Food Fight Q & A: Are Microwave Ovens Safe?

They’re in almost every home, hospital, hotel, business, school, and every other place people eat food, but some still wonder – are microwaves safe?  If you search the internet for answers, you’ll find some starkly different assessments, which is very frustrating as a parent trying to protect your children’s health.

We get asked about the issue all the time, especially with the necessary use of microwaves to heat broth and homemade foods in the hospital, so we decided to dive deep into the science to find out what’s what. MaxLove Project is an organization founded, in part, to provide families facing childhood cancers and related pediatric illnesses with evidence-based health research and information to help them feel more empowered in the face of tremendous disagreements and internet clamour. Here’s what we learned.

How do microwaves work?

Microwaves are a form of electromagnetic radiation (EMR) — waves of electrical and magnetic energy. “Radiation” makes it sound a bit scary, but EMR ranges in strength. The highest energy EMR includes gamma rays and x-rays and on the lower end are radio and microwaves. Microwaves don’t sound nearly as formidable when you know they’re almost as weak as radio wavelengths. (Are you concerned about listening to the radio? Probably not.) Know what puts microwaves into an even clearer context of safety? The fact that microwaves are thousands of times weaker than visible light and UV light waves. (Another quick fact: microwaves are also used to send telephone and television communications.) 

So, how do microwaves heat food? Each level of radiation has different effects on the molecules they interact with. Microwaves contain enough energy to create what’s called “molecular rotation” (the lowest energy form of interaction), which have the biggest impact on water molecules. Microwaves cause water molecules to vibrate, which transfers energy as heat to other molecules in food.

Do microwaves leak radiation?

Electromagnetic radiation (EMR) is all around us every day. As mentioned above, visible light and sunlight are both forms of EMR. EMR is emitted from cable lines, electronics, electrical wiring, computers, cell phones, and more. So, yes, microwave ovens leak EMR. Still, the Food and Drug Administration (FDA) has very strict standards for microwaves to assure that radiation emissions do not pose a hazard to public health.

The amount of microwaves that can leak from an oven throughout its lifetime is 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface – a limit far below the level known to harm people. Microwave energy also decreases dramatically as you move away from the source. 20 inches from an oven would be approximately one one-hundredth of the value measured at 2 inches.

So, if you want to avoid radiation from your microwave, all you have to do is step away from it while it’s on. Once the oven is off, it stops creating microwaves. And you don’t need to worry about any lingering microwaves – they’re gone in less than a millionth of a second. It’s like turning off a light switch.

But, let’s put this radiation into more context to better understand potential risks:

  • Microwave ovens must emit less than 5 mW/cm2  of radiation within 2 inches of the surface.
  • Since the power level drops quickly as you back away, 20 inches away it can be no more than 0.05 mW/cm2.
  • Sunlight generates 100 mW/cm2 during the summer months – and this is infrared, ultraviolet, and visible light radiation – all of which are stronger than microwave radiation.

Is exposure to microwave radiation linked to cancer and infertility?


Yes and no. How can that be? Because it depends on the specific microwave radiation. A big problem that causes misinformation about the safety of microwave ovens is that some people apply the results of studies of all types of microwaves (radiation) to microwave ovens (device), but microwaves (radiation) vary in strength/frequency (it’s all a part of the EMR spectrum as mentioned above). Microwaves can range in frequency from 1 GHz to 300 GHz and microwave ovens operate at 2.4 GHz – the weak end of the spectrum. Clearly, a study on exposures in the 200 GHz range is going to have very different results than one at 2.4 GHz. Not all microwave radiation is equal.

On to the research: The majority of studies have found that low-level microwave exposure doesn’t present a significant risk to human health (1-6). The studies finding evidence of harm are generally in regards to high level occupational exposures and exposures at the level of what’s happening inside the microwave – and even then, sometimes the results are inconsistent (4,7,8).  

Does microwaving food make it less nutritious?

Cooking food, in general, can impact the nutrients regardless what method you use. Here are a few examples:

  • Nutrients can leach out into water when vegetables are boiled. For example, boiled broccoli loses glucosinolate, the sulfur-containing compound that may give the vegetable its cancer-fighting properties. Steamed broccoli holds on to more glucosinolate (9).
  • Raw spinach retains water-soluble nutrients like vitamin C and folate, but consider the benefits of cooked spinach:
    • Cooked spinach reduces in volume making it easier to eat more of it.
    • Cooking spinach softens the plant cells making Vitamin A, iron, and calcium become more bioavailable. One study found that three times as much beta-carotene was absorbed from cooked spinach compared to raw (10).
  • A study conducted on chicken found that 21–49% of vitamin B6 was retained when it was conventionally roasted, but 60–87% was retained when it was microwaved (11).

Ultimately, the cooking method that best retains nutrients is one that cooks quickly and uses as little liquid as possible. Microwaving fits the bill and study after study has shown that microwaving food (when done properly) retains nutrients as well as conventional cooking and sometimes even better (12-17).

