Medical Did Eating Meat Help Our Brains Evolve?

[Si14]

Hi everyone:

Have you ever heard anything about the effects of the microwave on body?

..

 

[Pythagorean]

I don't know about the food; I trust it in general, but I can tell you something about frustrated total internal reflection:

Under "ordinary conditions" it is true that the creation of an evanescent wave does not affect the conservation of energy, i.e. the evanescent wave transmits zero net energy. However, if a third medium with a higher refractive index than the second medium is placed within less than several wavelengths distance from the interface between the first medium and the second medium, the evanescent wave will be different from the one under "ordinary conditions" and it will pass energy across the second into the third medium.

When teaching us about frustrated total internal refraction, my optics teacher stated that he never got his face close to the microwave to check his food while it was running anymore.

 

[Moonbear]

Hi everyone:

Have you ever heard anything about the effects of the microwave on body?

..

Yeah, it's bad to microwave your body. Did you have a more specific question? Are you asking about eating the foods cooked in a microwave, or the shielding on microwave ovens, or something else entirely?

 

[Si14]

I don't know about the food; I trust it in general, but I can tell you something about frustrated total internal reflection:



When teaching us about frustrated total internal refraction, my optics teacher stated that he never got his face close to the microwave to check his food while it was running anymore.

Thank you. but I didn't understand, what does it mean by 1st, 2nd and 3rd medium? Is the 3rd medium food? and the 2nd medium air? and 1st is the medium where microwave generated?
Am I correct?

Yeah, it's bad to microwave your body. Did you have a more specific question? Are you asking about eating the foods cooked in a microwave, or the shielding on microwave ovens, or something else entirely?

Thank you. Of course they have some standards for radiation dosage emitted from microwave ovens. And they can test them simply by measuring the radiation and power around and far away from ovens, BUT, how about the food which is prepared by this method? I think I read some where that some Russian groups are working on the effects of microwave cooked foods on body? Have you heard about that?

 

[D H]

Of course they have some standards for radiation dosage emitted from microwave ovens.

Of course they don't, because microwave ovens do not emit *any* ionizing radiation.

 

[Si14]

Of course they don't, because microwave ovens do not emit *any* ionizing radiation.

wait a minute, as far as I know, these ovens are working with high frequency waves. at those frequencies, if you stand near them, they will penetrate to your body and damage your tissues. but they damp in the air, so standing far away form them can reduce this damage. in ovens, they shield the device, that means it will absorb the waves and keeps them inside. so it minimizes the radiation dose outside the shield. But what is Ionizing radiation? you mean after bombarding the food by these waves, they will be ionized (for example hydrogen or carbon) and will radiate also?

 

[D H]

wait a minute, as far as I know, these ovens are working with high frequency waves. ... so it minimizes the radiation dose outside the shield. But what is Ionizing radiation? you mean after bombarding the food by these waves, they will be ionized (for example hydrogen or carbon) and will radiate also?

Your use of words such as "high frequency waves" and "radiation dose" makes me think that you are thinking of things like x-rays and gammas given off by radioactive elements such as uranium, radium, etc. That is not what goes on in a microwave oven. The electromagnetic radiation in a microwave is of a much lower frequency than the electromagnetic radiation that comes out of the light bulbs in your house. It is a very low frequency compared to the radiation you are familiar with. It is an extremely low frequency compared to the damaging ionizing radiation associated with radioactive elements. The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.

The problem with microwaves isn't that they are radioactive. The problem is that the very feature that makes microwaves able to cook foods placed inside the oven makes microwaves able to heat things up outside the oven if the oven is not properly shielded.

 

[Pythagorean]

Thank you. but I didn't understand, what does it mean by 1st, 2nd and 3rd medium? Is the 3rd medium food? and the 2nd medium air? and 1st is the medium where microwave generated?
Am I correct?

I was referring to when you get your face close to an operating microwave. There's a glass wall between you and the microwaves, so we normally assume total internal reflection: that is, the microwaves are bouncing around inside the microwave, and staying inside there.

BUT, frustrated total internal reflection happens when you get your face close to the microwave. The waves will transmit through the 2nd medium (the air) to the third medium (your face) because the distance between your face and the microwave is on the order of microwaves (meters to millimeters). I don't know if enough power actually makes it through to be concerned about, but I don't NEED to put my face there, so I won't test it, personally.

 

[waht]

The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.

