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Microwaves--nutritionally harmful?  RSS feed

 
pollinator
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Location: Stevensville, MT
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I was wondering if there were any folks out there who were knowledgeable about how microwaves affect the nutrition of what we eat. I feel like I read some study a while back that said things did not digest as well when microwaved, and cell function slowed down or something. What have people found?
 
Posts: 66
Location: Spokane and near Diamond Lake, WA
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I haven't been able to find a really solid web page on this issue. This page has some shaky speculations, but it does mention some studies showing harm from eating microwaved food:

http://www.herbalhealer.com/microwave.html
 
Suzy Bean
pollinator
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Location: Stevensville, MT
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Thanks Ran. I also just found some tests where water that has been microwaved (then cooled) is used to water one plant, and water that has been boiled (then cooled) is used for comparison. The microwaved water plant dies. Also, Dr. Emoto (the pictures of crystallized water guy) did a picture of some microwaved water, and, although I haven't been able to find a pic online, a friend who has the book told me it was "messed up."
 
Posts: 62
Location: Western Pennsylvania
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I read about it some years ago that it kills a large amount of vitamins in vegetables.  I also remember reading a study in Europe where people in one group ate a vegan diet cooked on the stove and the other group ate the same diet cooked in a microwave and the microwave people had an increase in their serum cholesterol. 

So, five years ago, when we moved into our new house our microwave got the toss and we don't use one at all.  I much prefer real popcorn with my stovetop popper and real butter and it does take longer to re-heat Thanksgiving leftovers in the toaster oven or a double boiler on the stove top, but we have worked it into our lives just fine.  People cooked for a few years before microwaves came around!!!

Tami
 
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This is not a simple issue unfortunately.  I'm a big proponent of scientific evidence since I work in a science lab.  On the other hand, I'm human and tend to have emotional attachments to things that "sound" or "feel" right.  To me, a microwave sounds/feels like it would be more damaging to food.  However, the scientific evidence is not holding that up.  For instance (all peer reviewed articles, emphasis mine):

The effects of microwave heating on the retention of selected nutritional components in animal muscle was studied. We determined the degree of retention of the thermolabile vitamin B6 and thiamine after thermal treatment of pork and chicken meat in a conventional oven (Tatramat) and in a microwave oven (model GUM 2S [A] and Toshiba ER-5300D ).

In conventionally roasted samples 48–96% of thiamine was retained, whereas microwave-treated samples showed retention as high as 85.6–94.2% (oven A) and 88–96% (oven B).

After conventional roasting, meat samples retained only 21.6–48.5% of vitamin B6. Microwave treatment, on the other hand, retained 59.9–80.9% (oven A) and 64.2–86.8% (oven B) of vitamin B6.

[b]The measured values of vitamin retention demonstrate clearly that heating of muscle tissue with microwaves is less destructive to heat-sensitive vitamins than is conventional roasting
and that, therefore, microwave cooking and roasting can be recommended for food preparation in the food industry, households, restaurants and hospitals.

source

The proximate composition, fatty acid and tocopherol levels of egg yolk were determined in raw eggs and after different cooking processes: boiling for 3 and 10 min, heating in a microwave oven, and frying. Of the protein, lipid, ash and moisture contents, only the last decreased with microwave cooking. The predominant fatty acid was oleic (18:1) (36.10–42.6%), followed in decreasing amounts by palmitic (16:0), linoleic (18:2), linolenic (18:3) = arachidonic(20:4) = docosanoic (22:0), docosahexanoic (22:6) and myristic acid (14:0). Of the polyunsaturated fatty acids, 18:2, 18:3, 20:4 and 22:6 decreased in the samples subjected to microwaves. α-Tocopherol (6.1–2.9 mg per 100g) was the predominant isomer in all the samples followed by (β + γ)-tocopherol and δ-tocopherol, while α-tocotrienol was detected in trace amounts. All these tocopherols were reduced during cooking by up to 50% in omelettes and microwave treatments.

