Can Microwaves Cause Cancer?

Microwaves may increase the risk of cancer, but so far there isn't any strong evidence to support this. Most of what we know about the risks of microwave cooking is hypothetical and dependent on other factors, such as the plastics microwaved food is cooked in.

In theory, the exposure of certain foods and plastics to microwave radiation may create cancer-causing substances, called carcinogens. Microwaves might also deplete nutrients that protect against cancer.

This article explains what the current research says about the risk of cancer from microwaves and microwave cooking. It also describes the benefits of microwave cooking while offering tips on how to use microwaves safely.

Microwaves and Cancer

Microwaves are a type of low-frequency radiation classified as non-ionizing. Non-ionizing radiation is not linked to cancer. Other forms of non-ionizing radiation include:

• Radio waves
• Infrared light waves

The type of radiation associated with cancer is called ionizing radiation. This includes higher-frequency radiation such as:

• Ultraviolet (UV) light
• X-rays
• Gamma radiation

Ionizing radiation causes electrons to be knocked off of atoms in molecules. This is what damages DNA in cells, causing some to turn cancerous.

Non-ionizing radiation from microwaves leaves atoms intact. It cannot make foods radioactive or change DNA.

How They Work and Potential Exposure

A microwave oven is powered by a device known as a magnetron. The magnetron converts electricity to microwave energy.

When food is placed in a microwave oven, the energy causes water molecules in the food to vibrate. These vibrations generate heat without altering the structure of the food.

When a microwave oven is working properly (and the door seal is intact), very little microwave energy leaks out. According to the U.S. Food and Drug Administration (FDA), the amount emitted is well below the level that is harmful to humans.

How Do Microwaves Impact Cancer Risk?

There is some evidence that microwave cooking can both increase and decrease the risk of cancer. Here is what the current evidence says:

Increased Risk

Though radiation from microwave ovens does not cause cancer, microwave cooking may pose an indirect risk due to its effects on foods or the containers the foods are cooked in. There is a possibility, albeit small, that microwaves can create carcinogens at higher power settings.

These include:

• Acrylamides: These carcinogens are formed when sugars and starches are heated at high temperatures. High microwave settings may also do the same.
• Bisphenol A (BPA): This is a potentially carcinogenic substance used to make plastics hard and clear. BPA can theoretically leach into food when overheated.
• Phthalates: These are potentially carcinogenic compounds added to plastics to make them softer and more flexible. They might also leach into food when overheated.

The risk is largely hypothetical and, to date, there is no strong evidence of such harm. Even so, for safety reasons, you should only use containers marked "microwave-safe" to cook or heat foods in the microwave.

Any method of heating can change the nutrient content of a food. When it comes to fighting cancer, the concern is largely related to how cooking affects substances in food known as antioxidants. Antioxidants neutralize molecules called free radicals that damage DNA in cells, causing them to mutate and possibly turn into cancer.

• Phytonutrients: These plant-based compounds, including flavonoids and beta-carotene, are potent antioxidants. Some studies have shown that microwaving plant-based foods reduce flavonoids by 97% compared to boiling (66%) and steaming (11.1%).
• Garlic: Garlic contains one of the most powerful antioxidants called allicin. Heating garlic in a microwave for just 60 seconds destroys all of the plant's antioxidant activity.

Decreased Risk 

Carcinogens called polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines are created when animal protein is grilled over a fire or an intense heat source. You may be able to reduce this risk by microwaving beef, pork, lamb, game, fish, or poultry for just 60 seconds before grilling. This appears to lower the level of PAH and heterocyclic amines in the animal proteins.

Benefits of Microwave Cooking

Because microwaves cook food faster than other methods and you don't need to add water, microwaved food may contain more vitamins and minerals than foods cooked in other ways.

Vitamin C, for example, is a potent antioxidant found in citrus, tomatoes, potatoes, peppers, broccoli, strawberries, Brussels sprouts, and cantaloupe. Because vitamin C is water-soluble, boiling and steaming reduce its content while microwaving does not.

Other Risks of Microwave Cooking

Here are some of the other risks associated with microwave cooking that differ from other methods of cooking.

Radiation Injuries

While rare, a few cases of radiation burns have been documented due to the improper repair of microwave ovens. In such cases, excessive amounts of microwave radiation leaked through improperly placed or missing oven seals.

A microwave oven should never be used if the door seal is broken or if the light or turntable remains on after the door is open.

Uneven/Irregular Heating

One of the most common problems of microwave cooking is uneven or irregular heating. Microwaves penetrate food to a depth of around one inch or so. For this reason, foods may be hot on the outside and cold or frozen on the inside.

Burns can occur if a person puts food in their mouth that they think is one temperature but turns out to be another. This is why baby bottles should never be heated in microwaves.

Another concern is food poisoning. Some foods—especially raw meats or poultry—may not be cooked enough to kill harmful microorganisms in them.

When cooking raw meats in the microwave, it's important to check the temperature with a food thermometer. Also, be sure to stir stews and soups one or more times in the cooking process to ensure they are heated through.

Explosion of Liquids

Normally, you can determine if a fluid is hot based on whether is it boiling. In the microwave, water can become superheated without ever boiling.

Removing superheated liquid from a microwave is a hazard because it can sometimes explode, causing a severe burn. The same might occur with potatoes or eggs baked in the microwave.

To avoid this, follow the recommended cooking times on the food product labels or use the preset cooking times on your microwave oven.

Metals in the Microwave

Placing metal in a microwave may damage the microwave more than the user, but is still a mistake. This not only includes pans, metal utensils, and aluminum foil but also metallic printing on cups or bowls, twist ties, and things like edible gold leaf.

Microwave Oven Safety

A few simple pointers can ensure your microwave is safe and effective in preparing the foods you eat.

Among the tips:

• Use microwave-safe containers only.
  
• Cover containers with paper plates or napkins to avoid splatter while cooking.
• Make sure the door is completely shut before cooking.
• Stir foods often while cooking to ensure they are heated through.
• Use a thermometer to check the internal temperature of meats to ensure it is properly done.
  
• Do not exceed recommended cooking times.
• Let hot foods rest for several minutes before removing them from the oven.
• Use a potholder when removing hot containers.

Summary

Microwaves utilize non-ionizing radiation that does cause cancer and does not make food radioactive. It may change nutrient levels in foods, such as antioxidants that help fight cancer, but generally poses no harm to foods.

Some research suggests that microwaves may create carcinogens either directly or via the containers foods are cooked in, but the risk is largely theoretical.