Yes that's true. Microwaves are not ionizing - the standard designation does not reflect the whole electromagnetic spectrum.

http://img405.imageshack.us/img405/6813/rfband2.jpg

 

[Pythagorean]

Yes that's true. Microwaves are not ionizing - the standard designation does not reflect the whole electromagnetic spectrum.

http://img405.imageshack.us/img405/6813/rfband2.jpg

hey, what is voice frequency doing in there? Isn't voice frequency a pressure wave?

 

[chroot]

I was referring to when you get your face close to an operating microwave. There's a glass wall between you and the microwaves, so we normally assume total internal reflection: that is, the microwaves are bouncing around inside the microwave, and staying inside there.

I believe you are spreading misinformation. Your thoughts on FTIR are accurate, but you are applying the concept indiscriminately. The glass is wholly irrelevant to the propagation of the microwaves, or the safety of the people who use the oven.

The microwave door includes a fine mesh of metal, behind the glass. The holes in the mesh are large enough for you to be able to see your food (high-frequency visible photons pass right through the holes), but too small for the low-frequency microwave photons to escape. The microwaves have wavelengths on the order of 12 centimeters, and the holes are much, much smaller. The mesh is essentially a solid piece of metal, as far as the 12 cm radiation is concerned. The oven cavity is completed contained by this conductive metal, forming a Faraday cage. As you are aware, conductors block EM radiation.

You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.

Your microwave oven is not unsafe, even if you put your face near it. Relax.

- Warren

 

[Si14]

D H and others:
Thank you for your time. Helpful answers.

The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.
.

This is applied to me. I am electrical eng. )

The electromagnetic radiation in a microwave is of a much lower frequency than the electromagnetic radiation that comes out of the light bulbs in your house.

exactly!

The problem with microwaves isn't that they are radioactive. The problem is that the very feature that makes microwaves able to cook foods placed inside the oven makes microwaves able to heat things up outside the oven if the oven is not properly shielded.

That's what I meant. and I think that they can make good shields for that. Since it looks simple, for shielding each frequency (at microwave ovens, I think they are around 2.5GHz), a good absorber needs to be fabricated.

The problem is with the high power at this frequency, I assume.

But my question is about the FOOD which is cooked with microwave oven.

Do you know what happens to them?

 

[Si14]

Thank you chroot and Pythagorean:

The oven cavity is completed contained by this conductive metal, forming a Faraday cage. As you are aware, conductors block EM radiation.

So, can we have evanescence waves (as Pythagorean mentioned)inside a metallic cavity? I mean there's no loss inside the cavity and if we assume that the cavity is designed for the operating frequency of the power generator (like a resonating cage), there should be a standing wave. Right?

 

[Pythagorean]

I believe you are spreading misinformation. Your thoughts on FTIR are accurate, but you are applying the concept indiscriminately. The glass is wholly irrelevant to the propagation of the microwaves, or the safety of the people who use the oven.

The microwave door includes a fine mesh of metal, behind the glass. The holes in the mesh are large enough for you to be able to see your food (high-frequency visible photons pass right through the holes), but too small for the low-frequency microwave photons to escape. The microwaves have wavelengths on the order of 12 centimeters, and the holes are much, much smaller. The mesh is essentially a solid piece of metal, as far as the 12 cm radiation is concerned. The oven cavity is completed contained by this conductive metal, forming a Faraday cage. As you are aware, conductors block EM radiation.

You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.

Your microwave oven is not unsafe, even if you put your face near it. Relax.

- Warren

So FTIR doesn't apply to conducting surfaces (remembering that they're not perfect conductors so there's some penetration depth)? It was my optics professor who brought up the concern, but he's a physicist, not an engineer.

You're right though, I've never seen a microwave without the mesh on the glass; I should have considered that.

 

[Pythagorean]

also, I do have a microwave meter, and i DO pickup over 1mw/cm^2 (the needle tops out) into the front of the meter. But I haven't measured area of the front of the box. It's roughly 4x6 cm^2. This has been true for all three of the microwaves (~10 year old models) that I've measured it on.

I don't know if that's significant with regards to biology. The device I used was the TriField Meter: http://www.trifield.com/EMF_meter.htm

Also, I don't trust manufacturer claims, as I've been taught not to in my engineering courses (especially considering the economics of LEDs), so this:

You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.

isn't satisfying to me. But then, on the same token, I don't know how trustworthy my TriField meter is.

 

[Moonbear]

But my question is about the FOOD which is cooked with microwave oven.

Do you know what happens to them?

It gets cooked. It's fine to eat, if that's your question. Once the microwave oven is turned off, there is no more emission of the microwaves. It's not like a radioactive isotope that would contaminate something and linger.