source

The effects of microwave cooking and other traditional cooking methods such as boiling and autoclaving on the nutritional composition and anti-nutritional factors of chickpeas (Cicer arietinum L.) were studied. Cooking treatments caused significant (P<0.05) decreases in fat, total ash, carbohydrate fractions (reducing sugars, sucrose, raffinose and stachyose, while verbascose was completely eliminated after cooking treatments), antinutritional factors (trypsin inhibitor, haemagglutinin activity, tannins, saponins and phytic acid), minerals and B-vitamins. Cooking treatments decreased the concentrations of lysine, tryptophan, total aromatic and sulfur-containing amino acids. However, cooked chickpeas were still higher in lysine, isoleucine and total aromatic amino acid contents than the FAO/WHO reference. The losses in B-vitamins and minerals in chickpeas cooked by microwaving were smaller than those cooked by boiling and autoclaving. In-vitro protein digestibility, protein efficiency ratio and essential amino acid index were improved by all cooking treatments. The chemical score and limiting amino acid of chickpeas subjected to the various cooking treatments varied considerably, depending on the type of treatment. Based on these results, microwave cooking is recommended for chickpea preparation, not only for improving nutritional quality (by reducing the level of antinutritional and flatulence factors as well as increasing in-vitro protein digestibility and retention rates of both B-vitamins and minerals), but also for reducing cooking time.

source

I have found several papers that talk about various things changing in foods but not what that means or if they change more or less than conventional cooking.  In short, I have yet to find a scientific paper showing MORE damage across the board for microwave cooking than for boiling/roasting.

Still...it never feels as "healthy" to cook in the microwave.  I don't get it.  My scientific brain should be able to accept these studies but something feels off!  Perhaps it's just the association with "microwave dinners" which are certainly worse for you than a real home cooked meal...
 
Ran Prieur
Posts: 66
Location: Spokane and near Diamond Lake, WA
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There are at least two issues here. One is: can we find harmful effects on food cooked in microwaves? To test this, you do a chemical analysis of the food itself. As far as I know, this kind of test has not yet found anything wrong.

The other issue is: can we find harmful effects on people who eat food cooked in microwaves. To test this, you get two groups of people and feed them the same food cooked both ways, and then test their health. I've seen studies (mentioned previously on this page) that do seem to show harm from microwaves. If these studies are accurate, and we can't find the mechanism by which the food is harmful, we need to keep looking.

Another issue is: can we trust the researchers? We already have double-blind experiments. I think we should do triple-blind experiments, where the people who analyze and report the results are blind to their source of funding!
 
                                
Posts: 62
Location: Western Pennsylvania
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AAhhh Ran Prieur nailed it with "can we trust the researchers?".  That is pretty much key with most everything.

I'm reading "Good Calories, Bad Calories" by Gary Taubes right now, and it's maddening how the science doesn't have to prove anything, people just go on to say what they "think" should be right regardless.

.......what the h*ll is good for us to eat anyway!!!?  It's making me nuts!


Tami 
 
Posts: 700
Location: rainier OR
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as uncomfortable as the thought is nutritional research is still in its infancy, making it more complicated humans seem to have adapted well to several different sorts of conditions for example Inuits with their super high fat native diet and certian Tibetan tribes who ate almost no meat, and Mongols whose diets consisted of up to 60% dairy products.  then all of these tribal traits have recently blended.

what I'm saying is the only way to find out what iis best for you to eat is to pay close atention to what you eat and how you feel.
 
Posts: 98
Location: Eastern Colorado, USA
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Marissa Little wrote:
I have found several papers that talk about various things changing in foods but not what that means or if they change more or less than conventional cooking.  In short, I have yet to find a scientific paper showing MORE damage across the board for microwave cooking than for boiling/roasting.



Couple of issues....

One of your quotes mentions autoclaving.  Who cooks that way?  The whole point of autoclaving is to sterilize, so it should come as no surprise that it would result in destroyed nutrient content!

Second, it does not appear they specify how long and at what temperatures they are conventionally cooking.  If you boil your carrots on the stove for an hour and turn them to mush, there sure as heck isn't going to be anything left of them.

Always cast a wary eye on "scientific studies."  They're often rigged. 

I was told of one that "conclusively proved" that high fructose corn syrup wasn't a factor for hyperactive kids.  Turns out, they gave the other half of the kids aspartame instead... which causes pretty much the same problems.  Any competent scientist would have used kids drinking only water as a control group, so it's pretty clear that study was deliberately flawed to produce a sponsored result.
 
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