Microwaves are the undeniable king of convenience; bung last night’s leftovers in one and a few minutes later you’ve got a delicious hot meal. Unfortunately, they can sometimes get a bit of a bad rap, with claims that microwaving food can cause us harm. It is, however, safe – here’s why.

Radiation

Long before the days of 5G conspiracies, it was microwaves that people were concerned about when it came to brain-frying. However, unless you’re planning on sticking yourself inside a microwave alongside your dinner (please don’t), or you don’t look after your microwave properly, the energy that’s used to heat food isn’t going to cause you any harm – nor is it going to make your food radioactive.

Microwave ovens use, well, microwaves, which are electromagnetic waves with a wavelength similar to that used in broadcasting or radar – a long way off the other end of the electromagnetic spectrum where X-ray and nuclear radiation live. If microwaving food made it radioactive, the world would be looking a lot more like the Spider-Verse (maybe) by now.

Microwaves are also designed to contain their energy, as long as they’re kept in good condition. Even if damage does cause a leak, the World Health Organization states that microwave energy can only cause heat damage to the body during long exposures to very high levels of power – far more than is typically measured around a microwave oven.

Bacteria

One concern with microwaving food is that it doesn’t kill off harmful bacteria, but if a microwave is used properly, that shouldn’t be a problem. 

Microwaves are known to heat food less evenly than a regular oven which, if you just left food alone for the entirety of the time that it’s in there, could mean that particular parts of the food don’t get hot enough for long enough to kill bacteria.

The solution to this is to properly follow cooking instructions if provided, stir, rotate, or turn food upside down halfway through the microwaving time in order to even cooking out, and use a food thermometer to check the internal temperature. It’s also recommended to allow standing time, as food continues to cook during this period.

Nutrients

There’s also something of a popular myth that microwaving food somehow makes it less nutritious, but any method of cooking will break down heat-sensitive nutrients to some degree. In the case of vegetables, nutrients can also be lost if you cook them in a lot of water.

“The cooking method that best retains nutrients is one that cooks quickly, heats food for the shortest amount of time, and uses as little liquid as possible,” says Harvard Health Publishing in a blog post. “Microwaving meets those criteria.”

Recent research appears to support that statement, at least when it comes to vegetables. A 2023 study published in the journal Heliyon found that out of microwaving, steaming, and boiling, “microwaving was the most effective method for retaining the nutritional value of vegetables.”

Plastic

Chemical leaching

Many of us will have used some sort of plastic container to microwave food in, whether it came prepackaged that way from the grocery store, or was put in a tub at home. There’s some concern, however, that certain compounds in plastic containers could be leaching into food when microwaved, and that those compounds could be causing harm to health.

One group of compounds that often hit the headlines is phthalates, which are used to “soften” plastic. Some studies have concluded that phthalates could potentially have an impact on human health, disrupting hormones and brain development, although more research needs to be done in order to determine if those links are concrete.

The US Food and Drug Administration (FDA) is in charge of regulating the use of phthalates in food packaging, with nine phthalates currently allowed. FDA regulation involves safety assessments, which means that plastic food packaging with these phthalates in it should be microwave safe.

There have been some criticisms of the FDA’s approach, with petitions calling for the agency to revoke authorization for the use of phthalates. While the FDA has said it is aware of concerns about high exposure, those petitions were denied due to a lack of scientific data to back the concerns up and its own research suggesting that “the use of phthalates in food contact applications is limited and consumer exposure to phthalates from food contact uses is decreasing” – though it continues to keep an eye on safety data.

Microplastics

Given everything we’ve heard of late about where microplastics end up, it’s not a huge surprise that a recent study found that microwaving plastic containers released microplastics and nanoplastics into a simulant of food.

“Some containers could release as many as 4.22 million microplastic and 2.11 billion nanoplastic particles from only one square centimeter of plastic area within 3 min of microwave heating,” the study’s authors write.

While an additional part of the study found that micro and nanoplastics released from the plastic food packaging caused the death of some human embryonic kidney cells, it’s important to note that such findings don’t necessarily scale up to an actual human body.

We also still know relatively little about the health effects of microplastics, so this isn’t yet cause for throwing away all your expensive Tupperware – but if you’re still concerned, there’s nothing to stop you from transferring food into a microwaveable glass or ceramic container. More washing up to do after though.

How not to use a microwave

All that being said, microwaving food can very quickly become unsafe depending on how you do it.

• While some foods might come packaged in microwave-safe foil packaging, it’s generally not recommended to use foil or metal containers or coverings – it can cause potentially dangerous sparks, known as arcing.
• Some foods are notoriously explosive after microwaving – eggs with intact shells in particular – so check if they’re suitable to be cooked in this way.
• As mentioned before, microwaves heat food unevenly – to avoid a bout of bacterial food poisoning, remember to stir and check food is thoroughly cooked.
• Don’t reheat food in the microwave more than once, especially when it comes to rice.

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.  

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.