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Do Microwave Ovens Destroy Nutrients?

9/25/2013

4 Comments

 
It sure is quick and convenient to heat up food in a microwave oven, especially when the food is already in a microwaveable container, because then it can go straight from the freezer or fridge into the microwave and be ready to eat in a matter of minutes! However, I’ve heard and been told that it’s bad to use a microwave oven to cook or heat up food because it destroys the nutrients in foods. It seemed to make sense, and I found myself obligingly turn to using the stove top or oven to heat my foods. Then I decided to find out for myself if it’s true that microwave ovens destroy nutrients.

I turned to the internet and found that there are two opposing viewpoints: 1) that microwave ovens do not destroy nutrients, and in fact, may be better than conventional cooking methods; and 2) that microwave ovens do destroy nutrients, even to the point of threatening your health. Now, keep in mind, I’m only addressing the effect of microwave ovens on nutrients. I’m not getting into whether or not microwave ovens are safe.

According to the Harvard Medical School Family Health Guide (1), some nutrients break down when exposed to heat, regardless of the source (microwave or regular oven), and the longer the exposure to heat, the more the nutrients break down. Nutrient content is probably better preserved when cooking with a microwave oven because of the shorter cooking times.

Cooking vegetables in water is problematic because many nutrients are water-soluble. Foods boiled in water will lose nutrients to the water, and the longer the foods are cooked in boiling water, the more nutrients are lost. For this reason, some say that cooking in a microwave oven is better because in addition to the shorter cooking times, there is little or no water to leach the nutrients from the food. (2, 3) The only time boiling in water is better is if you’re making a soup or stew, in which case you retain the nutrients in the broth. Studies at Cornell University looked at the effects of cooking on water-soluble vitamins in vegetables and found that folate was almost completely retained in spinach when cooked in a microwave oven, yet 77% was lost when cooked on a stove. (4)

According to Dr. Mike Roussell, PhD, microwaving can make certain nutrients more available to your body, and cited research from the University of Oslo that found that microwaving or steaming carrots, spinach, mushrooms, asparagus, broccoli, cabbage, green and red peppers, and tomatoes caused antioxidants to become more available for absorption. (5)

On the other hand, several websites cited specific studies from the scientific literature (6, 7, 8, 9), including a study published in the November 2003 issue of the Journal of the Science of Food and Agriculture that found that broccoli microwaved with a little water lost up to 97 percent of its beneficial antioxidants while steamed broccoli lost no more than 11 percent of its antioxidants. In addition, there were losses in phenolic compounds and glucosinolates. A 1999 study in Scandanavia found a reduction in vitamin C when asparagus spears were cooked in the microwave. A study of garlic found that allinase, garlic’s principle active cancer-fighting ingredient, was inactivated in as little as 60 seconds. Watanabe did a study in Japan showing that 30-40 percent of vitamin B12 in milk becomes inert after 6 minutes of microwave heating. An Australian study showed a higher degree of protein unfolding from microwaves than conventional heating, which deactivates proteins.

Microwaves excite water molecules inside food, causing the water molecules to vibrate at high frequencies, creating internal friction that heats foods wherever there’s water inside the food. That’s why microwave ovens don’t evenly heat food. According to Mike Adams at Natural News (8) microwaving results in a cell-by-cell “nuking” of food causing near-total molecular decomposition of the vitamins and phytonutrients.

I came across interesting reports that described a science fair project in which two plants were watered side-by-side, one with water that was boiled in the microwave, then cooled, and one with fresh water. (10, 11) After nine days, the one watered with the “nuked” water was dead while the one watered with the fresh water was thriving. It was assumed that the microwaved water killed the plant. Yet snopes.com repeated the experiment with three plants using water that was boiled in the microwave oven then cooled, boiled on the stove then cooled, and water that hadn’t been boiled as a control. (12) All the water used in the experiment came from the same source. In their experiment, all three plants thrived.

So where do I stand on the issue now? It’s really hard for me to say because the information I found about the effect of microwave ovens on nutrients is contradictory and I was unable to find direct evidence. Most of what I found were other people’s summaries of studies, and without seeing the actual journal articles where the original studies were published, I don’t know how accurately those studies were summarized.

I will say this, for now I will continue to do all my cooking on the stove, the grill, or in the oven, and continue to eat lots of raw veggies.