The only potential issue is whether some foods are exposed to the microwaves long enough to kill bacteria with such a short cooking time.

 

[Si14]

It gets cooked. It's fine to eat, if that's your question. Once the microwave oven is turned off, there is no more emission of the microwaves. It's not like a radioactive isotope that would contaminate something and linger.

The only potential issue is whether some foods are exposed to the microwaves long enough to kill bacteria with such a short cooking time.

Thank you. I somehow got the answer.

 

[russ_watters]

...isn't satisfying to me. But then, on the same token, I don't know how trustworthy my TriField meter is.

Though I'm not sure of the mechanism for enforcement, they are required to be tested to meet government standards on leakage:

All new microwave ovens produced for sale in the United States must meet the Food and Drug Administration/Center for Devices and Radiological Health (FDA/CDRH) performance requirements in Title 21, CFR, Part 1030.10. This requirement states that new ovens may not leak microwave radiation in excess of 1 mW cm–2 at 5 cm from the oven surface. It also states that ovens, once placed into service, may not leak microwave radiation in excess of 5 mW cm–2 at 5 cm from the oven surface. The "Procedure for Field Testing Microwave Ovens" (HEW Publication (FDA) 77-8037) is the standard method for verifying that these oven performance criteria are met.

http://www.hps.org/hpspublications/articles/microwaveoven.html

 

[russ_watters]

It's not like a radioactive isotope that would contaminate something and linger.

Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.

http://en.wikipedia.org/wiki/Food_irradiation

 

[Pythagorean]

Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.

http://en.wikipedia.org/wiki/Food_irradiation

What kind of materials can store radiation, and then release it as radiation anyway?

 

[chroot]

What kind of materials can store radiation, and then release it as radiation anyway?

Depending upon what you mean by "radiation," the answer might be any material. If you bombard just about anything with protons or neutrons, it'll end up radioactive.

- Warren

 

[Pythagorean]

Depending upon what you mean by "radiation," the answer might be any material. If you bombard just about anything with protons or neutrons, it'll end up radioactive.

- Warren

I suppose I was referring to electromagnetic radiation, specifically microwaves in this case. Is there even a material that you could stick in the microwave oven and "charge up" and then it would release microwaves after it's taken out of the microwave oven?

 

[Moonbear]

Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.

http://en.wikipedia.org/wiki/Food_irradiation

Yes, they're generally the same question, because people simply don't understand enough about radiation vs. radioactive materials to know the difference. I thought we'd answered that question here before. It's a pretty common fear due to ignorance issue.

 

[chroot]

I suppose I was referring to electromagnetic radiation, specifically microwaves in this case. Is there even a material that you could stick in the microwave oven and "charge up" and then it would release microwaves after it's taken out of the microwave oven?

One could probably invent a device with an antenna and a battery that could do the job, but no ordinary, simple materials -- certainly not foods -- would do this.

- Warren

 

[Pythagorean]

thank you for your input, russ and chroot.

 

[Jasongreat]

What is the purpose of the shield in a microwave? Isnt it to keep the dangerous microwaves inside the oven? Since microwaves are not good for organic material outside the oven wouldn't it be not good to the organic material inside? Granted the organic matter outside is alive and the organic matter inside is dead and that could be the reason microwaves are dangerous to us but not to the food we are cooking, but I am not so sure. I am probably over reacting but I try not to use the microwave for anything if at all feasible.

 

[D H]

False analogy.

The heat of your oven or range is not all that great for living tissue, either. One of the key reasons we cook food is precisely because heat is not all that great for living tissue. That heat kills all of (or at least most of) those nasty microbes that grow on our food. Moonbear in post #16 did raise one issue regarding microwave ovens: The short cooking time might not be hostile enough to living tissue.

 

[mgb_phys]

Is there even a material that you could stick in the microwave oven and "charge up" and then it would release microwaves after it's taken out of the microwave oven?

Any material above absolute zero should manage to do that

 

[Jasongreat]

=D H;2432070]

The heat of your oven or range is not all that great for living tissue, either.

Agreed, however I haven't noticed a shield around my conventional oven to keep the microwave radiation in. I don't think that it is just about heat, but how that heat is made. I am probably wrong and over reacting like I said before, but when it comes to radiation I am very conservative, I try not to eat irradiated foods either.

One of the key reasons we cook food is precisely because heat is not all that great for living tissue. That heat kills all of (or at least most of) those nasty microbes that grow on our food.

