Thursday, January 13, 2011

microwave ovens

Popcorn   |  Fir0002
This post started off innocently enough as a Facebook post in response to a question about if and how I use my microwave oven*.  The posting engendered a lively response from a number of people but brought up more questions.

Generally I use Facebook for quick links of interest, small notes and updates, that sort of thing.  I try to use this blog for longer responses so that they can be found from the tags rather than getting lost in that endless chronological feed.

Because the answer was more than a quick response I decided to move it over here to the blog.  I'd like to thank those Facebook fans who shared their answers, it enabled me to write a thoughtful, supported response about the issue.  The section marked Addendum is where the answers grew into this post.  I'd truly like to keep the discussion going...let me know your thoughts, how you use your microwave oven and/or if you are considering changing what you do based on the information you find here.


I just had someone ask me what I use my microwave oven for. Here goes:

  1. microwaving sponges to kill bacteria - two minutes every morning
  2. proofing space for rising bread - it's a perfect draft free space
  3. draft free space for making sprouts
  4. warming oven for waffles and pancakes - I put a cooling rack in there and then pile the waffles and pancakes on the rack.  The proofing box space keeps everything warm and moist, the rack keeps the ones on the bottom from getting soggy
  5. to heat my buckwheat filled neckwrap when I need a hot pack - great for a sore back, sore neck, or to warm your feet in bed on a cold night

Honesty requires me to admit I rewarm my tea in it and my husband loves it for reheating leftovers (I prefer steaming on the stovetop). But we don't cook in it and if it weren't built in I might consider doing without it.

What do you use yours for?


So a couple of important comments came up prompting me to add to this note:

1.  Microwave popcorn.  I'm really sorry but this is a bad bad bad bad bad idea.  And did I mention that it's bad?  Why you ask?  Perfluorooctanoic acid (PFOA) is a known cancer causing teflon agent.  Admittedly all of the studies have only been done it rats but it's generally true that if it causes cancer in rats it will cause cancer in humans but that's another subject and I won't go there right now.  That bag lining is the same material that is in teflon pans. I tell people to throw out all of their teflon cookware and invest in non-teflon.  I rarely tell people to throw things out but this is one area where I feel it is never to soon to abandon the stuff.  The problem with PFOA's is that when you open that hot steamy bag of popcorn you are exposing yourself far more than when you cook on a teflon pan, through the steam and through what has leached into the popcorn itself.

According to one scientist, "It is estimated that microwave popcorn may account for more than 20% of the average PFOA levels measured in American residents."

Not only that there's the "butter" (in quotes because it isn't) which is linked to lung disease in factory workers exposed to the vapors.  This is from the Diacetyl which is so toxic that "Significant new information regarding the health effects of diacetyl and food flavorings containing diacetyl (FFCD) affects the information that must be conveyed to employers and employees under the Occupational Safety and Health Administration’s (OSHA) Hazard Communication standard."

Bottom line:  shift to hot air or stove-top popped popcorn and don't eat the microwave stuff.

2.  Cooking. Microwave ovens work differently than other cooking methods and there are some health risks that go along with it.  A study published in the American Journal of Epidemiology showed that cooking meat in a microwave oven does not kill bacteria (in this case salmonella).  The study concluded, "Compared with conventional methods of reheating, microwave ovens had no protective effect in preventing illness. To prevent outbreaks such as this one, care must be taken to assure that food is both properly cooked and handled and properly reheated." 

Another study, from CEBAS-CSIC in Spain, comparing various cooking methods and their effect on the nutrient status of food showed that steaming is the best way to cook vegetables. The worst is to microwave them; more nutrients are lost during the microwave cooking process.

Cooking in a microwave oven has also been shown to convert B12 to the inactive form thereby depleting its bioavailability by denaturing up to 40% of it in the food.  We all need B12, if you're a vegetarian or a vegan this is even more critical.

To be fair all methods of cooking will reduce nutrient status somewhat, that is part of the process from heat.  And if you are steaming, especially vegetables, you would be well served to drink the nutrient rich broth that remains behind.  But overall microwave 'cooking' is, in my book, not a good idea.

So the end result?  I certainly have no complaint with people wanting to reheat their food or beverage in a microwave oven.  I do, however, think it's not a good idea to cook in it.  And I think if you are re-heating something you are best served to remove it from any plastic or coated surface, put in it ceramic and use the oven that way to avoid any potential fumes or chemical leaching.

*  A small nerd-humor note.  I find myself consciously referring to microwave ovens as microwave ovens rather than as 'a microwave', 'the microwave', etc.  The reason?  My husband delights in telling me that "Microwaves are itty bitty little particles that you cannot see."


microwaveguru said...

The comment on microwave popcorn is absolutely erroneous. I am a microwave scientist and over 50 years have popped hundreds and hundreds of bags of microwave popcorn, and the things that are said are absolutely without merit.

As to the comments about cooking meat in microwave ovens, that too is largely incorrect. To begin with, any time you cook meat, if it is not heated thoroughly it will not destroy salmonella or other microorganisms. That's why a you are told to be sure that the meat has reached an internal temperature of at least 165°F, or in the case of fish at least 145°F.

As to destroying nutrients, that's absolutely nonsense. Numerous scientific studies published in peer-reviewed journals have consistently shown that microwave cooking is at least as good as or better than any other way in retaining the nutrient quality of the foods that are being cooked. And the comment about B12 is also absolutely false.

These kinds of comments float around the blogosphere are and are totally without merit.

One thing I would caution you about is eating your sponges in a microwave oven because if you overheat them they will catch fire.

Cindi said...

I'm quite the microwave queen. Couldn't live without it. I do buy popcorn without the Diacetyl (boy scout popcorn just to give them a plug.) I guess I'll have to investigate more on this issue. Good luck on this blog. From the looks of the last comment, it could get interesting. ;-)
thanks for the info. as usual.

Sara said...

Hi Mira - I applaud the idea of creating a safer home, and because there's so much misinformation out there about Teflon, I'm not surprised that you are concerned. I'm a representative of DuPont though, and hope you'll let me share some information with you and your readers, so that everyone can make truly informed decisions.
In regards to PFOA and cancer - The weight of evidence gathered from a number of significant health studies continues to indicate to us that there is no health risk to the general public from exposure to PFOA. Additionally, no authoritative body has designated PFOA as a human carcinogen. The U.S. EPA stated that it is premature to conclude that PFOA causes cancer. For more information, please visit and can provide you with additional information.

Cindi said...

I just had to repost a comment here. I've thought about how much I really do use and rely on the microwave. I decided to try to remove my microwave queen crown off my head. I didn't realize that I only learned to cook in a microwave. I grew up with one, it was normal cooking. Now I'm so lost once again in my very own kitchen. And what a hard transition it is. But I will keep trying to figure out that, oven, as you call it, over there, covered in dust in the corner. It's not just a bread maker, I guess.