Take the 2-minute tour ×
Seasoned Advice is a question and answer site for professional and amateur chefs. It's 100% free, no registration required.

After answering this article, I did some research on microwaving killing vitamins and nutrients in food.

I very quickly learned that this is a touchy subject, even among nutritionists, and nobody (at least, nobody I saw) seems to have a "this is the science behind it and here is a definite answer" answer. Some articles claim "there is no hard evidence" while others point to studies from Stanford and other respected institutions that back the "yes" answer.

Some quick articles with conflicting information, if you're only going to read one please read the first and last as they seem the most reputable to me:

  1. The Straight Dope: Scientists are not sure yet, but it's likely in some cases
  2. Microwaving can be like boiling, which kills nutrients
  3. Microwaving is the best way of cooking for preserving nutrients
  4. Microwaving hurts broccoli, but is good for potatoes
  5. Harvard: Microwaving may preserve nutrients, like Vitamin C

As an interesting note, the "use less water" idea, which most of us take as common sense when cooking vegetables, may also be under scrutiny. From the Harvard article above:

But this is nutrition, and nothing in nutrition is simple. Italian researchers published results in 2008 of an experiment comparing three cooking methods — boiling, steaming, and frying — and the effect they had on the nutritional content of broccoli, carrots, and zucchini. Boiling carrots actually increased their carotenoid content, while steaming and frying reduced it. Carotenoids are compounds like lutein, which may be good for the eyes, and beta carotene. One possible explanation is that it takes longer for vegetables to get tender when they’re steamed, so the extra cooking time results in more degradation of some nutrients and longer exposure to oxygen and light.

So, my questions are: Is microwaving known to kill nutrients in foods? Is there a way to minimize this effect? Can any nutritionists weigh in here with their experience, and ideally, the science behind their answers? This has been a very confusing research path full of conflicting information, so all answers are appreciated.

share|improve this question
2  
I realize that this may end up being a list of "this food is fine in the microwave, but this food loses all its value", but I'm trying to avoid that and look for a general case here. The article KeithB points to says this: "Recent reports reveal that cooking vegetables in a microwave oven leads to a greater loss of soluble phenolic antioxidant compounds than does conventional cooking. However, this appears to have been at least partly due to the use of more cooking water than is necessary with microwaves." This is the kind of answer I'm looking for, "use less water for maximum retention". –  stephennmcdonald Aug 17 '10 at 16:09
    
edited to remove [health] and [nutrition] and add [food-science] as per this discussion: meta.cooking.stackexchange.com/questions/613/… –  stephennmcdonald Aug 18 '10 at 17:44

5 Answers 5

up vote 15 down vote accepted

Anything that breaks down due to heat is going to break down no matter HOW you cook it. Boiling only "destroys" nutrients by leaching them away into the water, which is the same reason that other people say that steaming/microwaving is better.

Thiamine, for example, is highly water soluble, so boiling is out. But it also breaks down at 100C, so you can't really cook it either. Niacin, on the other hand, leeches into water, but it's not heat-sensitive, so you can cook the hell out of it, as long as you don't get it wet. Folate is so fragile you can't leave your leafy greens in the sun without it breaking down (common with acids).

Basically, almost everything is better uncooked, but a lot of things are impossible to eat if you don't cook them enough to break down the cellulose. So eat a balanced diet, and stop worrying about the microwave.

share|improve this answer
1  
Comment appreciated, and some good info. I do understand that anything that breaks down due to heat is going to break down no matter how you cook it, but if you read the fourth article in my question, there seems to be research implying that how the microwave heats causes more nutrients to be lost than normal heating methods. FTA: doctors at Stanford University...reported that microwaving frozen breast milk sharply reduced the potency of the natural infection-fighting agents it contained. "The adverse effects...are difficult to explain on the basis of hyperthermia [high heat] alone," –  stephennmcdonald Aug 17 '10 at 16:02
    
Edit: I rearranged the links in the question so the most important was on top, now please refer to my first link, not my fourth. Forgot I can't edit comments after a certain time. –  stephennmcdonald Aug 17 '10 at 16:14
    
@stephenmcdonald: There's nothing magical about microwaves. It's just your basic EMF. Microwaves affect b12, but so does sunlight. It's better for spinach, however, than stovetop cooking. I hesitate to weigh in on breast milk because everyone has an opinion, but there aren't a whole lot of facts. One thing is certain, however, which is that breast milk being high in fats and proteins, will heat unevenly in the microwave. The water content will heat much more rapidly, and that may cause some issues. It's also a very high degree of heating, not slow as with a bottle warmer. –  Satanicpuppy Aug 17 '10 at 16:19
    
That response makes a lot of sense, thank you! –  stephennmcdonald Aug 17 '10 at 16:24

Without answering the question I would like to make a brief digression into physics:

Microwaves work by exciting the rotational modes of water molecules, after which the energy is distributed into all the available kinetic modes (this is called the equipartition theorem and is very well established). That randomized kinetic energy is called "heat".

The microwaves are very low energy, orders of magnitude below ionization and still far below the threshold for almost all chemistry. They can only do their work at all because the rotational modes are very low lying states.