I agree, but do we use heat because it is the best/only way or is it just the the easiest way? When governments started to mandate cooking milk to kill the microbes it was far easier and less expensive than making the dairies clean up, atleast from what I've read on that subject. Or the fact that it is pretty much impossible to order a hamburger less than well done, we can get away with a far dirtier food supply if we just accept the fact that everything needs to be cooked until it has been killed twice. Like today it is far easier to irradiate food than to clean up the food supply. I could be wrong and am probably so, but it only takes a little longer and the food tastes better when cooked conventionally imo, so I will continue not cooking in the microwave.

Moonbear in post #16 did raise one issue regarding microwave ovens: The short cooking time might not be hostile enough to living tissue.

Isnt it the heat value that kills microbes and not the length of time? On cooking shows they say you need to cook to a certain temp, not that you need to hold at that temp for a certain amount of time. Moonbear is far smarter than me though so I will accept that opinion and I have one more reason not to use a microwave.

 

[mgb_phys]

but when it comes to radiation I am very conservative, I try not to eat irradiated foods either.

Microwave radiation is only radiation in the electro-magnetic sense, your regular stove uses infrared radiation, a light bulb uses visible radiation

but do we use heat because it is the best/only way or is it just the the easiest way?

It also breaks down tissue to make it easier to eat - it's a lot easier to eat chicken casserole than raw chicken.

When governments started to mandate cooking milk to kill the microbes it was far easier and less expensive than making the dairies clean up,...impossible to order a hamburger less than well done, we can get away with a far dirtier food supply

Sometimes the bacteria are in the source however clean the processing. Milk inside the cow can contain dangerous bacteria. You can get a variety of diseases straight form the teat, just as you could 100 years ago.
Pasteurizing is a cheap and easy way of partially cleaning milk - at least enough for it to be safe for two weeks. If you want it to last longer you can heat it more to kill more bacteria but you destroy more milk proteins and end up with nasty sterilized milk.

You can eat (almost) raw steak because unless the animal is badly diseased there are no bacteria in the meat, there is only a risk of contmination on the surface. The problem with hamburger is that you take surface and mix it right through the meat. If you start with steak and mince it (in a clena kitchen) just before serving it's safe = steak tartare.

Isnt it the heat value that kills microbes and not the length of time? On cooking

It's the energy that the microbes absorbs - which is a combination of heat and time. The danger of a microwave is that the food might not have time to heat up fully all the way through and so the centre might not get hot enough for long enough to kill the microbe.

 

[Jasongreat]

mgb_phys;2432361]Microwave radiation is only radiation in the electro-magnetic sense, your regular stove uses infrared radiation, a light bulb uses visible radiation

I was wondering about that after I made my post, the fact that all heat is a form of radiation. I think it was Moonbear who stated in an earlier post that laymen get confused when it comes to radiation vs radioactive. However I haven't read of any dangers associated with infared or visible radiation but lately there seems to be lots of studies showing or atleast claiming the dangers of electro-magnetic radiation such as all the cell phones causing cancer claims or that living under power lines is dangerous. I am not saying they are true or false but they do raise questions in my mind.

It also breaks down tissue to make it easier to eat - it's a lot easier to eat chicken casserole than raw chicken.

The example you give about made me toss my cookies, raw chicken, although I did see a show on the travel channel where there is a place in japan where they eat raw chicken, however they are raised in the guys backyard and don't have to travel through the food supply picking up microbes along the way. Local supplies seem to be far less dangerous than a supply that travels a long way. Fermentation, brining, and other methods will also break down meat and veggies making them easier to eat and as far as fermenting goes it is my understanding that it increases enzymes and the solubility of the vitamins and minerals making the food better for you, whereas cooking reduces those and makes them not as good for you but a lot safer.

Sometimes the bacteria are in the source however clean the processing. Milk inside the cow can contain dangerous bacteria. You can get a variety of diseases straight form the teat, just as you could 100 years ago.
Pasteurizing is a cheap and easy way of partially cleaning milk - at least enough for it to be safe for two weeks. If you want it to last longer you can heat it more to kill more bacteria but you destroy more milk proteins and end up with nasty sterilized milk.

The cleaner you keep the dairy the less chance of bacteria in the milk, although I agree that it is still possible, if we kept cows out in pasture there would be less chance than if they were kept in a feed yard since the pasture is far more steril than a garbagety coral. I worked on a dairy about 12 yrs ago and IMO there is nothing better than fresh raw milk, most of the dairy farmers I know drink their milk raw and I don't know of one that has ever gotten sick, but here again I think that might have a lot to do with local supply since imo it would be harder to contaminate milk if you produce it yourself, but if milk in california has to travel to new york to be consumed there would be a far greater chance of contamination. Your last sentence above makes me ask if the original cooking(pasteurization) doesn't destroy some proteins, enzymes and such as well as the bacteria? According to the raw milk supporters lactose intollerant people can drink raw milk since it still has the enzymes to allow them to make use of the lactose where pasteurized milk has those enzymes destroyed. Is there any truth to this or is it just propaganda to support their cause?

