How safe is the microwave oven?

• Some say this modern kitchen appliance pumps cancer-causing waves into food during cooking, while others say it is as safe as they come. Who’s telling the truth, and who’s baking fibs?

A decade ago, the microwave oven was a key indicator of the standards of living in a country. Now you can get one for as little as Sh5,000.

Yet the fact that it can be found everywhere, including backstreet food kiosks, hasn’t helped to dispel the myths and the fears, real or imagined, about it.

The fantastic heating speeds of a microwave oven make it a very convenient appliance. The device uses relatively less-understood heating technology, fuelling suspicion that it might release radiation that is harmful to health.

In 1946, Dr Percy Spencer, a curious engineer, was developing a tube called magnetron for Raytheon Corporation in the US when a candy bar in his pocket melted. Voila! He realised that the magnetron could be used to heat food.

Magnetron, the main component in the oven, generates the microwaves used to heat food. Following the melting of the candy, Dr Spencer placed popcorn kernels near the tube, and they popped. Curiosity mounting, he placed an egg near the magnetron, and it exploded. The rest is history.

Before Spencer’s discovery, during World War II, magnetron was used by the British to detect German warplanes as microwave radar. It is after World War II, while Spencer was working on a new type of magnetron for American radar system, that he bumped onto the food heating effect.

From that coincidence, the microwave is today found in almost every kitchen in the developed world and most middle class homes in developing countries­.

Food regulating organisations, such as the Food and Drug Administration (FDA) and the World Health Organisation (WHO), have approved the use of the microwave oven. However, some believe that microwaved food is unsafe for human consumption.

Understanding the risks associated with the oven, or the lack of such risks, requires thorough familiarity with the mechanism the appliance employs to heat food.

Is microwaved food safe for human consumption?

Yes. According to the World Health organisation (WHO), if the microwave oven is used according to the manufacturer’s instructions, the food is safe and of the same nutrient value to that cooked by conventional methods.

The term ‘nuke the food’ is frequently used when warming food in a microwave, suggesting that food becomes radioactive because the term “nuke” refers to radioactive material. Using this reference in association to warming food in a microwave oven is misleading. Microwaves are not radioactive and do not cause the microwave oven or the food to become radioactive.

Is it safe to use containers in a microwave oven?

Always use containers labeled “microwave safe”. Using unsuitable containers to warm food in a microwave might cause toxic compounds to migrate from those containers to the food. Those compounds might be extremely toxic, and may actually be cancer-causing.

Fats and foods high in fat content can hit very high temperatures in a microwave oven, making them attract compounds from containers.

Most plastic containers found in the kitchen — water bottles, plastic tubs or containers made to hold margarine, cooking fat, yoghurt and so on, can be used in a microwave. However, this doesn’t mean they are microwave-safe. Don’t use them. They are only ideal for holding cold foods and not suitable for reheating.

Also, never use metallic utensils inside a microwave oven. Metals, including aluminium foil, reflect micro-waves, leading to generation of sparks that can lead to fire.

Microwaved food cools faster than food cooked over open fire, gas or electric cooker. Why?