Why a Microwave Oven Is Bad for Your Health

First, let me state that I don’t walk around with aluminum foil wrapped around my head in an effort to shield my thoughts from the aliens. And I’m not trying to spread fear or perpetuate a hoax. What I want to do here is present scientific facts explaining exactly why cooking in the microwave is worse than cooking over the traditional cave-man fire, or your GE stove at home.

I was instantly skeptical the first time I heard that microwaving your food was bad. I read about a study that measured nutrients in cooked broccoli [1], comparing it cooked on the stove vs. in the microwave oven. I figured there was something biased about the study, like only cooking on high. Or maybe they were using the same cook time for both the stove and the microwave oven. Or maybe the microwave oven was heating the food hotter than the stove. I was in disbelief. After all, a microwave oven shortens cooking times, and that’s good, right?

I thought that all a microwave oven did was heat the food by moving the molecules faster. I was ignoring one very important characteristic of radio waves. Eventually, I put two and two together and realized something important.

But first, I need to explain how a microwave oven works. A microwave oven creates radio waves at a frequency of about 2.45 GHz [2, 3]. All radio waves are electromagnetic radiation.

When a polar molecule is placed in an electric field, it lines up with that field. It is similar to how a compass needle lines up with a magnetic field. Depending on the strength of the electric field, it will even stretch the polar molecule. But it will spring back as soon as the electric field is removed. So, the way a microwave works is, the rapidly oscillating electric field causes the polar molecules to move back and forth, increasing their kinetic energy (or heat). When matter is heated, the atoms and molecules start to vibrate faster. So far, it sounds like the heat from microwaves is no different than the stove. But there is one major difference. Microwaves have a strong electric field.

Electromagnetic radiation is a self-propagating wave composed of two components: an electric field, and a magnetic field. The two fields expand and collapse as they propagate through space. As the electric field collapses, it produces an expanding magnetic field. Conversely, as the magnetic field collapses, it produces an expanding electric field [4]. This is a simple explanation, and there are more details involved.

If the electric field is strong enough, not only will it stretch the molecule, it can also separate the charges enough so that an atom loses an electron. This is ionizing. Or it can separate a molecule. This is similar to electrolysis.

When electricity flows in a conductor, free electrons drift easily in the direction of the electric field. In a non-conductive material, the electrons are tightly bound to the atoms. If the electric field is strong enough, electricity will flow. The non-conductive material often gets destroyed when the electric field is strong enough to ionize the atoms and force conduction, which creates a plasma such as a spark.

A plasma is made of ionized atoms or molecules. A plasma can be formed in a gas, a solid, or even a liquid, but not in a pure vacuum. A plasma being formed in a solid is a foreign concept to some, but familiar to semiconductor physicists. Once the plasma is formed, the resistance drops very low and it conducts electricity easily. This is why arc-welders don’t need to use megawatt power supplies. The plasma in the arc has a low resistance.

The electrical resistance of foods can range from low to very high. Many foods will conduct some electricity when placed in an electric field. The electric field in the microwave ovencauses electric currents to flow in the food. This is similar to what happens when an antenna picks up current from a radio wave.

Electrical current can also rearrange atoms. For example, in microchips, the wires have to be big enough or the force of the electrons actually can move enough metal so the wire distorts until it breaks [5].

If electric current can rearrange metal, it can also rearrange the atoms in your food, changing the molecular structure. This happens either by ionization, or by momentum transfer from the electron to the atom. This is one reason why nutrients can be destroyed more easily in a microwave oven than on the stove. Even though microwaves are classified as non-ionizing radiation, at sufficient power levels, they can cause ionization such as a plasma [6, 7, 8].

Despite the slang term ‘nuke’, microwaves are not nuclear radiation. Nuclear radiation consists of high speed alpha particles (helium nucleus), beta particles (high velocity electrons), neutrinos, gamma rays (extremely high energy photons), or high speed neutrons [9]. Nuclear radiation is classified as ionizing radiation [10] because it will ionize matter at any level of radiation. Every radioactive particle has the potential to ionize when it interacts with matter.

Ionizing, or simply displacing a single electron sounds harmless enough, but this is enough energy to destroy biological molecules. This is what kills every living organism that goes through the irradiation [11] process, including the food. Cold pasteurization (a nice name for irradiation) really is nuking your food.

There is a tendency for most microwave users to cook everything on high power, except when defrosting. High is the default setting. The maximum power is also a major selling point for a microwave oven. The higher the power, the stronger the electric field, and the more damaging it is to nutrients. So, the lower the power, the safer. But only some microwave ovens are capable of true low power cooking. The microwave ovens equipped with inverter magnetrons actually reduce the power instead of just cycling it between high and off.

I decided to try microwaving some audio CDs to prove that the power level had an effect on the amount of damage done while cooking to the same temperature. Although it would be an honorable sacrifice in the name of science, rather than use my wife’s Barry Manilow collection, I thought it would be more prudent to burn some songs onto identical CDs and experiment on those instead.

I set my inverter-magnetron microwave to cook at 30% power for 3 1/2 minutes. I placed the CD in a plastic bowl and added 1 cup of water at 74°F. After cooking, the temperature was 158°F. I dried off the CD and stuck it in my CD player. It still played. All 16 songs were still ok. I then placed a second, identical CD in the bowl and again added 1 cup of water. I cooked it for one minute on high power. It went from 73°F to 162°F, so it got approximately the same amount of heat. But the CD was visibly very damaged. The CD player obviously couldn’t even read it.

Although this was a crude experiment, it illustrates the fact that cooking on high power causes more damage than cooking on low power. So, the higher the power, the more damage it causes, even if the final temperature is the same.

It is a well known fact that raw food is more nutritious than cooked. Cooking food destroys nutrients, whether it’s on a stove, or in the microwave oven. But microwaving food on high power can be more destructive than cooking on the stove. So if you use a microwave, use one with an inverter magnetron, and cook on low power. Cooking on true low power (not intermittent high) will greatly reduce the amount of damage done to the food.