It's the energy that the microbes absorbs - which is a combination of heat and time. The danger of a microwave is that the food might not have time to heat up fully all the way through and so the centre might not get hot enough for long enough to kill the microbe.

I thought that microwaves cooked from the inside out but it wouldn't be the first nor the last time(i'm sure) i have found out i am wrong in this forum. Although that really wouldn't change your point since if they do cook from the inside out, that would still mean the outer edge might not get hot enough for long enough and since all/most bacteria is on the surface unless it has been ground and mixed we could still be in danger.

 

[mgb_phys]

Ibut lately there seems to be lots of studies showing or atleast claiming the dangers of electro-magnetic radiation

Electromagnetic radiation is dangerous, but due to it's heating effect (at > visible wavelengths) if you stand in front of a powerful enough microwave transmitter for long enough you will be damaged. It's unlikely that a 1W cell phone outside your head could do much heating.

The example you give about made me toss my cookies, raw chicken, although I did see a show on the travel channel where there is a place in japan where they eat raw chicken,

You eat raw fish! The danger with chicken is that they are generally raised in less than sanitary conditions so the disease risk is rather high.
The point remains that we cook food both for texture/taste and safety.

The cleaner you keep the dairy the less chance of bacteria in the milk,

True but there is still a chance of mastitus/bovine TB/ etc. There is probably less risk in hand reared hand milked cows simply because the farmer would notice any illness and there is less chance of transferring contamination through milking machines.

You are also going to consume the milk immediately, like anything else it's a time/growth thing. If you want milk to last 1 month you need to kill off more bacteria than if it only needs to last 1 week. The standards for the allowable level of bacteria in Eu milk are much lower than in the US and milk in Europe definitely lasts longer than in the US.

Your last sentence above makes me ask if the original cooking(pasteurization) doesn't destroy some proteins, enzymes and such as well as the bacteria?

Probably too low a temperature to destroy milk protein.

According to the raw milk supporters lactose intollerant people can drink raw milk since it still has the enzymes to allow them to make use of the lactose where pasteurized milk has those enzymes destroyed.

Not sure, lactose does depend on the amount of fat so there might be a differnet reaction to full fat milk than 2% supermarket milk.

I thought that microwaves cooked from the inside out

Common urban myth. In fact because of the short cooking time and poor thermal conductivity you can end up with the inside much less cooked than in a stove.

since all/most bacteria is on the surface unless it has been ground and mixed we could still be in danger.

True of steak, not true of hamburger - once you mince it you mix 'surface' all through the meat.

 

[russ_watters]

What is the purpose of the shield in a microwave? Isnt it to keep the dangerous microwaves inside the oven?

Yes.

Since microwaves are not good for organic material outside the oven wouldn't it be not good to the organic material inside? Granted the organic matter outside is alive and the organic matter inside is dead and that could be the reason microwaves are dangerous to us but not to the food we are cooking, but I am not so sure.

Yes, the reason microwaves are bad for us is because we are alive: it is dangerous to cook a person while they are alive!

Agreed, however I haven't noticed a shield around my conventional oven to keep the microwave radiation in.

Your microwave has a shield to prevent microwaves from escaping and cooking you. Similarly, your normal oven has a shield to keep heat (hot air) from escaping and cooking you.

 

[Jasongreat]

=mgb_phys;2432549]Electromagnetic radiation is dangerous, but due to it's heating effect (at > visible wavelengths) if you stand in front of a powerful enough microwave transmitter for long enough you will be damaged. It's unlikely that a 1W cell phone outside your head could do much heating.

The only danger of emf waves is the heating caused? EMFs don't cause any other damage to the molecular structure? If the answers are yes and no respectively, i guess i have been over reacting as far as the danger of microwaves.

The point remains that we cook food both for texture/taste and safety.

I agree but we eat food for the nutrition, if the way we are cooking could be damaging the nutritional value of the food, I would consider that harmful even if it is safer.

Probably too low a temperature to destroy milk protein.

I'm sorry I mis-spoke, does the temperature damage the milk protein?
This part of our discussion has strayed way off topic so I will not be continuing any further, unless of course I decide to start a new thread on raw vs cooked food.

