Story at a Glance.
Microwaving changes the molecules of any substance you put inside your microwave. And that goes for the plastic containers you put in there as well. The problem is as you heat the plastic or cardboard containers they leach carcinogenic toxins into your food.
Chemicals included polyethylene terpthalate (PET), benzene, toluene, and xylene. Some plastics contain BPA, or bisphenol A. BPA is an oestrogen like compound that is used extensively in making plastic products.
Whilst there has been a backlash toward BPA in plastics, Scientific American reported in their article, BPA-Free Plastic Containers May Be Just as Hazardous, that a chemical called bisphenol-S (BPS) is a common replacement for BPA because it’s thought to be “more resistant to leaching.”
However, the chemical has its own set of problems as the researchers at the University of Calgary discovered.
The University of Calgary scientists reviewed the adverse effects of BPS, the chemical often used in “BPA-free” products. And what they found was that it lead to abnormal brain cell growth and hyperactivity in zebrafish4.
Tests were done on hundreds of plastic products put through “real world” scenarios, including getting warmed in the microwave, showed that estrogenic chemicals seeped out of 95 percent of the plastic products.
The problem, Deborah Kurrasch, the lead scientist on the BPS study, pointed out, is that,
“A lot of the alternative chemicals have not been adequately tested because they don’t have to be… A compound is considered safe [by the FDA] until proven otherwise.”
Then there’s the debate about microwaves used to warm blood products. The appeal of the microwave oven was that it could provide shorter heating times than the conventional heating process of the day, using a water bath. After the introduction of the microwave in the mid 50’s it was soon picked up by the medical fraternity. There were several studies at that time that indicated complications from overheating of blood products5,6 which all but put a complete stop to using microwaves as blood warmers.
But lately scientist have been studying the effects of microwaves again and finding the difference between traditional blood warming techniques and microwaves to be negligible.7
Harvard Health Publications of Harvard Medical school recently published an article, Microwave cooking and nutrition – Is microwave food healthy? And what did the Harvard Med School find, but a glowing review!
They sum up their feelings about the safety of using a microwave to cook with as follows,
“And the microwave oven? A marvel of engineering, a miracle of convenience — and sometimes nutritionally advantageous to boot.”
Hard to know what to believe?
Well we clearly require further scientific studies to ascertain what happens to food nutritionally when it is microwaved. But what we can and do know is that the container you choose to microwave your food in will determine how healthy or toxic the end result is.
The rest as they say, is up to you.
 Phenolic compound contents in edible parts of broccoli inflorescences after domestic cooking. F Vallejo, FA Tomás-Barberán andC García-Viguera. Journal of the Science of Food and Agriculture Version of Record online: 15 OCT 2003 DOI: 10.1002/jsfa.1585
 Changes in Texture and Nutritional Quality of Green Asparagus Spears (Asparagus officinalis L.) during Microwave Blanching and Cryogenic Freezing. Ulla Kidmose & Karl Kaack Acta Agriculturae Scandinavica, Section B — Soil & Plant Science, Pages 110-116 Published online: 05 Nov 2010
 Low-dose exposure to bisphenol A and replacement bisphenol S induces precocious hypothalamic neurogenesis in embryonic zebrafish. Cassandra D. Kinch, Kingsley Ibhazehiebo, Joo-Hyun Jeong, Hamid R. Habibi, and Deborah M. Kurrasch. PNAS vol. 112 no. 5
 Iatrogenic hemolysis: a complication of blood warmed by a microwave device. McCullough J, Polesky HF, Nelson C, Hoff T. Anesth Analg 1972;51:102-106.
 Extracorporeal hemolysis of blood in a microwave blood warmer. Staples PJ, Griner PF. N Engl J Med 1971;285:317-319.
 Indicators of Erythrocyte Damage after Microwave Warming of Packed Red Blood Cells. Jan Hirsch, Axel Menzebach, Ingeborg Dorothea Welters, Gerald Volker Dietrich, Norbert Katz, Gunter Hempelmann. Clinical Chemistry DOI: 10.1373/49.5.792 Published May 2003.