This is very basic physics and it is not in question.

What that means is that they heat food up. For food with low water content they do so fairly evenly through a considerable thickness. For foods with a high water content the heating happens more towards the surfaces, but still penetrates a non-trivial distance.

From a fundamental point of view there is no reason to believe that this will cause more nutrient destruction than any other form of heating.

share|improve this answer
1  
Good info, love the physics answer, thank you. However it seems like your answer (the part about penetration) actually implies that there is a difference - some of the articles I've read say that because food cooks faster and more thoroughly in a microwave (in the sense that it reaches the inside faster), it may retain nutrients better than other methods that cook from the outside in (see Harvard link). Although that lends to nutrients being spared with the microwave as opposed to lost, at the very least it implies a difference between cooking methods. –  stephennmcdonald Aug 17 '10 at 16:36
    
Isn't it true that microwaves heat up little spots much hotter then other spots. Thats why you have to leave the food inside the microwave for a while so the heat can spread through the food. The hot spots might destroy more vitamins etc. then just cooking it. –  Barfieldmv Jan 26 '11 at 12:10
    
@Barfieldmv: If you've used a lot of microwaves you probably noted that some have a more pronounced nodal behavior then others, but even in the worst case the effect is roughly one of heating half the volume (in cm scale patches). The important question is do the anti-nodes (hot spots) get hotter than they would if cooked by conventional techniques. For high water food the answer is almost certainly "no". –  dmckee Jan 26 '11 at 17:45
    
I'm more curious about the molecule level. Water molecules get super hot and have to dissipate the heat around the rest of the food. Sure this heat spreads quickly but it might just damage nutrients. This is a bit like normal radiation is mostly harmless but it might just destroy you're dna. And oxygen Ions are mostly harmless but they can damage you're cells. –  Barfieldmv Jan 28 '11 at 9:32

I think that the question is phrased poorly. For some foods and some cooking methods, the answer might be yes, to some extent. But that doesn't mean that you shouldn't cook anything in a microwave.

Here is an overview article from Australia's national science agency Safety of Microwave Ovens. Unfortunately, it doesn't have any links to the primary literature.

The majority of reports published on the nutritive value of foods cooked in microwave ovens indicate that food prepared in this manner is at least as nutritious as comparable food cooked by conventional methods.

Most of these studies have concentrated on vitamin retention and indicate that cooking in minimal water for a reduced time, as occurs with microwaving, promotes the retention of the water-soluble vitamins particularly of vitamin C and thiamin.

share|improve this answer
    
I didn't want to phrase it as a "which foods lose nutrients when microwaved" question because I'm not a huge fan of list questions, but that might be applicable here. If everyone finds my question difficult to answer I'll gladly consider rewording it :) –  stephennmcdonald Aug 17 '10 at 16:00
    
Also, don't worry, I never said not to cook anything in the microwave - we use our microwave quite a bit in my house as my wife and I both work long hours. :) I'm just curious about what I may be missing if I'm microwaving broccoli vs steaming it (for example). The article you link to also says this: "Recent reports reveal that cooking vegetables in a microwave oven leads to a greater loss of soluble phenolic antioxidant compounds than does conventional cooking." It says that it's due to overuse of water - but since this is how a lot of people use their microwave, it's a concern IMO. –  stephennmcdonald Aug 17 '10 at 16:07
    
BTW - thank you for the link, I hadn't come across that one myself! –  stephennmcdonald Aug 17 '10 at 16:33

According to a recent article (summarized here), microwave vs stovetop does not affect the nutrient contents of vegetables. Two things affect the nutrient content: intensity of heat and volume of water used in cooking:

"Nutrients tend to be both heat-intolerant and water-soluble," the article says, which means that any method that requires a) cooking at a high temperature for a long time, and b) uses a lot of water will result in the greatest nutrient loss. (So by this measure, boiling vegetables is likely the worst offender.) It goes without saying then that cooking at a lower temperature for a shorter amount of time and with less water would result in the least amount of nutrients lost, and that's what the microwave accomplishes.

This means that the microwave is actually better at preserving nutrients than boiling the veggies (though steaming is also a significant improvement, and if you boil them inside a soup where you drink the broth, you lose very little as well).

share|improve this answer
    
Not part of the answer, but additional info: this isn't too much in the way of new information, but the question asked for sources and this hit my rss feed today, so I figured I'd toss it in. –  Yamikuronue Oct 3 '12 at 16:13

Just submitting this article on LIVESTRONG.COM for consideration: http://www.livestrong.com/article/371758-the-effects-of-microwaving-on-food/

It states that microwaving has no more adverse affect than traditional cooking methods, and that your body will also denature proteins and nutrients (breakdown) in its digestion process; your body does not simply consume proteins and nutrients as is.

Heating is the culprit to be concerned with, and the length of which food is heated for. The longer, the more denaturing occurs; and because microwaves cook food faster, it has less of an adverse affect. The only negative affect of heating food, according to this article, is that it reduces vitamin content.

share|improve this answer

protected by rumtscho Jan 9 '13 at 15:39

Thank you for your interest in this question. Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.