Common urban myth. In fact because of the short cooking time and poor thermal conductivity you can end up with the inside much less cooked than in a stove.

Thanks for correcting me. Thats what I love about this forum, I learn something new quite often.

 

[Jasongreat]

russ_watters;2432616] Yes, the reason microwaves are bad for us is because we are alive: it is dangerous to cook a person while they are alive!

The part I wasnt sure about wasnt that its dangerous to cook a living thing, but that the microwaves don't cause other changes to the thing getting cooked other than just heating it up.

Your microwave has a shield to prevent microwaves from escaping and cooking you. Similarly, your normal oven has a shield to keep heat (hot air) from escaping and cooking you

.

Oh, I thought the door on my normal oven was to keep the heat from escaping so I can cook at the temperature of my choosing.

 

[mgb_phys]

EMFs don't cause any other damage to the molecular structure?

Not at microwave energies - these are much lower energy than any of the molecular bonds and so don't cause any chemical changes other than heat. The same isn't true of UV that can do chemical damage without heating.

I agree but we eat food for the nutrition, if the way we are cooking could be damaging the nutritional value of the food, I would consider that harmful even if it is safer.

For meat, heating is probably a benefit - it breaks down muscle fibre and makes it more digestible. It denutures some proteins but you don't use protein directly you break it down into amino acids. For vegatables heating is more a loss, a lot of vitamins are destroyed by heating, especially cooking in water.

 

[russ_watters]

Oh, I thought the door on my normal oven was to keep the heat from escaping so I can cook at the temperature of my choosing.

Good point, it works both ways - as does the door on the microwave!

I agree but we eat food for the nutrition, if the way we are cooking could be damaging the nutritional value of the food, I would consider that harmful even if it is safer.

There is an awful lot of info out there about the effects of cooking on nutritional value of foods. Yes, various forms of cooking can have an effect:

Q: What's the best way to cook vegetables to keep the most nutrition intact?

A: As with all colors of vegetables, the more they're cooked the more vitamins and minerals are lost. The vegetables tend to break down when exposed to heat. "The longer and hotter you cook them, the more nutrients you are likely to lose.

The ideal way to eat vegetables and preserve the biggest amount of nutrients is to eat them raw, but if you are cooking your vegetables, try steaming them either in a steamer or in the microwave. Stir frying also can be a good way to preserve the nutrients. Always use as little water as possible, and avoid boiling vegetables, as the vitamins, minerals and phytochemicals will escape into the water rather than remaining in the vegetables. Also try to keep the vegetables in larger pieces when cooking. The more their surface is exposed to air and/or water, the more likely you will lose those important vitamins and minerals.

http://www.recipestoday.com/expertqa/cooking/what-s-the-best-way-to-cook-vegetables-to-keep-the-5791

 

[Proton Soup]

the biggest sin of microwave cooking is that the food comes out tasting like crap. i believe much of this is because the microwaves overheat the food. with water, you only get up to a temp of 212 (or a little higher i think can happen under certain situations), but with oil/grease, the boiling point is much higher. this may actually be dangerous, as it changes the chemical composition of the food compared to what it would be cooked by traditional methods.

Effect of different cooking methods on some lipid and protein components of hamburgers
Purchase the full-text article



References and further reading may be available for this article. To view references and further reading you must purchase this article.

M. T. Rodriguez-Estrada, G. Penazzi, M. F. Caboni, G. Bertacco and G. LerckerCorresponding Author Contact Information, E-mail The Corresponding Author

Istituto di Industrie Agrarie, via S. Giacomo 7, 40126, Bologna, Italy

Received 11 April 1996;
revised 21 August 1996;
accepted 18 October 1996. ;
Available online 8 December 1997.

Abstract

The effects of different cooking methods on the lipid and protein fractions of hamburger were evaluated. The lipid component was subjected to the following analyses: peroxide value; p-anisidine; total and free fatty acids; cholesterol and its oxidation products (quantified as 7-ketocholesterol). Lysinoalanine (LAL), free amino acids and D-amino acids (D-AA) were also determined in the protein fraction. All results were compared with a raw control. No significant differences were found among the cooking treatments with respect to D-AA and LAL. The degree of proteolysis, lipolysis and lipid oxidation varied depending on the treatment conditions. Regarding cholesterol oxidation, the combination of roasting and microwave heating caused more oxidation than the other treatments. The raw meat, however, showed an advanced degree of oxidation (25.2 ppm of total 7-ketocholesterol/120 g ground meat).

microwaving also destroys B12 and who knows what else

J Agric Food Chem. 1998 Jan 19;46(1):206-210.
Effects of Microwave Heating on the Loss of Vitamin B(12) in Foods.

