Cooking with a microwave oven is highly convenient.
It's simple, doesn't require stirring or flipping things, and is incredibly fast.
However, many people believe that this convenience must come at a cost.
They believe that microwaves produce harmful radiation and cause damage to healthy nutrients.
This article takes a detailed look at microwave ovens, and how they affect the nutrients and health effects of foods.
Microwave ovens are kitchen appliances that turn electric energy into electromagnetic waves, called microwaves.
These waves can stimulate molecules in the food, making them start to vibrate, spin around and clash with each other, which turns the energy into heat.
This is similar to how your hands heat up when you rub them together really fast, except that it is happening on the molecular level.
Microwaves primarily work on water molecules, but they can also heat up fats/oils and sugars, just to a lesser extent than water.
Because the waves are dispensed throughout the food, it can heat up much more evenly compared to other cooking methods like frying.
Bottom Line: Microwave ovens turn electric energy into electromagnetic waves. These waves stimulate molecules in the food, making them heat up.
Microwave ovens produce electromagnetic radiation.
You may find this concerning because of the negative connotation of the word "radiation." However, this is NOT the type of radiation associated with atomic bombs and nuclear disasters.
Microwave ovens produce non-ionizing radiation, which is similar to the radiation from your cellphone except that it is much stronger.
Keep in mind that light is also electromagnetic radiation, so clearly not all "radiation" is bad.
Microwave ovens have metal shields (and metal screens over the window) that prevent the radiation from leaving the oven, so there shouldn't be any risk of harm.
Given that microwaves are a relatively minor source of radiation, compared to things like cell phones, then I don't believe this is a good argument against using them.
Just to be on the safe side, don't press your face against the window and keep your head at least a foot (30 cm) away from the oven. Radiation decreases rapidly with distance.
Also, make sure that your microwave oven is in good repair. If it looks old or broken, or if the door doesn't close properly, then consider getting a new one.
Bottom Line: Microwaves are a form of electromagnetic radiation, similar to the radiation from cell phones. The way the ovens are designed prevents the radiation from escaping.
Every form of cooking reduces the nutrient value.The main factors that contribute to this are high temperatures, long cooking times, and using added water (which makes water-soluble nutrients leak out of the food).
Microwave ovens do really well in all three of those. For this reason, you would expect microwave ovens to retain more nutrients than methods like frying and boiling.
There are actually a number of studies that have looked at this.
One study also compared the effects of cooking methods on the antioxidant content of 20 different vegetables.
They found microwaving and baking to do best with regards to nutrient preservation, while pressure cooking and boiling did the worst (3).
This study is often cited by people who are against microwaves, but the truth is that they used added water when microwaving the broccoli, which is a bad idea.
Although microwaving infant formula is fine, it is not recommended to heat human milk in a microwave, because it can damage bacteria fighting agents in the milk (6).
So, it appears that the effects depend on the type of food and the type of nutrient.
With a few exceptions, microwaves tend to do very well when it comes to preserving the nutrients.
Bottom Line: All cooking methods reduce nutrient value, but microwaving is generally effective at preserving the nutrient value compared to methods like boiling and frying.
One advantage of microwaving is that the food doesn't heat up nearly as much as it does with other cooking methods, like frying.
Usually, the temperature doesn't go much above 100°C/212°F, which is the boiling point of water.
However, fatty foods like bacon can become hotter than that.
Bacon is one food that is believed to form harmful compounds when cooked. These compounds are called nitrosamines, and are formed when nitrites in foods are heated excessively.
Another study showed that microwaving chicken caused much less heterocyclic amines (another harmful compound) to form, compared to frying (8).
Bottom Line: Microwaving is a good way to minimize the formation of harmful compounds that can form when cooking at a high heat.
Many plastics contain hormone-disrupting compounds that can cause harm.
For this reason, do not microwave your food in a plastic container unless it is labelled with "microwave safe." Keep in mind that this is not specific to microwaves. Heating your food inside a plastic container is a bad idea, no matter which heating method you use.
Bottom Line: Many plastics contain hormone-disrupting compounds like BPA, which can leak out when heated. Never heat your food in a plastic container.
One safety issue with microwaves, is that they may not be as effective as other cooking methods at killing bacteria and other pathogens.
The heat tends to be lower and the cooking time much shorter, and sometimes the food heats unevenly.
Using a microwave with a rotating turntable can spread the heat more evenly, and making sure that your food is heated sufficiently can help ensure that you kill all the harmful microorganisms.
It's also important to be careful when heating liquids. There are some reports of "exploding" cups when you heat them above boiling temperature, then as soon as you stir the liquid, the energy is released in a violent manner.
At the end of the day, microwaves are a safe, effective and highly convenient way of cooking your food.
There is zero evidence that they cause harm, and some evidence that they are even better at preserving nutrients and preventing formation of harmful compounds, compared to other cooking methods.
I personally have a microwave in my kitchen and use it a few times per week, usually to re-heat leftovers.
As long as you take the necessary precautions and are using it to cook real food, then you have nothing to worry about.