Friday, November 12, 2010

Microwave cooking

Microwaves are very short waves of electromagnetic energy travelling at 186,282mps (that is the speed of light). They are used to transmit telephone-, radio-, television- and computer signals around the world. The shorter the wavelength, the higher the energy. Radio waves have the longest wavelengths, X- rays and gamma rays have the shortest. But if we think about microwaves at all, we will think of them in terms of that great kitchen appliance, the microwave oven; fast, convenient and energy-efficient. The radiation from microwave ovens has a longer wavelength than infrared radiation and visible light, but shorter than that of the VHF and UHF broadcasting bands.

When I Googled ‘microwave safety’ I got over 9.5 million results in 0.15 seconds. Obviously, I haven’t read them all (and don’t intend to!). A lot of these links are re-iterations, mostly concerned with the radiation produced by microwave oven magnetrons, and the possible leakage of radiation from the ovens – which no-one seems terribly alarmed about. Some of them state safety considerations that one normally thinks of in connection with any kind of cooking anyway: which type of container to use, use of oven mitts, caution with high temperature foods and liquids, uneven heating etcetera.

But how do microwaves actually work?

Food molecules – or the water molecules in food – are polar; like a magnet has a north and south pole, water molecules have a negative end and a positive end. Microwave radiation interacts with food molecules. All radio wave energies change polarity from positive to negative with each wave cycle. In microwave ovens these changes occur millions of times per second. It is these changes which generate friction, and friction generates heat; that’s how your food gets cooked. But friction causes substantial damage to food molecules, tearing them apart or forcefully deforming them (only with microwave cooking? I'm not sure.); this is called ‘structural isomerism’. Doesn’t sound too healthy, does it?

I’m interested in the work of Dr. Hans Hertel (food scientist with a major Swiss food company) and Dr. Bernard H. Blanc (of the Swiss Federal Institute of Biochemistry). They collaborated and made (supposedly) in-depth studies of the effects on the human body of eating microwaved foods. Their findings were published in “Search for Health” in the spring of 1992 (and then withdrawn). Because of the very negative nature of their findings , a ‘gag’ order was placed on their report. They were told that they would face heavy fines and up to one year in prison if they tried to publish their report again. In response to this, Blanc recanted but Hertel stood his ground and went on a lecture tour, giving talks about his results. The gag order was rescinded in 1998. You can read an article here which covers Hertel’s results and some of the other research that has been conducted. Russia did extensive research along similar lines – and even banned microwave ovens in 1976, though the ban was lifted in 1985.

The problem with scientific research is that, at a minimum: the experiment must be repeatable; the variables must be controlled; the results must be verifiable; there must be a ‘control group’. In the write-ups I have read of  Hertel’s work, there are too many unknowns. And I can’t find the original research report to get clarification. The test group (which was also the control group) consisted of only eight male vegetarians, tested over a period of two months. Is that long enough? Large enough? This article is slightly less alarmist. And this one pretty much decries the other two. (I hope you follow these links and read at least some of the information, otherwise you won't really know what I'm talking about.)

So who do we believe? We’re often told not to believe everything we read – but that goes for negative AND positive reports. I don’t think I’m going to toss out my microwave just yet, but I will limit my usage (not that I use it that much now), and I certainly won’t use it for heating my grandson’s food any more. Maybe I’ll unplug it for a week, and see if I feel any healthier. I’m sure that eating only foods that have been microwaved doesn’t constitute healthy eating.
And it never hurts to err on the side of caution.


Helen said...

Thankfully about the only thing I heat in the microwave is baked beans - and we don't have them too often.

Sphinx said...

I haven't used my mw in over a week now - but I can't say that I feel any better or worse than before. Perhaps it has more to do with frequency of use.
mmm... baked beans... I might have some for lunch today!