Watanabe F, Abe K, Fujita T, Goto M, Hiemori M, Nakano Y.

Department of Food and Nutrition, Kochi Women's University, Kochi 780, Japan, and Department of Applied Biological Chemistry, Osaka Prefecture University, Sakai 593, Japan.

To clarify the effects of microwave heating on the loss of vitamin B(12) in foods, raw beef, pork, and milk were treated by microwave heating and then their vitamin B(12) contents were determined according to a chemiluminescent vitamin B(12) assay with hog intrinsic factor. Appreciable loss ( approximately 30-40%) of vitamin B(12) occurred in the foods during microwave heating due to the degradation of vitamin B(12) molecule by microwave heating. When hydroxo vitamin B(12), which predominates in foods, was treated by microwave heating and then analyzed by silica gel 60 thin layer chromatography, two vitamin B(12) degradation products were found. One of the compounds with a R(f)() of 0.16 was purified and partially characterized. The vitamin B(12) degradation product did not show any biological activity in the growth of a vitamin B(12) requiring microorganism, Euglena gracilis Z, and was not bound to hog intrinsic factor, a mammalian vitamin B(12) binding protein. Intravenous administration of the compound (1 µg/day) for 7 days to rats showed that the compound neither has toxicity nor acts as a vitamin B(12) antagonist in mammals. These results indicate that the conversion of vitamin B(12) to the inactive vitamin B(12) degradation products occurs in foods during microwave heating.

PMID: 10554220 [PubMed - as supplied by publisher]

 

[vanesch]

But my question is about the FOOD which is cooked with microwave oven.

Do you know what happens to them?

I once heard the silly comment that it is safer for microwaved food to leave a few minutes open in the air before eating it, so that the microwaves that got into it have time to escape

 

[jreelawg]

I once heard the silly comment that it is safer for microwaved food to leave a few minutes open in the air before eating it, so that the microwaves that got into it have time to escape

I've heard this one before. The claim was that certain molecules can absorb the frequencies of the radiation and re-emit it. This is true of certain gas molecules in the air absorbing and re-emitting harmful UV radiation, but I haven't verified if molecules can do this with microwave radiation or not, or if it did, how long after bombardment it could pull this off. I think that this probably happens practically instantly.
What's the word for this anyways?

 

[vanesch]

I've heard this one before. The claim was that certain molecules can absorb the frequencies of the radiation and re-emit it. This is true of certain gas molecules in the air absorbing and re-emitting harmful UV radiation, but I haven't verified if molecules can do this with microwave radiation or not, or if it did, how long after bombardment it could pull this off. I think that this probably happens practically instantly.
What's the word for this anyways?

Fluorescence (fast) or phosphorescence (slow). Don't think it is possible with microwaves, but I'm not sure.

In any case, it wouldn't do anything to you, as it would be very low power. Heated food (no matter how) will radiate away much more high-frequency infrared radiation than it will radiate away low-frequency microwaves.

In fact, it happens more with traditionally heated food, which radiates away part of the infrared radiation it received during classical heating. This is also called "cooling". If you wait for a few hours, most of the extra infrared radiation is radiated away (and hence the food is cold again).

 

[alxm]

Fluorescence (fast) or phosphorescence (slow). Don't think it is possible with microwaves, but I'm not sure.

Fluorescence, yes, but with a much much lower probability, because the excited state will easily undergo non-radiative relaxation (= get hotter. Which is the point.) Phosphorescence is not possible.

To whatever extent there is fluorescence, you're talking about picoseconds. Not only will it have radiated off before you have a chance to open the microwave, it'll have radiated off before you even heard the microwave's beep.


Anyway it's all been studied and no, microwave ovens aren't dangerous. Microwaved food isn't dangerous, and nor does it contain less nutrition or anything else. (If anything, it contains more. Since conventional heating heats from the outside-in, it requires a longer time to cook things and destroys more nutrients in the process.) The one plausible health-drawback is bacteria in food that's been unevenly cooked.

 

[mheslep]

...
You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.

Your microwave oven is not unsafe, even if you put your face near it. Relax.

- Warren

Though I'm not sure of the mechanism for enforcement, they are required to be tested to meet government standards on leakage:
http://www.hps.org/hpspublications/articles/microwaveoven.html

Certainly microwave ovens have EM radiation standards and are tested. However, as I recall some of the earlier ovens (decades ago) used inadequately specified door gaskets and developed leaks exceeding standards over time due to use, abuse, and heating cycles. The risk in such a case would be tissue heating and not ionization - particularly in the eye lens which is susceptible to heating, causing cataracts.