Resources
  1. http://www.health.harvard.edu/fhg/updates/Microwave-cooking-and-nutrition.shtml
  2. http://www.thekitchn.com/fact-or-fiction-microwaving-vegetables-destroys-nutrients-178081
  3. http://grist.org/living/ask-umbra-does-microwaving-vegetables-zap-their-nutritional-value/
  4. http://www.nytimes.com/2006/10/17/health/17real.html
  5. http://www.shape.com/healthy-eating/diet-tips/ask-diet-doctor-does-microwaving-vegetables-really-kill-nutrients
  6. http://articles.mercola.com/sites/articles/archive/2010/05/18/microwave-hazards.aspx
  7. http://www.greenmedinfo.com/blog/studies-show-microwaves-drastically-reduce-nutrients-food
  8. http://www.naturalnews.com/039404_microwave_ovens_vitamins_nutrients.html
  9. http://www.cookforlife.com/index.php/articles/21-articles/457-are-you-cooking-nutrients-out-of-your-foods
  10. http://healthfree.com/blog/blog/microwaves-nuking-nutrients-from-your-diet/
  11. http://www.naturalnews.com/031929_microwaved_water_plants.html
  12. http://www.snopes.com/science/microwave/plants.asp
4 Comments
kiwi-ian
2/27/2014 09:10:00 am

Good to see that someone has tried to look at both sides and not just the "microwaves are dangerous, get rid of your oven" brigade, most of whom I'm afraid misunderstand some of the elementary concepts of physics.

The Spanish study on broccoli has been criticised for steaming for 3.5 minutes but microwaving for nearly 6 minutes in a lot of water, the equivalent of perhaps 10-15 minutes steaming. Many other studies do not compare with similar times of conventional cooking, when this is done, microwaving becomes just another cooking method.

I've not read Mike Adams, but it sounds like his source is Mercola.com, an infamous website notorious for unscientific blather. Microwaving simply does not "nuke" cells causing molecular decomposition other than with thermic effects, the same as any other cooking method. Such scientifically impossible claims pepper the internet and scare sincere, innocent people into doing silly unnecessary things (like buying Mercola's turbo ovens).

Concerning the well known microwaved water on plants story, do it yourself. "Replication" is a fundamental part of scientific method, so do exactly as the girl did in the experiment.
1) Take 2 identical plants
2) Cut the leaves off the one you like least
3) Blame whatever or whoever you want.

If you look at that study, you never see any sick leaves - they have all been cut off!! Do you really believe the plant was sick?

One thing I would advise all those concerned to do. Study a little physics, go to Wikipedia or similar, but get a grounding. Find out what "radiation" really means (it is NOT a synonym for radio-activity).

Reply
Terri link
2/28/2014 01:42:45 pm

Hi kiwi-ian. Thank you for your comments! You are absolutely right that when comparing a microwave oven to other cooking methods, the cooking exposure must be equivalent in order to compare the results and reach meaningful conclusions. You are also right about the plant study that the results of the original study are not due to the water having been boiled in the microwave oven. As you know, when it comes to cooking in the microwave oven, microwave radiation increases the vibrational energies of water molecules in food, which raises the temperature. All cooking methods that raise the temperature of food may result in a loss of nutrients or deactivation of enzymes. On the other hand, some nutrients require heat to become accessible for absorption by our bodies. What I believe to be more important than whether or not to use a microwave oven is to not overcook foods, regardless of the cooking method, and to include a variety of cooked and raw vegetables in your diet.

Reply
kiwi-ian
4/16/2015 12:46:58 pm

Absolutely. All types of cooking can be overdone. My arguments are based on the irrational, unsubstantiated and frankly biased and one sided and even ignorant arguments of many in the anti-MW oven militia.

Having said that, and recognising that MW ovens have their place, we rarely use ours as we cook on a stove top and with my wife being a vegetarian, we do eat well. There IS a taste and texture difference.

Reply
Jiya Palit link
10/23/2017 05:53:17 am

Very informative article. I don't know how much microwave oven radiation effects our health. But I feels your article gives us a very clear overview.

Reply



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    Terri Quenzer, PhD

    Terri has a passion for good health and for helping others find happiness in themselves through better health! Through her scientific and life experiences, her goal is to help you reach your healthy goals!

    ​Be The Healthy U!: nominated for San Diego's Best Nutrition/Cooking Classes of 2016!

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