Does microwaving food make it radioactive or contaminated?

No. The microwaves are transformed into heat as they are absorbed by the food.

Does microwaving food in plastic cause chemicals to leach into the food?

Yes, it can. Many companies make “microwave safe” containers, but in a 2011 study in Environmental Health Perspectives, researchers tested 455 plastic products, from baby bottles to food containers, and found nearly all of them still leached hormone disrupting chemicals linked to health issues like obesity and some forms of cancer (18). It’s difficult to avoid plastics completely, but when you can, transfer food to a glass or ceramic dish before microwaving. If you need to use something like cling wrap to prevent the food from spattering the inside of the microwave, put the food in a glass or ceramic container and then place the wrap on in a way that prevents direct touching between the food and the plastic.

Still have questions? Let us know and we’ll do our best to find the answers!

References:

  1. Jauchem, J. R. (2008). Effects of low-level radio-frequency (3kHz to 300GHz) energy on human cardiovascular, reproductive, immune, and other systems: a review of the recent literature. International journal of hygiene and environmental health, 211(1), 1-29.
  2. Leonard, A., Berteaud, A. J., & Bruyere, A. (1983). An evaluation of the mutagenic, carcinogenic and teratogenic potential of microwaves. Mutation Research/Reviews in Genetic Toxicology, 123(1), 31-46.
  3. McGill, J. J., & Agarwal, A. (2014). The impact of cell phone, laptop computer, and microwave oven usage on male fertility. In Male Infertility (pp. 161-177). Springer New York.
  4. Breckenkamp, J., Berg, G., & Blettner, M. (2003). Biological effects on human health due to radiofrequency/microwave exposure: a synopsis of cohort studies. Radiation and environmental biophysics, 42(3), 141-154.
  5. Frei, M. R., Jauchem, J. R., Dusch, S. J., Merritt, J. H., Berger, R. E., & Stedham, M. A. (1998). Chronic, low-level (1.0 W/kg) exposure of mice prone to mammary cancer to 2450 MHz microwaves. Radiation research, 150(5), 568-576.
  6. Szmigielski, S., Szudzinski, A., Pietraszek, A., Bielec, M., Janiak, M., & Wrembel, J. K. (1982). Accelerated development of spontaneous and benzopyreneinduced skin cancer in mice exposed to 2450MHz microwave radiation. Bioelectromagnetics, 3(2), 179-191.
  7. Sheiner, E. K., Sheiner, E., Hammel, R. D., Potashnik, G., & Carel, R. (2003). Effect of occupational exposures on male fertility: literature review.Industrial health, 41(2), 55-62.
  8. Goldsmith, J. R. (1997). Epidemiologic evidence relevant to radar (microwave) effects. Environmental health perspectives, 105(Suppl 6), 1579.
  9. Francisco, M., Velasco, P., Moreno, D. A., García-Viguera, C., & Cartea, M. E. (2010). Cooking methods of Brassica rapa affect the preservation of glucosinolates, phenolics and vitamin C. Food Research International, 43(5), 1455-1463.
  10. Eating Defensively: The Nutrition and Food Safety Benefits of Cooked Produce1. (n.d.). Retrieved February 14, 2016, from http://edis.ifas.ufl.edu/fy1395
  11. Uherova, R., Hozova, B., & Smirnov, V. (1993). The effect of microwave heating on retention of some B vitamins. Food chemistry, 46(3), 293-295.
  12. Cross, G. A., Fung, D. Y., & Decareau, R. V. (1982). The effect of microwaves on nutrient value of foods. Critical Reviews in Food Science & Nutrition, 16(4), 355-381.
  13. Lassen, A., & Ovesen, L. (1995). Nutritional effects of microwave cooking.Nutrition & Food Science, 95(4), 8-10.
  14. Ramesh, M. N., Wolf, W., Tevini, D., & Bognar, A. (2002). Microwave blanching of vegetables. Journal of Food Science, 67(1), 390-398.
  15. Huang, Y., Sheng, J., Yang, F., & Hu, Q. (2007). Effect of enzyme inactivation by microwave and oven heating on preservation quality of green tea. Journal of food engineering, 78(2), 687-692.
  16. Natella, F., Belelli, F., Ramberti, A., & Scaccini, C. (2010). Microwave and traditional cooking methods: effect of cooking on antioxidant capacity and phenolic compounds content of seven vegetables. Journal of food biochemistry, 34(4), 796-810.
  17. Turkmen, N., Sari, F., & Velioglu, Y. S. (2005). The effect of cooking methods on total phenolics and antioxidant activity of selected green vegetables. Food chemistry, 93(4), 713-718.
  18. Yang, C. Z., Yaniger, S. I., Jordan, V. C., Klein, D. J., & Bittner, G. D. (2011). Most plastic products release estrogenic chemicals: a potential health problem that can be solved. Environmental Health Perspectives, 119(7), 989.

~ An MLP Staff & Advisory Board Collaborative