 

[Dale]

There are two big dangers with microwave ovens (assuming it is correctly functioning):

1) the food can be undercooked and still have some pathogen
2) you can burn yourself with the food after taking it out

Both are also dangers with regular ovens.

 

[Proton Soup]

Anyway it's all been studied and no, microwave ovens aren't dangerous. Microwaved food isn't dangerous, and nor does it contain less nutrition or anything else. (If anything, it contains more. Since conventional heating heats from the outside-in, it requires a longer time to cook things and destroys more nutrients in the process.) The one plausible health-drawback is bacteria in food that's been unevenly cooked.

well, I've provided some evidence that suggests otherwise.

 

[russ_watters]

well, I've provided some evidence that suggests otherwise.

While you are right in that alxm's post was overly positive toward microwaves, yours didn't really add much since there was very little in the way of substantive differences shown in what you posted/quoted. Heating, whether via microwaves or any other method, does have an affect on food's nutritional value. Does microwaving food decrease nutritional value more than other methods? I don't know, but your links/quotes don't make much of a case either way.

On the general point:

Nearly every food preparation process reduces the amount of nutrients in food. In particular, processes that expose foods to high levels of heat, light, and/or oxygen cause the greatest nutrient loss. Nutrients can also be "washed out" of foods by fluids that are introduced during a cooking process. For example, boiling a potato can cause much of the potato's B and C vitamins to migrate to the boiling water. You'll still benefit from those nutrients if you consume the liquid (i.e. if the potato and water are being turned into potato soup), but not if you throw away the liquid. Similar losses also occur when you broil, roast, or fry in oil, and then drain off the drippings.

The table below compares the typical maximum nutrient losses for common food processing methods.

http://www.nutritiondata.com/topics/processing

 

[Proton Soup]

While you are right in that alxm's post was overly positive toward microwaves, yours didn't really add much since there was very little in the way of substantive differences shown in what you posted/quoted. Heating, whether via microwaves or any other method, does have an affect on food's nutritional value. Does microwaving food decrease nutritional value more than other methods? I don't know, but your links/quotes don't make much of a case either way.

On the general point: http://www.nutritiondata.com/topics/processing

i don't think I'm disagreeing with that, only that microwaving has the worst effect.

also, what do you mean by substantive, statistically significant? anyhoo, i appreciate your nutritiondata link, but something more "substantive" that addresses the issue at hand (microwave cooking) would be nice.

 

[mheslep]

i don't think I'm disagreeing with that, only that microwaving has the worst effect...

Where is the comparison made? I only saw the evidence regarding uwaving in of itself reducing nutrition (as does convection heating).

 

[Proton Soup]

Where is the comparison made? I only saw the evidence regarding uwaving in of itself reducing nutrition (as does convection heating).

in the screenshot from google books that i posted, it gives a little more information than what is in the abstract regarding 7-ketocholesterol production. combined microwaving and roasting produced the most, followed by microwaving alone. ergo, microwaving is the worst when considering each individually.

 

[russ_watters]

i don't think I'm disagreeing with that, only that microwaving has the worst effect.

Yes, I know that's what you are claiming. What I am saying is that your post doesn't really help you much with that claim.

also, what do you mean by substantive, statistically significant?

Substantive means relevant and substantial. What you provided is just really really thin.

anyhoo, i appreciate your nutritiondata link, but something more "substantive" that addresses the issue at hand (microwave cooking) would be nice.

My link certainly had more overall relevance than yours because it is broader and it points directly to a particular flaw in your information! The B12 study talks only about one vitamin and only about microwaving. But if "cooking" (methods not specified) can reduce B12 by up to 50%, well then the study that says microwave cooking reduces it by 30-35% in a particular test is completely useless for addressing the claim that microwave cooking reduces nutrition more than other methods, isn't it? As mhselp said, it needs to compare microwaving to other methods to have any value at all.

Your first study is perhaps more useful, but it doesn't say how much difference it noted between the cooking methods and what is done to cholesterol is just one small piece of the puzzle. Obviously, meat is always cooked, but what is probably a bigger issue is nutrients lost in veggies and the differences in losses can be huge, not to mention the difference between cooking and eating them raw! And I don't know anyone who would cook a hamburger in a microwave anyway. If nothing else, cooking on a grill let's fat drain away from it.

My point here is that characterizing this as an issue specific to microwave ovens just isn't realistic and your links just aren't that useful or compelling.