Does microwave radiation make food cause cancer?

Almost all the anxiety about microwave ovens comes from a single word. Radiation is used for x-rays, for nuclear accidents, and for the thing that reheats your soup. Those are not the same phenomenon.

FDA draws the line explicitly: microwaves are non-ionising radiation, so they do not have the same risks as x-rays or other types of ionising radiation.

Ionising radiation carries enough energy to knock electrons loose and damage DNA. That is the property that makes it a cancer concern. Microwaves do not have it. What they do is make water molecules move, which produces heat.

FDA's description is straightforward. The microwave energy is changed to heat as it is absorbed by food, and does not make food radioactive or contaminated.

Energy goes in, becomes heat, and is used up doing so. Nothing is stored in the food waiting to be eaten later. When the oven stops, the process stops.

FDA also addresses the related worry about nutrients, noting that microwave cooking does not reduce the nutritional value of foods any more than conventional cooking does. All cooking changes food somewhat. Microwaving is not a special case.

Heat is heat. A microwave gets there by a different route than a hob, and the food ends up in the same place.

The second worry is about standing near the appliance while it runs.

FDA enforces a limit under federal regulation restricting leakage to 5 milliwatts of microwave radiation per square centimetre at approximately 2 inches from the oven surface. The agency describes this limit as far below the level known to harm people.

Two inches is closer than anyone stands. FDA also notes that radiation decreases dramatically as you move away from the source, so the exposure at normal kitchen distance is smaller still.

There are real microwave safety issues, and they are not the ones the internet worries about.

• Do not use an oven whose door does not close properly or whose seal is damaged.
• Use containers made for microwave use, since some plastics can melt at the temperature the food reaches.
• Watch out for uneven heating, which leaves cold spots where bacteria survive. Stirring and standing time help.
• Take care with liquids, which can superheat and then boil over suddenly.

Notice that these are burn and food-poisoning issues. None of them is about cancer.

If you are trying to reduce cancer risk in your kitchen, the evidence points at what you cook and how hot you cook it far more than at which appliance you use. Cooking methods that char meat over flames form different compounds than reheating leftovers does.

Meanwhile, the appliance sitting on your counter has a federal safety standard, decades of use behind it, and an agency willing to say plainly that it does not make food dangerous. That is a worry you can genuinely set down.

The split between ionising and non-ionising radiation is one of the more valuable ideas to carry out of an article like this, because it applies far beyond the kitchen.

Ionising radiation carries enough energy to knock electrons out of atoms and damage DNA. X-rays and CT scans fall into this group, which is why medical imaging involves a considered decision about whether the information is worth the exposure.

Non-ionising radiation does not have that energy. Microwaves sit here, as do radio waves and the signals from everyday household devices. Federal guidance describes microwaves as non-ionising specifically to make this point, and it is why the risks are not treated as equivalent.

Whenever you meet a claim about radiation and cancer, working out which type is being discussed clears up most of the confusion before you get to the details. The two categories share a word and very little else.