwave levels within the kitchen are likely to be significantly higher than those from any nearby cellular phone base-stations. 

Be Careful with Plastics

Microwaving plastics is a no-no because it can lead to the containers breaking down and allowing more chemicals like BPA and phthalates to leach into your food. Many companies today make BPA-free and “microwave safe” containers, however, in a 2011 study in Environmental Health Perspectives, researchers tested 455 plastic products, from baby bottles to food containers, and found nearly all of them still leached estrogenic chemicals, which have been linked to obesity and some forms of cancer. Even plastics marketed as BPA-free were guilty.  The best advice is to avoid plastics when you can, and always transfer food into a glass or ceramic dish before microwaving.

The Take-Home Message

So, are microwaves safe? The fact that microwaves are approved as safe doesn’t mean much, as we’ve seen with several other examples such as PCB’s and glyphosate. Just because a government health agency approves something as safe, doesn’t necessarily mean it is safe. A few decades from now, it may well be common knowledge that using microwave radiation to heat food is harmful to human health. It’s certainly a possibility, and some information is already emerging which shows cause for concern.

So, to retain as many nutrients in the food that we eat as possible, we need to consider not only where we buy it, but also how we cook it and what we cook it in.