Does Cooking in a Microwave Oven Make Food Toxic?

Does cooking in a microwave oven make food toxic?

Does cooking in a microwave oven make food toxic?

Check out this answer from Consensus:

Current research indicates that microwave cooking does not inherently make food toxic. While it can effectively reduce certain pathogens and toxins, it may also impact the nutritional quality of food. Ensuring even heating and following manufacturer guidelines are critical for safe microwave cooking. Overall, when used correctly, microwave ovens are a safe and convenient method for cooking food.


Microwave ovens have become a staple in modern kitchens due to their convenience and speed. However, concerns about the safety and nutritional quality of microwave-cooked food persist. This article explores whether cooking food in a microwave oven makes it toxic, drawing on findings from various research studies.

Microwave Cooking and Toxicity

Comparative Toxicity Studies

A comprehensive study compared the effects of microwave and conventional cooking on mixed human diets fed to rats over 13 weeks. The study assessed various health parameters, including clinical observations, organ weights, and microscopic examination of organs. The results indicated no adverse effects from diets cooked by microwave compared to those cooked conventionally, suggesting that microwave cooking does not introduce toxic elements into food1.

Formation of Mutagenic Substances

Another study focused on the potential formation of mutagenic substances during the cooking process. It compared beef cooked on a grid at high temperatures with beef cooked in a microwave oven. The findings revealed no mutagenic activity in the extracts of meat cooked in microwave ovens, while mutagenic activity was present in meat cooked on a grid6. This suggests that microwave cooking does not produce harmful mutagenic substances.

Microbial Safety

Pathogen Inactivation

Microwave cooking has been shown to inactivate certain foodborne pathogens. For instance, a study on fish fillets inoculated with E. coli, Staphylococcus aureus, and Listeria monocytogenes found significant reductions in pathogen counts when the internal temperature reached 70°C. However, lower temperatures were less effective, indicating the importance of achieving adequate internal temperatures to ensure microbial safety7.

Listeria Survival

Despite the general effectiveness of microwave cooking in reducing pathogens, some studies highlight its limitations. One study found that Listeria spp. survived in a small percentage of microwave-cooked chickens, particularly in larger roasters. This underscores the need for careful attention to cooking times and temperatures to ensure food safety2.

Nutritional Impact

Nutrient Retention

Microwave cooking can affect the nutritional value of food. A study on the inactivation of Shiga toxin in milk found that high-energy microwave exposure degraded the toxin’s structure but also destroyed essential nutrients in the milk. This suggests that while microwaves can effectively reduce certain toxins, they may also impact the nutritional quality of food3.

Cyanobacterial Toxins

Research on the effects of microwave cooking on fish muscle spiked with cyanobacterial toxins showed a reduction in toxin concentration after microwave treatment. However, boiling was more effective in reducing toxin levels, indicating that different cooking methods may vary in their ability to mitigate specific toxins5.

Food Safety Recommendations

Even Heating

Microwave ovens can cook unevenly, leaving cold spots where harmful bacteria can survive. It is crucial to use a food thermometer to check the temperature in multiple locations to ensure that food has reached a safe temperature throughout9.

Manufacturer Guidelines

Following manufacturer guidelines for cooking times and weights is essential to ensure food safety. Deviations from these guidelines can result in undercooked food, posing a risk of foodborne illness8.


Does cooking in a microwave oven make food toxic?

Louise E Bennett has answered Unlikely

An expert from Monash University in Food Science

The answer is usually ‘it depends’ and this is the case here. The radiation used in microwave cooking promotes selective ‘excitation’ of water in food, which can have a number of effects, most of which also occur during convection or other types of cooking. The heat created can accelerate physical and chemical reactivity between components, particularly ‘hydrolytic’ reactions that involve water, so any risk of toxicity is related to the small possibility that reaction products create more of toxicity ‘risk’ than the initial components. Given that foods usually cooked or heated in a microwave are typical of foods cooked in other heating methods, the likelihood of producing novel, microwave-specific toxic products is very low. The highest ‘risk’ foods for microwave or heat-induced chemical reactivity would be processed foods containing preservatives, which are inherently chemically reactive, as required to exert their ‘preservation’ effect.


Does cooking in a microwave oven make food toxic?

Arjen van den Berg has answered Extremely Unlikely

An expert from Cardiff University in Condensed Matter Physics, Physics, Electromagnetism

There is a lot of fear around the word “radiation”. Electromagnetic radiation comes in two types: Ionising and non-ionising.

Ionising radiation is the one that you should be careful with, this includes X-rays and gamma rays.

Then you have the non-ionising radiation in the electromagnetic spectrum, this is stuff like infrared, microwaves and visible light. Your microwave works using microwaves with a very specific wavelength which excites water. The excited water molecules bounce around this is what makes the food hot. The microwaves themselves do not change any of the chemical properties of the food.

Of course one could imagine there being some reagents in the food that, when heated, react to form toxic chemicals. This would be a function of heat, not radiation and would happen just as well if heated in any other way.


Does cooking in a microwave oven make food toxic?

Antonija Grubisic-Cabo has answered Unlikely

An expert from Monash University in Physics, Materials Science

Microwave ovens use microwaves, a type of electromagnetic radiation (it is not ionising radiation) with wavelength in range of 1m to 1mm. This radiation is used to excite water molecules making them oscillate and produce heat.

Microwave radiation is confined within the oven, and it is highly unlikely that it will leak outside even if the oven doors are open, as the microvawe ovens are equipped with interlocks that turn them off if the door is open. Also, standing close to microwave ovens is safe. There is a possibility that a minute amount of microwaves will leak if you open the microwave door before turning it off, but this is extremely small and the radiation also falls off exponentially with distance, so even standing 5cm away is safe.

Once the oven is turned off, water molecules are not excited any more and no radiation is retained in food.


Does cooking in a microwave oven make food toxic?

Aman Ullah has answered Unlikely

An expert from University of Alberta in Agricultural Science

Overcooking and burning can lead to some toxic compounds otherwise microwaves themselves do not induce any chemical reactions. They just rotate polar molecules like water in food and generate heat by molecular friction and dielectric loss.


Does cooking in a microwave oven make food toxic?

Annette Dowd has answered Unlikely

An expert from University of Technology, Sydney in Physics, Biophysics, Microscopy, Nanotechnology, Materials Science, Biological Materials

The radiation used in microwave ovens is a type of radiofrequency wave. Its effect is to make the water molecules flip back and forth, colliding with other molecules and heating them. There’s almost always water in food so this is a pretty efficient method of heating food. The container holding the food and the oven itself don’t need to be heated which saves considerable energy.

Unfortunately microwaves only penetrate an inch or so into food. Cooking pieces of food larger than this require longer times so the heat from the outer part of the food can flow to the inner unexposed part. If care isn’t taken the inside of the food may remain undercooked, which is a potential source of toxins, bacteria, etc.

The cooking temperature in a microwave oven isn’t high enough to create the chemical reactions important for delicious caramelization and browning. Because the food is heated by boiling the water inside it, the temperature is only about 100 degrees Celsius. Although this is a disadvantage from the point of view of flavour and appearance, some of the chemicals produced in browning are actually toxic!

The use of radiation for cooking isn’t a new phenomenon. Grilling and broiling primarily occur by the food absorbing the infrared and visible radiation from the fire or electric element. Infrared and visible radiation are of course in the same electromagnetic family as microwave radiation.

Finally, to answer a common misconception: as soon as the microwave is turned off the water molecules stop flipping – there is no “residual radiation”.

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