Do Microwaves Cause Cancer?

I don’t know about you, but I use my microwave oven every day from cooking oatmeal to heating up leftover. To be on the safe side, I always stand far away and even block my child from entering the kitchen.

Am I overreactive? Should I worry about microwaves leaking from the oven and cause cancer? The answer is No – microwaves do not cause cancer. Because the forms of radiation that are typically linked to cancer are those with high enough energies or frequencies to ionize atoms or molecules, and thus are able to cause damage in our cells. Microwaves are a much lower energy form of radiation. 

Microwave ovens are an accidental discovery that changes people’s lives for the better. You’ll feel completely comfortable with using them after understanding the different types of radiation, how microwave ovens work,  how safe they are (with some tips) and whether microwaves change the composition of the food.

Understanding Ionizing And Non-ionizing Radiation

We live with low doses of ionizing and non-ionizing radiation throughout the day, from sources of heat and light to waves from cell phones and microwaves.

Microwaves are a type of Radiofrequency (RF) radiation at the low-energy end of the electromagnetic spectrum. RF radiation is a type of non-ionizing radiation, which means it has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to ionize (remove charged particles such as electrons). RF radiation does not cause cancer by damaging DNA in cells the way ionizing radiation does.

In contrast to low-energy radiation such as microwaves, high-energy radiation have enough energy to remove an electron from (ionize) an atom or molecule. High-energy radiation includes x-rays, gamma rays as well as higher energy UV radiation. They are called ionizing radiation. High doses of ionizing radiation may damage organs and cause blood diseases, neurologic disorders or cancer.

How Does Microwave Oven Work?

The simple answer is: microwaves heat food like the sun heats your face—by radiation.

A microwave is an invisible up-and-down pattern of electricity and magnetism that races through the air at the speed of light (300,000 km or 186,000 miles per second). Microwave ovens are so quick and efficient because they channel heat energy directly to the molecules (tiny particles) inside the food. A microwave oven is designed like a metal box. When it’s in operation, a microwave generator called magnetron can convert electricity to high-powered radio waves. The microwaves bounce back and forth off the reflective metal walls and penetrate inside the food. As they travel through it, they make the water molecules inside it vibrate more quickly.

Depending on the size, shape, and composition of food, microwave ovens cook food a little bit differently. Microwaves can’t penetrate more than a centimeter or two (perhaps an inch or so) into food. As they go deeper into the food, they don’t have enough energy left to penetrate food anymore. You may end up getting something that’s cooked on the outside and uncooked inside, or overdone on the outside and cooked just right in the middle. In situations like this, you may want to try using conventional ways to heat the food again just to make sure it’s safe to eat.

Because microwaves excite the liquids in foods more strongly, something like an apple pie with a higher liquid content in the center will cook from the inside out. That’s why people often say be careful eating microwaved food because there are some hot spots. It’s very deceiving when the outside crust of the apple pie is barely even warm. This is a tricky situation, but now you know the reason behind it. With other foods, where the water content is more evenly dispersed, you probably won’t have this issue as they are cooked just like in a conventional oven, from outside in.  Since they work by energizing water molecules, microwaves also tend to dry food out more than conventional ovens.

Are Microwave Ovens Safe For Health?

Microwave ovens are essential to everyday cooking, but have you ever worried about standing too close to your microwaves as it heats up your dinner? Is it safe?

Yes, it is perfectly safe. The World Health Organization is reassuring on this point: “thermal damage would only occur from long exposures to very high power levels, well in excess of those measured around microwave ovens.” Put another word, the power is too little to heat your body tissue up enough to do any damage.

So how does the microwave oven work safely? It’s designed this way. All microwave ovens are like sealed metal containers. Microwaves bounce back and forth off the reflective metal walls. Unless the door is shut, no microwaves are able to emit. If you look closely at the inside of the glass door, you’ll find there is a grid of metal stuck to the back; those holes you can see in it are too small to let microwaves through, but large enough that visible light can still pass through. Another safety feature is called an interlock. If you try to open the door, the magnetron stops buzzing immediately. Most microwaves actually have two independent interlocks in case one fails.

Of course, it still pays to take precautions. If you notice any signs of damage on the door or the grid on the back of the glass or if the interlocks don’t work, you should get it repaired or replaced straight away.

Even if your microwave is “leaking,” it’s unlikely to do you any harm.  According to the American Cancer Society, the amount of radiation that is allowed to leak out of microwaves based on federal laws in the US is far below the level that could potentially cause harm. However, this only applies to well-functioning microwaves.

Another good thing to put your concern at ease is that the high power inside drops off very quickly the further away you go. In some distance away from the ovens, only tiny amounts of electromagnetic radiation—less than you’d pick up from a cellphone, will be produced. To put any real risk to your health, you’d need to be exposed to much higher levels of radiation for much longer. It’s a safe bet that nobody ever spends hours near a microwave.

Does Microwaving Food Alter Its Composition?

Yes and No.

Any form of cooking will change the chemical makeup of food because of the heat, no matter where it is cooked — stovetop, pressure cooker, conventional oven, or microwave oven. The heat initiates a number of chemical reactions, most of which are desirable. Proteins become more digestible and various flavored compounds are produced. Certain vitamins will be destroyed, and proteins and carbohydrates may be hydrolyzed.

However, Microwaves have no nonthermal effect on food. Microwaves are non-ionizing waves and do not leave a residue. They can cause molecules to vibrate, like the water molecules in our leftovers, but they do not change the chemical structure of the food by ionizing it. There is no evidence that eating microwaved foods is detrimental to our health; rather, it may be quite beneficial when compared to other heat sources.

When it comes to cooking food, a general rule of thumb is that longer heating periods can lead to greater physical and chemical changes. Microwave ovens are the most efficient ways of cooking among all these sources. Therefore, the nutritional quality of microwaved foods is actually superior. Unlike cooking on stovetops where the water used to cover the vegetables can leach away some vitamins, no additional water is needed in a microwave. Heterocyclic aromatic amines (HAAs), which have been linked to cancer, are far more likely to form in fried, grilled or broiled meats than in those that have been microwaved.

Safety Concerns on Using Microwave Ovens

One of the first such reports appeared in the New England Journal of Medicine back in 1991. A young man heated seven eggs in their shells in a microwave oven at full power for five minutes. It was all good until he sat down and all eggs spontaneously exploded causing severe injuries on the face. The pressure buildup inside the eggs is so quick that eventually bursts through the shell. The best practice is to puncture the shells before cooking to release the steam. To avoid this risk altogether, you may just want to remove the shell completely.

For the same reason, it’s also recommended to pierce the yoke in an unbeaten egg. Several people have been injured when they pierced the yolk of a microwaved egg with a fork. The cooked membrane around the yolk can sustain a great deal of pressure, at least until it is pierced.  Then it retaliates by releasing a jet of steam.

Microwaves can only penetrate around 1cm to most food. If you don’t stir food constantly, it’s very likely to leave a cold spot. Even you see some bubbling and steaming, don’t be fooled by that. Remember, microwaves don’t kill bacteria; only the heat does.  So it’s important to heat food to a safe internal temperature. But microwaved foods can cook unevenly because of the size, shape, and composition of food (like what we’ve discussed above), how do you keep the food free from bacteria? Stir it often, allow adequate standing times and check the temperature of microwaved foods with a food thermometer in several spots.

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