Does Cooking in a Microwave Oven Make Food Toxic?

Check out this answer from Consensus:

Current scientific evidence indicates that cooking food in a microwave oven does not make it toxic. Microwave cooking can effectively reduce the presence of certain pathogens and toxins, and it does not lead to the formation of harmful mutagenic substances. However, it is essential to ensure that food is cooked evenly and reaches the appropriate internal temperature to guarantee safety.

Microwave ovens have become a staple in modern kitchens due to their convenience and efficiency. However, concerns about the safety and potential toxicity of microwave-cooked food persist. This article explores whether cooking food in a microwave oven makes it toxic by examining various scientific studies.

Effects on Nutritional Value and Toxicity

Several studies have investigated the potential toxic effects of microwave cooking compared to conventional methods. A comprehensive study on rats fed with diets cooked by both microwave and conventional methods found no adverse effects attributable to microwave cooking1. This suggests that microwave cooking does not inherently make food toxic.

Microbial Safety

Microwave cooking is effective in reducing the presence of certain foodborne pathogens. For instance, microwave cooking significantly reduced the population of E. coli O157:H7, Staphylococcus aureus, and Listeria monocytogenes in fish fillets when cooked to an internal temperature of 70°C6. However, it was noted that microwave cooking might not be as effective as conventional methods in completely eliminating these pathogens7. This highlights the importance of ensuring that food reaches the appropriate internal temperature to ensure safety.

Formation of Harmful Substances

One of the primary concerns with cooking meat is the formation of mutagenic and carcinogenic substances. A study comparing meat cooked in a microwave oven to meat cooked on a grid found no mutagenic activity in the microwave-cooked meat, whereas mutagenic activity was present in the grid-cooked meat8. This indicates that microwave cooking does not lead to the formation of harmful substances that could induce tumors.

Impact on Toxins

Microwave cooking has also been shown to inactivate certain toxins. For example, high-energy microwave exposure was found to degrade the structure of Shiga toxin 2 (Stx2) in milk, reducing its activity2. Similarly, microwave cooking reduced the concentration of microcystins in fish muscle, although not as effectively as continuous boiling5. These findings suggest that microwave cooking can help mitigate the risk of certain toxins in food.

Safety Considerations

While microwave ovens are generally safe, they can cook unevenly, potentially leaving cold spots where harmful bacteria can survive. It is crucial to use a food thermometer to ensure that food reaches the recommended safe temperature9. Additionally, exposure to microwave radiation leakage, although minimal, should be avoided, especially by sensitive groups such as children and pregnant women10.

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”.